1
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Zhang C, Jiang Z, Jiang J, He W, Zhang J, Hu F, Zhao S, Yang D, Liu Y, Peng Y, Yang H, Yang H. Above-room-temperature chiral skyrmion lattice and Dzyaloshinskii-Moriya interaction in a van der Waals ferromagnet Fe 3-xGaTe 2. Nat Commun 2024; 15:4472. [PMID: 38796498 PMCID: PMC11127993 DOI: 10.1038/s41467-024-48799-9] [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: 09/23/2023] [Accepted: 05/14/2024] [Indexed: 05/28/2024] Open
Abstract
Skyrmions in existing 2D van der Waals (vdW) materials have primarily been limited to cryogenic temperatures, and the underlying physical mechanism of the Dzyaloshinskii-Moriya interaction (DMI), a crucial ingredient for stabilizing chiral skyrmions, remains inadequately explored. Here, we report the observation of Néel-type skyrmions in a vdW ferromagnet Fe3-xGaTe2 above room temperature. Contrary to previous assumptions of centrosymmetry in Fe3-xGaTe2, the atomic-resolution scanning transmission electron microscopy reveals that the off-centered FeΙΙ atoms break the spatial inversion symmetry, rendering it a polar metal. First-principles calculations further elucidate that the DMI primarily stems from the Te sublayers through the Fert-Lévy mechanism. Remarkably, the chiral skyrmion lattice in Fe3-xGaTe2 can persist up to 330 K at zero magnetic field, demonstrating superior thermal stability compared to other known skyrmion vdW magnets. This work provides valuable insights into skyrmionics and presents promising prospects for 2D material-based skyrmion devices operating beyond room temperature.
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Affiliation(s)
- Chenhui Zhang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Ze Jiang
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Jiawei Jiang
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China
| | - Wa He
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Junwei Zhang
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Fanrui Hu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Shishun Zhao
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Dongsheng Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yakun Liu
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore
| | - Yong Peng
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China.
| | - Hongxin Yang
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
- Center for Quantum Matter, School of Physics, Zhejiang University, Hangzhou, 310058, China.
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, 117576, Singapore.
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2
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Pantazopoulos PA, Feist J, García-Vidal FJ, Kamra A. Unconventional magnetism mediated by spin-phonon-photon coupling. Nat Commun 2024; 15:4000. [PMID: 38734667 PMCID: PMC11088681 DOI: 10.1038/s41467-024-48404-z] [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: 10/10/2023] [Accepted: 04/30/2024] [Indexed: 05/13/2024] Open
Abstract
Magnetic order typically emerges due to the short-range exchange interaction between the constituent electronic spins. Recent discoveries have found a crucial role for spin-phonon coupling in various phenomena from optical ultrafast magnetization switching to dynamical control of the magnetic state. Here, we demonstrate theoretically the emergence of a biquadratic long-range interaction between spins mediated by their coupling to phonons hybridized with vacuum photons into polaritons. The resulting ordered state enabled by the exchange of virtual polaritons between spins is reminiscent of superconductivity mediated by the exchange of virtual phonons. The biquadratic nature of the spin-spin interaction promotes ordering without favoring ferro- or antiferromagnetism. It further makes the phase transition to magnetic order a first-order transition, unlike in conventional magnets. Consequently, a large magnetization develops abruptly on lowering the temperature which could enable magnetic memories admitting ultralow-power thermally-assisted writing while maintaining a high data stability. The role of photons in the phenomenon further enables an in-situ static control over the magnetism. These unique features make our predicted spin-spin interaction and magnetism highly unconventional paving the way for novel scientific and technological opportunities.
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Affiliation(s)
- Petros Andreas Pantazopoulos
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
| | - Johannes Feist
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
| | - Francisco J García-Vidal
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
| | - Akashdeep Kamra
- Departamento de Física Teórica de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, E-28049, Spain.
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3
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Zhang Y, Tang J, Wu Y, Shi M, Xu X, Wang S, Tian M, Du H. Stable skyrmion bundles at room temperature and zero magnetic field in a chiral magnet. Nat Commun 2024; 15:3391. [PMID: 38649678 PMCID: PMC11035646 DOI: 10.1038/s41467-024-47730-6] [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: 11/20/2023] [Accepted: 04/10/2024] [Indexed: 04/25/2024] Open
Abstract
Topological spin textures are characterized by magnetic topological charges, Q, which govern their electromagnetic properties. Recent studies have achieved skyrmion bundles with arbitrary integer values of Q, opening possibilities for exploring topological spintronics based on Q. However, the realization of stable skyrmion bundles in chiral magnets at room temperature and zero magnetic field - the prerequisite for realistic device applications - has remained elusive. Here, through the combination of pulsed currents and reversed magnetic fields, we experimentally achieve skyrmion bundles with different integer Q values - reaching a maximum of 24 at above room temperature and zero magnetic field - in the chiral magnet Co8Zn10Mn2. We demonstrate the field-driven annihilation of high-Q bundles and present a phase diagram as a function of temperature and field. Our experimental findings are consistently corroborated by micromagnetic simulations, which reveal the nature of the skyrmion bundle as that of skyrmion tubes encircled by a fractional Hopfion.
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Grants
- This work was supported by the National Key R&D Program of China, Grant No. 2022YFA1403603 (H.D.); the Natural Science Foundation of China, Grants No. 12174396 (J.T.), 12104123 (Y.W.), and 12241406 (H.D.); the National Natural Science Funds for Distinguished Young Scholar, Grant No. 52325105 (H.D.); the Anhui Provincial Natural Science Foundation, Grant No. 2308085Y32 (J.T.); the Natural Science Project of Colleges and Universities in Anhui Province, Grant No. 2022AH030011 (J.T.); the Strategic Priority Research Program of Chinese Academy of Sciences, Grant No. XDB33030100 (H.D.); CAS Project for Young Scientists in Basic Research, Grant No. YSBR-084 (H.D.); Systematic Fundamental Research Program Leveraging Major Scientific and Technological Infrastructure, Chinese Academy of Sciences, Grant No. JZHKYPT-2021-08 (H.D.);Anhui Province Excellent Young Teacher Training Project Grant No. YQZD2023067 (Y.W.); and the China Postdoctoral Science Foundation Grant No. 2023M743543 (Y.W.).
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Affiliation(s)
- Yongsen Zhang
- Science Island Branch, Graduate School of USTC, Hefei, 230026, China
- Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
| | - Jin Tang
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei, 230601, China.
| | - Yaodong Wu
- School of Physics and Materials Engineering, Hefei Normal University, Hefei, 230601, China
| | - Meng Shi
- Science Island Branch, Graduate School of USTC, Hefei, 230026, China
- Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
| | - Xitong Xu
- Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
| | - Shouguo Wang
- Anhui Key Laboratory of Magnetic Functional Materials and Devices, School of Materials Science and Engineering, Anhui University, Hefei, 230601, China
| | - Mingliang Tian
- Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei, 230601, China
| | - Haifeng Du
- Anhui Province Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China.
