1
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Johansson A. Theory of spin and orbital Edelstein effects. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:423002. [PMID: 38955339 DOI: 10.1088/1361-648x/ad5e2b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/25/2024] [Accepted: 07/01/2024] [Indexed: 07/04/2024]
Abstract
In systems with broken spatial inversion symmetry, such as surfaces, interfaces, or bulk systems lacking an inversion center, the application of a charge current can generate finite spin and orbital densities associated with a nonequilibrium magnetization, which is known as spin and orbital Edelstein effect (SEE and OEE), respectively. Early reports on this current-induced magnetization focus on two-dimensional Rashba systems, in which an in-plane nonequilibrium spin density is generated perpendicular to the applied charge current. However, until today, a large variety of materials have been theoretically predicted and experimentally demonstrated to exhibit a sizeable Edelstein effect, which comprises contributions from the spin as well as the orbital degrees of freedom, and whose associated magnetization may be out of plane, nonorthogonal, and even parallel to the applied charge current, depending on the system's particular symmetries. In this review, we give an overview on the most commonly used theoretical approaches for the discussion and prediction of the SEE and OEE. Further, we introduce a selection of the most intensely discussed materials exhibiting a finite Edelstein effect, and give a brief summary of common experimental techniques.
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Affiliation(s)
- Annika Johansson
- Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
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2
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Grochot K, Ogrodnik P, Mojsiejuk J, Mazalski P, Guzowska U, Skowroński W, Stobiecki T. Influence of ferromagnetic interlayer exchange coupling on current-induced magnetization switching and Dzyaloshinskii-Moriya interaction in Co/Pt/Co multilayer system. Sci Rep 2024; 14:9938. [PMID: 38688928 PMCID: PMC11061319 DOI: 10.1038/s41598-024-60492-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Accepted: 04/23/2024] [Indexed: 05/02/2024] Open
Abstract
This paper investigates the relationship among interlayer exchange coupling (IEC), Dzyaloshinskii-Moriya interaction (DMI), and multilevel magnetization switching within a Co/Pt/Co heterostructure, where varying Pt thicknesses enable control over the coupling strength. Employing Brillouin Light Scattering to quantify the effective DMI, we explore its potential role in magnetization dynamics and multilevel magnetization switching. Experimental findings show four distinct resistance states under an external magnetic field and spin Hall effect related spin current. We explain this phenomenon based on the asymmetry between Pt/Co and Co/Pt interfaces and the interlayer coupling, which, in turn, influences the DMI and subsequently impacts the magnetization dynamics. Numerical simulations, including macrospin, 1D domain wall, and simple spin wave models, further support the experimental observations of multilevel switching and help uncover the underlying mechanisms. Our proposed explanation, supported by magnetic domain observation using polar-magnetooptical Kerr microscopy, offers insights into both the spatial distribution of magnetization and its dynamics for different IECs, thereby shedding light on its interplay with DMI, which may lead to potential applications in storage devices.
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Affiliation(s)
- Krzysztof Grochot
- Institute of Electronics, AGH University of Krakow, Krakow, Poland.
- Faculty of Physics and Computer Science, AGH University of Krakow, Krakow, Poland.
| | - Piotr Ogrodnik
- Faculty of Physics, Warsaw University of Technology, Warsaw, Poland.
| | - Jakub Mojsiejuk
- Institute of Electronics, AGH University of Krakow, Krakow, Poland
| | - Piotr Mazalski
- Faculty of Physics, University of Bialystok, Bialystok, Poland
| | | | | | - Tomasz Stobiecki
- Institute of Electronics, AGH University of Krakow, Krakow, Poland
- Faculty of Physics and Computer Science, AGH University of Krakow, Krakow, Poland
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3
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Jain R, Stanley M, Bose A, Richardella AR, Zhang XS, Pillsbury T, Muller DA, Samarth N, Ralph DC. Thermally generated spin current in the topological insulator Bi 2Se 3. SCIENCE ADVANCES 2023; 9:eadi4540. [PMID: 38091392 PMCID: PMC10848729 DOI: 10.1126/sciadv.adi4540] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2023] [Accepted: 11/14/2023] [Indexed: 02/12/2024]
Abstract
We present measurements of thermally generated transverse spin currents in the topological insulator Bi2Se3, thereby completing measurements of interconversions among the full triad of thermal gradients, charge currents, and spin currents. We accomplish this by comparing the spin Nernst magneto-thermopower to the spin Hall magnetoresistance for bilayers of Bi2Se3/CoFeB. We find that Bi2Se3 does generate substantial thermally driven spin currents. A lower bound for the ratio of spin current density to thermal gradient is [Formula: see text] = (4.9 ± 0.9) × 106 [Formula: see text], and a lower bound for the magnitude of the spin Nernst ratio is -0.61 ± 0.11. The spin Nernst ratio for Bi2Se3 is the largest among all materials measured to date, two to three times larger compared to previous measurements for the heavy metals Pt and W. Strong thermally generated spin currents in Bi2Se3 can be understood via Mott relations to be due to an overall large spin Hall conductivity and its dependence on electron energy.
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Affiliation(s)
- Rakshit Jain
- Department of Physics, Cornell University, Ithaca, NY 14853, USA
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Max Stanley
- Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA
| | - Arnab Bose
- Department of Physics, Cornell University, Ithaca, NY 14853, USA
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Anthony R. Richardella
- Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA
| | - Xiyue S. Zhang
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Timothy Pillsbury
- Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA
| | - David A. Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, USA
| | - Nitin Samarth
- Department of Physics and Materials Research Institute, Pennsylvania State University, University Park, PA 16802, USA
| | - Daniel C. Ralph
- Department of Physics, Cornell University, Ithaca, NY 14853, USA
- Kavli Institute at Cornell for Nanoscale Science, Ithaca, NY 14853, USA
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Liu W, Liu L, Cui B, Cheng S, Wu X, Cheng B, Miao T, Ren X, Chu R, Liu M, Zhao X, Wu S, Qin H, Hu J. Manipulation of Spin-Orbit Torque in Tungsten Oxide/Manganite Heterostructure by Ionic Liquid Gating and Orbit Engineering. ACS NANO 2023. [PMID: 37988035 DOI: 10.1021/acsnano.3c06686] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Spin-orbit coupling (SOC) is the interaction between electron's spin and orbital motion, which could realize a charge-to-spin current conversion and enable an innovative method to switch the magnetization by spin-orbit torque (SOT). Varied techniques have been developed to manipulate and improve the SOT, but the role of the orbit degree of freedom, which should have a crucial bearing on the SOC and SOT, is still confusing. Here, we find that the charge-to-spin current conversion and SOT in W3O8-δ/(La, Sr)MnO3 could be produced or eliminated by ionic liquid gating. Through tuning the preferential occupancy of Mn/W-d electrons from the in-plane (dx2-y2) to out-of-plane (d3z2-r2) orbit, the SOT damping-like field efficiency is nearly doubled due to the enhanced spin Hall effect and interfacial Rashba-Edelstein effect. These findings not only offer intriguing opportunities to control the SOT for high-efficient spintronic devices but also could be a fundamental step toward spin-orbitronics in the future.
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Affiliation(s)
- Weikang Liu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Liang Liu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Bin Cui
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Shaobo Cheng
- Henan Key Laboratory of Diamond Optoelectronic Materials and Devices, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450000, China
| | - Xinyi Wu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Bin Cheng
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Tingting Miao
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Xue Ren
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Ruiyue Chu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Min Liu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Xiangxiang Zhao
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Shuyun Wu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Hongwei Qin
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
| | - Jifan Hu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan 250100, China
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Binda F, Fedel S, Alvarado SF, Noël P, Gambardella P. Spin-Orbit Torques and Spin Hall Magnetoresistance Generated by Twin-Free and Amorphous Bi 0.9 Sb 0.1 Topological Insulator Films. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2304905. [PMID: 37568279 DOI: 10.1002/adma.202304905] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2023] [Revised: 07/28/2023] [Indexed: 08/13/2023]
Abstract
Topological insulators have attracted great interest as generators of spin-orbit torques (SOTs) in spintronic devices. Bi1-x Sbx is a prominent topological insulator that has a high charge-to-spin conversion efficiency. However, the origin and magnitude of the SOTs induced by current-injection in Bi1-x Sbx remain controversial. Here, the investigation of the SOTs and spin Hall magnetoresistance resulting from charge-to-spin conversion in twin-free epitaxial layers of Bi0.9 Sb0.1 (0001) coupled to FeCo are investigated, and compared with those of amorphous Bi0.9 Sb0.1 . A large charge-to-spin conversion efficiency of 1 in the first case and less than 0.1 in the second is found, confirming crystalline Bi0.9 Sb0.1 as a strong spin-injector material. The SOTs and spin Hall magnetoresistance are independent of the direction of the electric current, indicating that charge-to-spin conversion in single-crystal Bi0.9 Sb0.1 (0001) is isotropic despite the strong anisotropy of the topological surface states. Further, it is found that the damping-like SOT has a non-monotonic temperature dependence with a minimum at 20 K. By correlating the SOT with resistivity and weak antilocalization measurements, charge-spin conversion is concluded to occur via thermally excited holes from the bulk states above 20 K, and conduction through the isotropic surface states with increasing spin polarization due to decreasing electron-electron scattering below 20 K.
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Affiliation(s)
- Federico Binda
- Department of Materials, ETH Zurich, CH-8093, Zurich, Switzerland
| | - Stefano Fedel
- Department of Materials, ETH Zurich, CH-8093, Zurich, Switzerland
| | | | - Paul Noël
- Department of Materials, ETH Zurich, CH-8093, Zurich, Switzerland
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6
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Sala G, Wang H, Legrand W, Gambardella P. Orbital Hanle Magnetoresistance in a 3d Transition Metal. PHYSICAL REVIEW LETTERS 2023; 131:156703. [PMID: 37897743 DOI: 10.1103/physrevlett.131.156703] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Accepted: 08/21/2023] [Indexed: 10/30/2023]
Abstract
The Hanle magnetoresistance is a telltale signature of spin precession in nonmagnetic conductors, in which strong spin-orbit coupling generates edge spin accumulation via the spin Hall effect. Here, we report the existence of a large Hanle magnetoresistance in single layers of Mn with weak spin-orbit coupling, which we attribute to the orbital Hall effect. The simultaneous observation of a sizable Hanle magnetoresistance and vanishing small spin Hall magnetoresistance in BiYIG/Mn bilayers corroborates the orbital origin of both effects. We estimate an orbital Hall angle of 0.016, an orbital relaxation time of 2 ps and diffusion length of the order of 2 nm in disordered Mn. Our findings indicate that current-induced orbital moments are responsible for magnetoresistance effects comparable to or even larger than those determined by spin moments, and provide a tool to investigate nonequilibrium orbital transport phenomena.
