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Zhang SH, Shao DF, Wang ZA, Yang J, Yang W, Tsymbal EY. Tunneling Valley Hall Effect Driven by Tilted Dirac Fermions. Phys Rev Lett 2023; 131:246301. [PMID: 38181146 DOI: 10.1103/physrevlett.131.246301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 11/21/2023] [Indexed: 01/07/2024]
Abstract
Valleytronics is a research field utilizing a valley degree of freedom of electrons for information processing and storage. A strong valley polarization is critical for realistic valleytronic applications. Here, we predict a tunneling valley Hall effect (TVHE) driven by tilted Dirac fermions in all-in-one tunnel junctions based on a two-dimensional (2D) valley material. Different doping of the electrode and spacer regions in these tunnel junctions results in momentum filtering of the tunneling Dirac fermions, generating a strong transverse valley Hall current dependent on the Dirac-cone tilting. Using the parameters of an existing 2D valley material, we demonstrate that such a strong TVHE can host a giant valley Hall angle even in the absence of the Berry curvature. Finally, we predict that resonant tunneling can occur in a tunnel junction with properly engineered device parameters such as the spacer width and transport direction, providing significant enhancement of the valley Hall angle. Our work opens a new approach to generate valley polarization in realistic valleytronic systems.
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Affiliation(s)
- Shu-Hui Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, China
| | - Ding-Fu Shao
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Zi-An Wang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Jin Yang
- Beijing Computational Science Research Center, Beijing 100193, China
| | - Wen Yang
- Beijing Computational Science Research Center, Beijing 100193, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
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2
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Wu Y, Zhang Y, Jiang J, Jiang L, Tang M, Zhou Y, Liao M, Yang Q, Tsymbal EY. Unconventional Polarization-Switching Mechanism in (Hf, Zr)O_{2} Ferroelectrics and Its Implications. Phys Rev Lett 2023; 131:226802. [PMID: 38101373 DOI: 10.1103/physrevlett.131.226802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Revised: 02/07/2023] [Accepted: 10/25/2023] [Indexed: 12/17/2023]
Abstract
HfO_{2}-based ferroelectric thin films are promising for their application in ferroelectric devices. Predicting the ultimate magnitude of polarization and understanding its switching mechanism are critical to realize the optimal performance of these devices. Here, a generalized solid-state variable cell nudged elastic band method is employed to predict the switching pathway associated with domain-wall motion in (Hf,Zr)O_{2} ferroelectrics. It is found that the polarization reversal pathway, where threefold coordinated O atoms pass across the nominal unit-cell boundaries defined by the Hf/Zr atomic planes, is energetically more favorable than the conventional pathway where the O atoms do not pass through these planes. This finding implies that the polarization orientation in the orthorhombic Pca2_{1} phase of HfO_{2} and its derivatives is opposite to that normally assumed, predicts the spontaneous polarization magnitude of about 70 μC/cm^{2} that is nearly 50% larger than the commonly accepted value, signifies a positive intrinsic longitudinal piezoelectric coefficient, and suggests growth of ferroelectric domains, in response to an applied electric field, structurally reversed to those usually anticipated. These results provide important insights into the understanding of ferroelectricity in HfO_{2}-based ferroelectrics.
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Affiliation(s)
- Yao Wu
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Yuke Zhang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Jie Jiang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Limei Jiang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Minghua Tang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Yichun Zhou
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Min Liao
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Qiong Yang
- Hunan Provincial Key Laboratory of Thin Film Materials and Devices, School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
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3
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Patton M, Gurung G, Shao DF, Noh G, Mittelstaedt JA, Mazur M, Kim JW, Ryan PJ, Tsymbal EY, Choi SY, Ralph DC, Rzchowski MS, Nan T, Eom CB. Symmetry Control of Unconventional Spin-Orbit Torques in IrO 2. Adv Mater 2023; 35:e2301608. [PMID: 37272785 DOI: 10.1002/adma.202301608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2023] [Revised: 05/27/2023] [Indexed: 06/06/2023]
Abstract
Spin-orbit torques generated by a spin current are key to magnetic switching in spintronic applications. The polarization of the spin current dictates the direction of switching required for energy-efficient devices. Conventionally, the polarizations of these spin currents are restricted to be along a certain direction due to the symmetry of the material allowing only for efficient in-plane magnetic switching. Unconventional spin-orbit torques arising from novel spin current polarizations, however, have the potential to switch other magnetization orientations such as perpendicular magnetic anisotropy, which is desired for higher density spintronic-based memory devices. Here, it is demonstrated that low crystalline symmetry is not required for unconventional spin-orbit torques and can be generated in a nonmagnetic high symmetry material, iridium dioxide (IrO2 ), using epitaxial design. It is shown that by reducing the relative crystalline symmetry with respect to the growth direction large unconventional spin currents can be generated and hence spin-orbit torques. Furthermore, the spin polarizations detected in (001), (110), and (111) oriented IrO2 thin films are compared to show which crystal symmetries restrict unconventional spin transport. Understanding and tuning unconventional spin transport generation in high symmetry materials can provide a new route towards energy-efficient magnetic switching in spintronic devices.
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Affiliation(s)
- Michael Patton
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Gautam Gurung
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Ding-Fu Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Gahee Noh
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
| | | | | | - Jong-Woo Kim
- X-Ray Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Philip J Ryan
- X-Ray Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA
- School of Physical Sciences, Dublin City University, Dublin, 9, Ireland
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Si-Young Choi
- Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Gyeongbuk, 37673, Republic of Korea
- Center for Van der Waals Quantum Solids, Institute for Basic Science (IBS), Pohang, 37673, Republic of Korea
- Semiconductor Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Daniel C Ralph
- Cornell University, Ithaca, NY, 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA
| | - Mark S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - Tianxiang Nan
- School of Integrated Circuits and Beijing National Research Center for Information Science and Technology (BNRist), Tsinghua University, Beijing, 100084, China
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
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4
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Shao DF, Jiang YY, Ding J, Zhang SH, Wang ZA, Xiao RC, Gurung G, Lu WJ, Sun YP, Tsymbal EY. Néel Spin Currents in Antiferromagnets. Phys Rev Lett 2023; 130:216702. [PMID: 37295086 DOI: 10.1103/physrevlett.130.216702] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Accepted: 04/19/2023] [Indexed: 06/12/2023]
Abstract
Ferromagnets are known to support spin-polarized currents that control various spin-dependent transport phenomena useful for spintronics. On the contrary, fully compensated antiferromagnets are expected to support only globally spin-neutral currents. Here, we demonstrate that these globally spin-neutral currents can represent the Néel spin currents, i.e., staggered spin currents flowing through different magnetic sublattices. The Néel spin currents emerge in antiferromagnets with strong intrasublattice coupling (hopping) and drive the spin-dependent transport phenomena such as tunneling magnetoresistance (TMR) and spin-transfer torque (STT) in antiferromagnetic tunnel junctions (AFMTJs). Using RuO_{2} and Fe_{4}GeTe_{2} as representative antiferromagnets, we predict that the Néel spin currents with a strong staggered spin polarization produce a sizable fieldlike STT capable of the deterministic switching of the Néel vector in the associated AFMTJs. Our work uncovers the previously unexplored potential of fully compensated antiferromagnets and paves a new route to realize the efficient writing and reading of information for antiferromagnetic spintronics.
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Affiliation(s)
- Ding-Fu Shao
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Yuan-Yuan Jiang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Jun Ding
- College of Science, Henan University of Engineering, Zhengzhou 451191, People's Republic of China
| | - Shu-Hui Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Zi-An Wang
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- University of Science and Technology of China, Hefei 230026, China
| | - Rui-Chun Xiao
- Institute of Physical Science and Information Technology, Anhui University, Hefei 230601, China
| | - Gautam Gurung
- Trinity College, University of Oxford, Broad Street, Oxford, OX1 3BH, United Kingdom
| | - W J Lu
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Y P Sun
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
- Collaborative Innovation Center of Microstructures, Nanjing University, Nanjing 210093, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
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5
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Cao T, Shao DF, Huang K, Gurung G, Tsymbal EY. Switchable Anomalous Hall Effects in Polar-Stacked 2D Antiferromagnet MnBi 2Te 4. Nano Lett 2023; 23:3781-3787. [PMID: 37115910 DOI: 10.1021/acs.nanolett.3c00047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
van der Waals (vdW) assembly of two-dimensional (2D) materials allows polar layer stacking to realize novel properties switchable by the induced electric polarization. Here, based on symmetry analyses and density-functional calculations, we explore the emergence of the anomalous Hall effect (AHE) in antiferromagnetic MnBi2Te4 films assembled by polar layer stacking. We demonstrate that breaking P̂T̂ symmetry in an MnBi2Te4 bilayer produces a magnetoelectric effect and a spontaneous AHE switchable by electric polarization. We find that reversible polarization at one of the interfaces in a three-layer MnBi2Te4 film drives a metal-insulator transition, as well as switching between the AHE and quantum AHE (QAHE). Finally, we predict that engineering interlayer polarization in a three-layer MnBi2Te4 film allows converting MnBi2Te4 from a trivial insulator to a Chern insulator. Overall, our work emphasizes the topological properties in 2D vdW antiferromagnets induced by polar layer stacking, which do not exist in a bulk material.
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Affiliation(s)
- Tengfei Cao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
| | - Ding-Fu Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
| | - Kai Huang
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
| | - Gautam Gurung
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
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6
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Dc M, Shao DF, Hou VDH, Vailionis A, Quarterman P, Habiboglu A, Venuti MB, Xue F, Huang YL, Lee CM, Miura M, Kirby B, Bi C, Li X, Deng Y, Lin SJ, Tsai W, Eley S, Wang WG, Borchers JA, Tsymbal EY, Wang SX. Observation of anti-damping spin-orbit torques generated by in-plane and out-of-plane spin polarizations in MnPd 3. Nat Mater 2023; 22:591-598. [PMID: 37012436 DOI: 10.1038/s41563-023-01522-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 03/02/2023] [Indexed: 05/05/2023]
Abstract
Large spin-orbit torques (SOTs) generated by topological materials and heavy metals interfaced with ferromagnets are promising for next-generation magnetic memory and logic devices. SOTs generated from y spin originating from spin Hall and Edelstein effects can realize field-free magnetization switching only when the magnetization and spin are collinear. Here we circumvent the above limitation by utilizing unconventional spins generated in a MnPd3 thin film grown on an oxidized silicon substrate. We observe conventional SOT due to y spin, and out-of-plane and in-plane anti-damping-like torques originated from z spin and x spin, respectively, in MnPd3/CoFeB heterostructures. Notably, we have demonstrated complete field-free switching of perpendicular cobalt via out-of-plane anti-damping-like SOT. Density functional theory calculations show that the observed unconventional torques are due to the low symmetry of the (114)-oriented MnPd3 films. Altogether our results provide a path toward realization of a practical spin channel in ultrafast magnetic memory and logic devices.