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4
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Jiang J, Tang J, Bai T, Wu Y, Qin J, Xia W, Chen R, Yan A, Wang S, Tian M, Du H. Thermal Stability of Skyrmion Tubes in Nanostructured Cuboids. NANO LETTERS 2024; 24:1587-1593. [PMID: 38259044 DOI: 10.1021/acs.nanolett.3c04181] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Magnetic skyrmions in bulk materials are typically regarded as two-dimensional structures. However, they also exhibit three-dimensional configurations, known as skyrmion tubes, that elongate and extend in-depth. Understanding the configurations and stabilization mechanism of skyrmion tubes is crucial for the development of advanced spintronic devices. However, the generation and annihilation of skyrmion tubes in confined geometries are still rarely reported. Here, we present direct imaging of skyrmion tubes in nanostructured cuboids of a chiral magnet FeGe using Lorentz transmission electron microscopy (TEM), while applying an in-plane magnetic field. It is observed that skyrmion tubes stabilize in a narrow field-temperature region near the Curie temperature (Tc). Through a field cooling process, metastable skyrmion tubes can exist in a larger region of the field-temperature diagram. Combining these experimental findings with micromagnetic simulations, we attribute these phenomena to energy differences and thermal fluctuations. Our results could promote topological spintronic devices based on skyrmion tubes.
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Affiliation(s)
- Jialiang Jiang
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei 230601, China
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, Hefei 230031, China
| | - Jin Tang
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei 230601, China
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, Hefei 230031, China
| | - Tian Bai
- CISRI & NIMTE Joint Innovation Center for Rare Earth Permanent Magnets, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201, China
| | - Yaodong Wu
- School of Physics and Materials Engineering, Hefei Normal University, Hefei 230601, China
| | - Jiazhuan Qin
- CISRI & NIMTE Joint Innovation Center for Rare Earth Permanent Magnets, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201, China
| | - Weixing Xia
- CISRI & NIMTE Joint Innovation Center for Rare Earth Permanent Magnets, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201, China
| | - Renjie Chen
- CISRI & NIMTE Joint Innovation Center for Rare Earth Permanent Magnets, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201, China
| | - Aru Yan
- CISRI & NIMTE Joint Innovation Center for Rare Earth Permanent Magnets, Ningbo Institute of Material Technology and Engineering, Chinese Academy of Science, Ningbo 315201, China
| | - Shouguo Wang
- Anhui Key Laboratory of Magnetic Functional Materials and Devices, School of Materials Science and Engineering, Anhui University, Hefei 230601, China
| | - Mingliang Tian
- School of Physics and Optoelectronic Engineering, Anhui University, Hefei 230601, China
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, Hefei 230031, China
| | - Haifeng Du
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, Hefei 230031, China
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5
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Li Z, Zhang H, Li G, Guo J, Wang Q, Deng Y, Hu Y, Hu X, Liu C, Qin M, Shen X, Yu R, Gao X, Liao Z, Liu J, Hou Z, Zhu Y, Fu X. Room-temperature sub-100 nm Néel-type skyrmions in non-stoichiometric van der Waals ferromagnet Fe 3-xGaTe 2 with ultrafast laser writability. Nat Commun 2024; 15:1017. [PMID: 38310096 PMCID: PMC10838308 DOI: 10.1038/s41467-024-45310-2] [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: 08/08/2023] [Accepted: 01/19/2024] [Indexed: 02/05/2024] Open
Abstract
Realizing room-temperature magnetic skyrmions in two-dimensional van der Waals ferromagnets offers unparalleled prospects for future spintronic applications. However, due to the intrinsic spin fluctuations that suppress atomic long-range magnetic order and the inherent inversion crystal symmetry that excludes the presence of the Dzyaloshinskii-Moriya interaction, achieving room-temperature skyrmions in 2D magnets remains a formidable challenge. In this study, we target room-temperature 2D magnet Fe3GaTe2 and unveil that the introduction of iron-deficient into this compound enables spatial inversion symmetry breaking, thus inducing a significant Dzyaloshinskii-Moriya interaction that brings about room-temperature Néel-type skyrmions with unprecedentedly small size. To further enhance the practical applications of this finding, we employ a homemade in-situ optical Lorentz transmission electron microscopy to demonstrate ultrafast writing of skyrmions in Fe3-xGaTe2 using a single femtosecond laser pulse. Our results manifest the Fe3-xGaTe2 as a promising building block for realizing skyrmion-based magneto-optical functionalities.
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Grants
- This work was supported by the National Key Research and Development Program of China at grant No. 2020YFA0309300, Science and Technology Projects in Guangzhou (grant No. 202201000008), the National Natural Science Foundation of China (NSFC) at grant No. 12304146, 11974191, 12127803, 52322108, 52271178, U22A20117 and 12241403, China Postdoctoral Science Foundation (2023M741828), Guangdong Basic and Applied Basic Research Foundation (grant No. 2021B1515120047 and 2023B1515020112), the Natural Science Foundation of Tianjin at grant No. 20JCJQJC00210, the 111 Project at grant No. B23045, and the “Fundamental Research Funds for the Central Universities”, Nankai University (grant No. 63213040, C029211101, C02922101, ZB22000104 and DK2300010207). This work was supported by the Synergetic Extreme Condition User Facility (SECUF).
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Affiliation(s)
- Zefang Li
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China
| | - Huai Zhang
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Guanqi Li
- School of Integrated Circuits, Guangdong University of Technology, Guangzhou, China
| | - Jiangteng Guo
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China
| | - Qingping Wang
- School of Physics and Electronic and Electrical Engineering, Aba Teachers University, Wenchuan, China
| | - Ying Deng
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China
| | - Yue Hu
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China
| | - Xuange Hu
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China
| | - Can Liu
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China
| | - Minghui Qin
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Xi Shen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Richeng Yu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Xingsen Gao
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
| | - Zhimin Liao
- State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-optoelectronics, School of Physics, Peking University, Beijing, China
| | - Junming Liu
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China
- Laboratory of Solid State Microstructures and Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, China
| | - Zhipeng Hou
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China.
| | - Yimei Zhu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York, USA.
| | - Xuewen Fu
- Ultrafast Electron Microscopy Laboratory, The MOE Key Laboratory of Weak-Light Nonlinear Photonics, School of Physics, Nankai University, Tianjin, China.
- School of Materials Science and Engineering, Smart Sensing Interdisciplinary Science Center, Nankai University, Tianjin, China.
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6
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Zhang X, Xia J, Tretiakov OA, Ezawa M, Zhao G, Zhou Y, Liu X, Mochizuki M. Chiral Skyrmions Interacting with Chiral Flowers. NANO LETTERS 2023; 23:11793-11801. [PMID: 38055779 PMCID: PMC10755743 DOI: 10.1021/acs.nanolett.3c03792] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2023] [Revised: 12/02/2023] [Accepted: 12/04/2023] [Indexed: 12/08/2023]
Abstract
The chiral nature of active matter plays an important role in the dynamics of active matter interacting with chiral structures. Skyrmions are chiral objects, and their interactions with chiral nanostructures can lead to intriguing phenomena. Here, we explore the random-walk dynamics of a thermally activated chiral skyrmion interacting with a chiral flower-like obstacle in a ferromagnetic layer, which could create topology-dependent outcomes. It is a spontaneous mesoscopic order-from-disorder phenomenon driven by the thermal fluctuations and topological nature of skyrmions that exists only in ferromagnetic and ferrimagnetic systems. The interactions between the skyrmions and chiral flowers at finite temperatures can be utilized to control the skyrmion position and distribution without applying any external driving force or temperature gradient. The phenomenon that thermally activated skyrmions are dynamically coupled to chiral flowers may provide a new way to design topological sorting devices.