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Affiliation(s)
- Giacomo Sala
- Department of Materials, ETH Zurich, Hönggerbergring 64, 8093 Zurich, Switzerland
| | - Hanchen Wang
- Department of Materials, ETH Zurich, Hönggerbergring 64, 8093 Zurich, Switzerland
| | - William Legrand
- Department of Materials, ETH Zurich, Hönggerbergring 64, 8093 Zurich, Switzerland
| | - Pietro Gambardella
- Department of Materials, ETH Zurich, Hönggerbergring 64, 8093 Zurich, Switzerland
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7
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Zhao Q, Zhu Y, Zhang H, Jiang B, Wang Y, Xie T, Lou K, Xia C, Yang H, Bi C. Proximity-Induced Interfacial Room-Temperature Ferromagnetism in Semiconducting Fe 3GeTe 2. ACS APPLIED MATERIALS & INTERFACES 2023; 15:46520-46526. [PMID: 37738105 DOI: 10.1021/acsami.3c09932] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/24/2023]
Abstract
The discoveries of two-dimensional ferromagnetism and magnetic semiconductors highly enrich the magnetic material family for constructing spin-based electronic devices, but with an acknowledged challenge that the Curie temperature (Tc) is usually far below room temperature. Many efforts such as voltage control and magnetic ion doping are currently underway to enhance the functional temperature, in which the involvement of additional electrodes or extra magnetic ions limits their application in practical devices. Here we demonstrate that the magnetic proximity, a robust effect but with elusive mechanisms, can induce room-temperature ferromagnetism at the interface between sputtered Pt and semiconducting Fe3GeTe2, both of which do not show ferromagnetism at 300 K. The independent electrical and magnetization measurements, structure analysis, and control samples with Ta highlighting the role of Pt confirm that the ferromagnetism with the Tc of above 400 K arises from the Fe3GeTe2/Pt interfaces, rather than Fe aggregation or other artificial effects. Moreover, contrary to conventional ferromagnet/Pt structures, the spin current generated by the Pt layer is enhanced more than two times at the Fe3GeTe2/Pt interfaces, indicating the potential applications of the unique proximity effect in building highly efficient spintronic devices. These results may pave a new avenue to create room-temperature functional spin devices based on low-Tc materials and provide clear evidence of magnetic proximity effects by using nonferromagnetic materials.
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Affiliation(s)
- Qianwen Zhao
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yingmei Zhu
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Hanying Zhang
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Baiqing Jiang
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yuan Wang
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Tunan Xie
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Kaihua Lou
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - ChaoChao Xia
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- School of Microelectronics, University of Science and Technology of China, Hefei 230026, China
| | - Hongxin Yang
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Chong Bi
- Laboratory of Microelectronic Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
- University of Chinese Academy of Sciences, Beijing 100049, China
- School of Microelectronics, University of Science and Technology of China, Hefei 230026, China
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8
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Yang H, Ormaza M, Chi Z, Dolan E, Ingla-Aynés J, Safeer CK, Herling F, Ontoso N, Gobbi M, Martín-García B, Schiller F, Hueso LE, Casanova F. Gate-Tunable Spin Hall Effect in an All-Light-Element Heterostructure: Graphene with Copper Oxide. NANO LETTERS 2023; 23:4406-4414. [PMID: 37140909 DOI: 10.1021/acs.nanolett.3c00687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Graphene is a light material for long-distance spin transport due to its low spin-orbit coupling, which at the same time is the main drawback for exhibiting a sizable spin Hall effect. Decoration by light atoms has been predicted to enhance the spin Hall angle in graphene while retaining a long spin diffusion length. Here, we combine a light metal oxide (oxidized Cu) with graphene to induce the spin Hall effect. Its efficiency, given by the product of the spin Hall angle and the spin diffusion length, can be tuned with the Fermi level position, exhibiting a maximum (1.8 ± 0.6 nm at 100 K) around the charge neutrality point. This all-light-element heterostructure shows a larger efficiency than conventional spin Hall materials. The gate-tunable spin Hall effect is observed up to room temperature. Our experimental demonstration provides an efficient spin-to-charge conversion system free from heavy metals and compatible with large-scale fabrication.
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Affiliation(s)
- Haozhe Yang
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Maider Ormaza
- Departamento de Polímeros y Materiales Avanzados: Física Química y Tecnología Facultad de Químicas, UPV/EHU, 20080 Donostia-San Sebastián, Basque Country, Spain
| | - Zhendong Chi
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Eoin Dolan
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Josep Ingla-Aynés
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - C K Safeer
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Franz Herling
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Nerea Ontoso
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Marco Gobbi
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
- Centro de Física de Materiales (CSIC-EHU/UPV) and Materials Physics Center (MPC), 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Beatriz Martín-García
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
| | - Frederik Schiller
- Centro de Física de Materiales (CSIC-EHU/UPV) and Materials Physics Center (MPC), 20018 Donostia-San Sebastian, Basque Country, Spain
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Luis E Hueso
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
| | - Fèlix Casanova
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
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Ham WS, Ho TH, Shiota Y, Iino T, Ando F, Ikebuchi T, Kotani Y, Nakamura T, Kan D, Shimakawa Y, Moriyma T, Im E, Lee N, Kim K, Hong SC, Rhim SH, Ono T, Kim S. Bulk Rashba-Type Spin Splitting in Non-Centrosymmetric Artificial Superlattices. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2206800. [PMID: 36808490 PMCID: PMC10131871 DOI: 10.1002/advs.202206800] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Revised: 01/25/2023] [Indexed: 06/18/2023]
Abstract
Spin current, converted from charge current via spin Hall or Rashba effects, can transfer its angular momentum to local moments in a ferromagnetic layer. In this regard, the high charge-to-spin conversion efficiency is required for magnetization manipulation for developing future memory or logic devices including magnetic random-access memory. Here, the bulk Rashba-type charge-to-spin conversion is demonstrated in an artificial superlattice without centrosymmetry. The charge-to-spin conversion in [Pt/Co/W] superlattice with sub-nm scale thickness shows strong W thickness dependence. When the W thickness becomes 0.6 nm, the observed field-like torque efficiency is about 0.6, which is an order larger than other metallic heterostructures. First-principles calculation suggests that such large field-like torque arises from bulk-type Rashba effect due to the vertically broken inversion symmetry inherent from W layers. The result implies that the spin splitting in a band of such an ABC-type artificial SL can be an additional degree of freedom for the large charge-to-spin conversion.
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Affiliation(s)
- Woo Seung Ham
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Thi Huynh Ho
- Department of PhysicsUniversity of UlsanUlsan44610Korea
| | - Yoichi Shiota
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Tatsuya Iino
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Fuyuki Ando
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Tetsuya Ikebuchi
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Yoshinori Kotani
- Japan Synchrotron Radiation Research Institute (JASRI)SayoHyogo679‐5198Japan
| | - Tetsuya Nakamura
- Japan Synchrotron Radiation Research Institute (JASRI)SayoHyogo679‐5198Japan
- International Center for Synchrotron Radiation Innovation SmartTohoku UniversitySendai980‐8572Japan
| | - Daisuke Kan
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Yuichi Shimakawa
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Takahiro Moriyma
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Eunji Im
- Department of PhysicsUniversity of UlsanUlsan44610Korea
| | - Nyun‐Jong Lee
- Department of PhysicsUniversity of UlsanUlsan44610Korea
| | - Kyoung‐Whan Kim
- Center for SpintronicsKorea Institute of Science and Technology (KIST)Seoul02792Korea
| | | | - Sonny H. Rhim
- Department of PhysicsUniversity of UlsanUlsan44610Korea
| | - Teruo Ono
- Institute for Chemical ResearchKyoto UniversityUjiKyoto611‐0011Japan
| | - Sanghoon Kim
- Department of PhysicsUniversity of UlsanUlsan44610Korea
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10
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Hui Y, Jiang H, Xie F, Lin W, Dong C, Dong K, He Q, Miao X. Maximizing spin Hall magnetoresistance in heavy metal/crystalline metallic ferromagnet multilayers with opposite spin Hall angles. NANOSCALE 2023; 15:820-827. [PMID: 36533700 DOI: 10.1039/d2nr02306g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Interconversion between charge and spin through spin-orbit coupling at a heavy metal (HM)/ferromagnet (FM) interface plays a key role in determining the amplitude of spin Hall magnetoresistance (SMR), which might maximally facilitate its applications in novel electronics. In this study, annealed NiFe films grown on MgO (100) substrates capped with Pt and Ta are reported to exhibit a maximum SMR. When the measuring temperature is reduced, the SMR rises and is significantly larger in crystalline NiFe than in amorphous NiFe. Another physical process for the negative SMR in Ta(dTa)/Pt(3 nm)/annealed NiFe samples is attributed to the interfacial spin-orbit coupling (ISOC) driven spin current (Js) generation and its reciprocal effects. Moreover, spin accumulation is enhanced at Pt(3 nm)/annealed NiFe interfaces after capping with a Ta layer, which functions as a spin sink in a certain thinner thickness range. With the cooperative interaction of choosing the proper Ta's thickness and annealing NiFe layers, the maximum SMR is obtained. Our results pave the way for rational interface engineering to enhance SMR for developing high-efficiency spintronic devices.
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Affiliation(s)
- Yajuan Hui
- School of Automation, China University of Geosciences, Wuhan, 430074, China.
- Hubei key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan, 430074, China
- Engineering Research Center of Intelligent Technology for Geo-Exploration, Ministry of Education, Wuhan 430074, China
| | - Hui Jiang
- School of Automation, China University of Geosciences, Wuhan, 430074, China.
- Hubei key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan, 430074, China
- Engineering Research Center of Intelligent Technology for Geo-Exploration, Ministry of Education, Wuhan 430074, China
| | - Fei Xie
- School of Automation, China University of Geosciences, Wuhan, 430074, China.
- Hubei key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan, 430074, China
- Engineering Research Center of Intelligent Technology for Geo-Exploration, Ministry of Education, Wuhan 430074, China
| | - Weinan Lin
- Department of Physics, Xiamen University, Xiamen 361005, China.
| | - Chao Dong
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Kaifeng Dong
- School of Automation, China University of Geosciences, Wuhan, 430074, China.
- Hubei key Laboratory of Advanced Control and Intelligent Automation for Complex Systems, Wuhan, 430074, China
- Engineering Research Center of Intelligent Technology for Geo-Exploration, Ministry of Education, Wuhan 430074, China
| | - Qiang He
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
- Wuhan National Lab for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Xiangshui Miao
- Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan 430074, China
- Wuhan National Lab for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
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11
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Hao R, Zhang K, Chen W, Qu J, Kang S, Zhang X, Zhu D, Zhao W. Significant Role of Interfacial Spin-Orbit Coupling in the Spin-to-Charge Conversion in Pt/NiFe Heterostructure. ACS APPLIED MATERIALS & INTERFACES 2022; 14:57321-57327. [PMID: 36525266 DOI: 10.1021/acsami.2c13434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
For the spin-to-charge conversion (SCC) in heavy metal/ferromagnet (HM/FM) heterostructure, the contribution of interfacial spin-orbit coupling (SOC) remains controversial. Here, we investigate the SCC process of the Pt/NiFe heterostructure by the spin pumping in YIG/Pt/NiFe/IrMn multilayers. Due to the exchange bias of NiFe/IrMn structure, the NiFe magnetization can be switched between magnetically unsaturated and saturated states by opposite resonance fields of YIG layer. The spin-pumping signal is found to decrease significantly when the NiFe magnetization is changed from the saturated state to the unsaturated state. Theoretical analysis indicates that the interfacial spin absorption is enhanced for the above-mentioned NiFe magnetic state change, which results in the increased and decreased spin flow in the Pt layer and across the Pt/NiFe interface, respectively. These results demonstrate that in our case the interfacial SOC effect at the Pt/NiFe interface is dominant over the bulk inverse spin Hall effect in the Pt layer. Our work reveals a significant role of interfacial SOC in the SCC in HM/FM heterostructure, which can promote the development of high-efficiency spintronic devices through interfacial engineering.