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Affiliation(s)
- Mahendra Dc
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
| | - Ding-Fu Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | | | - Arturas Vailionis
- Stanford Nano Shared Facilities, Stanford University, Stanford, CA, USA
- Department of Physics, Kaunas University of Technology, Kaunas, Lithuania
| | - P Quarterman
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | - Ali Habiboglu
- Department of Physics, University of Arizona, Tucson, AZ, USA
| | - M B Venuti
- Department of Physics, Colorado School of Mines, Golden, CO, USA
| | - Fen Xue
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Yen-Lin Huang
- Taiwan Semiconductor Manufacturing Company, Hsinchu, Taiwan
- Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu, Taiwan
| | - Chien-Min Lee
- Taiwan Semiconductor Manufacturing Company, Hsinchu, Taiwan
| | - Masashi Miura
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
- Graduate School of Science and Technology, Seikei University, Tokyo, Japan
| | - Brian Kirby
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | - Chong Bi
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Xiang Li
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Yong Deng
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Shy-Jay Lin
- Taiwan Semiconductor Manufacturing Company, Hsinchu, Taiwan
| | - Wilman Tsai
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA
| | - Serena Eley
- Department of Physics, Colorado School of Mines, Golden, CO, USA
| | - Wei-Gang Wang
- Department of Physics, University of Arizona, Tucson, AZ, USA
| | - Julie A Borchers
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Shan X Wang
- Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
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7
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Shi S, Xi H, Cao T, Lin W, Liu Z, Niu J, Lan D, Zhou C, Cao J, Su H, Zhao T, Yang P, Zhu Y, Yan X, Tsymbal EY, Tian H, Chen J. Interface-engineered ferroelectricity of epitaxial Hf 0.5Zr 0.5O 2 thin films. Nat Commun 2023; 14:1780. [PMID: 36997572 PMCID: PMC10063548 DOI: 10.1038/s41467-023-37560-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2022] [Accepted: 03/22/2023] [Indexed: 04/01/2023] Open
Abstract
Ferroelectric hafnia-based thin films have attracted intense attention due to their compatibility with complementary metal-oxide-semiconductor technology. However, the ferroelectric orthorhombic phase is thermodynamically metastable. Various efforts have been made to stabilize the ferroelectric orthorhombic phase of hafnia-based films such as controlling the growth kinetics and mechanical confinement. Here, we demonstrate a key interface engineering strategy to stabilize and enhance the ferroelectric orthorhombic phase of the Hf0.5Zr0.5O2 thin film by deliberately controlling the termination of the bottom La0.67Sr0.33MnO3 layer. We find that the Hf0.5Zr0.5O2 films on the MnO2-terminated La0.67Sr0.33MnO3 have more ferroelectric orthorhombic phase than those on the LaSrO-terminated La0.67Sr0.33MnO3, while with no wake-up effect. Even though the Hf0.5Zr0.5O2 thickness is as thin as 1.5 nm, the clear ferroelectric orthorhombic (111) orientation is observed on the MnO2 termination. Our transmission electron microscopy characterization and theoretical modelling reveal that reconstruction at the Hf0.5Zr0.5O2/ La0.67Sr0.33MnO3 interface and hole doping of the Hf0.5Zr0.5O2 layer resulting from the MnO2 interface termination are responsible for the stabilization of the metastable ferroelectric phase of Hf0.5Zr0.5O2. We anticipate that these results will inspire further studies of interface-engineered hafnia-based systems.
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Affiliation(s)
- Shu Shi
- Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore
| | - Haolong Xi
- School of Materials and Energy, Electron Microscopy Centre of Lanzhou University and Key Laboratory of Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou, 730000, PR China
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Tengfei Cao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA
| | - Weinan Lin
- Department of physics, Xiamen University, Xiamen, 361005, China
| | - Zhongran Liu
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China
| | - Jiangzhen Niu
- Key Laboratory of Brain-Like Neuromorphic Devices and Systems of Hebei Province, Hebei University, Baoding, 071002, PR China
| | - Da Lan
- Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore
| | - Chenghang Zhou
- Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore
| | - Jing Cao
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 138634, Singapore, Singapore
| | - Hanxin Su
- Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore
| | - Tieyang Zhao
- Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore
| | - Ping Yang
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, 117603, Singapore, Singapore
| | - Yao Zhu
- Institute of Microelectronics, Agency for Science, Technology and Research (A*STAR), 138634, Singapore, Singapore
| | - Xiaobing Yan
- Key Laboratory of Brain-Like Neuromorphic Devices and Systems of Hebei Province, Hebei University, Baoding, 071002, PR China.
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA.
| | - He Tian
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China.
- School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, 450052, China.
| | - Jingsheng Chen
- Department of Materials Science and Engineering, National University of Singapore, 117575, Singapore, Singapore.
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8
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Sun H, Gu J, Li Y, Paudel TR, Liu D, Wang J, Zang Y, Gu C, Yang J, Sun W, Gu Z, Tsymbal EY, Liu J, Huang H, Wu D, Nie Y. Prominent Size Effects without a Depolarization Field Observed in Ultrathin Ferroelectric Oxide Membranes. Phys Rev Lett 2023; 130:126801. [PMID: 37027865 DOI: 10.1103/physrevlett.130.126801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 06/28/2022] [Accepted: 02/02/2023] [Indexed: 06/19/2023]
Abstract
The increasing miniaturization of electronics requires a better understanding of material properties at the nanoscale. Many studies have shown that there is a ferroelectric size limit in oxides, below which the ferroelectricity will be strongly suppressed due to the depolarization field, and whether such a limit still exists in the absence of the depolarization field remains unclear. Here, by applying uniaxial strain, we obtain pure in-plane polarized ferroelectricity in ultrathin SrTiO_{3} membranes, providing a clean system with high tunability to explore ferroelectric size effects especially the thickness-dependent ferroelectric instability with no depolarization field. Surprisingly, the domain size, ferroelectric transition temperature, and critical strain for room-temperature ferroelectricity all exhibit significant thickness dependence. These results indicate that the stability of ferroelectricity is suppressed (enhanced) by increasing the surface or bulk ratio (strain), which can be explained by considering the thickness-dependent dipole-dipole interactions within the transverse Ising model. Our study provides new insights into ferroelectric size effects and sheds light on the applications of ferroelectric thin films in nanoelectronics.
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Affiliation(s)
- Haoying Sun
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jiahui Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yongqiang Li
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- State Key Laboratory of Laser Interaction with Matter, Northwest Institute of Nuclear Technology, Xi'an, Shaanxi 710024, China
| | - Tula R Paudel
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68583, USA
- Department of Physics, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701, USA
| | - Di Liu
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing 100081, China
| | - Jierong Wang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yipeng Zang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- School of Materials Science and Engineering, Anhui University, Hefei 230601, China
| | - Chengyi Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Jiangfeng Yang
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Wenjie Sun
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Zhengbin Gu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68583, USA
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, USA
| | - Junming Liu
- National Laboratory of Solid State Microstructures and Department of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Houbing Huang
- Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, Beijing 100081, China
| | - Di Wu
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
| | - Yuefeng Nie
- National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
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9
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Liu Z, Wang H, Li M, Tao L, Paudel TR, Yu H, Wang Y, Hong S, Zhang M, Ren Z, Xie Y, Tsymbal EY, Chen J, Zhang Z, Tian H. In-plane charged domain walls with memristive behaviour in a ferroelectric film. Nature 2023; 613:656-661. [PMID: 36653455 DOI: 10.1038/s41586-022-05503-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 11/01/2022] [Indexed: 01/19/2023]
Abstract
Domain-wall nanoelectronics is considered to be a new paradigm for non-volatile memory and logic technologies in which domain walls, rather than domains, serve as an active element. Especially interesting are charged domain walls in ferroelectric structures, which have subnanometre thicknesses and exhibit non-trivial electronic and transport properties that are useful for various nanoelectronics applications1-3. The ability to deterministically create and manipulate charged domain walls is essential to realize their functional properties in electronic devices. Here we report a strategy for the controllable creation and manipulation of in-plane charged domain walls in BiFeO3 ferroelectric films a few nanometres thick. By using an in situ biasing technique within a scanning transmission electron microscope, an unconventional layer-by-layer switching mechanism is detected in which ferroelectric domain growth occurs in the direction parallel to an applied electric field. Based on atomically resolved electron energy-loss spectroscopy, in situ charge mapping by in-line electron holography and theoretical calculations, we show that oxygen vacancies accumulating at the charged domain walls are responsible for the domain-wall stability and motion. Voltage control of the in-plane domain-wall position within a BiFeO3 film gives rise to multiple non-volatile resistance states, thus demonstrating the key functional property of being a memristor a few unit cells thick. These results promote a better understanding of ferroelectric switching behaviour and provide a new strategy for creating unit-cell-scale devices.
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Affiliation(s)
- Zhongran Liu
- Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
| | - Han Wang
- Department of Materials Science and Engineering, National University of Singapore, Singapore City, Singapore.,Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang, China
| | - Ming Li
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, NE, USA
| | - Lingling Tao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, NE, USA
| | - Tula R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, NE, USA.,Department of Physics, South Dakota School of Mines and Technology, Rapid City, SD, USA
| | - Hongyang Yu
- Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
| | - Yuxuan Wang
- Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
| | - Siyuan Hong
- Department of Physics, Zhejiang University, Hangzhou, China
| | - Meng Zhang
- Department of Physics, Zhejiang University, Hangzhou, China
| | - Zhaohui Ren
- State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China
| | - Yanwu Xie
- Department of Physics, Zhejiang University, Hangzhou, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, NE, USA.
| | - Jingsheng Chen
- Department of Materials Science and Engineering, National University of Singapore, Singapore City, Singapore.
| | - Ze Zhang
- Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China. .,State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China.
| | - He Tian
- Center of Electron Microscopy, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China. .,State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, China. .,School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, China.
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10
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Ma Z, Zhang Q, Tao L, Wang Y, Sando D, Zhou J, Guo Y, Lord M, Zhou P, Ruan Y, Wang Z, Hamilton A, Gruverman A, Tsymbal EY, Zhang T, Valanoor N. A Room-Temperature Ferroelectric Resonant Tunneling Diode. Adv Mater 2022; 34:e2205359. [PMID: 35801685 DOI: 10.1002/adma.202205359] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Indexed: 06/15/2023]
Abstract
Resonant tunneling is a quantum-mechanical effect in which electron transport is controlled by the discrete energy levels within a quantum-well (QW) structure. A ferroelectric resonant tunneling diode (RTD) exploits the switchable electric polarization state of the QW barrier to tune the device resistance. Here, the discovery of robust room-temperature ferroelectric-modulated resonant tunneling and negative differential resistance (NDR) behaviors in all-perovskite-oxide BaTiO3 /SrRuO3 /BaTiO3 QW structures is reported. The resonant current amplitude and voltage are tunable by the switchable polarization of the BaTiO3 ferroelectric with the NDR ratio modulated by ≈3 orders of magnitude and an OFF/ON resistance ratio exceeding a factor of 2 × 104 . The observed NDR effect is explained an energy bandgap between Ru-t2g and Ru-eg orbitals driven by electron-electron correlations, as follows from density functional theory calculations. This study paves the way for ferroelectric-based quantum-tunneling devices in future oxide electronics.
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Affiliation(s)
- Zhijun Ma
- Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062, P. R. China
- School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, Australia
| | - Qi Zhang
- School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, Australia
- The Australian Research Council Centre for Excellence in Future Low Energy Electronics Technologies, UNSW, Sydney, 2052, Australia
| | - Lingling Tao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Yihao Wang
- Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062, P. R. China
| | - Daniel Sando
- School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, Australia
- The Australian Research Council Centre for Excellence in Future Low Energy Electronics Technologies, UNSW, Sydney, 2052, Australia
| | - Jinling Zhou
- School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, Australia
- The Australian Research Council Centre for Excellence in Future Low Energy Electronics Technologies, UNSW, Sydney, 2052, Australia
| | - Yizhong Guo
- Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, Beijing, 100124, P. R. China
| | - Michael Lord
- School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, Australia
- The Australian Research Council Centre for Excellence in Future Low Energy Electronics Technologies, UNSW, Sydney, 2052, Australia
| | - Peng Zhou
- Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062, P. R. China
| | - Yongqi Ruan
- Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062, P. R. China
| | - Zhiwei Wang
- Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062, P. R. China
| | - Alex Hamilton
- The Australian Research Council Centre for Excellence in Future Low Energy Electronics Technologies, UNSW, Sydney, 2052, Australia
- School of Physics, University of New South Wales, Sydney, 2052, Australia
| | - Alexei Gruverman
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Tianjin Zhang
- Ministry of Education Key Laboratory for the Synthesis and Application of Organic Functional Molecules, Ministry of Education Key Laboratory for the Green Preparation and Application of Functional Materials, Hubei University, Wuhan, 430062, P. R. China
| | - Nagarajan Valanoor
- School of Materials Science and Engineering, University of New South Wales, Sydney, 2052, Australia
- The Australian Research Council Centre for Excellence in Future Low Energy Electronics Technologies, UNSW, Sydney, 2052, Australia
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11
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Hu S, Shao DF, Yang H, Pan C, Fu Z, Tang M, Yang Y, Fan W, Zhou S, Tsymbal EY, Qiu X. Efficient perpendicular magnetization switching by a magnetic spin Hall effect in a noncollinear antiferromagnet. Nat Commun 2022; 13:4447. [PMID: 35915121 PMCID: PMC9343665 DOI: 10.1038/s41467-022-32179-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/19/2022] [Indexed: 11/28/2022] Open
Abstract
Current induced spin-orbit torques driven by the conventional spin Hall effect are widely used to manipulate the magnetization. This approach, however, is nondeterministic and inefficient for the switching of magnets with perpendicular magnetic anisotropy that are demanded by the high-density magnetic storage and memory devices. Here, we demonstrate that this limitation can be overcome by exploiting a magnetic spin Hall effect in noncollinear antiferromagnets, such as Mn3Sn. The magnetic group symmetry of Mn3Sn allows generation of the out-of-plane spin current carrying spin polarization collinear to its direction induced by an in-plane charge current. This spin current drives an out-of-plane anti-damping torque providing the deterministic switching of the perpendicular magnetization of an adjacent Ni/Co multilayer. Due to being odd with respect to time reversal symmetry, the observed magnetic spin Hall effect and the resulting spin-orbit torque can be reversed with reversal of the antiferromagnetic order. Contrary to the conventional spin-orbit torque devices, the demonstrated magnetization switching does not need an external magnetic field and requires much lower current density which is useful for low-power spintronics. Spin-orbit torques driven by the conventional spin Hall effect are widely used to switch magnetization, but this approach is nondeterministic and inefficient for magnets with perpendicular magnetic anisotropy. Here, the authors demonstrate deterministic, field-free switching in a Ni/Co multilayer by exploiting the magnetic spin Hall effect in adjacent Mn3Sn.