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Affiliation(s)
- Xichao Zhang
- Department
of Applied Physics, Waseda University, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
| | - Jing Xia
- Department
of Electrical and Computer Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
| | - Oleg A. Tretiakov
- School
of Physics, The University of New South
Wales, Sydney 2052, Australia
| | - Motohiko Ezawa
- Department
of Applied Physics, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan
| | - Guoping Zhao
- College
of Physics and Electronic Engineering, Sichuan
Normal University, Chengdu 610068, China
| | - Yan Zhou
- School
of
Science and Engineering, The Chinese University
of Hong Kong, Shenzhen, Guangdong 518172, China
| | - Xiaoxi Liu
- Department
of Electrical and Computer Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
| | - Masahito Mochizuki
- Department
of Applied Physics, Waseda University, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan
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7
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Song Y, Xu T, Zhao G, Xu Y, Zhong Z, Zheng X, Shi N, Zhou C, Hao Y, Huang Q, Xing X, Zhang Y, Chen J. High-density, spontaneous magnetic biskyrmions induced by negative thermal expansion in ferrimagnets. SCIENCE ADVANCES 2023; 9:eadi1984. [PMID: 37672584 PMCID: PMC10482331 DOI: 10.1126/sciadv.adi1984] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2023] [Accepted: 08/04/2023] [Indexed: 09/08/2023]
Abstract
Magnetic skyrmions are topologically protected quasiparticles that are promising for applications in spintronics. However, the low stability of most magnetic skyrmions leads to either a narrow temperature range in which they can exist, a low density of skyrmions, or the need for an external magnetic field, which greatly limits their wide application. In this study, high-density, spontaneous magnetic biskyrmions existing within a wide temperature range and without the need for a magnetic field were formed in ferrimagnets owing to the existence of a negative thermal expansion of the lattice. Moreover, a strong connection between the atomic-scale ferrimagnetic structure and nanoscale magnetic domains in Ho(Co,Fe)3 was revealed via in situ neutron powder diffraction and Lorentz transmission electron microscopy measurements. The critical role of the negative thermal expansion in generating biskyrmions in HoCo3 based on the magnetoelastic coupling effect is further demonstrated by comparing the behavior of HoCo2.8Fe0.2 with a positive thermal expansion.
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Affiliation(s)
- Yuzhu Song
- Beijing Advanced Innovation Center for Materials Genome Engineering, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Tiankuo Xu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Guoping Zhao
- College of Physics and Electronic Engineering and Institute of Solid State Physics, Sichuan Normal University, Chengdu 610066, China
| | - Yuanji Xu
- Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083, China
| | - Zhicheng Zhong
- Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Xinqi Zheng
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Naike Shi
- Beijing Advanced Innovation Center for Materials Genome Engineering, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Chang Zhou
- State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
| | - Yiqing Hao
- State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
| | - Qingzhen Huang
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg MD, 20899-6102, USA
| | - Xianran Xing
- Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China
| | - Ying Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jun Chen
- Beijing Advanced Innovation Center for Materials Genome Engineering, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China
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8
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He Z, Du W, Dou K, Dai Y, Huang B, Ma Y. Ferroelectrically tunable magnetic skyrmions in two-dimensional multiferroics. MATERIALS HORIZONS 2023; 10:3450-3457. [PMID: 37345913 DOI: 10.1039/d3mh00572k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/23/2023]
Abstract
Magnetic skyrmions are topologically protected entities that are promising for information storage and processing. Currently, an essential challenge for future advances of skyrmionic devices lies in achieving effective control of skyrmion properties. Here, through first-principles and Monte-Carlo simulations, we report the identification of nontrivial topological magnetism in two-dimensional multiferroics of Co2NF2. Because of ferroelectricity, monolayer Co2NF2 exhibits a large Dzyaloshinskii-Moriya interaction. This together with exchange interaction can stabilize magnetic skyrmions with the size of sub-10 nm under a moderate magnetic field. Importantly, arising from the magnetoelectric coupling effect, the chirality of magnetic skyrmions is ferroelectrically tunable, producing the four-fold degenerate skyrmions. When interfacing with monolayer MoSe2, the creation and annihilation of magnetic skyrmions, as well as phase transition between skyrmion and skyrmion lattice, can be realized in a ferroelectrically controllable fashion. A dimensionless parameter κ' is further proposed as the criterion for stabilizing magnetic skyrmions in such multiferroic lattices. Our work greatly enriches the two-dimensional skyrmionics and multiferroics research.
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Affiliation(s)
- Zhonglin He
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Shandanan Street 27, Jinan 250100, China.
| | - Wenhui Du
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Shandanan Street 27, Jinan 250100, China.
| | - Kaiying Dou
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Shandanan Street 27, Jinan 250100, China.
| | - Ying Dai
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Shandanan Street 27, Jinan 250100, China.
| | - Baibiao Huang
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Shandanan Street 27, Jinan 250100, China.
| | - Yandong Ma
- School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Shandanan Street 27, Jinan 250100, China.
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9
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Yagan R, Cheghabouri AM, Onbasli MC. Stabilization and adiabatic control of antiferromagnetically coupled skyrmions without the topological Hall effect. NANOSCALE ADVANCES 2023; 5:4470-4479. [PMID: 37638152 PMCID: PMC10448311 DOI: 10.1039/d3na00236e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 07/26/2023] [Indexed: 08/29/2023]
Abstract
Synthetic antiferromagnetically coupled (SAF) multilayers provide different physics of stabilizing skyrmions while eliminating the topological Hall effect (THE), enabling efficient and stable control. The effects of material parameters, external current drive, and a magnetic field on the skyrmion equilibrium and propagation characteristics are largely unresolved. Here, we present a computational and theoretical demonstration of the large window of material parameters that stabilize SAF skyrmions determined by saturation magnetization, uniaxial anisotropy, and Dzyaloshinskii-Moriya interaction. Current-driven SAF skyrmion velocities reach ∼200 m s-1 without the THE. The SAF velocities are about 3-10 times greater than the typical ferromagnetic skyrmion velocities. The current densities needed for driving SAF skyrmions could be reduced to 108 A m-2, while 1011 A m-2 or above is needed for ferromagnetic skyrmions. By reducing the SAF skyrmion drive current by 3 orders, Joule heating is reduced by 6 orders of magnitude. These results pave the way for new SAF interfaces with improved equilibrium, dynamics, and power savings in THE-free skyrmionics.