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Affiliation(s)
- Runrun Hao
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
| | - Kun Zhang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
| | - Weibin Chen
- School of Physics, Shandong University, Jinan 250100, China
| | - Junda Qu
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
| | - Shishou Kang
- School of Physics, Shandong University, Jinan 250100, China
| | - Xueying Zhang
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
- Truth Instruments Co. Ltd., Qingdao 266000, China
| | - Dapeng Zhu
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
| | - Weisheng Zhao
- Fert Beijing Institute, MIIT Key Laboratory of Spintronics, School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao 266000, China
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12
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Feng T, Wang P, Wu D. 金属/铁磁绝缘体异质结中的自旋霍尔磁电阻. CHINESE SCIENCE BULLETIN-CHINESE 2022. [DOI: 10.1360/tb-2022-0186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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13
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Ding S, Liang Z, Go D, Yun C, Xue M, Liu Z, Becker S, Yang W, Du H, Wang C, Yang Y, Jakob G, Kläui M, Mokrousov Y, Yang J. Observation of the Orbital Rashba-Edelstein Magnetoresistance. PHYSICAL REVIEW LETTERS 2022; 128:067201. [PMID: 35213174 DOI: 10.1103/physrevlett.128.067201] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2021] [Revised: 12/06/2021] [Accepted: 01/07/2022] [Indexed: 06/14/2023]
Abstract
We report the observation of magnetoresistance (MR) that could originate from the orbital angular momentum (OAM) transport in a permalloy (Py)/oxidized Cu (Cu^{*}) heterostructure: the orbital Rashba-Edelstein magnetoresistance. The angular dependence of the MR depends on the relative angle between the induced OAM and the magnetization in a similar fashion as the spin Hall magnetoresistance. Despite the absence of elements with large spin-orbit coupling, we find a sizable MR ratio, which is in contrast to the conventional spin Hall magnetoresistance which requires heavy elements. Through Py thickness-dependence studies, we conclude another mechanism beyond the conventional spin-based scenario is responsible for the MR observed in Py/Cu^{*} structures-originated in a sizable transport of OAM. Our findings not only suggest the current-induced torques without using any heavy elements via the OAM channel but also provide an important clue towards the microscopic understanding of the role that OAM transport can play for magnetization dynamics.
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Affiliation(s)
- Shilei Ding
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Zhongyu Liang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Dongwook Go
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg-University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Chao Yun
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Mingzhu Xue
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Zhou Liu
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Sven Becker
- Institute of Physics, Johannes Gutenberg-University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Wenyun Yang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Honglin Du
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Changsheng Wang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Yingchang Yang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
| | - Gerhard Jakob
- Institute of Physics, Johannes Gutenberg-University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - Mathias Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
| | - Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg-University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Jinbo Yang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, People's Republic of China
- Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
- Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing 100871, People's Republic of China
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14
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Saha R, Wu K, Bloom RP, Liang S, Tonini D, Wang JP. A review on magnetic and spintronic neurostimulation: challenges and prospects. NANOTECHNOLOGY 2022; 33:182004. [PMID: 35013010 DOI: 10.1088/1361-6528/ac49be] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/09/2021] [Accepted: 01/10/2022] [Indexed: 06/14/2023]
Abstract
In the treatment of neurodegenerative, sensory and cardiovascular diseases, electrical probes and arrays have shown quite a promising success rate. However, despite the outstanding clinical outcomes, their operation is significantly hindered by non-selective control of electric fields. A promising alternative is micromagnetic stimulation (μMS) due to the high permeability of magnetic field through biological tissues. The induced electric field from the time-varying magnetic field generated by magnetic neurostimulators is used to remotely stimulate neighboring neurons. Due to the spatial asymmetry of the induced electric field, high spatial selectivity of neurostimulation has been realized. Herein, some popular choices of magnetic neurostimulators such as microcoils (μcoils) and spintronic nanodevices are reviewed. The neurostimulator features such as power consumption and resolution (aiming at cellular level) are discussed. In addition, the chronic stability and biocompatibility of these implantable neurostimulator are commented in favor of further translation to clinical settings. Furthermore, magnetic nanoparticles (MNPs), as another invaluable neurostimulation material, has emerged in recent years. Thus, in this review we have also included MNPs as a remote neurostimulation solution that overcomes physical limitations of invasive implants. Overall, this review provides peers with the recent development of ultra-low power, cellular-level, spatially selective magnetic neurostimulators of dimensions within micro- to nano-range for treating chronic neurological disorders. At the end of this review, some potential applications of next generation neuro-devices have also been discussed.
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Affiliation(s)
- Renata Saha
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Kai Wu
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Robert P Bloom
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Shuang Liang
- Department of Chemical Engineering and Material Science, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Denis Tonini
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, United States of America
| | - Jian-Ping Wang
- Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, MN 55455, United States of America
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15
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Liu G, Wang XG, Luan ZZ, Zhou LF, Xia SY, Yang B, Tian YZ, Guo GH, Du J, Wu D. Magnonic Unidirectional Spin Hall Magnetoresistance in a Heavy-Metal-Ferromagnetic-Insulator Bilayer. PHYSICAL REVIEW LETTERS 2021; 127:207206. [PMID: 34860044 DOI: 10.1103/physrevlett.127.207206] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2021] [Accepted: 09/23/2021] [Indexed: 06/13/2023]
Abstract
We report the observation of the unidirectional spin Hall magnetoresistance (USMR), which depends on the current or magnetization direction, in heavy-metal-ferromagnetic-insulator bilayer, Pt-Y_{3}Fe_{5}O_{12} (YIG). This USMR is apparently not caused by the mechanisms established in metallic bilayer, in which the ferromagnetic layer is required to be electrically conductive. From the magnetic field, current, temperature, and YIG thickness dependent measurements, the USMR is attributed to the asymmetric magnon creation and annihilation induced by the spin-orbit torque. This asymmetry and the resultant USMR are further revealed by the micromagnetic simulations combined with the spin-orbit torque and the spin drift-diffusion model. Our finding exhibits a nonlinear manipulation of magnons with the charge current.
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Affiliation(s)
- G Liu
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Xi-Guang Wang
- School of Physics and Electronics, Central South University, Changsha 410083, People's Republic of China
| | - Z Z Luan
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - L F Zhou
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - S Y Xia
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - B Yang
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Y Z Tian
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - Guang-Hua Guo
- School of Physics and Electronics, Central South University, Changsha 410083, People's Republic of China
| | - J Du
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
| | - D Wu
- National Laboratory of Solid State Microstructures, Jiangsu Provincial Key Laboratory for Nanotechnology, Collaborative Innovation Center of Advanced Microstructures and Department of Physics, Nanjing University, Nanjing 210093, People's Republic of China
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16
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Freimuth F, Blügel S, Mokrousov Y. Theory of unidirectional magnetoresistance and nonlinear Hall effect. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 34:055301. [PMID: 34678787 DOI: 10.1088/1361-648x/ac327f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/22/2021] [Indexed: 06/13/2023]
Abstract
We study the unidirectional magnetoresistance (UMR) and the nonlinear Hall effect (NLHE) in the ferromagnetic Rashba model. For this purpose we derive expressions to describe the response of the electric current quadratic in the applied electric field. We compare two different formalisms, namely the standard Keldysh nonequilibrium formalism and the Moyal-Keldysh formalism, to derive the nonlinear conductivities of UMR and NLHE. We find that both formalisms lead to identical numerical results when applied to the ferromagnetic Rashba model. The UMR and the NLHE nonlinear conductivities tend to be comparable in magnitude according to our calculations. Additionally, their dependencies on the Rashba parameter and on the quasiparticle broadening are similar. The nonlinear zero-frequency response considered here is several orders of magnitude higher than the one at optical frequencies that describes the photocurrent generation in the ferromagnetic Rashba model. Additionally, we compare our Keldysh nonequilibrium expression in the independent-particle approximation to literature expressions of the UMR that have been obtained within the constant relaxation time approximation of the Boltzmann formalism. We find that both formalisms converge to the same analytical formula in the limit of infinite relaxation time. However, remarkably, we find that the Boltzmann result does not correspond to the intraband term of the Keldysh expression. Instead, the Boltzmann result corresponds to the sum of the intraband term and an interband term that can be brought into the form of an effective intraband term due to thef-sum rule.
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Affiliation(s)
- Frank Freimuth
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
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17
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Ogrodnik P, Grochot K, Karwacki Ł, Kanak J, Prokop M, Chȩciński J, Skowroński W, Ziȩtek S, Stobiecki T. Study of Spin-Orbit Interactions and Interlayer Ferromagnetic Coupling in Co/Pt/Co Trilayers in a Wide Range of Heavy-Metal Thickness. ACS APPLIED MATERIALS & INTERFACES 2021; 13:47019-47032. [PMID: 34558910 PMCID: PMC8519406 DOI: 10.1021/acsami.1c11675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/22/2021] [Accepted: 09/14/2021] [Indexed: 06/13/2023]
Abstract
The spin-orbit torque, a torque induced by a charge current flowing through the heavy-metal-conducting layer with strong spin-orbit interactions, provides an efficient way to control the magnetization direction in heavy-metal/ferromagnet nanostructures, required for applications in the emergent magnetic technologies like random access memories, high-frequency nano-oscillators, or bioinspired neuromorphic computations. We study the interface properties, magnetization dynamics, magnetostatic features, and spin-orbit interactions within the multilayer system Ti(2)/Co(1)/Pt(0-4)/Co(1)/MgO(2)/Ti(2) (thicknesses in nanometers) patterned by optical lithography on micrometer-sized bars. In the investigated devices, Pt is used as a source of the spin current and as a nonmagnetic spacer with variable thickness, which enables the magnitude of the interlayer ferromagnetic exchange coupling to be effectively tuned. We also find the Pt thickness-dependent changes in magnetic anisotropies, magnetoresistances, effective Hall angles, and, eventually, spin-orbit torque fields at interfaces. The experimental findings are supported by the relevant interface structure-related simulations, micromagnetic, macrospin, as well as the spin drift-diffusion models. Finally, the contribution of the spin-orbital Edelstein-Rashba interfacial fields is also briefly discussed in the analysis.
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Affiliation(s)
- Piotr Ogrodnik
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
- Faculty of Physics, Warsaw University of
Technology, 00-662 Warsaw, Poland
| | - Krzysztof Grochot
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
- Faculty of Physics and Applied Computer Science,
AGH University of Science and Technology, 30-059
Kraków, Poland
| | - Łukasz Karwacki
- Institute for Theoretical Physics,
Utrecht University, Princetonplein 5, 3584 CC Utrecht,
The Netherlands
- Institute of Molecular Physics, Polish Academy
of Sciences, ul. M. Smoluchowskiego 17, 60-179 Poznań,
Poland
| | - Jarosław Kanak
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
| | - Michał Prokop
- Catalan Institute of Nanoscience and Nanotechnology
(ICN2), CSIC and BIST, Campus UAB, Bellaterra, 08193 Barcelona,
Spain
| | - Jakub Chȩciński
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
| | - Witold Skowroński
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
| | - Sławomir Ziȩtek
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
| | - Tomasz Stobiecki
- Institute of Electronics, AGH University
of Science and Technology, 30-059 Kraków,
Poland
- Faculty of Physics and Applied Computer Science,
AGH University of Science and Technology, 30-059
Kraków, Poland
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18
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Isogami S, Shiokawa Y, Tsumita A, Komura E, Ishitani Y, Hamanaka K, Taniguchi T, Mitani S, Sasaki T, Hayashi M. Spin-orbit torque driven magnetization switching in W/CoFeB/MgO-based type-Y three terminal magnetic tunnel junctions. Sci Rep 2021; 11:16676. [PMID: 34404830 PMCID: PMC8371175 DOI: 10.1038/s41598-021-95422-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 07/19/2021] [Indexed: 11/09/2022] Open
Abstract
We have studied current induced magnetization switching in W/CoFeB/MgO based three terminal magnetic tunnel junctions. The switching driven by spin—orbit torque (SOT) is evaluated in the so-called type-Y structure, in which the magnetic easy-axis of the CoFeB layer lies in the film plane and is orthogonal to the current flow. The effective spin Hall angle estimated from the bias field dependence of critical current (Ic) is ~ 0.07. The field and current dependence of the switching probability are studied. The field and DC current induced switching can be described using a model based on thermally assisted magnetization switching. In contrast, the 50 ns long pulse current dependence of the switching probability shows significant deviation from the model, even if contribution from the field-like torque is included. The deviation is particularly evident when the threshold switching current is larger. These results show that conventional thermally assisted magnetization switching model cannot be used to describe SOT induced switching using short current pulses.