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Affiliation(s)
- Shuai Hu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Ding-Fu Shao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA.,Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
| | - Huanglin Yang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Chang Pan
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Zhenxiao Fu
- School of Information Science and Technology, ShanghaiTech University, Shanghai, 201210, China.,Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, ShanghaiTech University, Shanghai, 201210, China
| | - Meng Tang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Yumeng Yang
- School of Information Science and Technology, ShanghaiTech University, Shanghai, 201210, China. .,Shanghai Engineering Research Center of Energy Efficient and Custom AI IC, ShanghaiTech University, Shanghai, 201210, China.
| | - Weijia Fan
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Shiming Zhou
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA.
| | - Xuepeng Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China.
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12
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Yun Y, Buragohain P, Li M, Ahmadi Z, Zhang Y, Li X, Wang H, Li J, Lu P, Tao L, Wang H, Shield JE, Tsymbal EY, Gruverman A, Xu X. Intrinsic ferroelectricity in Y-doped HfO 2 thin films. Nat Mater 2022; 21:903-909. [PMID: 35761058 DOI: 10.1038/s41563-022-01282-6] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Accepted: 05/09/2022] [Indexed: 06/15/2023]
Abstract
Ferroelectric HfO2-based materials hold great potential for the widespread integration of ferroelectricity into modern electronics due to their compatibility with existing Si technology. Earlier work indicated that a nanometre grain size was crucial for the stabilization of the ferroelectric phase. This constraint, associated with a high density of structural defects, obscures an insight into the intrinsic ferroelectricity of HfO2-based materials. Here we demonstrate that stable and enhanced polarization can be achieved in epitaxial HfO2 films with a high degree of structural order (crystallinity). An out-of-plane polarization value of 50 μC cm-2 has been observed at room temperature in Y-doped HfO2(111) epitaxial thin films, with an estimated full value of intrinsic polarization of 64 μC cm-2, which is in close agreement with density functional theory calculations. The crystal structure of films reveals the Pca21 orthorhombic phase with small rhombohedral distortion, underlining the role of the structural constraint in stabilizing the ferroelectric phase. Our results suggest that it could be possible to exploit the intrinsic ferroelectricity of HfO2-based materials, optimizing their performance in device applications.
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Affiliation(s)
- Yu Yun
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Pratyush Buragohain
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Ming Li
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Zahra Ahmadi
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Yizhi Zhang
- School of Materials Engineering, Purdue University, West Lafayette, IN, USA
| | - Xin Li
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Haohan Wang
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Jing Li
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Ping Lu
- Sandia National Laboratories, Albuquerque, NM, USA
| | - Lingling Tao
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Haiyan Wang
- School of Materials Engineering, Purdue University, West Lafayette, IN, USA
| | - Jeffrey E Shield
- Department of Mechanical and Materials Engineering, University of Nebraska-Lincoln, Lincoln, NE, USA
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA.
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Alexei Gruverman
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA.
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
| | - Xiaoshan Xu
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, USA.
- Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, USA.
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13
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Dong J, Li X, Gurung G, Zhu M, Zhang P, Zheng F, Tsymbal EY, Zhang J. Tunneling Magnetoresistance in Noncollinear Antiferromagnetic Tunnel Junctions. Phys Rev Lett 2022; 128:197201. [PMID: 35622046 DOI: 10.1103/physrevlett.128.197201] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 02/18/2022] [Accepted: 04/21/2022] [Indexed: 06/15/2023]
Abstract
Antiferromagnetic (AFM) spintronics has emerged as a subfield of spintronics driven by the advantages of antiferromagnets producing no stray fields and exhibiting ultrafast magnetization dynamics. The efficient method to detect an AFM order parameter, known as the Néel vector, by electric means is critical to realize concepts of AFM spintronics. Here, we demonstrate that noncollinear AFM metals, such as Mn_{3}Sn, exhibit a momentum dependent spin polarization which can be exploited in AFM tunnel junctions to detect the Néel vector. Using first-principles calculations, we predict a tunneling magnetoresistance (TMR) effect as high as 300% in AFM tunnel junctions with Mn_{3}Sn electrodes, where the junction resistance depends on the relative orientation of their Néel vectors and exhibits four nonvolatile resistance states. We argue that the spin-split band structure and the related TMR effect can also be realized in other noncollinear AFM metals like Mn_{3}Ge, Mn_{3}Ga, Mn_{3}Pt, and Mn_{3}GaN. Our work provides a robust method for detecting the Néel vector in noncollinear antiferromagnets via the TMR effect, which may be useful for their application in AFM spintronic devices.
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Affiliation(s)
- Jianting Dong
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Xinlu Li
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Gautam Gurung
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Meng Zhu
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Peina Zhang
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Fanxing Zheng
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Jia Zhang
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
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14
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Abstract
Magnetic skyrmions are chiral nanoscale spin textures which are usually induced by the Dzyaloshinskii-Moriya interaction (DMI). Recently, magnetic skyrmions have been observed in two-dimensional (2D) van der Waals (vdW) ferromagnetic materials, such as Fe3GeTe2. The electric control of skyrmions is important for their potential application in low-power memory technologies. Here, we predict that DMI and magnetic skyrmions in a Fe3GeTe2 monolayer can be controlled by ferroelectric polarization of an adjacent 2D vdW ferroelectric In2Se3. Based on density functional theory and atomistic spin-dynamics modeling, we find that the interfacial symmetry breaking produces a sizable DMI in a Fe3GeTe2/In2Se3 vdW heterostructure. We show that the magnitude of DMI can be controlled by ferroelectric polarization reversal, leading to creation and annihilation of skyrmions. Furthermore, we find that the sign of DMI in a In2Se3/Fe3GeTe2/In2Se3 heterostructure changes with ferroelectric switching reversing the skyrmion chirality. The predicted electrically controlled skyrmion formation may be interesting for spintronic applications.
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Affiliation(s)
- Kai Huang
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
| | - Ding-Fu Shao
- Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei 230031, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, United States
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15
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Eom K, Paik H, Seo J, Campbell N, Tsymbal EY, Oh SH, Rzchowski MS, Schlom DG, Eom C. Oxide Two-Dimensional Electron Gas with High Mobility at Room-Temperature. Adv Sci (Weinh) 2022; 9:e2105652. [PMID: 35187807 PMCID: PMC9036036 DOI: 10.1002/advs.202105652] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Indexed: 06/14/2023]
Abstract
The prospect of 2-dimensional electron gases (2DEGs) possessing high mobility at room temperature in wide-bandgap perovskite stannates is enticing for oxide electronics, particularly to realize transparent and high-electron mobility transistors. Nonetheless only a small number of studies to date report 2DEGs in BaSnO3 -based heterostructures. Here, 2DEG formation at the LaScO3 /BaSnO3 (LSO/BSO) interface with a room-temperature mobility of 60 cm2 V-1 s-1 at a carrier concentration of 1.7 × 1013 cm-2 is reported. This is an order of magnitude higher mobility at room temperature than achieved in SrTiO3 -based 2DEGs. This is achieved by combining a thick BSO buffer layer with an ex situ high-temperature treatment, which not only reduces the dislocation density but also produces a SnO2 -terminated atomically flat surface, followed by the growth of an overlying BSO/LSO interface. Using weak beam dark-field transmission electron microscopy imaging and in-line electron holography technique, a reduction of the threading dislocation density is revealed, and direct evidence for the spatial confinement of a 2DEG at the BSO/LSO interface is provided. This work opens a new pathway to explore the exciting physics of stannate-based 2DEGs at application-relevant temperatures for oxide nanoelectronics.
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Affiliation(s)
- Kitae Eom
- Department of Materials Science and EngineeringUniversity of Wisconsin‐MadisonMadisonWI53706USA
| | - Hanjong Paik
- Department of Material Science and EngineeringCornell UniversityIthacaNY14853USA
- Platform for the Accelerated Realization, Analysis, and Discovery of Interface Materials (PARADIM)Cornell UniversityIthacaNY14853USA
| | - Jinsol Seo
- Department of Energy ScienceSungkyunkwan University (SKKU)Suwon16419Republic of Korea
| | - Neil Campbell
- Department of PhysicsUniversity of WisconsinMadisonWI53706USA
| | - Evgeny Y. Tsymbal
- Department of Physics and AstronomyUniversity of NebraskaLincolnNE68588USA
| | - Sang Ho Oh
- Department of Energy ScienceSungkyunkwan University (SKKU)Suwon16419Republic of Korea
| | | | - Darrell G. Schlom
- Department of Material Science and EngineeringCornell UniversityIthacaNY14853USA
- Kavli Institute at Cornell for Nanoscale ScienceIthacaNY14850USA
- Leibniz‐Institut für KristallzüchtungBerlin12489Germany
| | - Chang‐Beom Eom
- Department of Materials Science and EngineeringUniversity of Wisconsin‐MadisonMadisonWI53706USA
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16
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Abstract
Electric currents carrying a net spin polarization are widely used in spintronics, whereas globally spin-neutral currents are expected to play no role in spin-dependent phenomena. Here we show that, in contrast to this common expectation, spin-independent conductance in compensated antiferromagnets and normal metals can be efficiently exploited in spintronics, provided their magnetic space group symmetry supports a non-spin-degenerate Fermi surface. Due to their momentum-dependent spin polarization, such antiferromagnets can be used as active elements in antiferromagnetic tunnel junctions (AFMTJs) and produce a giant tunneling magnetoresistance (TMR) effect. Using RuO2 as a representative compensated antiferromagnet exhibiting spin-independent conductance along the [001] direction but a non-spin-degenerate Fermi surface, we design a RuO2/TiO2/RuO2 (001) AFMTJ, where a globally spin-neutral charge current is controlled by the relative orientation of the Néel vectors of the two RuO2 electrodes, resulting in the TMR effect as large as ~500%. These results are expanded to normal metals which can be used as a counter electrode in AFMTJs with a single antiferromagnetic layer or other elements in spintronic devices. Our work uncovers an unexplored potential of the materials with no global spin polarization for utilizing them in spintronics.
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Affiliation(s)
- Ding-Fu Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588-0299, USA.
| | - Shu-Hui Zhang
- grid.48166.3d0000 0000 9931 8406College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing, 100029 People’s Republic of China
| | - Ming Li
- grid.24434.350000 0004 1937 0060Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299 USA
| | - Chang-Beom Eom
- grid.14003.360000 0001 2167 3675Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 3706 US
| | - Evgeny Y. Tsymbal
- grid.24434.350000 0004 1937 0060Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299 USA
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17
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Dmitriyeva A, Mikheev V, Zarubin S, Chouprik A, Vinai G, Polewczyk V, Torelli P, Matveyev Y, Schlueter C, Karateev I, Yang Q, Chen Z, Tao L, Tsymbal EY, Zenkevich A. Magnetoelectric Coupling at the Ni/Hf 0.5Zr 0.5O 2 Interface. ACS Nano 2021; 15:14891-14902. [PMID: 34468129 DOI: 10.1021/acsnano.1c05001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Composite multiferroics containing ferroelectric and ferromagnetic components often have much larger magnetoelectric coupling compared to their single-phase counterparts. Doped or alloyed HfO2-based ferroelectrics may serve as a promising component in composite multiferroic structures potentially feasible for technological applications. Recently, a strong charge-mediated magnetoelectric coupling at the Ni/HfO2 interface has been predicted using density functional theory calculations. Here, we report on the experimental evidence of such magnetoelectric coupling at the Ni/Hf0.5Zr0.5O2(HZO) interface. Using a combination of operando XAS/XMCD and HAXPES/MCDAD techniques, we probe element-selectively the local magnetic properties at the Ni/HZO interface in functional Au/Co/Ni/HZO/W capacitors and demonstrate clear evidence of the ferroelectric polarization effect on the magnetic response of a nanometer-thick Ni marker layer. The observed magnetoelectric effect and the electronic band lineup of the Ni/HZO interface are interpreted based on the results of our theoretical modeling. It elucidates the critical role of an ultrathin NiO interlayer, which controls the sign of the magnetoelectric effect as well as provides a realistic band offset at the Ni/HZO interface, in agreement with the experiment. Our results hold promise for the use of ferroelectric HfO2-based composite multiferroics for the design of multifunctional devices compatible with modern semiconductor technology.