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Affiliation(s)
- Rawana Yagan
- Department of Electrical and Electronics Engineering, Koç University Sarıyer Istanbul 34450 Turkey
| | | | - Mehmet C Onbasli
- Department of Electrical and Electronics Engineering, Koç University Sarıyer Istanbul 34450 Turkey
- Department of Physics, Koç University Sarıyer Istanbul 34450 Turkey
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10
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Meisenheimer P, Zhang H, Raftrey D, Chen X, Shao YT, Chan YT, Yalisove R, Chen R, Yao J, Scott MC, Wu W, Muller DA, Fischer P, Birgeneau RJ, Ramesh R. Ordering of room-temperature magnetic skyrmions in a polar van der Waals magnet. Nat Commun 2023; 14:3744. [PMID: 37353526 DOI: 10.1038/s41467-023-39442-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2023] [Accepted: 06/13/2023] [Indexed: 06/25/2023] Open
Abstract
Control and understanding of ensembles of skyrmions is important for realization of future technologies. In particular, the order-disorder transition associated with the 2D lattice of magnetic skyrmions can have significant implications for transport and other dynamic functionalities. To date, skyrmion ensembles have been primarily studied in bulk crystals, or as isolated skyrmions in thin film devices. Here, we investigate the condensation of the skyrmion phase at room temperature and zero field in a polar, van der Waals magnet. We demonstrate that we can engineer an ordered skyrmion crystal through structural confinement on the μm scale, showing control over this order-disorder transition on scales relevant for device applications.
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Affiliation(s)
- Peter Meisenheimer
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
| | - Hongrui Zhang
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA.
| | - David Raftrey
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Santa Cruz, CA, USA
| | - Xiang Chen
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Yu-Tsun Shao
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Ying-Ting Chan
- Department of Physics, Rutgers University, New Brunswick, NJ, USA
| | - Reed Yalisove
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
| | - Rui Chen
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
| | - Jie Yao
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
| | - Mary C Scott
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Weida Wu
- Department of Physics, Rutgers University, New Brunswick, NJ, USA
| | - David A Muller
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY, USA
| | - Peter Fischer
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Santa Cruz, CA, USA
| | - Robert J Birgeneau
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
| | - Ramamoorthy Ramesh
- Department of Materials Science and Engineering, University of California, Berkeley, CA, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
- Department of Physics, University of California, Berkeley, CA, USA
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11
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Ahrens V, Kiesselbach C, Gnoli L, Giuliano D, Mendisch S, Kiechle M, Riente F, Becherer M. Skyrmions Under Control-FIB Irradiation as a Versatile Tool for Skyrmion Circuits. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2207321. [PMID: 36255142 DOI: 10.1002/adma.202207321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Magnetic data storage and processing offer certain advances over conventional technologies, amongst which nonvolatility and low power operation are the most outstanding ones. Skyrmions are a promising candidate as a magnetic data carrier. However, the sputtering of skyrmion films and the control of the skyrmion nucleation, motion, and annihilation remains challenging. This work demonstrates that using optimized focused ion beam irradiation and annealing protocols enables the skyrmion phase in W/CoFeB/MgO thin films to be accessed easily. By analyzing ion-beam-engineered skyrmion hosting wires, excited by sub-100 ns current pulses, possibilities to control skyrmion nucleation, guide their motion, and control their annihilation unfold. Overall, the key elements needed to develop extensive skyrmion networks are presented.
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Affiliation(s)
- Valentin Ahrens
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Clara Kiesselbach
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Luca Gnoli
- Department of Electronics and Telecommunications, Politecnico di Torino, Torino, 10129, Italy
| | - Domenico Giuliano
- Department of Electronics and Telecommunications, Politecnico di Torino, Torino, 10129, Italy
| | - Simon Mendisch
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Martina Kiechle
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Fabrizio Riente
- Department of Electronics and Telecommunications, Politecnico di Torino, Torino, 10129, Italy
| | - Markus Becherer
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
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12
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Oyeka EE, Winiarski MJ, Świątek H, Balliew W, McMillen CD, Liang M, Sorolla M, Tran TT. Ln 2 (SeO 3 ) 2 (SO 4 )(H 2 O) 2 (Ln=Sm, Dy, Yb): A Mixed-Ligand Pathway to New Lanthanide(III) Multifunctional Materials Featuring Nonlinear Optical and Magnetic Anisotropy Properties. Angew Chem Int Ed Engl 2022; 61:e202213499. [PMID: 36194725 PMCID: PMC9828156 DOI: 10.1002/anie.202213499] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Indexed: 11/07/2022]
Abstract
Bottom-up assembly of optically nonlinear and magnetically anisotropic lanthanide materials involving precisely placed spin carriers and optimized metal-ligand coordination offers a potential route to developing electronic architectures for coherent radiation generation and spin-based technologies, but the chemical design historically has been extremely hard to achieve. To address this, we developed a worthwhile avenue for creating new noncentrosymmetric chiral Ln3+ materials Ln2 (SeO3 )2 (SO4 )(H2 O)2 (Ln=Sm, Dy, Yb) by mixed-ligand design. The materials exhibit phase-matching nonlinear optical responses, elucidating the feasibility of the heteroanionic strategy. Ln2 (SeO3 )2 (SO4 )(H2 O)2 displays paramagnetic property with strong magnetic anisotropy facilitated by large spin-orbit coupling. This study demonstrates a new chemical pathway for creating previously unknown polar chiral magnets with multiple functionalities.
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Affiliation(s)
- Ebube E. Oyeka
- Department of ChemistryClemson UniversityClemsonSC 29630USA
| | - Michał J. Winiarski
- Faculty of Applied Physics and Mathematics and Advanced Materials CenterGdansk University of Technologyul Narutowicza 11/1280-233GdanskPoland
| | - Hanna Świątek
- Faculty of Applied Physics and Mathematics and Advanced Materials CenterGdansk University of Technologyul Narutowicza 11/1280-233GdanskPoland
| | - Wyatt Balliew
- Department of ChemistryClemson UniversityClemsonSC 29630USA
| | | | - Mingli Liang
- Department of ChemistryUniversity of HoustonHoustonTX 77204USA
| | - Maurice Sorolla
- Department of Chemical EngineeringUniversity of the Philippines DilimanQuezon City1101Philippines
| | - Thao T. Tran
- Department of ChemistryClemson UniversityClemsonSC 29630USA
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13
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Zhang C, Liu C, Zhang S, Zhou B, Guan C, Ma Y, Algaidi H, Zheng D, Li Y, He X, Zhang J, Li P, Hou Z, Yin G, Liu K, Peng Y, Zhang XX. Magnetic Skyrmions with Unconventional Helicity Polarization in a Van Der Waals Ferromagnet. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2204163. [PMID: 35975291 DOI: 10.1002/adma.202204163] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 08/10/2022] [Indexed: 06/15/2023]
Abstract
Skyrmion helicity, which defines the spin swirling direction, is a fundamental parameter that may be utilized to encode data bits in future memory devices. Generally, in centrosymmetric ferromagnets, dipole skyrmions with helicity of -π/2 and π/2 are degenerate in energy, leading to equal populations of both helicities. On the other hand, in chiral materials where the Dzyaloshinskii-Moriya interaction (DMI) prevails and the dipolar interaction is negligible, only a preferred helicity is selected by the type of DMI. However, whether there is a rigid boundary between these two regimes remains an open question. Herein, the observation of dipole skyrmions with unconventional helicity polarization in a van der Waals ferromagnet, Fe5- δ GeTe2 , is reported. Combining magnetometry, Lorentz transmission electron microscopy, electrical transport measurements, and micromagnetic simulations, the short-range superstructures in Fe5- δ GeTe2 resulting in a localized DMI contribution, which breaks the degeneracy of the opposite helicities and leads to the helicity polarization, is demonstrated. Therefore, the helicity feature in Fe5- δ GeTe2 is controlled by both the dipolar interaction and DMI that the former leads to Bloch-type skyrmions with helicity of ±π/2 whereas the latter breaks the helicity degeneracy. This work provides new insights into the skyrmion topology in van der Waals materials.