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Affiliation(s)
- Shinji Isogami
- National Institute for Materials Science, Tsukuba, 305-0047, Japan.
| | | | | | | | | | | | - Tomohiro Taniguchi
- Research Center for Emerging Computing Technologies, National Institute of Advanced Industrial Science and Technology, Tsukuba, 305-8560, Japan.
| | - Seiji Mitani
- National Institute for Materials Science, Tsukuba, 305-0047, Japan
| | | | - Masamitsu Hayashi
- National Institute for Materials Science, Tsukuba, 305-0047, Japan.,The University of Tokyo, Tokyo, 113-8654, Japan
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19
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Holanda J, Santos OA, Mendes JBS, Rezende SM. Spin-to-charge conversion and interface-induced spin Hall magnetoresistance in yttrium iron garnet/metallic bilayers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:435803. [PMID: 34293724 DOI: 10.1088/1361-648x/ac16f7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Accepted: 07/22/2021] [Indexed: 06/13/2023]
Abstract
We report the investigation of spin-to-charge current interconversion process in hybrid structures of yttrium iron garnet (YIG)/metallic bilayers by means of two different experimental techniques: spin pumping effect (SPE) and spin Hall magnetoresistance (SMR). We demonstrate the evidence of a correlation between spin-to-charge conversion and SMR in bilayers of YIG/Pd, YIG/Pt, and YIG/IrMn. The correlation was verified directly in the spin Hall angles and the amplitudes of the voltage signals measured by the SPE and SMR techniques. The detection of SMR was carried out using the modulated magnetoresistance technique and lock-in amplifier detection. For these measurements, we present a simple model for the interpretation of the results. The results allow us to conclude that indeed the interface in the YIG/metallic bilayers has a dominant role in the spin-to-charge current conversion and SMR.
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Affiliation(s)
- J Holanda
- Departamento de Física, Universidade Federal do Espírito Santo, 29075-910, Vitória, ES, Brazil
| | - O Alves Santos
- Physics of Nanodevices, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, Groningen, AG 9747, The Netherlands
| | - J B S Mendes
- Departamento de Física, Universidade Federal de Viçosa, 36570-900 Viçosa, MG, Brazil
| | - S M Rezende
- Departamento de Física, Universidade Federal de Pernambuco, 50670-901, Recife, PE, Brazil
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20
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Panda SN, Majumder S, Bhattacharyya A, Dutta S, Choudhury S, Barman A. Structural Phase-Dependent Giant Interfacial Spin Transparency in W/CoFeB Thin-Film Heterostructures. ACS APPLIED MATERIALS & INTERFACES 2021; 13:20875-20884. [PMID: 33886256 DOI: 10.1021/acsami.1c03776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Pure spin current has transformed the research field of conventional spintronics due to its various advantages, including energy efficiency. An efficient mechanism for generation of pure spin current is spin pumping, and high effective spin-mixing conductance (Geff) and interfacial spin transparency (T) are essential for its higher efficiency. By employing the time-resolved magneto-optical Kerr effect technique, we report here a giant value of T in substrate/W (t)/Co20Fe60B20 (d)/SiO2 (2 nm) thin-film heterostructures in the beta-tungsten (β-W) phase. We extract the spin diffusion length of W and spin-mixing conductance of the W/CoFeB interface from the variation of damping as a function of W and CoFeB thickness. This leads to a value of T = 0.81 ± 0.03 for the β-W/CoFeB interface. A stark variation of Geff and T with the thickness of the W layer is obtained in accordance with the structural phase transition and resistivity variation of W with its thickness. Effects such as spin memory loss and two-magnon scattering are found to have minor contributions to damping modulation in comparison to the spin pumping effect which is reconfirmed from the unchanged damping constant with the variation of Cu spacer layer thickness inserted between W and CoFeB. The giant interfacial spin transparency and its strong dependence on crystal structures of W will be important for future spin-orbitronic devices based on pure spin current.
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Affiliation(s)
- Surya Narayan Panda
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | - Sudip Majumder
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | - Arpan Bhattacharyya
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | - Soma Dutta
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | - Samiran Choudhury
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
| | - Anjan Barman
- Department of Condensed Matter Physics and Material Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, Salt Lake, Kolkata 700 106, India
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21
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Lou PC, Katailiha A, Bhardwaj RG, Beyermann WP, Juraschek DM, Kumar S. Large Magnetic Moment in Flexoelectronic Silicon at Room Temperature. NANO LETTERS 2021; 21:2939-2945. [PMID: 33739114 DOI: 10.1021/acs.nanolett.1c00052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Time-dependent rotational electric polarizations have been proposed to generate temporally varying magnetic moments, for example, through a combination of ferroelectric polarization and optical phonons. This phenomenon has been called dynamical multiferroicity, but explicit experimental demonstrations have been elusive to date. Here, we report the detection of a temporal magnetic moment as high as 1.2 μB/atom in a charge-doped thin film of silicon under flexural strain. We demonstrate that the magnetic moment is generated by a combination of electric polarization arising from a flexoelectronic charge separation along the strain gradient and the deformation potential of phonons. The effect can be controlled by adjusting the external strain gradient, doping concentration, and dopant and can be regarded as a dynamical multiferroic effect involving flexoelectronic polarization instead of ferroelectricity. The discovery of a large magnetic moment in silicon may enable the use of nonmagnetic and nonferroelectric semiconductors in various multiferroic and spintronic applications.
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Affiliation(s)
- Paul C Lou
- Department of Mechanical Engineering, University of California, Riverside, California 92521, United States
| | - Anand Katailiha
- Department of Mechanical Engineering, University of California, Riverside, California 92521, United States
| | - Ravindra G Bhardwaj
- Department of Mechanical Engineering, University of California, Riverside, California 92521, United States
| | - Ward P Beyermann
- Department of Physics and Astronomy, University of California, Riverside, California 92521, United States
| | - Dominik M Juraschek
- Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02145, United States
| | - Sandeep Kumar
- Department of Mechanical Engineering, University of California, Riverside, California 92521, United States
- Materials Science and Engineering Program, University of California, Riverside, California 92521, United States
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22
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Kawada T, Kawaguchi M, Funato T, Kohno H, Hayashi M. Acoustic spin Hall effect in strong spin-orbit metals. SCIENCE ADVANCES 2021; 7:7/2/eabd9697. [PMID: 33523974 PMCID: PMC7787480 DOI: 10.1126/sciadv.abd9697] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Accepted: 11/13/2020] [Indexed: 06/12/2023]
Abstract
We report on the observation of the acoustic spin Hall effect that facilitates lattice motion-induced spin current via spin-orbit interaction (SOI). Under excitation of surface acoustic wave (SAW), we find that a spin current flows orthogonal to the SAW propagation in nonmagnetic metals (NMs). The acoustic spin Hall effect manifests itself in a field-dependent acoustic voltage in NM/ferromagnetic metal bilayers. The acoustic voltage takes a maximum when the NM layer thickness is close to its spin diffusion length, vanishes for NM layers with weak SOI, and increases linearly with the SAW frequency. To account for these results, we find that the spin current must scale with the SOI and the time derivative of the lattice displacement. These results, which imply the strong coupling of electron spins with rotating lattices via the SOI, show the potential of lattice dynamics to supply spin current in strong spin-orbit metals.
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Affiliation(s)
- Takuya Kawada
- Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan
| | - Masashi Kawaguchi
- Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan.
| | - Takumi Funato
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan
| | - Hiroshi Kohno
- Department of Physics, Nagoya University, Nagoya 464-8602, Japan
| | - Masamitsu Hayashi
- Department of Physics, The University of Tokyo, Tokyo 113-0033, Japan.
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23
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Wang Z, Cheng H, Shi K, Liu Y, Qiao J, Zhu D, Cai W, Zhang X, Eimer S, Zhu D, Zhang J, Fert A, Zhao W. Modulation of field-like spin orbit torque in heavy metal/ferromagnet heterostructures. NANOSCALE 2020; 12:15246-15251. [PMID: 32643741 DOI: 10.1039/d0nr02762f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Spin orbit torque (SOT) has drawn widespread attention in the emerging field of magnetic memory devices, such as magnetic random access memory (MRAM). To promote the performance of SOT-MRAM, most efforts have been devoted to enhance the SOT switching efficiency by improving the damping-like torque. Recently, some studies noted that the field-like torque also plays a crucial role in the nanosecond-timescale SOT dynamics. However, there is not yet an effective way to tune its relative amplitude. Here, we experimentally modulate the field-like SOT in W/CoFeB/MgO trilayers through tuning the interfacial spin accumulation. By performing spin Hall magnetoresistance measurement, we find that the CoFeB with enhanced spin dephasing, either generated from larger layer thickness or from proper annealing, can distinctly boost the spin absorption and enhance the interfacial spin mixing conductance Gr. While the damping-like torque efficiency increases with Gr, the field-like torque efficiency is found to decrease with it. The results suggest that the interfacial spin accumulation, which largely contributes to the field-like torque, is reduced by higher interfacial spin transparency. Our work shows a new path to further improve the performance of SOT-based ultrafast magnetic devices.
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Affiliation(s)
- Zilu Wang
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao, China and Hefei Innovation Research Institute, Beihang University, Hefei 230013, China
| | - Houyi Cheng
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Hefei Innovation Research Institute, Beihang University, Hefei 230013, China
| | - Kewen Shi
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
| | - Yang Liu
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
| | - Junfeng Qiao
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
| | - Daoqian Zhu
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
| | - Wenlong Cai
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
| | - Xueying Zhang
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao, China
| | - Sylvain Eimer
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Hefei Innovation Research Institute, Beihang University, Hefei 230013, China
| | - Dapeng Zhu
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao, China
| | - Jie Zhang
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China.
| | - Albert Fert
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Unité Mixte de Physique, CNRS, Thales, University of Paris-Saclay, Palaiseau, France
| | - Weisheng Zhao
- Fert Beijing Institute, School of Microelectronics, Beijing Advanced Innovation Center for Big Data and Brain Computing, Beihang University, 100191, China. and Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute, Beihang University, Qingdao, China and Hefei Innovation Research Institute, Beihang University, Hefei 230013, China
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24
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Kang MG, Go G, Kim KW, Choi JG, Park BG, Lee KJ. Negative spin Hall magnetoresistance of normal metal/ferromagnet bilayers. Nat Commun 2020; 11:3619. [PMID: 32681024 PMCID: PMC7367820 DOI: 10.1038/s41467-020-17463-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2020] [Accepted: 06/27/2020] [Indexed: 11/21/2022] Open
Abstract
Interconversion between charge and spin through spin-orbit coupling lies at the heart of condensed-matter physics. In normal metal/ferromagnet bilayers, a concerted action of the interconversions, the spin Hall effect and its inverse effect of normal metals, results in spin Hall magnetoresistance, whose sign is always positive regardless of the sign of spin Hall conductivity of normal metals. Here we report that the spin Hall magnetoresistance of Ta/NiFe bilayers is negative, necessitating an additional interconversion process. Our theory shows that the interconversion owing to interfacial spin-orbit coupling at normal metal/ferromagnet interfaces can give rise to negative spin Hall magnetoresistance. Given that recent studies found the conversion from charge currents to spin currents at normal metal/ferromagnet interfaces, our work provides a missing proof of its reciprocal spin-current-to-charge-current conversion at same interface. Our result suggests that interfacial spin-orbit coupling effect can dominate over bulk effects, thereby demanding interface engineering for advanced spintronics devices.