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Affiliation(s)
- Anna Dmitriyeva
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow Region, 141700, Russia
| | - Vitalii Mikheev
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow Region, 141700, Russia
| | - Sergei Zarubin
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow Region, 141700, Russia
| | - Anastasia Chouprik
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow Region, 141700, Russia
| | - Giovanni Vinai
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. 14 km 163.5, Trieste I-34149, Italy
| | - Vincent Polewczyk
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. 14 km 163.5, Trieste I-34149, Italy
| | - Piero Torelli
- Istituto Officina dei Materiali (IOM)-CNR, Laboratorio TASC, Area Science Park, S.S. 14 km 163.5, Trieste I-34149, Italy
| | - Yury Matveyev
- Deutsches Elektronen-Synchrotron, 85 Notkestraße, Hamburg, D-22607, Germany
| | | | - Igor Karateev
- National Research Center "Kurchatov Institute", Moscow, 123182, Russia
| | - Qiong Yang
- School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Zhaojin Chen
- School of Materials Science and Engineering, Xiangtan University, Xiangtan, Hunan 411105, China
| | - Lingling Tao
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
| | - Andrei Zenkevich
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow Region, 141700, Russia
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18
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Li D, Sun S, Xiao Z, Song J, Shao DF, Tsymbal EY, Ducharme S, Hong X. Giant Transport Anisotropy in ReS_{2} Revealed via Nanoscale Conducting-Path Control. Phys Rev Lett 2021; 127:136803. [PMID: 34623838 DOI: 10.1103/physrevlett.127.136803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 05/28/2021] [Accepted: 07/19/2021] [Indexed: 06/13/2023]
Abstract
The low in-plane symmetry in layered 1T'-ReS_{2} results in strong band anisotropy, while its manifestation in the electronic properties is challenging to resolve due to the lack of effective approaches for controlling the local current path. In this work, we reveal the giant transport anisotropy in monolayer to four-layer ReS_{2} by creating directional conducting paths via nanoscale ferroelectric control. By reversing the polarization of a ferroelectric polymer top layer, we induce a conductivity switching ratio of >1.5×10^{8} in the ReS_{2} channel at 300 K. Characterizing the domain-defined conducting nanowires in an insulating background shows that the conductivity ratio between the directions along and perpendicular to the Re chain can exceed 5.5×10^{4} in monolayer ReS_{2}. Theoretical modeling points to the band origin of the transport anomaly and further reveals the emergence of a flat band in few-layer ReS_{2}. Our work paves the path for implementing highly anisotropic 2D materials for designing novel collective phenomena and electron lensing applications.
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Affiliation(s)
- Dawei Li
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Shuo Sun
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Zhiyong Xiao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Jingfeng Song
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Ding-Fu Shao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Stephen Ducharme
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
| | - Xia Hong
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0299, USA
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19
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Abstract
The discovery of ferroelectricity in polycrystalline thin films of doped HfO2 has reignited the expectations of developing competitive ferroelectric non-volatile memory devices. To date, it is widely accepted that the performance of HfO2-based ferroelectric devices during their life cycle is critically dependent on the presence of point defects as well as structural phase polymorphism, which mainly originates from defects either. The purpose of this review article is to overview the impact of defects in ferroelectric HfO2 on its functional properties and the resulting performance of memory devices. Starting from the brief summary of defects in classical perovskite ferroelectrics, we then introduce the known types of point defects in dielectric HfO2 thin films. Further, we discuss main analytical techniques used to characterize the concentration and distribution of defects in doped ferroelectric HfO2 thin films as well as at their interfaces with electrodes. The main part of the review is devoted to the recent experimental studies reporting the impact of defects in ferroelectric HfO2 structures on the performance of different memory devices. We end up with the summary and perspectives of HfO2-based ferroelectric competitive non-volatile memory devices.
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Affiliation(s)
- Anastasia Chouprik
- Moscow Institute of Physics and Technology, Dolgoprudny, Moscow region, Russia.
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20
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Zhou J, Shu X, Lin W, Shao DF, Chen S, Liu L, Yang P, Tsymbal EY, Chen J. Modulation of Spin-Orbit Torque from SrRuO 3 by Epitaxial-Strain-Induced Octahedral Rotation. Adv Mater 2021; 33:e2007114. [PMID: 34145647 DOI: 10.1002/adma.202007114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 03/30/2021] [Indexed: 06/12/2023]
Abstract
Spin-orbit torque (SOT), which arises from the spin-orbit coupling of conduction electrons, is believed to be the key route for developing low-power, high-speed, and nonvolatile memory devices. Despite the theoretical prediction of pronounced Berry phase curvatures in certain transition-metal perovskite oxides, which lead to considerable intrinsic spin Hall conductivity, SOT from this class of materials has rarely been reported until recently. Here, the SOT generated by epitaxial SrRuO3 of three different crystal structures is systematically studied. The results of both spin-torque ferromagnetic resonance and in-plane harmonic Hall voltage measurements concurrently reveal that the intrinsic SOT efficiency of SrRuO3 decreases when the epitaxial strain changes from tensile to compressive. The X-ray diffraction data demonstrate a strong correlation between the magnitude of SOT and octahedral rotation around the in-plane axes of SrRuO3 , consistent with the theoretical prediction. This work offers new possibilities of tuning SOT with crystal structures and novel opportunities of integrating the unique properties of perovskite oxides with spintronic functionalities.
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Affiliation(s)
- Jing Zhou
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Xinyu Shu
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Weinan Lin
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Ding Fu Shao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Shaohai Chen
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Liang Liu
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
| | - Ping Yang
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
- Singapore Synchrotron Light Source (SSLS), National University of Singapore, 5 Research Link, Singapore, 117603, Singapore
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Jingsheng Chen
- Materials Science and Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore, 117575, Singapore
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21
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Abstract
A synthetic ferroelectric is made from a van der Waals assembly of boron nitride
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Affiliation(s)
- Evgeny Y. Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
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22
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Guo R, Tao L, Li M, Liu Z, Lin W, Zhou G, Chen X, Liu L, Yan X, Tian H, Tsymbal EY, Chen J. Interface-engineered electron and hole tunneling. Sci Adv 2021; 7:7/13/eabf1033. [PMID: 33762343 PMCID: PMC7990336 DOI: 10.1126/sciadv.abf1033] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
Although the phenomenon of tunneling has been known since the advent of quantum mechanics, it continues to enrich our understanding of many fields of science. Commonly, this effect is described in terms of electrons traversing the potential barrier that exceeds their kinetic energy due to the wave nature of electrons. This picture of electron tunneling fails, however, for tunnel junctions, where the Fermi energy lies sufficiently close to the insulator valence band, in which case, hole tunneling dominates. We demonstrate the deterministic control of electron and hole tunneling in interface-engineered Pt/BaTiO3/La0.7Sr0.3MnO3 ferroelectric tunnel junctions by reversal of tunneling electroresistance. Our electrical measurements, electron microscopy and spectroscopy characterization, and theoretical modeling unambiguously point out to electron or hole tunneling regimes depending on interface termination. The interface control of the tunneling regime offers designed functionalities of electronic devices.
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Affiliation(s)
- Rui Guo
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore, Singapore
- College of Electron and Information Engineering, Hebei University, Baoding 071002, China
| | - Lingling Tao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299, USA
| | - Ming Li
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299, USA
| | - Zhongran Liu
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Weinan Lin
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore, Singapore
| | - Guowei Zhou
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore, Singapore
- Key Laboratory of Magnetic Molecules and Magnetic Information Materials of Ministry of Education, School of Chemistry and Materials Science, Shanxi Normal University, Linfen 041004, China
| | - Xiaoxin Chen
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Liang Liu
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore, Singapore
| | - Xiaobing Yan
- College of Electron and Information Engineering, Hebei University, Baoding 071002, China
| | - He Tian
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou 310027, China.
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299, USA.
| | - Jingsheng Chen
- Department of Materials Science and Engineering, National University of Singapore, 117575 Singapore, Singapore.
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23
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Ding J, Shao DF, Li M, Wen LW, Tsymbal EY. Two-Dimensional Antiferroelectric Tunnel Junction. Phys Rev Lett 2021; 126:057601. [PMID: 33605764 DOI: 10.1103/physrevlett.126.057601] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2020] [Revised: 05/17/2020] [Accepted: 01/08/2021] [Indexed: 06/12/2023]
Abstract
Ferroelectric tunnel junctions (FTJs), which consist of two metal electrodes separated by a thin ferroelectric barrier, have recently aroused significant interest for technological applications as nanoscale resistive switching devices. So far, most existing FTJs have been based on perovskite-oxide barrier layers. The recent discovery of the two-dimensional (2D) van der Waals ferroelectric materials opens a new route to realize tunnel junctions with new functionalities and nm-scale dimensions. Because of the weak coupling between the atomic layers in these materials, the relative dipole alignment between them can be controlled by applied voltage. This allows transitions between ferroelectric and antiferroelectric orderings, resulting in significant changes of the electronic structure. Here, we propose to realize 2D antiferroelectric tunnel junctions (AFTJs), which exploit this new functionality, based on bilayer In_{2}X_{3} (X=S, Se, Te) barriers and different 2D electrodes. Using first-principles density functional theory calculations, we demonstrate that the In_{2}X_{3} bilayers exhibit stable ferroelectric and antiferroelectric states separated by sizable energy barriers, thus supporting a nonvolatile switching between these states. Using quantum-mechanical modeling of the electronic transport, we explore in-plane and out-of-plane tunneling across the In_{2}S_{3} van der Waals bilayers, and predict giant tunneling electroresistance effects and multiple nonvolatile resistance states driven by ferroelectric-antiferroelectric order transitions. Our proposal opens a new route to realize nanoscale memory devices with ultrahigh storage density using 2D AFTJs.
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Affiliation(s)
- Jun Ding
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
- College of Science, Henan University of Engineering, Zhengzhou 451191, People's Republic of China
| | - Ding-Fu Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
| | - Ming Li
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
| | - Li-Wei Wen
- College of Science, Henan University of Engineering, Zhengzhou 451191, People's Republic of China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
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24
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Abstract
Multiferroic tunnel junctions (MFTJs) have aroused significant interest due to their functional properties useful for nonvolatile memory devices. So far, however, all of the existing MFTJs have been based on perovskite-oxide heterostructures limited by a relatively high resistance-area (RA) product unfavorable for practical applications. Here, using first-principles calculations, we explore spin-dependent transport properties of van der Waals (vdW) MFTJs which consist of two-dimensional (2D) ferromagnetic FenGeTe2 (n = 3, 4, 5) electrodes and 2D ferroelectric In2Se3 barrier layers. We demonstrate that such FemGeTe2/In2Se3/FenGeTe2 (m, n = 3, 4, 5; m ≠ n) MFTJs exhibit multiple nonvolatile resistance states associated with different polarization orientation of the ferroelectric In2Se3 layer and magnetization alignment of the two ferromagnetic FenGeTe2 layers. We find a remarkably low RA product (less than 1 Ω·μm2) which makes the proposed vdW MFTJs superior to the conventional MFTJs in terms of their promise for nonvolatile memory applications.