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Affiliation(s)
- Chenhui Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Chen Liu
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Senfu Zhang
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, School of Physical Science and Technology, Lanzhou University, Lanzhou, 730000, China
| | - Bojian Zhou
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Chaoshuai Guan
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Yinchang Ma
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Hanin Algaidi
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Dongxing Zheng
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Yan Li
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Xin He
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Junwei Zhang
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Peng Li
- State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, China
| | - Zhipeng Hou
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, 510006, China
- National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, 510006, China
| | - Gen Yin
- Physics Department, Georgetown University, Washington, DC, 20057, USA
| | - Kai Liu
- Physics Department, Georgetown University, Washington, DC, 20057, USA
| | - Yong Peng
- School of Materials and Energy and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, 730000, China
| | - Xi-Xiang Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
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14
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Hayami S. Square skyrmion crystal in centrosymmetric systems with locally inversion-asymmetric layers. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2022; 34:365802. [PMID: 35738246 DOI: 10.1088/1361-648x/ac7bcb] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Accepted: 06/23/2022] [Indexed: 06/15/2023]
Abstract
We investigate an instability toward a square-lattice formation of magnetic skyrmions in centrosymmetric layered systems. By focusing on a bilayer square-lattice structure with the inversion center at the interlayer bond instead of the atomic site, we numerically examine the stability of the square skyrmion crystal (SkX) based on an effective spin model with the momentum-resolved interaction in the ground state through the simulated annealing. As a result, we find that a layer-dependent staggered Dzyaloshinskii-Moriya (DM) interaction built in the lattice structure becomes the origin of the square SkX in an external magnetic field irrespective of the sign of the interlayer exchange interaction. The obtained square SkX is constituted of the SkXs with different helicities in each layer due to the staggered DM interaction. Furthermore, we show that the interplay between the staggered DM interaction and the interlayer exchange interaction gives rise to a double-Qstate with a uniform component of the scalar chirality in the low-field region. The present results provide another way of stabilizing the square SkX in centrosymmetric magnets, which will be useful to explore further exotic topological spin textures.
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Affiliation(s)
- Satoru Hayami
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
- Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
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15
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Oyeka EE, Winiarski MJ, Tran TT. Study of Integer Spin S = 1 in the Polar Magnet β-Ni(IO 3) 2. Molecules 2021; 26:molecules26237210. [PMID: 34885793 PMCID: PMC8658994 DOI: 10.3390/molecules26237210] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 11/23/2021] [Accepted: 11/26/2021] [Indexed: 11/16/2022] Open
Abstract
Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics.
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Affiliation(s)
- Ebube E. Oyeka
- Department of Chemistry, Clemson University, Clemson, SC 29634, USA;
| | - Michał J. Winiarski
- Advanced Materials Center, Faculty of Applied Physics and Mathematics, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland;
| | - Thao T. Tran
- Department of Chemistry, Clemson University, Clemson, SC 29634, USA;
- Correspondence:
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16
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Oyeka EE, Winiarski MJ, Sorolla Ii M, Taddei KM, Scheie A, Tran TT. Spin and Orbital Effects on Asymmetric Exchange Interaction in Polar Magnets: M(IO 3) 2 (M = Cu and Mn). Inorg Chem 2021; 60:16544-16557. [PMID: 34637293 DOI: 10.1021/acs.inorgchem.1c02432] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Magnetic polar materials feature an astonishing range of physical properties, such as magnetoelectric coupling, chiral spin textures, and related new spin topology physics. This is primarily attributable to their lack of space inversion symmetry in conjunction with unpaired electrons, potentially facilitating an asymmetric Dzyaloshinskii-Moriya (DM) exchange interaction supported by spin-orbital and electron-lattice coupling. However, engineering the appropriate ensemble of coupled degrees of freedom necessary for enhanced DM exchange has remained elusive for polar magnets. Here, we study how spin and orbital components influence the capability of promoting the magnetic interaction by studying two magnetic polar materials, α-Cu(IO3)2 (2D) and Mn(IO3)2 (6S), and connecting their electronic and magnetic properties with their structures. The chemically controlled low-temperature synthesis of these complexes resulted in pure polycrystalline samples, providing a viable pathway to prepare bulk forms of transition-metal iodates. Rietveld refinements of the powder synchrotron X-ray diffraction data reveal that these materials exhibit different crystal structures but crystallize in the same polar and chiral P21 space group, giving rise to an electric polarization along the b-axis direction. The presence and absence of an evident phase transition to a possible topologically distinct state observed in α-Cu(IO3)2 and Mn(IO3)2, respectively, imply the important role of spin-orbit coupling. Neutron diffraction experiments reveal helpful insights into the magnetic ground state of these materials. While the long-wavelength incommensurability of α-Cu(IO3)2 is in harmony with sizable asymmetric DM interaction and low dimensionality of the electronic structure, the commensurate stripe AFM ground state of Mn(IO3)2 is attributed to negligible DM exchange and isotropic orbital overlapping. The work demonstrates connections between combined spin and orbital effects, magnetic coupling dimensionality, and DM exchange, providing a worthwhile approach for tuning asymmetric interaction, which promotes evolution of topologically distinct spin phases.
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Affiliation(s)
- Ebube E Oyeka
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Michał J Winiarski
- Faculty of Applied Physics and Mathematics and Advanced Materials Center, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland
| | - Maurice Sorolla Ii
- Department of Chemical Engineering, University of the Philippines Diliman, Quezon City 1101, Philippines
| | - Keith M Taddei
- Neutron Scattering Division, Oak Ridge National Laboratory, 9500 Spallation Dr, Oak Ridge, Tennessee 37830, United States
| | - Allen Scheie
- Neutron Scattering Division, Oak Ridge National Laboratory, 9500 Spallation Dr, Oak Ridge, Tennessee 37830, United States
| | - Thao T Tran
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
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17
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Tang J, Wu Y, Wang W, Kong L, Lv B, Wei W, Zang J, Tian M, Du H. Magnetic skyrmion bundles and their current-driven dynamics. NATURE NANOTECHNOLOGY 2021; 16:1086-1091. [PMID: 34341518 DOI: 10.1038/s41565-021-00954-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Accepted: 07/05/2021] [Indexed: 06/13/2023]
Abstract
Topological charge Q classifies non-trivial spin textures and determines many of their characteristics. Most abundant are topological textures with |Q| ≤ 1, such as (anti)skyrmions, (anti)merons or (anti)vortices. In this study we created and imaged in real space magnetic skyrmion bundles, that is, multi-Q three-dimensional skyrmionic textures. These textures consist of a circular spin spiral that ties together a discrete number of skyrmion tubes. We observed skyrmion bundles with integer Q values up to 55. We show here that electric currents drive the collective motion of these particle-like textures similar to skyrmions. Bundles with Q ≠ 0 exhibit a skyrmion Hall effect with a Hall angle of ~62°, whereas Q = 0 bundles, the so-called skyrmioniums, propagate collinearly with respect to the current flow, that is, with a skyrmion Hall angle of ~0°. The experimental observation of multi-Q spin textures adds another member to the family of magnetic topological textures, which may serve in future spintronic devices.