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Affiliation(s)
- Min-Gu Kang
- Department of Materials Science and Engineering, KAIST, Daejeon, 34141, Korea
| | - Gyungchoon Go
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, Korea
| | - Kyoung-Whan Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Korea
| | - Jong-Guk Choi
- Department of Materials Science and Engineering, KAIST, Daejeon, 34141, Korea
| | - Byong-Guk Park
- Department of Materials Science and Engineering, KAIST, Daejeon, 34141, Korea.
| | - Kyung-Jin Lee
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, Korea.
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea.
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25
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Karwacki Ł, Grochot K, Łazarski S, Skowroński W, Kanak J, Powroźnik W, Barnaś J, Stobiecki F, Stobiecki T. Optimization of spin Hall magnetoresistance in heavy-metal/ferromagnetic-metal bilayers. Sci Rep 2020; 10:10767. [PMID: 32612163 PMCID: PMC7329912 DOI: 10.1038/s41598-020-67450-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Accepted: 06/08/2020] [Indexed: 11/22/2022] Open
Abstract
We present experimental data and their theoretical description on spin Hall magnetoresistance (SMR) in bilayers consisting of a heavy metal (H) coupled to in-plane magnetized ferromagnetic metal (F), and determine contributions to the magnetoresistance due to SMR and anisotropic magnetoresistance (AMR) in five different bilayer systems: [Formula: see text], [Formula: see text], [Formula: see text], W/Co, and Co/Pt. The devices used for experiments have different interfacial properties due to either amorphous or crystalline structures of constitutent layers. To determine magnetoresistance contributions and to allow for optimization, the AMR is explicitly included in the diffusion transport equations in the ferromagnets. The results allow determination of different contributions to the magnetoresistance, which can play an important role in optimizing prospective magnetic stray field sensors. They also may be useful in the determination of spin transport properties of metallic magnetic heterostructures in other experiments based on magnetoresistance measurements.
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Affiliation(s)
- Łukasz Karwacki
- Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179, Poznań, Poland.
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland.
| | - Krzysztof Grochot
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland.
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059, Kraków, Poland.
| | - Stanisław Łazarski
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland
| | - Witold Skowroński
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland
| | - Jarosław Kanak
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland
| | - Wiesław Powroźnik
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland
| | - Józef Barnaś
- Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179, Poznań, Poland
- Faculty of Physics, Adam Mickiewicz University, ul. Uniwersytetu Poznańskiego 2, 61-614, Poznań, Poland
| | - Feliks Stobiecki
- Institute of Molecular Physics, Polish Academy of Sciences, ul. M. Smoluchowskiego 17, 60-179, Poznań, Poland
| | - Tomasz Stobiecki
- Department of Electronics, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059, Kraków, Poland
- Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059, Kraków, Poland
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26
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Safranski C, Sun JZ, Xu JW, Kent AD. Planar Hall Driven Torque in a Ferromagnet/Nonmagnet/Ferromagnet System. PHYSICAL REVIEW LETTERS 2020; 124:197204. [PMID: 32469573 DOI: 10.1103/physrevlett.124.197204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 04/22/2020] [Indexed: 06/11/2023]
Abstract
An important goal of spintronics is to covert a charge current into a spin current with a controlled spin polarization that can exert torques on an adjacent magnetic layer. Here we demonstrate such torques in a two ferromagnet system. A CoNi multilayer is used as a spin current source in a sample with structure CoNi/Au/CoFeB. Spin torque ferromagnetic resonance is used to measure the torque on the CoFeB layer. The response as a function of the applied field angle and current is consistent with the symmetry expected for a torque produced by the planar Hall effect originating in CoNi. We find the strength of this effect to be comparable to that of the spin Hall effect in platinum, indicating that the planar Hall effect holds potential as a spin current source with a controllable polarization direction.
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Affiliation(s)
| | - Jonathan Z Sun
- IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA
| | - Jun-Wen Xu
- Center for Quantum Phenomena, Department of Physics, New York University, New York, New York 10003, USA
| | - Andrew D Kent
- Center for Quantum Phenomena, Department of Physics, New York University, New York, New York 10003, USA
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27
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Chi Z, Lau YC, Xu X, Ohkubo T, Hono K, Hayashi M. The spin Hall effect of Bi-Sb alloys driven by thermally excited Dirac-like electrons. SCIENCE ADVANCES 2020; 6:eaay2324. [PMID: 32181344 PMCID: PMC7060068 DOI: 10.1126/sciadv.aay2324] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Accepted: 11/27/2019] [Indexed: 05/26/2023]
Abstract
We have studied the charge to spin conversion in Bi1-x Sb x /CoFeB heterostructures. The spin Hall conductivity (SHC) of the sputter-deposited heterostructures exhibits a high plateau at Bi-rich compositions, corresponding to the topological insulator phase, followed by a decrease of SHC for Sb-richer alloys, in agreement with the calculated intrinsic spin Hall effect of Bi1-x Sb x . The SHC increases with increasing Bi1-x Sb x thickness before it saturates, indicating that it is the bulk of the alloy that predominantly contributes to the generation of spin current; the topological surface states, if present, play little role. Unexpectedly, the SHC is found to increase with increasing temperature, following the trend of carrier density. These results suggest that the large SHC at room temperature, with a spin Hall efficiency exceeding 1 and an extremely large spin current mobility, is due to increased number of thermally excited Dirac-like electrons in the L valley of the narrow gap Bi1-x Sb x alloy.
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Affiliation(s)
- Zhendong Chi
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - Yong-Chang Lau
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
- Institute for Materials Research (IMR), Tohoku University, Sendai 980-8577, Japan
| | - Xiandong Xu
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - Tadakatsu Ohkubo
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - Kazuhiro Hono
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - Masamitsu Hayashi
- Department of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
- National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
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28
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Dyrdał A, Barnaś J, Fert A. Spin-Momentum-Locking Inhomogeneities as a Source of Bilinear Magnetoresistance in Topological Insulators. PHYSICAL REVIEW LETTERS 2020; 124:046802. [PMID: 32058752 DOI: 10.1103/physrevlett.124.046802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 12/15/2019] [Indexed: 06/10/2023]
Abstract
A new mechanism of bilinear magnetoresistance (BMR) is proposed and studied theoretically within the minimal model describing surface electronic states in topological insulators. The BMR appears as a consequence of the second-order response to electric field, and depends linearly on both magnetic field and current (electric field). The mechanism is based on the interplay of current-induced spin polarization and scattering processes due to inhomogeneities of spin-momentum locking, that unavoidably appear as a result of structural defects in topological insulators. The proposed mechanism leads to the BMR even if the electronic band structure is isotropic (e.g., absence of hexagonal warping), and is shown to be dominant at lower Fermi energies.
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Affiliation(s)
- A Dyrdał
- Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
- Institut für Physik, Martin-Luther-Universität HalleWittenberg, 06099 Halle (Saale), Germany
| | - J Barnaś
- Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań, Poland
| | - A Fert
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
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29
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Guillet T, Zucchetti C, Barbedienne Q, Marty A, Isella G, Cagnon L, Vergnaud C, Jaffrès H, Reyren N, George JM, Fert A, Jamet M. Observation of Large Unidirectional Rashba Magnetoresistance in Ge(111). PHYSICAL REVIEW LETTERS 2020; 124:027201. [PMID: 32004027 DOI: 10.1103/physrevlett.124.027201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 09/04/2019] [Indexed: 06/10/2023]
Abstract
Relating magnetotransport properties to specific spin textures at surfaces or interfaces is an intense field of research nowadays. Here, we investigate the variation of the electrical resistance of Ge(111) grown epitaxially on semi-insulating Si(111) under the application of an external magnetic field. We find a magnetoresistance term that is linear in current density j and magnetic field B, hence, odd in j and B, corresponding to a unidirectional magnetoresistance. At 15 K, for I=10 μA (or j=0.33 A m^{-1}) and B=1 T, it represents 0.5% of the zero field resistance, a much higher value compared to previous reports on unidirectional magnetoresistance (UMR). We ascribe the origin of this magnetoresistance to the interplay between the externally applied magnetic field and the pseudomagnetic field generated by the current applied in the spin-splitted subsurface states of Ge(111). This unidirectional magnetoresistance is independent of the current direction with respect to the Ge crystal axes. It progressively vanishes, either using a negative gate voltage due to carrier activation into the bulk (without spin-splitted bands), or by increasing the temperature due to the Rashba energy splitting of the subsurface states lower than ∼58k_{B}. We believe that UMR could be used as a powerful probe of the spin-orbit interaction in a wide range of materials.
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Affiliation(s)
- T Guillet
- Université Grenoble Alpes, CEA, CNRS, Grenoble INP, IRIG-SPINTEC, 38000 Grenoble, France
| | - C Zucchetti
- LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - Q Barbedienne
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - A Marty
- Université Grenoble Alpes, CEA, CNRS, Grenoble INP, IRIG-SPINTEC, 38000 Grenoble, France
| | - G Isella
- LNESS-Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy
| | - L Cagnon
- Université Grenoble Alpes, CNRS, Grenoble INP, Institut NEEL, 38000 Grenoble, France
| | - C Vergnaud
- Université Grenoble Alpes, CEA, CNRS, Grenoble INP, IRIG-SPINTEC, 38000 Grenoble, France
| | - H Jaffrès
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - N Reyren
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - J-M George
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - A Fert
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, 91767, Palaiseau, France
| | - M Jamet
- Université Grenoble Alpes, CEA, CNRS, Grenoble INP, IRIG-SPINTEC, 38000 Grenoble, France
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30
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Philippi-Kobs A, Farhadi A, Matheis L, Lott D, Chuvilin A, Oepen HP. Impact of Symmetry on Anisotropic Magnetoresistance in Textured Ferromagnetic Thin Films. PHYSICAL REVIEW LETTERS 2019; 123:137201. [PMID: 31697508 DOI: 10.1103/physrevlett.123.137201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Indexed: 06/10/2023]
Abstract
We report on the magnetoresistance of textured films consisting of 3d-ferromagnetic layers sandwiched by Pt. While the conventional cos^{2}φ behavior of the anisotropic magnetoresistance (AMR) is found when the magnetization M is varied in the film plane, cos^{2n}θ contributions (2n≤6) exist for rotating M in the plane perpendicular to the current. This finding is explained by the symmetry-adapted modeling of AMR of textured films demonstrating that the cos^{2}θ behavior cannot be used as a fingerprint for the presence of spin Hall magnetoresistance (SMR). Further, the interfacial MR contributions for Pt/Ni/Pt contradict the SMR behavior confirming the dominant role of AMR in all-metallic systems.