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Affiliation(s)
- Yurong Su
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Xinlu Li
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Meng Zhu
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Jia Zhang
- School of Physics and Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Long You
- School of Optical and Electronic Information, Huazhong University of Science and Technology, 430074 Wuhan, China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, United States
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25
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Nan T, Quintela CX, Irwin J, Gurung G, Shao DF, Gibbons J, Campbell N, Song K, Choi SY, Guo L, Johnson RD, Manuel P, Chopdekar RV, Hallsteinsen I, Tybell T, Ryan PJ, Kim JW, Choi Y, Radaelli PG, Ralph DC, Tsymbal EY, Rzchowski MS, Eom CB. Controlling spin current polarization through non-collinear antiferromagnetism. Nat Commun 2020; 11:4671. [PMID: 32938910 PMCID: PMC7494910 DOI: 10.1038/s41467-020-17999-4] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 07/22/2020] [Indexed: 11/09/2022] Open
Abstract
The interconversion of charge and spin currents via spin-Hall effect is essential for spintronics. Energy-efficient and deterministic switching of magnetization can be achieved when spin polarizations of these spin currents are collinear with the magnetization. However, symmetry conditions generally restrict spin polarizations to be orthogonal to both the charge and spin flows. Spin polarizations can deviate from such direction in nonmagnetic materials only when the crystalline symmetry is reduced. Here, we show control of the spin polarization direction by using a non-collinear antiferromagnet Mn3GaN, in which the triangular spin structure creates a low magnetic symmetry while maintaining a high crystalline symmetry. We demonstrate that epitaxial Mn3GaN/permalloy heterostructures can generate unconventional spin-orbit torques at room temperature corresponding to out-of-plane and Dresselhaus-like spin polarizations which are forbidden in any sample with two-fold rotational symmetry. Our results demonstrate an approach based on spin-structure design for controlling spin-orbit torque, enabling high-efficient antiferromagnetic spintronics. In the typical spin-hall effect, spin-current, charge current, and spin polarisation are all mutually perpendicular, a feature enforced by symmetry. Here, using an anti-ferromagnet with a triangular spin structure, the authors demonstrate a spin-hall effect without a perpendicular spin alignment.
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Affiliation(s)
- T Nan
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - C X Quintela
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - J Irwin
- Department of Physics, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - G Gurung
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - D F Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - J Gibbons
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, 14853, USA
| | - N Campbell
- Department of Physics, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - K Song
- Department of Materials Modeling and Characterization, KIMS, Changwon, 51508, South Korea
| | - S -Y Choi
- Department of Materials Science and Engineering, POSTECH, Pohang, 37673, South Korea
| | - L Guo
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - R D Johnson
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, UK.,ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK.,Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
| | - P Manuel
- Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
| | - R V Chopdekar
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA, 94720, USA
| | - I Hallsteinsen
- Advanced Light Source, Lawrence Berkeley National Laboratory (LBNL), 1 Cyclotron Road, Berkeley, CA, 94720, USA.,Department of Electronic Systems, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - T Tybell
- Department of Electronic Systems, Norwegian University of Science and Technology, Trondheim, 7491, Norway
| | - P J Ryan
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA.,School of Physical Sciences, Dublin City University, Dublin, 11, Ireland
| | - J -W Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - Y Choi
- Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA
| | - P G Radaelli
- Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU, UK
| | - D C Ralph
- Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY, 14853, USA.,Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, 14853, USA
| | - E Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - M S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, 53706, USA
| | - C B Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, 53706, USA.
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26
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Quintela CX, Song K, Shao DF, Xie L, Nan T, Paudel TR, Campbell N, Pan X, Tybell T, Rzchowski MS, Tsymbal EY, Choi SY, Eom CB. Epitaxial antiperovskite/perovskite heterostructures for materials design. Sci Adv 2020; 6:eaba4017. [PMID: 32832665 PMCID: PMC7439405 DOI: 10.1126/sciadv.aba4017] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/30/2019] [Accepted: 06/10/2020] [Indexed: 06/11/2023]
Abstract
Engineered heterostructures formed by complex oxide materials are a rich source of emergent phenomena and technological applications. In the quest for new functionality, a vastly unexplored avenue is interfacing oxide perovskites with materials having dissimilar crystallochemical properties. Here, we propose a unique class of heterointerfaces based on nitride antiperovskite and oxide perovskite materials as a previously unidentified direction for materials design. We demonstrate the fabrication of atomically sharp interfaces between nitride antiperovskite Mn3GaN and oxide perovskites (La0.3Sr0.7)(Al0.65Ta0.35)O3 and SrTiO3. Using atomic-resolution imaging/spectroscopic techniques and first-principles calculations, we determine the atomic-scale structure, composition, and bonding at the interface. The epitaxial antiperovskite/perovskite heterointerface is mediated by a coherent interfacial monolayer that interpolates between the two antistructures. We anticipate our results to be an important step for the development of functional antiperovskite/perovskite heterostructures, combining their unique characteristics such as topological properties for ultralow-power applications.
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Affiliation(s)
- Camilo X. Quintela
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Kyung Song
- Department of Materials Modeling and Characterization, KIMS, Changwon 51508, South Korea
| | - Ding-Fu Shao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
| | - Lin Xie
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing, Jiangsu 210093, People’s Republic of China
| | - Tianxiang Nan
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Tula R. Paudel
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
| | - Neil Campbell
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Xiaoqing Pan
- Department of Materials Science and Engineering and Department of Physics and Astronomy, University of California-Irvine, Irvine, CA 92697, USA
| | - Thomas Tybell
- Department of Electronic Systems, Norwegian University of Science and Technology, Trondheim 7491, Norway
| | - Mark S. Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Evgeny Y. Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588, USA
| | - Si-Young Choi
- Department of Materials Science and Engineering, POSTECH, Pohang 37673, South Korea
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
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27
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Paudel TR, Tsymbal EY. Evaluating the Thermoelectric Properties of BaTiS 3 by Density Functional Theory. ACS Omega 2020; 5:12385-12390. [PMID: 32548422 PMCID: PMC7271404 DOI: 10.1021/acsomega.0c01139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Accepted: 05/14/2020] [Indexed: 06/11/2023]
Abstract
BaTiS3 is a semiconductor with a small bandgap of ∼0.5 eV and strong transport anisotropy caused primarily by structural anisotropy; it contains well-separated octahedral columns along the [0001] direction and low lattice thermal conductivity, appealing for thermoelectric applications. Here, we evaluate the prospect of BaTiS3 as a thermoelectric material by using the linearized electron and phonon Boltzmann transport theory based on the first-principles density functional band structure calculations. We find sizable values of the key thermoelectric parameters, such as the maximum power factor PF = 928 μW K-2 and the maximum figure of merit ZT = 0.48 for an electron-doped sample and PF = 74 μW K-2 and ZT = 0.17 for a hole-doped sample at room temperature, and a small doping level of ±0.25e per unit cell. The increase in temperature yields an increase in both the power factor and the figure of merit, reaching large values of PF = 3078 μW K-2 and ZT = 0.77 for the electron-doped sample and PF = 650 μW K-2 and ZT = 0.62 for the hole-doped sample at 800 K. Our results elucidate the promise of BaTiS3 as a material for the thermoelectric power generator.
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28
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Li D, Huang X, Xiao Z, Chen H, Zhang L, Hao Y, Song J, Shao DF, Tsymbal EY, Lu Y, Hong X. Polar coupling enabled nonlinear optical filtering at MoS 2/ferroelectric heterointerfaces. Nat Commun 2020; 11:1422. [PMID: 32184400 PMCID: PMC7078226 DOI: 10.1038/s41467-020-15191-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 02/14/2020] [Indexed: 11/09/2022] Open
Abstract
Complex oxide heterointerfaces and van der Waals heterostructures present two versatile but intrinsically different platforms for exploring emergent quantum phenomena and designing new functionalities. The rich opportunity offered by the synergy between these two classes of materials, however, is yet to be charted. Here, we report an unconventional nonlinear optical filtering effect resulting from the interfacial polar alignment between monolayer MoS2 and a neighboring ferroelectric oxide thin film. The second harmonic generation response at the heterointerface is either substantially enhanced or almost entirely quenched by an underlying ferroelectric domain wall depending on its chirality, and can be further tailored by the polar domains. Unlike the extensively studied coupling mechanisms driven by charge, spin, and lattice, the interfacial tailoring effect is solely mediated by the polar symmetry, as well explained via our density functional theory calculations, pointing to a new material strategy for the functional design of nanoscale reconfigurable optical applications.
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Affiliation(s)
- Dawei Li
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Xi Huang
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588-0511, USA
| | - Zhiyong Xiao
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Hanying Chen
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Le Zhang
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Yifei Hao
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Jingfeng Song
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Ding-Fu Shao
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA.,Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, 68588-0298, USA
| | - Yongfeng Lu
- Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, NE, 68588-0511, USA. .,Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, 68588-0298, USA.
| | - Xia Hong
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE, 68588-0299, USA. .,Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE, 68588-0298, USA.
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29
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Shao DF, Zhang SH, Gurung G, Yang W, Tsymbal EY. Nonlinear Anomalous Hall Effect for Néel Vector Detection. Phys Rev Lett 2020; 124:067203. [PMID: 32109084 DOI: 10.1103/physrevlett.124.067203] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 01/23/2020] [Indexed: 06/10/2023]
Abstract
Antiferromagnetic (AFM) spintronics exploits the Néel vector as a state variable for novel spintronic devices. Recent studies have shown that the fieldlike and antidamping spin-orbit torques (SOTs) can be used to switch the Néel vector in antiferromagnets with proper symmetries. However, the precise detection of the Néel vector remains a challenging problem. In this Letter, we predict that the nonlinear anomalous Hall effect (AHE) can be used to detect the Néel vector in most compensated antiferromagnets supporting the antidamping SOT. We show that the magnetic crystal group symmetry of these antiferromagnets combined with spin-orbit coupling produce a sizable Berry curvature dipole and hence the nonlinear AHE. As a specific example, we consider the half-Heusler alloy CuMnSb, in which the Néel vector can be switched by the antidamping SOT. Based on density-functional theory calculations, we show that the nonlinear AHE in CuMnSb results in a measurable Hall voltage under conventional experimental conditions. The strong dependence of the Berry curvature dipole on the Néel vector orientation provides a new detection scheme of the Néel vector based on the nonlinear AHE. Our predictions enrich the material platform for studying nontrivial phenomena associated with the Berry curvature and broaden the range of materials useful for AFM spintronics.
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Affiliation(s)
- Ding-Fu Shao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
| | - Shu-Hui Zhang
- College of Mathematics and Physics, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Gautam Gurung
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
| | - Wen Yang
- Beijing Computational Science Research Center, Beijing 100193, People's Republic of China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
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30
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Abstract
Ferroelectric tunnel junctions (FTJs) utilizing an in-plane head-to-head ferroelectric domain wall (DW) have recently been realized, showing interesting physics and new functionalities. However, the DW state in these junctions was found to be metastable and not reversible after applying an electric field. In this work, we demonstrate that a stable and reversible head-to-head DW state can be achieved in FTJs by proper engineering of polar interfaces. Using density functional theory (DFT) calculations and phenomenological modeling, we explore the DW stability by varying stoichiometry of the La_{1-x}Sr_{x}O/TiO_{2} interfaces in FTJs with La_{0.5}Sr_{0.5}MnO_{3} electrodes and a ferroelectric BaTiO_{3} tunnel barrier. For, x≤0.4 we find that the DW state becomes a global minimum and the calculated hysteresis loops exhibit three reversible polarization states. For such FTJs, our quantum transport calculations predict the emergence of a DW tunneling electroresistance effect-reversible switching of the tunneling conductance between the highly conductive DW state and two much less conductive uniform polarization states.
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Affiliation(s)
- M Li
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - L L Tao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
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31
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Matveyev Y, Mikheev V, Negrov D, Zarubin S, Kumar A, Grimley ED, LeBeau JM, Gloskovskii A, Tsymbal EY, Zenkevich A. Polarization-dependent electric potential distribution across nanoscale ferroelectric Hf 0.5Zr 0.5O 2 in functional memory capacitors. Nanoscale 2019; 11:19814-19822. [PMID: 31624822 DOI: 10.1039/c9nr05904k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The emergence of ferroelectricity in nanometer-thick films of doped hafnium oxide (HfO2) makes this material a promising candidate for use in Si-compatible non-volatile memory devices. The switchable polarization of ferroelectric HfO2 controls functional properties of these devices through the electric potential distribution across the capacitor. The experimental characterization of the local electric potential at the nanoscale has not so far been realized in practice. Here, we develop a new methodology which allows us, for the first time, to experimentally quantify the polarization-dependent potential profile across few-nanometer-thick ferroelectric Hf0.5Zr0.5O2 thin films. Using a standing-wave excitation mode in synchrotron based hard X-ray photoemission spectroscopy, we depth-selectively probe TiN/Hf0.5Zr0.5O2/W prototype memory capacitors and determine the local electrostatic potential by analyzing the core-level line shifts. We find that the electric potential profile across the Hf0.5Zr0.5O2 layer is non-linear and changes with in situ polarization switching. Combined with our scanning transmission electron microscopy data and theoretical modeling, we interpret the observed non-linear potential behavior in terms of defects in Hf0.5Zr0.5O2, at both interfaces, and their charge state modulated by the ferroelectric polarization. Our results provide an important insight into the intrinsic electronic properties of HfO2 based ferroelectric capacitors and are essential for engineering memory devices.