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Affiliation(s)
- Jin Tang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, and University of Science and Technology of China, Hefei, China
| | - Yaodong Wu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, and University of Science and Technology of China, Hefei, China
- Key Laboratory for Photoelectric Detection Science and Technology of Education Department of Anhui Province, School of Physics and Materials Engineering, Hefei Normal University, Hefei, China
| | - Weiwei Wang
- Institutes of Physical Science and Information Technology, Anhui University, Hefei, China
| | - Lingyao Kong
- School of Physics and Materials Science, Anhui University, Hefei, China
| | - Boyao Lv
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, and University of Science and Technology of China, Hefei, China
| | - Wensen Wei
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, and University of Science and Technology of China, Hefei, China
| | - Jiadong Zang
- Department of Physics and Astronomy, University of New Hampshire, Durham, NH, USA
- Materials Science Program, University of New Hampshire, Durham, NH, USA
| | - Mingliang Tian
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, and University of Science and Technology of China, Hefei, China
- School of Physics and Materials Science, Anhui University, Hefei, China
| | - Haifeng Du
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Anhui, Chinese Academy of Sciences, and University of Science and Technology of China, Hefei, China.
- Institutes of Physical Science and Information Technology, Anhui University, Hefei, China.
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18
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Zhang C, Zhang J, Liu C, Zhang S, Yuan Y, Li P, Wen Y, Jiang Z, Zhou B, Lei Y, Zheng D, Song C, Hou Z, Mi W, Schwingenschlögl U, Manchon A, Qiu ZQ, Alshareef HN, Peng Y, Zhang XX. Chiral Helimagnetism and One-Dimensional Magnetic Solitons in a Cr-Intercalated Transition Metal Dichalcogenide. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2101131. [PMID: 34302387 DOI: 10.1002/adma.202101131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 04/25/2021] [Indexed: 06/13/2023]
Abstract
Chiral magnets endowed with topological spin textures are expected to have promising applications in next-generation magnetic memories. In contrast to the well-studied 2D or 3D magnetic skyrmions, the authors report the discovery of 1D nontrivial magnetic solitons in a transition metal dichalcogenide 2H-TaS2 via precise intercalation of Cr elements. In the synthetic Cr1/3 TaS2 (CTS) single crystal, the coupling of the strong spin-orbit interaction from TaS2 and the chiral arrangement of the magnetic Cr ions evoke a robust Dzyaloshinskii-Moriya interaction. A magnetic helix having a short spatial period of ≈25 nm is observed in CTS via Lorentz transmission electron microscopy. In a magnetic field perpendicular to the helical axis, the helical spin structure transforms into a chiral soliton lattice (CSL) with the spin structure evolution being consistent with the chiral sine-Gordon theory, which opens promising perspectives for the application of CSL to fast-speed nonvolatile magnetic memories. This work introduces a new paradigm to soliton physics and provides an effective strategy for seeking novel 2D magnets.
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Affiliation(s)
- Chenhui Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Junwei Zhang
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, School of Physical Science and Technology and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, Gansu Province, 730000, China
| | - Chen Liu
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Senfu Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Ye Yuan
- Songshan Lake Materials Laboratory, Dongguan, Guangdong, 523808, China
| | - Peng Li
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Yan Wen
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Ze Jiang
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, School of Physical Science and Technology and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, Gansu Province, 730000, China
| | - Bojian Zhou
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, School of Physical Science and Technology and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, Gansu Province, 730000, China
| | - Yongjiu Lei
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Dongxing Zheng
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Chengkun Song
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, School of Physical Science and Technology and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, Gansu Province, 730000, China
| | - Zhipeng Hou
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute for Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province, 510006, China
- National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou, Guangdong Province, 510006, China
| | - Wenbo Mi
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Processing Technology, Institute of Advanced Materials Physics, Faculty of Science, Tianjin University, Tianjin, Tianjin Municipality, 300354, China
| | - Udo Schwingenschlögl
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | | | - Zi Qiang Qiu
- Department of Physics, University of California, Berkeley, CA, 94720, USA
| | - Husam N Alshareef
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
| | - Yong Peng
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of Education, School of Physical Science and Technology and Electron Microscopy Centre of Lanzhou University, Lanzhou University, Lanzhou, Gansu Province, 730000, China
| | - Xi-Xiang Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia
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19
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Hayami S, Motome Y. Topological spin crystals by itinerant frustration. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:443001. [PMID: 34343975 DOI: 10.1088/1361-648x/ac1a30] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 08/03/2021] [Indexed: 06/13/2023]
Abstract
Spin textures with nontrivial topology, such as vortices and skyrmions, have attracted attention as a source of unconventional magnetic, transport, and optical phenomena. Recently, a new generation of topological spin textures has been extensively studied in itinerant magnets; in contrast to the conventional ones induced, e.g., by the Dzyaloshinskii-Moriya interaction in noncentrosymmetric systems, they are characterized by extremely short magnetic periods and stable even in centrosymmetric systems. Here we review such new types of topological spin textures with particular emphasis on their stabilization mechanism. Focusing on the interplay between charge and spin degrees of freedom in itinerant electron systems, we show that itinerant frustration, which is the competition among electron-mediated interactions, plays a central role in stabilizing a variety of topological spin crystals including a skyrmion crystal with unconventional high skyrmion number, meron crystals, and hedgehog crystals. We also show that the essential ingredients in the itinerant frustration are represented by bilinear and biquadratic spin interactions in momentum space. This perspective not only provides a unified understanding of the unconventional topological spin crystals but also stimulates further exploration of exotic topological phenomena in itinerant magnets.
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Affiliation(s)
- Satoru Hayami
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
| | - Yukitoshi Motome
- Department of Applied Physics, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
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20
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Unconventional Hall effect and its variation with Co-doping in van der Waals Fe 3GeTe 2. Sci Rep 2021; 11:14121. [PMID: 34238967 PMCID: PMC8266818 DOI: 10.1038/s41598-021-93402-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 06/16/2021] [Indexed: 11/18/2022] Open
Abstract
Two-dimensional (2D) van der Waals (vdW) magnetic materials have attracted a lot of attention owing to the stabilization of long range magnetic order down to atomic dimensions, and the prospect of novel spintronic devices with unique functionalities. The clarification of the magnetoresistive properties and its correlation to the underlying magnetic configurations is essential for 2D vdW-based spintronic devices. Here, the effect of Co-doping on the magnetic and magnetotransport properties of Fe3GeTe2 have been investigated. Magnetotransport measurements reveal an unusual Hall effect behavior whose strength was considerably modified by Co-doping and attributed to arise from the underlying complicated spin textures. The present results provide a clue to tailoring of the underlying interactions necessary for the realization of a variety of unconventional spin textures for 2D vdW FM-based spintronics.