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Affiliation(s)
- A Philippi-Kobs
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany
- Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - A Farhadi
- Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - L Matheis
- Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
| | - D Lott
- Institute for Materials Research, Helmholtz-Zentrum Geesthacht, Max-Planck-Straße 1, 21502 Geesthacht, Germany
| | - A Chuvilin
- Centro de Investigación Cooperativa nanoGUNE, Av. de Tolosa 76, E-20018 San Sebastian, Spain
- IKERBASQUE, Basque Foundation for Science, Maria Diaz de Haro 3, E-480013 Bilbao, Spain
| | - H P Oepen
- Institut für Nanostruktur- und Festkörperphysik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
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31
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Chen S, Yu J, Xie Q, Zhang X, Lin W, Liu L, Zhou J, Shu X, Guo R, Zhang Z, Chen J. Free Field Electric Switching of Perpendicularly Magnetized Thin Film by Spin Current Gradient. ACS APPLIED MATERIALS & INTERFACES 2019; 11:30446-30452. [PMID: 31347362 DOI: 10.1021/acsami.9b09146] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
To realize high-speed nonvolatile magnetic memory with low energy consumption, electric switching of perpendicular magnetization by spin-orbit torque in the heavy metal/ferromagnetic (HM/FM) structure has recently attracted intensive attention. Conventionally, an external in-plane magnetic field for breaking the symmetry is required for achieving electric switching of perpendicular magnetization. However, electric switching without external field is the prerequisite for the integration of magnetic functionality into the integrated circuit devices. Here, we propose a new method of utilizing a W wedge in the Pt/W/FM structure to induce a spin current gradient, which can result in an in-plane equivalent field along the wedge thickness gradient direction. We experimentally demonstrate the deterministic magnetization switching of perpendicular Co/Ni multilayers without external magnetic field when the electric current is along the wedge thickness gradient direction. Our findings shed light on free field electric switching of magnetization by a new physical parameter-an asymmetric spin current induced by a bilayer wedge structure.
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Affiliation(s)
- Shaohai Chen
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Jihang Yu
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Qidong Xie
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Xiangli Zhang
- Key Lab of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering , Fudan University , Shanghai 200433 , China
| | - Weinan Lin
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Liang Liu
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Jing Zhou
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Xinyu Shu
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Rui Guo
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
| | - Zongzhi Zhang
- Key Lab of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering , Fudan University , Shanghai 200433 , China
| | - Jingsheng Chen
- Department of Materials Science and Engineering , National University of Singapore , 117576 , Singapore
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32
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Zhu L, Ralph DC, Buhrman RA. Effective Spin-Mixing Conductance of Heavy-Metal-Ferromagnet Interfaces. PHYSICAL REVIEW LETTERS 2019; 123:057203. [PMID: 31491309 DOI: 10.1103/physrevlett.123.057203] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Indexed: 06/10/2023]
Abstract
The effective spin-mixing conductance (G_{eff}^{↑↓}) of a heavy-metal-ferromagnet (HM-FM) interface characterizes the efficiency of the interfacial spin transport. Accurately determining G_{eff}^{↑↓} is critical to the quantitative understanding of measurements of direct and inverse spin Hall effects. G_{eff}^{↑↓} is typically ascertained from the inverse dependence of magnetic damping on the FM thickness under the assumption that spin pumping is the dominant mechanism affecting this dependence. We report that this assumption fails badly in many in-plane magnetized prototypical HM-FM systems in the nanometer-scale thickness regime. Instead, the majority of the damping is from two-magnon scattering at the FM interface, while spin-memory-loss scattering at the interface can also be significant. If these two effects are neglected, the results will be an unphysical "giant" apparent G_{eff}^{↑↓} and hence considerable underestimation of both the spin Hall ratio and the spin Hall conductivity in inverse or direct spin Hall experiments.
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Affiliation(s)
- Lijun Zhu
- Cornell University, Ithaca, New York 14850, USA
| | - Daniel C Ralph
- Cornell University, Ithaca, New York 14850, USA
- Kavli Institute at Cornell, Ithaca, New York 14853, USA
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33
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Fan Y, Shao Q, Pan L, Che X, He Q, Yin G, Zheng C, Yu G, Nie T, Masir MR, MacDonald AH, Wang KL. Unidirectional Magneto-Resistance in Modulation-Doped Magnetic Topological Insulators. NANO LETTERS 2019; 19:692-698. [PMID: 30685979 DOI: 10.1021/acs.nanolett.8b03702] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Nonlinear unidirectional spin Hall magnetoresistance (USMR) has been reported in heavy metal/ferromagnet bilayers, which could be employed as an effective method in detecting the magnetization orientation in spintronic devices with two-terminal geometry. Recently, another unidirectional magnetoresistance (UMR) was reported in magnetic topological insulator (TI)-based heterostructures at cryogenic temperature, whose amplitude is orders of magnitude larger than the USMR measured in heavy metal-based magnetic heterostructures at room temperature. Here, we report the UMR effect in the modulation-doped magnetic TI structures. This UMR arises due to the interplay between the magnetic dopant's magnetization and the current-induced surface spin polarization, when they are parallel or antiparallel to each other in the TI material. By varying the dopant's position in the structure, we reveal that the UMR is mainly originating from the interaction between the magnetization and the surface spin-polarized carriers (not bulk carriers). Furthermore, from the magnetic field-, the angular rotation-, and the temperature-dependence, we highlight the correlation between the UMR effect and the magnetism in the structures. The large UMR versus current ratio in TI-based magnetic bilayers promises the easy readout in TI-based spintronic devices with two-terminal geometry.
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Affiliation(s)
- Yabin Fan
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
- Microsystems Technology Laboratories , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Qiming Shao
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Lei Pan
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Xiaoyu Che
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Qinglin He
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Gen Yin
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Cheng Zheng
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Guoqiang Yu
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
| | - Tianxiao Nie
- Fert Beijing Institute, BDBC, and School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Massoud R Masir
- Department of Physics and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712-0264 , United States
| | - Allan H MacDonald
- Department of Physics and Center for Complex Quantum Systems , University of Texas at Austin , Austin , Texas 78712-0264 , United States
| | - Kang L Wang
- Department of Electrical and Computer Engineering , University of California , Los Angeles , California 90095 , United States
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34
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Huang Z, Renshaw Wang X, Rusydi A, Chen J, Yang H, Venkatesan T. Interface Engineering and Emergent Phenomena in Oxide Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1802439. [PMID: 30133012 DOI: 10.1002/adma.201802439] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Revised: 07/06/2018] [Indexed: 06/08/2023]
Abstract
Complex oxide interfaces have mesmerized the scientific community in the last decade due to the possibility of creating tunable novel multifunctionalities, which are possible owing to the strong interaction among charge, spin, orbital, and structural degrees of freedom. Artificial interfacial modifications, which include defects, formal polarization, structural symmetry breaking, and interlayer interaction, have led to novel properties in various complex oxide heterostructures. These emergent phenomena not only serve as a platform for investigating strong electronic correlations in low-dimensional systems but also provide potentials for exploring next-generation electronic devices with high functionality. Herein, some recently developed strategies in engineering functional oxide interfaces and their emergent properties are reviewed.
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Affiliation(s)
- Zhen Huang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Xiao Renshaw Wang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Andrivo Rusydi
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Jingsheng Chen
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Hyunsoo Yang
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
| | - Thirumalai Venkatesan
- NUSNNI-NanoCore, National University of Singapore, 5A Engineering Drive 1, Singapore, 117411, Singapore
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35
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Pham TKH, Ribeiro M, Park JH, Lee NJ, Kang KH, Park E, Nguyen VQ, Michel A, Yoon CS, Cho S, Kim TH. Interface morphology effect on the spin mixing conductance of Pt/Fe 3O 4 bilayers. Sci Rep 2018; 8:13907. [PMID: 30224773 PMCID: PMC6141513 DOI: 10.1038/s41598-018-31915-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 08/29/2018] [Indexed: 11/25/2022] Open
Abstract
Non-magnetic (NM) metals with strong spin-orbit coupling have been recently explored as a probe of interface magnetism on ferromagnetic insulators (FMI) by means of the spin Hall magnetoresistance (SMR) effect. In NM/FMI heterostructures, increasing the spin mixing conductance (SMC) at the interface comes as an important step towards devices with maximized SMR. Here we report on the study of SMR in Pt/Fe3O4 bilayers at cryogenic temperature, and identify a strong dependence of the determined real part of the complex SMC on the interface roughness. We tune the roughness of the Pt/Fe3O4 interface by controlling the growth conditions of the Fe3O4 films, namely by varying the thickness, growth technique, and post-annealing processes. Field-dependent and angular-dependent magnetoresistance measurements sustain the clear observation of SMR. The determined real part of the complex SMC of the Pt/Fe3O4 bilayers ranges from 4.96 × 1014 Ω−1 m−2 to 7.16 × 1014 Ω−1 m−2 and increases with the roughness of the Fe3O4 underlayer. We demonstrate experimentally that the interface morphology, acting as an effective interlayer potential, leads to an enhancement of the spin mixing conductance.
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Affiliation(s)
- Thi Kim Hang Pham
- Center for Quantum Nanoscience, Institute for Basic Science, Ewha Womans University, Seoul, 03760, Korea.,Department of Physics, Ewha Womans University, Seoul, 03760, Korea
| | - Mário Ribeiro
- Center for Quantum Nanoscience, Institute for Basic Science, Ewha Womans University, Seoul, 03760, Korea.,Department of Physics, Ewha Womans University, Seoul, 03760, Korea
| | - Jun Hong Park
- Center for Quantum Nanoscience, Institute for Basic Science, Ewha Womans University, Seoul, 03760, Korea.,Department of Physics, Ewha Womans University, Seoul, 03760, Korea
| | - Nyun Jong Lee
- Spin Engineering Physics Team, Division of Scientific Instrumentation, Korea Basic Science Institute, Daejeon, 34133, Korea
| | - Ki Hoon Kang
- Division of Materials Science & Engineering, Hanyang University, Seoul, 04763, Korea
| | - Eunsang Park
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
| | - Van Quang Nguyen
- Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan, 44610, Korea
| | - Anny Michel
- Départment de Physique et Mécanique des Matériaux, Institut Pprime, UPR 3346, CNRS-Université de Poitiers-ENSMA, Poitiers, France
| | - Chong Seung Yoon
- Division of Materials Science & Engineering, Hanyang University, Seoul, 04763, Korea
| | - Sunglae Cho
- Department of Physics and Energy Harvest Storage Research Center, University of Ulsan, Ulsan, 44610, Korea
| | - Tae Hee Kim
- Center for Quantum Nanoscience, Institute for Basic Science, Ewha Womans University, Seoul, 03760, Korea. .,Department of Physics, Ewha Womans University, Seoul, 03760, Korea.
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36
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Avci CO, Mendil J, Beach GSD, Gambardella P. Origins of the Unidirectional Spin Hall Magnetoresistance in Metallic Bilayers. PHYSICAL REVIEW LETTERS 2018; 121:087207. [PMID: 30192570 DOI: 10.1103/physrevlett.121.087207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Indexed: 06/08/2023]
Abstract
Recent studies evidenced the emergence of asymmetric electron transport in layered conductors owing to the interplay between electrical conductivity, magnetization, and the spin Hall or Rashba-Edelstein effects. Here, we investigate the unidirectional magnetoresistance (UMR) caused by the current-induced spin accumulation in Co/Pt and CoCr/Pt bilayers. We identify three competing mechanisms underpinning the resistance asymmetry, namely, interface and bulk spin-dependent electron scattering and electron-magnon scattering. Our measurements provide a consistent description of the current, magnetic field, and temperature dependence of the UMR and show that both positive and negative UMR can be obtained by tuning the interface and bulk spin-dependent scattering.