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Affiliation(s)
- Yury Matveyev
- Deutsches Elektronen-Synchrotron, 85 Notkestraße, Hamburg, D-22607, Germany and Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Vitalii Mikheev
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Dmitry Negrov
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Sergei Zarubin
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Abinash Kumar
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
| | - Everett D Grimley
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
| | - James M LeBeau
- Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA
| | - Andrei Gloskovskii
- Deutsches Elektronen-Synchrotron, 85 Notkestraße, Hamburg, D-22607, Germany
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska-Lincoln, Lincoln, NE 68588, USA and Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
| | - Andrei Zenkevich
- Moscow Institute of Physics and Technology, 9, Institutskiy lane, Dolgoprudny, Moscow region, 141700, Russia.
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32
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Yang Q, Tao L, Zhang Y, Li M, Jiang Z, Tsymbal EY, Alexandrov V. Ferroelectric Tunnel Junctions Enhanced by a Polar Oxide Barrier Layer. Nano Lett 2019; 19:7385-7393. [PMID: 31514498 DOI: 10.1021/acs.nanolett.9b03056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Ferroelectric tunnel junctions (FTJs) have recently aroused significant interest due to the interesting physics controlling their properties and potential application in nonvolatile memory devices. In this work, we propose a new concept to design high-performance FTJs based on ferroelectric/polar-oxide composite barriers. Using density functional theory calculations, we model electronic and transport properties of LaNiO3/PbTiO3/LaAlO3/LaNiO3 tunnel junctions and demonstrate that an ultrathin polar LaAlO3(001) layer strongly enhances their performance. We predict a tunneling electroresistance (TER) effect in these FTJs with an OFF/ON resistance ratio exceeding a factor of 104 and ON state resistance as low as about 1 kΩμm2. Such an enhanced performance is driven by the ionic charge at the PbTiO3/LaAlO3 interface, which significantly increases transmission across the FTJ when the ferroelectric polarization of PbTiO3 is pointing against the intrinsic electric field produced by this ionic charge. This is due to the formation of a two-dimensional (2D) electron or hole gas, depending on the LaAlO3 termination being (LaO)+ or (AlO2)-, respectively, which is formed to screen the polarization charge of the nonuniform polarization state. This 2D electron (hole) gas can be switched ON and OFF by the reversal of ferroelectric polarization, resulting in the giant TER effect. The proposed design suggests a new direction for creating FTJs with a stable and reversible ferroelectric polarization, a sizable TER effect, and a low-resistance-area product, as required for memory applications.
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Affiliation(s)
- Qiong Yang
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
- School of Materials Science and Engineering , Xiangtan University , Xiangtan , Hunan 411105 , China
| | - Lingling Tao
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Yuke Zhang
- School of Materials Science and Engineering , Xiangtan University , Xiangtan , Hunan 411105 , China
| | - Ming Li
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Zhen Jiang
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Vitaly Alexandrov
- Department of Chemical and Biomolecular Engineering , University of Nebraska , Lincoln , Nebraska 68588 , United States
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33
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Li X, Lü JT, Zhang J, You L, Su Y, Tsymbal EY. Spin-Dependent Transport in van der Waals Magnetic Tunnel Junctions with Fe 3GeTe 2 Electrodes. Nano Lett 2019; 19:5133-5139. [PMID: 31276417 DOI: 10.1021/acs.nanolett.9b01506] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
van der Waals (vdW) heterostructures, stacking different two-dimensional materials, have opened up unprecedented opportunities to explore new physics and device concepts. Especially interesting are recently discovered two-dimensional magnetic vdW materials, providing new paradigms for spintronic applications. Here, using density functional theory (DFT) calculations, we investigate the spin-dependent electronic transport across vdW magnetic tunnel junctions (MTJs) composed of Fe3GeTe2 ferromagnetic electrodes and a graphene or hexagonal boron nitride (h-BN) spacer layer. For both types of junctions, we find that the junction resistance changes by thousands of percent when the magnetization of the electrodes is switched from parallel to antiparallel. Such a giant tunneling magnetoresistance (TMR) effect is driven by dissimilar electronic structure of the two spin-conducting channels in Fe3GeTe2, resulting in a mismatch between the incoming and outgoing Bloch states in the electrodes and thus suppressed transmission for an antiparallel-aligned MTJ. The vdW bonding between electrodes and a spacer layer makes this result virtually independent of the type of the spacer layer, making the predicted giant TMR effect robust with respect to strain, interface distance, and other parameters, which may vary in the experiment. We hope that our results will further stimulate experimental studies of vdW MTJs and pave the way for their applications in spintronics.
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Affiliation(s)
- Xinlu Li
- School of Physics and Wuhan National High Magnetic Field Center , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Jing-Tao Lü
- School of Physics and Wuhan National High Magnetic Field Center , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Jia Zhang
- School of Physics and Wuhan National High Magnetic Field Center , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Long You
- School of Optical and Electronic Information , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Yurong Su
- School of Optical and Electronic Information , Huazhong University of Science and Technology , Wuhan 430074 , China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience , University of Nebraska , Lincoln , Nebraska 68588 , United States
- Moscow Institute of Physics and Technology , Dolgoprudny , Moscow Region 141700 , Russia
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34
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Sharma P, Xiang FX, Shao DF, Zhang D, Tsymbal EY, Hamilton AR, Seidel J. A room-temperature ferroelectric semimetal. Sci Adv 2019; 5:eaax5080. [PMID: 31281902 PMCID: PMC6611688 DOI: 10.1126/sciadv.aax5080] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Accepted: 05/24/2019] [Indexed: 05/13/2023]
Abstract
Coexistence of reversible polar distortions and metallicity leading to a ferroelectric metal, first suggested by Anderson and Blount in 1965, has so far remained elusive. Electrically switchable intrinsic electric polarization, together with the direct observation of ferroelectric domains, has not yet been realized in a bulk crystalline metal, although incomplete screening by mobile conduction charges should, in principle, be possible. Here, we provide evidence that native metallicity and ferroelectricity coexist in bulk crystalline van der Waals WTe2 by means of electrical transport, nanoscale piezoresponse measurements, and first-principles calculations. We show that, despite being a Weyl semimetal, WTe2 has switchable spontaneous polarization and a natural ferroelectric domain structure at room temperature. This new class of materials has tantalizing potential for functional nanoelectronics applications.
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Affiliation(s)
- Pankaj Sharma
- School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, NSW 2052, Australia
- Corresponding author. (P.S.); (F.-X.X.); (E.Y.T.); (A.R.H.); (J.S.)
| | - Fei-Xiang Xiang
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, NSW 2052, Australia
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
- Corresponding author. (P.S.); (F.-X.X.); (E.Y.T.); (A.R.H.); (J.S.)
| | - Ding-Fu Shao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299, USA
| | - Dawei Zhang
- School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
| | - Evgeny Y. Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE 68588-0299, USA
- Corresponding author. (P.S.); (F.-X.X.); (E.Y.T.); (A.R.H.); (J.S.)
| | - Alex R. Hamilton
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, NSW 2052, Australia
- School of Physics, University of New South Wales, Sydney, NSW 2052, Australia
- Corresponding author. (P.S.); (F.-X.X.); (E.Y.T.); (A.R.H.); (J.S.)
| | - Jan Seidel
- School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
- ARC Centre of Excellence in Future Low-Energy Electronics Technologies, University of New South Wales, Sydney, NSW 2052, Australia
- Corresponding author. (P.S.); (F.-X.X.); (E.Y.T.); (A.R.H.); (J.S.)
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35
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Li M, Tang C, Paudel TR, Song D, Lü W, Han K, Huang Z, Zeng S, Renshaw Wang X, Yang P, Chen J, Venkatesan T, Tsymbal EY, Li C, Pennycook SJ. Controlling the Magnetic Properties of LaMnO 3 /SrTiO 3 Heterostructures by Stoichiometry and Electronic Reconstruction: Atomic-Scale Evidence. Adv Mater 2019; 31:e1901386. [PMID: 31099075 DOI: 10.1002/adma.201901386] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 04/10/2019] [Indexed: 06/09/2023]
Abstract
Interface-driven magnetic effects and phenomena associated with spin-orbit coupling and intrinsic symmetry breaking are of importance for fundamental physics and device applications. How interfaces affect the interplay between charge, spin, orbital, and lattice degrees of freedom is the key to boosting device performance. In LaMnO3 /SrTiO3 (LMO/STO) polar-nonpolar heterostructures, electronic reconstruction leads to an antiferromagnetic to ferromagnetic transition, making them viable for spin filter applications. The interfacial electronic structure plays a critical role in the understanding of the microscopic origins of the observed magnetic phase transition, from antiferromagnetic at 5 unit cells (ucs) of LMO or below to ferromagnetic at 6 ucs or above, yet such a study is missing. Here, an atomic scale understanding of LMO/STO ambipolar ferromagnetism is offered by quantifying the interface charge distribution and performing first-principles density functional theory (DFT) calculations across this abrupt magnetic transition. It is found that the electronic reconstruction is confined within the first 3 ucs of LMO from the interface, and more importantly, it is robust against oxygen nonstoichiometry. When restoring stoichiometry, an enhanced ferromagnetic insulating state in LMO films with a thickness as thin as 2 nm (5 uc) is achieved, making LMO readily applicable as barriers in spin filters.
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Affiliation(s)
- Mengsha Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Chunhua Tang
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Tula R Paudel
- Department of Physics and Astronomy and Nebraska, Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Dongsheng Song
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
| | - Weiming Lü
- Spintronics Institute, University of Jinan, Jinan, 250022, China
- Condensed Matter Science and Technology Institute and Department of Physics, Harbin Institute of Technology, Harbin, 150001, China
| | - Kun Han
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
| | - Zhen Huang
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
| | - Shengwei Zeng
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
| | - Xiao Renshaw Wang
- School of Physical and Mathematical Sciences and School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore
| | - Ping Yang
- Singapore Synchrotron Light Source National University of Singapore 5 Research Link, Singapore, 117603, Singapore
| | - Jingsheng Chen
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | | | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska, Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Changjian Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Stephen John Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
- NUSNNI-Nanocore, National University of Singapore, Singapore, 117411, Singapore
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36
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Wang H, Chi X, Liu Z, Yoong H, Tao L, Xiao J, Guo R, Wang J, Dong Z, Yang P, Sun CJ, Li C, Yan X, Wang J, Chow GM, Tsymbal EY, Tian H, Chen J. Atomic-Scale Control of Magnetism at the Titanite-Manganite Interfaces. Nano Lett 2019; 19:3057-3065. [PMID: 30964306 DOI: 10.1021/acs.nanolett.9b00441] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Complex oxide thin-film heterostructures often exhibit magnetic properties different from those known for bulk constituents. This is due to the altered local structural and electronic environment at the interfaces, which affects the exchange coupling and magnetic ordering. The emergent magnetism at oxide interfaces can be controlled by ferroelectric polarization and has a strong effect on spin-dependent transport properties of oxide heterostructures, including magnetic and ferroelectric tunnel junctions. Here, using prototype La2/3Sr1/3MnO3/BaTiO3 heterostructures, we demonstrate that ferroelectric polarization of BaTiO3 controls the orbital hybridization and magnetism at heterointerfaces. We observe changes in the enhanced orbital occupancy and significant charge redistribution across the heterointerfaces, affecting the spin and orbital magnetic moments of the interfacial Mn and Ti atoms. Importantly, we find that the exchange coupling between Mn and Ti atoms across the interface is tuned by ferroelectric polarization from ferromagnetic to antiferromagnetic. Our findings provide a viable route to electrically control complex magnetic configurations at artificial multiferroic interfaces, taking a step toward low-power spintronics.