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21
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Zheng G, Wang M, Zhu X, Tan C, Wang J, Albarakati S, Aloufi N, Algarni M, Farrar L, Wu M, Yao Y, Tian M, Zhou J, Wang L. Tailoring Dzyaloshinskii-Moriya interaction in a transition metal dichalcogenide by dual-intercalation. Nat Commun 2021; 12:3639. [PMID: 34131134 PMCID: PMC8206329 DOI: 10.1038/s41467-021-23658-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 05/07/2021] [Indexed: 11/09/2022] Open
Abstract
Dzyaloshinskii-Moriya interaction (DMI) is vital to form various chiral spin textures, novel behaviors of magnons and permits their potential applications in energy-efficient spintronic devices. Here, we realize a sizable bulk DMI in a transition metal dichalcogenide (TMD) 2H-TaS2 by intercalating Fe atoms, which form the chiral supercells with broken spatial inversion symmetry and also act as the source of magnetic orderings. Using a newly developed protonic gate technology, gate-controlled protons intercalation could further change the carrier density and intensely tune DMI via the Ruderman-Kittel-Kasuya-Yosida mechanism. The resultant giant topological Hall resistivity [Formula: see text] of [Formula: see text] at [Formula: see text] (about [Formula: see text] larger than the zero-bias value) is larger than most known chiral magnets. Theoretical analysis indicates that such a large topological Hall effect originates from the two-dimensional Bloch-type chiral spin textures stabilized by DMI, while the large anomalous Hall effect comes from the gapped Dirac nodal lines by spin-orbit interaction. Dual-intercalation in 2H-TaS2 provides a model system to reveal the nature of DMI in the large family of TMDs and a promising way of gate tuning of DMI, which further enables an electrical control of the chiral spin textures and related electromagnetic phenomena.
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Affiliation(s)
- Guolin Zheng
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia
| | - Maoyuan Wang
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China.,Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China.,International Center for Quantum Materials, School of Physics, Peking University, Beijing, 100871, China
| | - Xiangde Zhu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences (CAS), Hefei, 230031, Anhui, China
| | - Cheng Tan
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia
| | - Jie Wang
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences (CAS), Hefei, 230031, Anhui, China.,University of Science and Technology of China, Hefei, 230026, Anhui, China
| | | | - Nuriyah Aloufi
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia
| | - Meri Algarni
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia
| | - Lawrence Farrar
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia
| | - Min Wu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences (CAS), Hefei, 230031, Anhui, China
| | - Yugui Yao
- Centre for Quantum Physics, Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurement (MOE), School of Physics, Beijing Institute of Technology, Beijing, 100081, China.,Beijing Key Lab of Nanophotonics & Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing, 100081, China
| | - Mingliang Tian
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences (CAS), Hefei, 230031, Anhui, China. .,Department of Physics, School of Physics and Materials Science, Anhui University, Hefei, 230601, Anhui, China. .,Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing, 210093, China.
| | - Jianhui Zhou
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences (CAS), Hefei, 230031, Anhui, China.
| | - Lan Wang
- School of Science, RMIT University, Melbourne, VIC, 3001, Australia.
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22
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Ohara K, Zhang X, Chen Y, Wei Z, Ma Y, Xia J, Zhou Y, Liu X. Confinement and Protection of Skyrmions by Patterns of Modified Magnetic Properties. NANO LETTERS 2021; 21:4320-4326. [PMID: 33950694 DOI: 10.1021/acs.nanolett.1c00865] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Magnetic skyrmions are versatile topological excitations that can be used as nonvolatile information carriers. The confinement of skyrmions in channels is fundamental for any application based on the accumulation and transport of skyrmions. Here, we report a method that allows effective position control of skyrmions in designed channels by engineered energy barriers and wells, which is realized in a magnetic multilayer film by harnessing the boundaries of patterns with modified magnetic properties. We experimentally and computationally demonstrate that skyrmions can be attracted or repelled by the boundaries of areas with modified perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction. By fabricating square and stripe patterns with modified magnetic properties, we show the possibility of building reliable channels for confinement, accumulation, and transport of skyrmions, which effectively protect skyrmions from being destroyed at the device edges. Our results are useful for the design of spintronic applications using either static or dynamic skyrmions.
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Affiliation(s)
- Kentaro Ohara
- Department of Electrical and Computer Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
| | - Xichao Zhang
- Department of Electrical and Computer Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
| | - Yinling Chen
- Department of Electrical and Computer Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
| | - Zonhan Wei
- School of Mechanics and Engineering Science, Zhengzhou University, Zhengzhou 450001, China
| | - Yungui Ma
- State Key Lab of Modern Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou 310027, China
| | - Jing Xia
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, China
| | - Yan Zhou
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, China
| | - Xiaoxi Liu
- Department of Electrical and Computer Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan
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23
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Abstract
Skyrmion, a concept originally proposed in particle physics half a century ago, can now find the most fertile field for its applicability, that is, the magnetic skyrmion realized in helimagnetic materials. The spin swirling vortex-like texture of the magnetic skyrmion can define the particle nature by topology; that is, all the constituent spin moments within the two-dimensional sheet wrap the sphere just one time. Such a topological nature of the magnetic skyrmion can lead to extraordinary metastability via topological protection and the driven motion with low electric-current excitation, which may promise future application to spintronics. The skyrmions in the magnetic materials frequently show up as the crystal lattice form, e.g., hexagonal lattice, but sometimes as isolated or independent particles. These skyrmions in magnets were initially found in acentric magnets, such as chiral, polar, and bilayered magnets endowed with antisymmetric spin exchange interaction, while the skyrmion host materials have been explored in a broader family of compounds including centrosymmetric magnets. This review describes the materials science and materials chemistry of magnetic skyrmions using the classification scheme of the skyrmion forming microscopic mechanisms. The emergent phenomena and functions mediated by skyrmions are described, including the generation of emergent magnetic and electric field by statics and dynamics of skrymions and the inherent magnetoelectric effect. The other important magnetic topological defects in two or three dimensions, such as biskyrmions, antiskyrmions, merons, and hedgehogs, are also reviewed in light of their interplay with the skyrmions.