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Affiliation(s)
- Can Onur Avci
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Johannes Mendil
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Geoffrey S D Beach
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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37
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Yang Y, Luo Z, Wu H, Xu Y, Li RW, Pennycook SJ, Zhang S, Wu Y. Anomalous Hall magnetoresistance in a ferromagnet. Nat Commun 2018; 9:2255. [PMID: 29884868 PMCID: PMC5993777 DOI: 10.1038/s41467-018-04712-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Accepted: 05/17/2018] [Indexed: 11/09/2022] Open
Abstract
The anomalous Hall effect, observed in conducting ferromagnets with broken time-reversal symmetry, offers the possibility to couple spin and orbital degrees of freedom of electrons in ferromagnets. In addition to charge, the anomalous Hall effect also leads to spin accumulation at the surfaces perpendicular to both the current and magnetization direction. Here, we experimentally demonstrate that the spin accumulation, subsequent spin backflow, and spin-charge conversion can give rise to a different type of spin current-related spin current related magnetoresistance, dubbed here as the anomalous Hall magnetoresistance, which has the same angular dependence as the recently discovered spin Hall magnetoresistance. The anomalous Hall magnetoresistance is observed in four types of samples: co-sputtered (Fe1-xMn x )0.6Pt0.4, Fe1-xMn x /Pt multilayer, Fe1-xMn x with x = 0.17-0.65 and Fe, and analyzed using the drift-diffusion model. Our results provide an alternative route to study charge-spin conversion in ferromagnets and to exploit it for potential spintronic applications.
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Affiliation(s)
- Yumeng Yang
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Ziyan Luo
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Haijun Wu
- Department of Materials Science & Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Yanjun Xu
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore
| | - Run-Wei Li
- Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 315201, Ningbo, Republic of China
| | - Stephen J Pennycook
- Department of Materials Science & Engineering, National University of Singapore, Singapore, 117575, Singapore
| | - Shufeng Zhang
- Department of Physics, University of Arizona, Tucson, AZ, 85721, USA
| | - Yihong Wu
- Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore, 117583, Singapore.
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38
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Tsai TY, Chen TY, Wu CT, Chan HI, Pai CF. Spin-orbit torque magnetometry by wide-field magneto-optical Kerr effect. Sci Rep 2018; 8:5613. [PMID: 29618741 PMCID: PMC5884866 DOI: 10.1038/s41598-018-23951-w] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Accepted: 03/23/2018] [Indexed: 11/09/2022] Open
Abstract
Magneto-optical Kerr effect (MOKE) is an efficient approach to probe surface magnetization in thin film samples. Here we present a wide-field MOKE technique that adopts a Köhler illumination scheme to characterize the current-induced damping-like spin-orbit torque (DL-SOT) in micron-sized and unpatterned magnetic heterostructures with perpendicular magnetic anisotropy. Through a current-induced hysteresis loop shift analysis, we quantify the DL-SOT efficiency of a Ta-based heterostructure with bar-shaped geometry, Hall-cross geometry, and unpatterned geometry to be |ξDL| ≈ 0.08. The proposed wide-field MOKE approach therefore provides an instant and direct characterization of DL-SOT, without the need of any further interpretation on electrical signals.
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Affiliation(s)
- Tsung-Yu Tsai
- Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan
| | - Tian-Yue Chen
- Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan
| | - Chun-Ting Wu
- Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan.,Department of Computer Science and Information Engineering, National Taiwan University, Taipei, 10617, Taiwan
| | - Hsin-I Chan
- Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan
| | - Chi-Feng Pai
- Department of Materials Science and Engineering, National Taiwan University, Taipei, 10617, Taiwan.
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39
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Unidirectional spin-Hall and Rashba-Edelstein magnetoresistance in topological insulator-ferromagnet layer heterostructures. Nat Commun 2018; 9:111. [PMID: 29317631 PMCID: PMC5760711 DOI: 10.1038/s41467-017-02491-3] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2017] [Accepted: 11/30/2017] [Indexed: 11/09/2022] Open
Abstract
The large spin−orbit coupling in topological insulators results in helical spin-textured Dirac surface states that are attractive for topological spintronics. These states generate an efficient spin−orbit torque on proximal magnetic moments. However, memory or logic spin devices based upon such switching require a non-optimal three-terminal geometry, with two terminals for the writing current and one for reading the state of the device. An alternative two-terminal device geometry is now possible by exploiting the recent discovery of the unidirectional spin Hall magnetoresistance in heavy metal/ferromagnet bilayers and unidirectional magnetoresistance in magnetic topological insulators. Here, we report the observation of such unidirectional magnetoresistance in a technologically relevant device geometry that combines a topological insulator with a conventional ferromagnetic metal. Our devices show a figure of merit (magnetoresistance per current density per total resistance) that is more than twice as large as the highest reported values in all-metal Ta/Co bilayers. Unidirectional spin Hall magnetoresistance enables the new spintronic devices but is limited by the low amplitude or working temperature. Here, the authors report the large unidirectional spin Hall magnetoresistance in a topological insulator and ferromagnetic metal bilayer system at relatively higher temperature.
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40
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Interface-induced spin Hall magnetoresistance enhancement in Pt-based tri-layer structure. Sci Rep 2018; 8:108. [PMID: 29311703 PMCID: PMC5758776 DOI: 10.1038/s41598-017-18369-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2017] [Accepted: 12/01/2017] [Indexed: 11/08/2022] Open
Abstract
In this study, we integrated bilayer structure of covered Pt on nickel zinc ferrite (NZFO) and CoFe/Pt/NZFO tri-layer structure by pulsed laser deposition system for a spin Hall magnetoresistance (SMR) study. In the bilayer structure, the angular-dependent magnetoresistance (MR) results indicate that Pt/NZFO has a well-defined SMR behavior. Moreover, the spin Hall angle and the spin diffusion length, which were 0.0648 and 1.31 nm, respectively, can be fitted by changing the Pt thickness in the longitudinal SMR function. Particularly, the MR ratio of the bilayer structure (Pt/NZFO) has the highest changing ratio (about 0.135%), compared to the prototype structure Pt/Y3Fe5O12 (YIG) because the NZFO has higher magnetization. Meanwhile, the tri-layer samples (CoFe/Pt/NZFO) indicate that the MR behavior is related with CoFe thickness as revealed in angular-dependent MR measurement. Additionally, comparison between the tri-layer structure with Pt/NZFO and CoFe/Pt bilayer systems suggests that the SMR ratio can be enhanced by more than 70%, indicating that additional spin current should be injected into Pt layer.
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41
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Zhou L, Song H, Liu K, Luan Z, Wang P, Sun L, Jiang S, Xiang H, Chen Y, Du J, Ding H, Xia K, Xiao J, Wu D. Observation of spin-orbit magnetoresistance in metallic thin films on magnetic insulators. SCIENCE ADVANCES 2018; 4:eaao3318. [PMID: 29344574 PMCID: PMC5768179 DOI: 10.1126/sciadv.aao3318] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 11/29/2017] [Indexed: 06/07/2023]
Abstract
A magnetoresistance (MR) effect induced by the Rashba spin-orbit interaction was predicted, but not yet observed, in bilayers consisting of normal metal and ferromagnetic insulator. We present an experimental observation of this new type of spin-orbit MR (SOMR) effect in the Cu[Pt]/Y3Fe5O12 (YIG) bilayer structure, where the Cu/YIG interface is decorated with nanosize Pt islands. This new MR is apparently not caused by the bulk spin-orbit interaction because of the negligible spin-orbit interaction in Cu and the discontinuity of the Pt islands. This SOMR disappears when the Pt islands are absent or located away from the Cu/YIG interface; therefore, we can unambiguously ascribe it to the Rashba spin-orbit interaction at the interface enhanced by the Pt decoration. The numerical Boltzmann simulations are consistent with the experimental SOMR results in the angular dependence of magnetic field and the Cu thickness dependence. Our finding demonstrates the realization of the spin manipulation by interface engineering.
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Affiliation(s)
- Lifan Zhou
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
| | - Hongkang Song
- Department of Physics, Beijing Normal University,
Beijing 100875, P. R. China
- Department of Physics and State Key Laboratory of
Surface Physics, Fudan University, Shanghai 200433, P. R. China
| | - Kai Liu
- Department of Physics and State Key Laboratory of
Surface Physics, Fudan University, Shanghai 200433, P. R. China
| | - Zhongzhi Luan
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
| | - Peng Wang
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
| | - Lei Sun
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
| | - Shengwei Jiang
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
| | - Hongjun Xiang
- Department of Physics and State Key Laboratory of
Surface Physics, Fudan University, Shanghai 200433, P. R. China
- Collaborative Innovation Center of Advanced
Microstructures, Nanjing 210093, P. R. China
| | - Yanbin Chen
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
- Collaborative Innovation Center of Advanced
Microstructures, Nanjing 210093, P. R. China
| | - Jun Du
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
- Collaborative Innovation Center of Advanced
Microstructures, Nanjing 210093, P. R. China
| | - Haifeng Ding
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
- Collaborative Innovation Center of Advanced
Microstructures, Nanjing 210093, P. R. China
| | - Ke Xia
- Department of Physics, Beijing Normal University,
Beijing 100875, P. R. China
| | - Jiang Xiao
- Department of Physics and State Key Laboratory of
Surface Physics, Fudan University, Shanghai 200433, P. R. China
- Collaborative Innovation Center of Advanced
Microstructures, Nanjing 210093, P. R. China
- Institute for Nanoelectronics Devices and Quantum
Computing, Fudan University, Shanghai 200433, P. R. China
| | - Di Wu
- National Laboratory of Solid State Microstructures
and Department of Physics, Nanjing University, Nanjing 210093, P. R.
China
- Collaborative Innovation Center of Advanced
Microstructures, Nanjing 210093, P. R. China
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42
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Kim DJ, Jeon CY, Choi JG, Lee JW, Surabhi S, Jeong JR, Lee KJ, Park BG. Observation of transverse spin Nernst magnetoresistance induced by thermal spin current in ferromagnet/non-magnet bilayers. Nat Commun 2017; 8:1400. [PMID: 29123123 PMCID: PMC5680200 DOI: 10.1038/s41467-017-01493-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2017] [Accepted: 09/21/2017] [Indexed: 11/09/2022] Open
Abstract
Electric generation of spin current via spin Hall effect is of great interest as it allows an efficient manipulation of magnetization in spintronic devices. Theoretically, pure spin current can be also created by a temperature gradient, which is known as spin Nernst effect. Here, we report spin Nernst effect-induced transverse magnetoresistance in ferromagnet/non-magnetic heavy metal bilayers. We observe that the magnitude of transverse magnetoresistance in the bilayers is significantly modified by heavy metal and its thickness. This strong dependence of transverse magnetoresistance on heavy metal evidences the generation of thermally induced pure spin current in heavy metal. Our analysis shows that spin Nernst angles of W and Pt have the opposite sign to their spin Hall angles. Moreover, our estimate implies that the magnitude of spin Nernst angle would be comparable to that of spin Hall angle, suggesting an efficient generation of spin current by the spin Nernst effect.
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Affiliation(s)
- Dong-Jun Kim
- Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon, 34141, Korea
| | - Chul-Yeon Jeon
- Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon, 34141, Korea
| | - Jong-Guk Choi
- Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon, 34141, Korea
| | - Jae Wook Lee
- Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon, 34141, Korea
| | - Srivathsava Surabhi
- Department of Materials Science and Engineering, Graduate School of Energy Science Technology, Chungnam National University, Daejeon, 34134, Korea
| | - Jong-Ryul Jeong
- Department of Materials Science and Engineering, Graduate School of Energy Science Technology, Chungnam National University, Daejeon, 34134, Korea
| | - Kyung-Jin Lee
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, Korea
| | - Byong-Guk Park
- Department of Materials Science and Engineering and KI for Nanocentury, KAIST, Daejeon, 34141, Korea.