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Affiliation(s)
- Han Wang
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - Xiao Chi
- Department of Physics , National University of Singapore , 2 Science Drive 3 , 117542 Singapore
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 117603 Singapore
| | - ZhongRan Liu
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - HerngYau Yoong
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - LingLing Tao
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience , University of Nebraska , Lincoln , Nebraska 68588-0299 , United States
| | - JuanXiu Xiao
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - Rui Guo
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - JingXian Wang
- School of Materials Science and Engineering , Nanyang Technological University , 639798 Singapore
| | - ZhiLi Dong
- School of Materials Science and Engineering , Nanyang Technological University , 639798 Singapore
| | - Ping Yang
- Singapore Synchrotron Light Source (SSLS) , National University of Singapore , 117603 Singapore
| | - Cheng-Jun Sun
- Advanced Photon Source , Argonne National Laboratory , Argonne , Illinois 60439 , United States
| | - ChangJian Li
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - XiaoBing Yan
- College of Electron and Information Engineering , Hebei University , Baoding 071002 , China
| | - John Wang
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - Gan Moog Chow
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience , University of Nebraska , Lincoln , Nebraska 68588-0299 , United States
| | - He Tian
- Center of Electron Microscope, State Key Laboratory of Silicon Materials, School of Materials Science and Engineering , Zhejiang University , Hangzhou 310027 , China
| | - Jingsheng Chen
- Department of Materials Science and Engineering , National University of Singapore , 117575 Singapore
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37
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Abstract
The recently discovered magnetism of two-dimensional (2D) van der Waals crystals has attracted a lot of attention. Among these materials is CrI3, a magnetic semiconductor, exhibiting transitions between ferromagnetic and antiferromagnetic orderings under the influence of an applied magnetic field. Here, using first-principles methods based on density functional theory, we explore spin-dependent transport in tunnel junctions formed of face-centered cubic Cu(111) electrodes and a CrI3 tunnel barrier. We find about 100% spin polarization of the tunneling current for a ferromagnetically ordered four-monolayer CrI3 and a tunneling magnetoresistance of about 3000% associated with a change of magnetic ordering in CrI3. This behavior is understood in terms of the spin and wave-vector-dependent evanescent states in CrI3, which control the tunneling conductance. We find a sizable charge transfer from Cu to CrI3, which adds new features to the mechanism of spin filtering in CrI3-based tunnel junctions. Our results elucidate the mechanisms of spin filtering in CrI3 tunnel junctions and provide important insights for the design of magnetoresistive devices based on 2D magnetic crystals.
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Affiliation(s)
- Tula R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience , University of Nebraska , Lincoln , Nebraska 68588 , United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience , University of Nebraska , Lincoln , Nebraska 68588 , United States
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38
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Shao DF, Gurung G, Zhang SH, Tsymbal EY. Dirac Nodal Line Metal for Topological Antiferromagnetic Spintronics. Phys Rev Lett 2019; 122:077203. [PMID: 30848649 DOI: 10.1103/physrevlett.122.077203] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Indexed: 06/09/2023]
Abstract
Topological antiferromagnetic (AFM) spintronics is an emerging field of research, which exploits the Néel vector to control the topological electronic states and the associated spin-dependent transport properties. A recently discovered Néel spin-orbit torque has been proposed to electrically manipulate Dirac band crossings in antiferromagnets; however, a reliable AFM material to realize these properties in practice is missing. In this Letter, we predict that room-temperature AFM metal MnPd_{2} allows the electrical control of the Dirac nodal line by the Néel spin-orbit torque. Based on first-principles density functional theory calculations, we show that reorientation of the Néel vector leads to switching between the symmetry-protected degenerate state and the gapped state associated with the dispersive Dirac nodal line at the Fermi energy. The calculated spin Hall conductivity strongly depends on the Néel vector orientation and can be used to experimentally detect the predicted effect using a proposed spin-orbit torque device. Our results indicate that AFM Dirac nodal line metal MnPd_{2} represents a promising material for topological AFM spintronics.
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Affiliation(s)
- Ding-Fu Shao
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
| | - Gautam Gurung
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
| | - Shu-Hui Zhang
- College of Science, Beijing University of Chemical Technology, Beijing 100029, People's Republic of China
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588-0299, USA
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39
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Zhang Y, Lu H, Xie L, Yan X, Paudel TR, Kim J, Cheng X, Wang H, Heikes C, Li L, Xu M, Schlom DG, Chen LQ, Wu R, Tsymbal EY, Gruverman A, Pan X. Publisher Correction: Anisotropic polarization-induced conductance at a ferroelectric-insulator interface. Nat Nanotechnol 2018; 13:1191. [PMID: 30291315 DOI: 10.1038/s41565-018-0295-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the version of this Letter originally published, the right-hand arrow in Fig. 3b was incorrectly labelled; see correction note for details. Also, ref. 29 was incorrectly included in the reference list; it has now been removed.
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Affiliation(s)
- Yi Zhang
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Haidong Lu
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Lin Xie
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Xingxu Yan
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Tula R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Jeongwoo Kim
- Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Xiaoxing Cheng
- Department of Materials Science and Engineering, Penn State University, University Park, PA, USA
| | - Hui Wang
- Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Colin Heikes
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
| | - Linze Li
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Mingjie Xu
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA
| | - Long-Qing Chen
- Department of Materials Science and Engineering, Penn State University, University Park, PA, USA
| | - Ruqian Wu
- Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Alexei Gruverman
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA.
| | - Xiaoqing Pan
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA.
- Department of Physics and Astronomy, University of California, Irvine, CA, USA.
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40
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Zhang Y, Lu H, Xie L, Yan X, Paudel TR, Kim J, Cheng X, Wang H, Heikes C, Li L, Xu M, Schlom DG, Chen LQ, Wu R, Tsymbal EY, Gruverman A, Pan X. Anisotropic polarization-induced conductance at a ferroelectric-insulator interface. Nat Nanotechnol 2018; 13:1132-1136. [PMID: 30250247 DOI: 10.1038/s41565-018-0259-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Accepted: 08/16/2018] [Indexed: 05/12/2023]
Abstract
Coupling between different degrees of freedom, that is, charge, spin, orbital and lattice, is responsible for emergent phenomena in complex oxide heterostrutures1,2. One example is the formation of a two-dimensional electron gas (2DEG) at the polar/non-polar LaAlO3/SrTiO3 (LAO/STO)3-7 interface. This is caused by the polar discontinuity and counteracts the electrostatic potential build-up across the LAO film3. The ferroelectric polarization at a ferroelectric/insulator interface can also give rise to a polar discontinuity8-10. Depending on the polarization orientation, either electrons or holes are transferred to the interface, to form either a 2DEG or two-dimensional hole gas (2DHG)11-13. While recent first-principles modelling predicts the formation of 2DEGs at the ferroelectric/insulator interfaces9,10,12-14, experimental evidence of a ferroelectrically induced interfacial 2DEG remains elusive. Here, we report the emergence of strongly anisotropic polarization-induced conductivity at a ferroelectric/insulator interface, which shows a strong dependence on the polarization orientation. By probing the local conductance and ferroelectric polarization over a cross-section of a BiFeO3-TbScO3 (BFO/TSO) (001) heterostructure, we demonstrate that this interface is conducting along the 109° domain stripes in BFO, whereas it is insulating in the direction perpendicular to these domain stripes. Electron energy-loss spectroscopy and theoretical modelling suggest that the anisotropy of the interfacial conduction is caused by an alternating polarization associated with the ferroelectric domains, producing either electron or hole doping of the BFO/TSO interface.
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Affiliation(s)
- Yi Zhang
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Haidong Lu
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Lin Xie
- National Laboratory of Solid State Microstructures and College of Engineering and Applied Sciences, Nanjing University, Nanjing, Jiangsu, China
| | - Xingxu Yan
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Tula R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Jeongwoo Kim
- Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Xiaoxing Cheng
- Department of Materials Science and Engineering, Penn State University, University Park, PA, USA
| | - Hui Wang
- Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Colin Heikes
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
| | - Linze Li
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Mingjie Xu
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA
| | - Darrell G Schlom
- Department of Materials Science and Engineering, Cornell University, Ithaca, NY, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY, USA
| | - Long-Qing Chen
- Department of Materials Science and Engineering, Penn State University, University Park, PA, USA
| | - Ruqian Wu
- Department of Physics and Astronomy, University of California, Irvine, CA, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Alexei Gruverman
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA.
| | - Xiaoqing Pan
- Department of Materials Science and Engineering, University of California, Irvine, CA, USA.
- Department of Physics and Astronomy, University of California, Irvine, CA, USA.
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41
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Affiliation(s)
- Evgeny Y Tsymbal
- Department of Physics and Astronomy, and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA.
| | - Christos Panagopoulos
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
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42
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Klyukin K, Tao LL, Tsymbal EY, Alexandrov V. Defect-Assisted Tunneling Electroresistance in Ferroelectric Tunnel Junctions. Phys Rev Lett 2018; 121:056601. [PMID: 30118295 DOI: 10.1103/physrevlett.121.056601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2018] [Revised: 04/27/2018] [Indexed: 06/08/2023]
Abstract
Recent experimental results have demonstrated ferroelectricity in thin films of SrTiO_{3} induced by antisite Ti_{Sr} defects. This opens a possibility to use SrTiO_{3} as a barrier layer in ferroelectric tunnel junctions (FTJs)-emerging electronic devices promising for applications in nanoelectronics. Here using density functional theory combined with quantum-transport calculations applied to a prototypical Pt/SrTiO_{3}/Pt FTJ, we demonstrate that the localized in-gap energy states produced by the antisite Ti_{Sr} defects are responsible for the enhanced electron tunneling conductance which can be controlled by ferroelectric polarization. Our tight-binding modeling, which takes into account multiple defects, shows that the predicted defect-assisted tunneling electroresistance effect is greatly amplified when the defect energy levels are brought to the Fermi energy by one of the polarization states. Our results have implications for FTJs based on conventional ferroelectric barriers with defects and can be employed for the design of new types of FTJs with enhanced performance.
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Affiliation(s)
- Konstantin Klyukin
- Department of Chemical and Biomolecular Engineering, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - L L Tao
- Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
- Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Vitaly Alexandrov
- Department of Chemical and Biomolecular Engineering, University of Nebraska, Lincoln, Nebraska 68588, USA
- Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
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Abstract
Persistent spin texture (PST) is the property of some materials to maintain a uniform spin configuration in the momentum space. This property has been predicted to support an extraordinarily long spin lifetime of carriers promising for spintronics applications. Here, we predict that there exists a class of noncentrosymmetric bulk materials, where the PST is enforced by the nonsymmorphic space group symmetry of the crystal. Around certain high symmetry points in the Brillouin zone, the sublattice degrees of freedom impose a constraint on the effective spin-orbit field, which orientation remains independent of the momentum and thus maintains the PST. We illustrate this behavior using density-functional theory calculations for a handful of promising candidates accessible experimentally. Among them is the ferroelectric oxide BiInO3-a wide band gap semiconductor which sustains a PST around the conduction band minimum. Our results broaden the range of materials that can be employed in spintronics.
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Affiliation(s)
- L L Tao
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, 68588, USA.
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44
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Song K, Ryu S, Lee H, Paudel TR, Koch CT, Park B, Lee JK, Choi SY, Kim YM, Kim JC, Jeong HY, Rzchowski MS, Tsymbal EY, Eom CB, Oh SH. Publisher Correction: Direct imaging of the electron liquid at oxide interfaces. Nat Nanotechnol 2018; 13:618. [PMID: 29849186 DOI: 10.1038/s41565-018-0137-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In the version of this Letter originally published, in two instances in Fig. 1 the layers in the cross-sectional view of the (001) interface were incorrectly labelled: in Fig. 1b SrO+ should have read SrO0; in Fig. 1c LaO+, AlO2-, LaO+, TiO20, SrO+, TiO20 should have read LaO33-, Al3+, LaO33-, Ti4+, SrO34-, Ti4+. In Fig. 3c the upper-right equation read -σs = -e/2a2 but should have read -σs = e/2a2 and in Fig. 3f the lower-right equation read -σs = -e/2√3a2 but should have read σs = -e/2√3a2. These errors have now been corrected in the online version of the Letter.
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Affiliation(s)
- Kyung Song
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Materials Modeling and Characterization Department, Korea Institute of Materials Science (KIMS), Changwon, Republic of Korea
| | - Sangwoo Ryu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Tula R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Christoph T Koch
- Department of Physics, Humboldt University of Berlin, Berlin, Germany
| | - Bumsu Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Republic of Korea
| | - Ja Kyung Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Si-Young Choi
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Materials Modeling and Characterization Department, Korea Institute of Materials Science (KIMS), Changwon, Republic of Korea
| | - Young-Min Kim
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Jong Chan Kim
- School of Materials Science and Engineering, Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Republic of Korea
| | - Hu Young Jeong
- School of Materials Science and Engineering, Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Republic of Korea
- UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Republic of Korea
| | - Mark S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Sang Ho Oh
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Republic of Korea.