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43
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Sheng P, Sakuraba Y, Lau YC, Takahashi S, Mitani S, Hayashi M. The spin Nernst effect in tungsten. SCIENCE ADVANCES 2017; 3:e1701503. [PMID: 29119140 PMCID: PMC5669613 DOI: 10.1126/sciadv.1701503] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 10/04/2017] [Indexed: 06/01/2023]
Abstract
The spin Hall effect allows the generation of spin current when charge current is passed along materials with large spin-orbit coupling. It has been recently predicted that heat current in a nonmagnetic metal can be converted into spin current via a process referred to as the spin Nernst effect. We report the observation of the spin Nernst effect in W. In W/CoFeB/MgO heterostructures, we find changes in the longitudinal and transverse voltages with magnetic field when temperature gradient is applied across the film. The field dependence of the voltage resembles that of the spin Hall magnetoresistance. A comparison of the temperature gradient-induced voltage and the spin Hall magnetoresistance allows direct estimation of the spin Nernst angle. We find the spin Nernst angle of W to be similar in magnitude but opposite in sign to its spin Hall angle. Under an open-circuit condition, this sign difference results in the spin current generation larger than otherwise. These results highlight the distinct characteristics of the spin Nernst and spin Hall effects, providing pathways to explore materials with unique band structures that may generate large spin current with high efficiency.
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Affiliation(s)
- Peng Sheng
- National Institute for Materials Science, Tsukuba 305-0047, Japan
| | - Yuya Sakuraba
- National Institute for Materials Science, Tsukuba 305-0047, Japan
| | - Yong-Chang Lau
- National Institute for Materials Science, Tsukuba 305-0047, Japan
- Department of Physics, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Saburo Takahashi
- Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
| | - Seiji Mitani
- National Institute for Materials Science, Tsukuba 305-0047, Japan
- Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8577, Japan
| | - Masamitsu Hayashi
- National Institute for Materials Science, Tsukuba 305-0047, Japan
- Department of Physics, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
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44
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Kim KW, Lee KJ, Sinova J, Lee HW, Stiles MD. Spin-orbit torques from interfacial spin-orbit coupling for various interfaces. PHYSICAL REVIEW. B 2017; 96:104438. [PMID: 29333523 PMCID: PMC5761703 DOI: 10.1103/physrevb.96.104438] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We use a perturbative approach to study the effects of interfacial spin-orbit coupling in magnetic multilayers by treating the two-dimensional Rashba model in a fully three-dimensional description of electron transport near an interface. This formalism provides a compact analytic expression for current-induced spin-orbit torques in terms of unperturbed scattering coefficients, allowing computation of spin-orbit torques for various contexts, by simply substituting scattering coefficients into the formulas. It applies to calculations of spin-orbit torques for magnetic bilayers with bulk magnetism, those with interface magnetism, a normal metal/ferromagnetic insulator junction, and a topological insulator/ferromagnet junction. It predicts a dampinglike component of spin-orbit torque that is distinct from any intrinsic contribution or those that arise from particular spin relaxation mechanisms. We discuss the effects of proximity-induced magnetism and insertion of an additional layer and provide formulas for in-plane current, which is induced by a perpendicular bias, anisotropic magnetoresistance, and spin memory loss in the same formalism.
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Affiliation(s)
- Kyoung-Whan Kim
- Institut für Physik, Johannes Gutenberg Universität Mainz, Mainz 55128, Germany
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
- Maryland NanoCenter, University of Maryland, College Park, Maryland 20742, USA
| | - Kyung-Jin Lee
- Department of Materials Science and Engineering, Korea University, Seoul 02841, Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul 02841, Korea
| | - Jairo Sinova
- Institut für Physik, Johannes Gutenberg Universität Mainz, Mainz 55128, Germany
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 53 Praha 6 Czech Republic
| | - Hyun-Woo Lee
- PCTP and Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea
| | - M D Stiles
- Center for Nanoscale Science and Technology, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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45
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Jie W, Yang Z, Zhang F, Bai G, Leung CW, Hao J. Observation of Room-Temperature Magnetoresistance in Monolayer MoS 2 by Ferromagnetic Gating. ACS NANO 2017; 11:6950-6958. [PMID: 28686411 DOI: 10.1021/acsnano.7b02253] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Room-temperature magnetoresistance (MR) effect is observed in heterostructures of wafer-scale MoS2 layers and ferromagnetic dielectric CoFe2O4 (CFO) thin films. Through the ferromagnetic gating, an MR ratio of -12.7% is experimentally achieved in monolayer MoS2 under 90 kOe magnetic field at room temperature (RT). The observed MR ratio is much higher than that in previously reported nonmagnetic metal coupled with ferromagnetic insulator, which generally exhibited MR ratio of less than 1%. The enhanced MR is attributed to the spin accumulation at the heterostructure interface and spin injection to the MoS2 layers by the strong spin-orbit coupling effect. The injected spin can contribute to the spin current and give rise to the MR by changing the resistance of MoS2 layers. Furthermore, the MR effect decreases as the thickness of MoS2 increases, and the MR ratio becomes negligible in MoS2 with thickness more than 10 layers. Besides, it is interesting to find a magnetic field direction dependent spin Hall magnetoresistance that stems from a combination of the spin Hall and the inverse spin Hall effects. Our research provides an insight into exploring RT MR in monolayer materials, which should be helpful for developing ultrathin magnetic storage devices in the atomically thin limit.
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Affiliation(s)
- Wenjing Jie
- Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China
- College of Chemistry and Materials Science, Sichuan Normal University , Chengdu 610068, China
| | - Zhibin Yang
- Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China
| | - Fan Zhang
- Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China
| | - Gongxun Bai
- Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China
| | - Chi Wah Leung
- Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China
| | - Jianhua Hao
- Department of Applied Physics, The Hong Kong Polytechnic University , Hung Hom, Kowloon, Hong Kong, China
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46
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Abstract
Spin-orbit-related effects offer a highly promising route for reading and writing information in magnetic units of future devices. These phenomena rely not only on the static magnetization orientation but also on its dynamics to achieve fast switchings that can reach the THz range. In this work, we consider Co/Pt and Fe/W bilayers to show that accounting for the phase difference between different processes is crucial to the correct description of the dynamical currents. By tuning each system towards its ferromagnetic resonance, we reveal that dynamical spin Hall angles can non-trivially change sign and be boosted by over 500%, reaching giant values. We demonstrate that charge and spin pumping mechanisms can greatly magnify or dwindle the currents flowing through the system, influencing all kinds of magnetoresistive and Hall effects, thus impacting also dc and second harmonic experimental measurements.
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47
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Influence of intermixing at the Ta/CoFeB interface on spin Hall angle in Ta/CoFeB/MgO heterostructures. Sci Rep 2017; 7:968. [PMID: 28428546 PMCID: PMC5430535 DOI: 10.1038/s41598-017-00994-z] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 03/17/2017] [Indexed: 11/08/2022] Open
Abstract
When a current is passed through a non-magnetic metal with strong spin-orbit coupling, an orthogonal spin current is generated. This spin current can be used to switch the magnetization of an adjacent ferromagnetic layer or drive its magnetization into continuous precession. The interface, which is not necessarily sharp, and the crystallographic structure of the nonmagnetic metal can both affect the strength of current-induced spin-orbit torques. Here, we investigate the effects of interface intermixing and film microstructure on spin-orbit torques in perpendicularly magnetized Ta/Co40Fe40B20/MgO trilayers with different Ta layer thickness (5 nm, 10 nm, 15 nm), greater than the spin diffusion length. Effective spin-orbit torques are determined from harmonic Hall voltage measurements performed at temperatures ranging from 20 K to 300 K. We account for the temperature dependence of damping-like and field-like torques by including an additional contribution from the Ta/CoFeB interface in the spin diffusion model. Using this approach, the temperature variations of the spin Hall angle in the Ta underlayer and at the Ta/CoFeB interface are determined separately. Our results indicate an almost temperature-independent spin Hall angle of \documentclass[12pt]{minimal}
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\begin{document}$${{\boldsymbol{\theta }}}_{{\boldsymbol{SH}}}^{{\boldsymbol{N}}}\approx -{\bf{0.2}}$$\end{document}θSHN≈−0.2 in Ta and a strongly temperature-dependent \documentclass[12pt]{minimal}
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\begin{document}$${{\boldsymbol{\theta }}}_{{\boldsymbol{SH}}}^{{\boldsymbol{N}}}$$\end{document}θSHN for the intermixed Ta/CoFeB interface.
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48
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Ok S, Chen W, Sigrist M, Manske D. Effect of quantum tunneling on spin Hall magnetoresistance. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:075802. [PMID: 28032615 DOI: 10.1088/1361-648x/aa50da] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We present a formalism that simultaneously incorporates the effect of quantum tunneling and spin diffusion on the spin Hall magnetoresistance observed in normal metal/ferromagnetic insulator bilayers (such as Pt/Y3Fe5O12) and normal metal/ferromagnetic metal bilayers (such as Pt/Co), in which the angle of magnetization influences the magnetoresistance of the normal metal. In the normal metal side the spin diffusion is known to affect the landscape of the spin accumulation caused by spin Hall effect and subsequently the magnetoresistance, while on the ferromagnet side the quantum tunneling effect is detrimental to the interface spin current which also affects the spin accumulation. The influence of generic material properties such as spin diffusion length, layer thickness, interface coupling, and insulating gap can be quantified in a unified manner, and experiments that reveal the quantum feature of the magnetoresistance are suggested.
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Affiliation(s)
- Seulgi Ok
- Institut für Theoretische Physik, ETH-Zürich, CH-8093 Zürich, Switzerland
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49
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Modulated switching current density and spin-orbit torques in MnGa/Ta films with inserting ferromagnetic layers. Sci Rep 2016; 6:38375. [PMID: 27910938 PMCID: PMC5133548 DOI: 10.1038/srep38375] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 11/08/2016] [Indexed: 11/09/2022] Open
Abstract
We report modulated switching current density and spin-orbit torques (SOT) in MnGa/Ta films with inserting very thin Co2FeAl and Co layers. Ferromagnetic coupling has been found in MnGa/Co2FeAl/Ta, resulting in a decreased effective anisotropy field. On the contrary, in MnGa/Co/Ta, antiferromagnetic coupling plays a dominant role. The switching current density Jc in MnGa/Ta is 8.5 × 107 A/cm2. After inserting 0.8-nm-thick Co2FeAl and Co, theJc becomes 5 × 107 A/cm2 and 9 × 107 A/cm2, respectively. By performing adiabatic harmonic Hall voltage measurements, it is demonstrated that the inserted Co2FeAl layer has mainly enhanced the field-like torques, while in MnGa/Co/Ta the damping-like torques have been enhanced. Finally, the enhanced spin Hall effect (SHE) has also been studied using the spin Hall magnetoresistance measurement. The modulated Jc and SOT are ascribed to the combination of magnetic coupling, Rashba effect and SHE at the interfaces.
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50
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Abstract
The time it takes to accelerate an object from zero to a given velocity depends on the applied force and the environment. If the force ceases, it takes exactly the same time to completely decelerate. A magnetic domain wall is a topological object that has been observed to follow this behaviour. Here we show that acceleration and deceleration times of chiral Neel walls driven by current are different in a system with low damping and moderate Dzyaloshinskii–Moriya exchange constant. The time needed to accelerate a domain wall with current via the spin Hall torque is much faster than the time it needs to decelerate once the current is turned off. The deceleration time is defined by the Dzyaloshinskii–Moriya exchange constant whereas the acceleration time depends on the spin Hall torque, enabling tunable inertia of chiral domain walls. Such unique feature of chiral domain walls can be utilized to move and position domain walls with lower current, key to the development of storage class memory devices. The controlled motion of magnetic domain walls in nanowire conduits forms the basis of emerging memory and information processing devices. Here, the authors report a pulse-length dependent quasi-static velocity of current-driven chiral domain walls, showing that their inertia is tunable.
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