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45
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Zheng LM, Wang XR, Lü WM, Li CJ, Paudel TR, Liu ZQ, Huang Z, Zeng SW, Han K, Chen ZH, Qiu XP, Li MS, Yang S, Yang B, Chisholm MF, Martin LW, Pennycook SJ, Tsymbal EY, Coey JMD, Cao WW. Ambipolar ferromagnetism by electrostatic doping of a manganite. Nat Commun 2018; 9:1897. [PMID: 29765044 PMCID: PMC5953920 DOI: 10.1038/s41467-018-04233-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 04/12/2018] [Indexed: 11/09/2022] Open
Abstract
Complex-oxide materials exhibit physical properties that involve the interplay of charge and spin degrees of freedom. However, an ambipolar oxide that is able to exhibit both electron-doped and hole-doped ferromagnetism in the same material has proved elusive. Here we report ambipolar ferromagnetism in LaMnO3, with electron-hole asymmetry of the ferromagnetic order. Starting from an undoped atomically thin LaMnO3 film, we electrostatically dope the material with electrons or holes according to the polarity of a voltage applied across an ionic liquid gate. Magnetotransport characterization reveals that an increase of either electron-doping or hole-doping induced ferromagnetic order in this antiferromagnetic compound, and leads to an insulator-to-metal transition with colossal magnetoresistance showing electron-hole asymmetry. These findings are supported by density functional theory calculations, showing that strengthening of the inter-plane ferromagnetic exchange interaction is the origin of the ambipolar ferromagnetism. The result raises the prospect of exploiting ambipolar magnetic functionality in strongly correlated electron systems.
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Affiliation(s)
- L M Zheng
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China
| | - X Renshaw Wang
- School of Physical and Mathematical Sciences & School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore, 639798, Singapore.
| | - W M Lü
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China.
| | - C J Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - T R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, 68588, USA
| | - Z Q Liu
- School of Materials Science and Engineering, Beihang University, Beijing, 100191, China
| | - Z Huang
- NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore
| | - S W Zeng
- NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore
| | - Kun Han
- NUSNNI-NanoCore, National University of Singapore, Singapore, 117411, Singapore
| | - Z H Chen
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.,School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen, Guangzhou, 518055, China
| | - X P Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology & Pohl Institute of Solid State Physics & School of Physics Science and Engineering, Tongji University, Shanghai, 200092, China
| | - M S Li
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Shize Yang
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - B Yang
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China
| | - Matthew F Chisholm
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - L W Martin
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, 94720, USA.,Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - S J Pennycook
- Department of Materials Science and Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - E Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska, 68588, USA
| | - J M D Coey
- School of Physics, Trinity College, Dublin, 2, Ireland.,Faculty of Materials Science and Engineering, Beihang University, Beijing, 100191, China
| | - W W Cao
- Condensed Matter Science and Technology Institute, School of Science, Harbin Institute of Technology, Harbin, 150081, China.,Department of Mathematics and Materials Research Institute, The Pennsylvania State University, University Park, PA, 16802, USA
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46
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Song K, Ryu S, Lee H, Paudel TR, Koch CT, Park B, Lee JK, Choi SY, Kim YM, Kim JC, Jeong HY, Rzchowski MS, Tsymbal EY, Eom CB, Oh SH. Direct imaging of the electron liquid at oxide interfaces. Nat Nanotechnol 2018; 13:198-203. [PMID: 29402977 DOI: 10.1038/s41565-017-0040-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 12/04/2017] [Indexed: 06/07/2023]
Abstract
The breaking of symmetry across an oxide heterostructure causes the electronic orbitals to be reconstructed at the interface into energy states that are different from their bulk counterparts 1 . The detailed nature of the orbital reconstruction critically affects the spatial confinement and the physical properties of the electrons occupying the interfacial orbitals2-4. Using an example of two-dimensional electron liquids forming at LaAlO3/SrTiO3 interfaces5,6 with different crystal symmetry, we show that the selective orbital occupation and spatial quantum confinement of electrons can be resolved with subnanometre resolution using inline electron holography. For the standard (001) interface, the charge density map obtained by inline electron holography shows that the two-dimensional electron liquid is confined to the interface with narrow spatial extension (~1.0 ± 0.3 nm in the half width). On the other hand, the two-dimensional electron liquid formed at the (111) interface shows a much broader spatial extension (~3.3 ± 0.3 nm) with the maximum density located ~2.4 nm away from the interface, in excellent agreement with density functional theory calculations.
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Affiliation(s)
- Kyung Song
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Materials Modeling and Characterization Department, Korea Institute of Materials Science (KIMS), Changwon, Republic of Korea
| | - Sangwoo Ryu
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Tula R Paudel
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Christoph T Koch
- Department of Physics, Humboldt University of Berlin, Berlin, Germany
| | - Bumsu Park
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Republic of Korea
| | - Ja Kyung Lee
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Si-Young Choi
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
- Materials Modeling and Characterization Department, Korea Institute of Materials Science (KIMS), Changwon, Republic of Korea
| | - Young-Min Kim
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Republic of Korea
- Center for Integrated Nanostructure Physics, Institute for Basic Science (IBS), Suwon, Republic of Korea
| | - Jong Chan Kim
- School of Materials Science and Engineering, Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Republic of Korea
| | - Hu Young Jeong
- School of Materials Science and Engineering, Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Republic of Korea
- UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and Engineering (UNIST), Ulsan, Republic of Korea
| | - Mark S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy & Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Sang Ho Oh
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea.
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Republic of Korea.
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47
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Lee H, Campbell N, Lee J, Asel TJ, Paudel TR, Zhou H, Lee JW, Noesges B, Seo J, Park B, Brillson LJ, Oh SH, Tsymbal EY, Rzchowski MS, Eom CB. Direct observation of a two-dimensional hole gas at oxide interfaces. Nat Mater 2018; 17:231-236. [PMID: 29403056 DOI: 10.1038/s41563-017-0002-4] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Accepted: 11/27/2017] [Indexed: 06/07/2023]
Abstract
The discovery of a two-dimensional electron gas (2DEG) at the LaAlO3/SrTiO3 interface 1 has resulted in the observation of many properties2-5 not present in conventional semiconductor heterostructures, and so become a focal point for device applications6-8. Its counterpart, the two-dimensional hole gas (2DHG), is expected to complement the 2DEG. However, although the 2DEG has been widely observed 9 , the 2DHG has proved elusive. Herein we demonstrate a highly mobile 2DHG in epitaxially grown SrTiO3/LaAlO3/SrTiO3 heterostructures. Using electrical transport measurements and in-line electron holography, we provide direct evidence of a 2DHG that coexists with a 2DEG at complementary heterointerfaces in the same structure. First-principles calculations, coherent Bragg rod analysis and depth-resolved cathodoluminescence spectroscopy consistently support our finding that to eliminate ionic point defects is key to realizing a 2DHG. The coexistence of a 2DEG and a 2DHG in a single oxide heterostructure provides a platform for the exciting physics of confined electron-hole systems and for developing applications.
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Affiliation(s)
- H Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - N Campbell
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - J Lee
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - T J Asel
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - T R Paudel
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - H Zhou
- X-Ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA
| | - J W Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - B Noesges
- Department of Physics, The Ohio State University, Columbus, OH, USA
| | - J Seo
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - B Park
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
- Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Korea
| | - L J Brillson
- Department of Physics, The Ohio State University, Columbus, OH, USA
- Department of Electrical and Computer Engineering, The Ohio State University, Columbus, OH, USA
| | - S H Oh
- Department of Energy Science, Sungkyunkwan University (SKKU), Suwon, Korea
| | - E Y Tsymbal
- Department of Physics and Astronomy, Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, NE, USA
| | - M S Rzchowski
- Department of Physics, University of Wisconsin-Madison, Madison, WI, USA
| | - C B Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison, Madison, WI, USA.
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48
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Huang W, Fang YW, Yin Y, Tian B, Zhao W, Hou C, Ma C, Li Q, Tsymbal EY, Duan CG, Li X. Solid-State Synapse Based on Magnetoelectrically Coupled Memristor. ACS Appl Mater Interfaces 2018; 10:5649-5656. [PMID: 29368507 DOI: 10.1021/acsami.7b18206] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Brain-inspired computing architectures attempt to emulate the computations performed in the neurons and the synapses in the human brain. Memristors with continuously tunable resistances are ideal building blocks for artificial synapses. Through investigating the memristor behaviors in a La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junction, it was found that the ferroelectric domain dynamics characteristics are influenced by the relative magnetization alignment of the electrodes, and the interfacial spin polarization is manipulated continuously by ferroelectric domain reversal, enriching our understanding of the magnetoelectric coupling fundamentally. This creates a functionality that not only the resistance of the memristor but also the synaptic plasticity form can be further manipulated, as demonstrated by the spike-timing-dependent plasticity investigations. Density functional theory calculations are carried out to describe the obtained magnetoelectric coupling, which is probably related to the Mn-Ti intermixing at the interfaces. The multiple and controllable plasticity characteristic in a single artificial synapse, to resemble the synaptic morphological alteration property in a biological synapse, will be conducive to the development of artificial intelligence.
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Affiliation(s)
- Weichuan Huang
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, University of Science and Technology of China , Hefei 230026, China
| | - Yue-Wen Fang
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University , Shanghai 200241, China
| | - Yuewei Yin
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, University of Science and Technology of China , Hefei 230026, China
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Bobo Tian
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University , Shanghai 200241, China
| | - Wenbo Zhao
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, University of Science and Technology of China , Hefei 230026, China
| | - Chuangming Hou
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, University of Science and Technology of China , Hefei 230026, China
| | - Chao Ma
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, University of Science and Technology of China , Hefei 230026, China
| | - Qi Li
- Department of Physics, Pennsylvania State University , University Park 16802, United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Chun-Gang Duan
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University , Shanghai 200241, China
- Collaborative Innovation Center of Extreme Optics, Shanxi University , Shanxi 030006, China
| | - Xiaoguang Li
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Physics, University of Science and Technology of China , Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures , Nanjing 210093, China
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Lu H, Lee D, Klyukin K, Tao L, Wang B, Lee H, Lee J, Paudel TR, Chen LQ, Tsymbal EY, Alexandrov V, Eom CB, Gruverman A. Tunneling Hot Spots in Ferroelectric SrTiO 3. Nano Lett 2018; 18:491-497. [PMID: 29236501 DOI: 10.1021/acs.nanolett.7b04444] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Strontium titanate (SrTiO3) is the "silicon" in the emerging field of oxide electronics. While bulk properties of this material have been studied for decades, new unexpected phenomena have recently been discovered at the nanoscale, when SrTiO3 forms an ultrathin film or an atomically sharp interface with other materials. One of the striking discoveries is room-temperature ferroelectricity in strain-free ultrathin films of SrTiO3 driven by the TiSr antisite defects, which generate a local dipole moment polarizing the surrounding nanoregion. Here, we demonstrate that these polar defects are not only responsible for ferroelectricity, but also propel the appearance of highly conductive channels, "hot spots", in the ultrathin SrTiO3 films. Using a combination of scanning probe microscopy experimental studies and theoretical modeling, we show that the hot spots emerge due to resonant tunneling through localized electronic states created by the polar defects and that the tunneling conductance of the hot spots is controlled by ferroelectric polarization. Our finding of the polarization-controlled defect-assisted tunneling reveals a new mechanism of resistive switching in oxide heterostructures and may have technological implications for ferroelectric tunnel junctions. It is also shown that the conductivity of the hot spots can be modulated by mechanical stress, opening a possibility for development of conceptually new electronic devices with mechanically tunable resistive states.
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Affiliation(s)
- Haidong Lu
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Daesu Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Konstantin Klyukin
- Department of Chemical and Biomolecular Engineering, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Lingling Tao
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Bo Wang
- Department of Materials Science and Engineering, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Hyungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Jungwoo Lee
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Tula R Paudel
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Long-Qing Chen
- Department of Materials Science and Engineering, Pennsylvania State University , University Park, Pennsylvania 16802, United States
| | - Evgeny Y Tsymbal
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
- Nebraska Center for Materials and Nanoscience, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Vitaly Alexandrov
- Department of Chemical and Biomolecular Engineering, University of Nebraska , Lincoln, Nebraska 68588, United States
- Nebraska Center for Materials and Nanoscience, University of Nebraska , Lincoln, Nebraska 68588, United States
| | - Chang-Beom Eom
- Department of Materials Science and Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Alexei Gruverman
- Department of Physics and Astronomy, University of Nebraska , Lincoln, Nebraska 68588, United States
- Nebraska Center for Materials and Nanoscience, University of Nebraska , Lincoln, Nebraska 68588, United States
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Affiliation(s)
- Evgeny Y Tsymbal
- Department of Physics and Astronomy and the Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588, USA
| | - Julian P Velev
- Department of Physics and Astronomy, University of Puerto Rico, Puerto Rico 00931, USA
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