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Affiliation(s)
- Yoshinori Tokura
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.,Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
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24
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Batle J. Topological structures, spontaneous symmetry breaking and energy spectra in dipole hexagonal lattices. Sci Rep 2021; 11:4154. [PMID: 33603046 PMCID: PMC7893179 DOI: 10.1038/s41598-021-83359-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 01/28/2021] [Indexed: 11/28/2022] Open
Abstract
The interplay between the special triangular/hexagonal two dimensional lattice and the long range dipole-dipole interaction gives rise to topological defects, specifically the vortex, formed by a particular arrangement of the interacting classic dipoles. The nature of such vortices has been traditionally explained on the basis of numerical evidence. Here we propose the emerging formation of vortices as the natural minimum energy configuration of interacting (in-plane) two-dimensional dipoles based on the mechanism of spontaneous symmetry breaking. As opposed to the quantal case, where spin textures such as skyrmions or bimerons occur due to non-linearities in their Hamiltonian, it is still possible to witness classic topological structures due only to the nature of the dipole-dipole force. We shall present other (new) topological structures for the in-plane honeycomb lattice, as well as for two-dimensional out-of-plane dipoles. These structures will prove to be essential in the minimum energy configurations for three-dimensional simple hexagonal and hexagonal-closed-packed structures, whose energies in the bulk are obtained for the first time.
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Affiliation(s)
- Josep Batle
- Departament de Física, Universitat de les Illes Balears, 07122, Palma de Mallorca, Balearic Islands, Spain.
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25
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Zou J, Zhang S, Tserkovnyak Y. Topological Transport of Deconfined Hedgehogs in Magnets. PHYSICAL REVIEW LETTERS 2020; 125:267201. [PMID: 33449784 DOI: 10.1103/physrevlett.125.267201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 09/07/2020] [Accepted: 11/23/2020] [Indexed: 06/12/2023]
Abstract
We theoretically investigate the dynamics of magnetic hedgehogs, which are three-dimensional topological spin textures that exist in common magnets, focusing on their transport properties and connections to spintronics. We show that fictitious magnetic monopoles carried by hedgehog textures obey a topological conservation law, based on which a hydrodynamic theory is developed. We propose a nonlocal transport measurement in the disordered phase, where the conservation of the hedgehog flow results in a nonlocal signal decaying inversely proportional to the distance. The bulk-edge correspondence between the hedgehog number and skyrmion number, the fictitious electric charges arising from magnetic dynamics, and the analogy between bound states of hedgehogs in ordered phase and the quark confinement in quantum chromodynamics are also discussed. Our study points to a practical potential in utilizing hedgehog flows for long-range neutral signal propagation or manipulation of skyrmion textures in three-dimensional magnetic materials.
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Affiliation(s)
- Ji Zou
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Shu Zhang
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
| | - Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, California 90095, USA
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26
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Yasui Y, Butler CJ, Khanh ND, Hayami S, Nomoto T, Hanaguri T, Motome Y, Arita R, Arima TH, Tokura Y, Seki S. Imaging the coupling between itinerant electrons and localised moments in the centrosymmetric skyrmion magnet GdRu 2Si 2. Nat Commun 2020; 11:5925. [PMID: 33230104 PMCID: PMC7684290 DOI: 10.1038/s41467-020-19751-4] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Accepted: 10/26/2020] [Indexed: 11/10/2022] Open
Abstract
Magnetic skyrmions were thought to be stabilised only in inversion-symmetry breaking structures, but skyrmion lattices were recently discovered in inversion symmetric Gd-based compounds, spurring questions of the stabilisation mechanism. A natural consequence of a recent theoretical proposal, a coupling between itinerant electrons and localised magnetic moments, is that the skyrmions are amenable to detection using even non-magnetic probes such as spectroscopic-imaging scanning tunnelling microscopy (SI-STM). Here SI-STM observations of GdRu2Si2 reveal patterns in the local density of states that indeed vary with the underlying magnetic structures. These patterns are qualitatively reproduced by model calculations which assume exchange coupling between itinerant electrons and localised moments. These findings provide a clue to understand the skyrmion formation mechanism in GdRu2Si2. GdRu2Si2 can host magnetic skyrmions, however, it does not have inversion symmetry breaking, a feature usually assumed necessary for skyrmion formation. Using scanning tunnelling microscopy, the authors visualise the double-Q structure in the itinerant electrons that mediate the skyrmion formation.
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Affiliation(s)
- Yuuki Yasui
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.
| | | | - Nguyen Duy Khanh
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.,Institute for Solid State Physics, The University of Tokyo, Chiba, 277-8581, Japan
| | - Satoru Hayami
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan.,Department of Physics, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
| | - Takuya Nomoto
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Tetsuo Hanaguri
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.
| | - Yukitoshi Motome
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Ryotaro Arita
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.,Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.,Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba, 277-8561, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science, Wako, Saitama, 351-0198, Japan.,Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan.,Tokyo College, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
| | - Shinichiro Seki
- Department of Applied Physics, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan.,PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, 332-0012, Japan.,Institute of Engineering Innovation, The University of Tokyo, Bunkyo, Tokyo, 113-8656, Japan
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27
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Bulk and surface topological indices for a skyrmion string: current-driven dynamics of skyrmion string in stepped samples. Sci Rep 2020; 10:20303. [PMID: 33219262 PMCID: PMC7680146 DOI: 10.1038/s41598-020-76469-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 10/28/2020] [Indexed: 11/21/2022] Open
Abstract
The magnetic skyrmion is a topological magnetic vortex, and its topological nature is characterized by an index called skyrmion number which is a mapping of the magnetic moments defined on a two-dimensional space to a unit sphere. In three-dimensions, a skyrmion, i.e., a vortex penetrating though the magnet naturally forms a string, which terminates at the surfaces of the magnet or in the bulk. For such a string, the topological indices, which control its topological stability are less trivial. Here, we study theoretically, in terms of numerical simulation, the dynamics of current-driven motion of a skyrmion string in a film sample with the step edges on the surface. In particular, skyrmion–antiskyrmion pair is generated by driving a skyrmion string through the side step with an enough height. We find that the topological indices relevant to the stability are the followings; (1) skyrmion number along the developed surface, and (2) the monopole charge in the bulk defined as the integral over the surface enclosing a singular magnetic configuration. As long as the magnetic configuration is slowly varying, the former is conserved while its changes is associated with nonzero monopole charge. The skyrmion number and the monoplole charge offer a coherent understanding of the stability of the topological magnetic texture and the nontrivial dynamics of skyrmion strings.
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28
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Hirosawa T, Díaz SA, Klinovaja J, Loss D. Magnonic Quadrupole Topological Insulator in Antiskyrmion Crystals. PHYSICAL REVIEW LETTERS 2020; 125:207204. [PMID: 33258632 DOI: 10.1103/physrevlett.125.207204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 09/20/2020] [Accepted: 10/15/2020] [Indexed: 06/12/2023]
Abstract
We uncover that antiskyrmion crystals provide an experimentally accessible platform to realize a magnonic quadrupole topological insulator, whose hallmark signatures are robust magnonic corner states. Furthermore, we show that tuning an applied magnetic field can trigger the self-assembly of antiskyrmions carrying a fractional topological charge along the sample edges. Crucially, these fractional antiskyrmions restore the symmetries needed to enforce the emergence of the magnonic corner states. Using the machinery of nested Wilson loops, adapted to magnonic systems supported by noncollinear magnetic textures, we demonstrate the quantization of the bulk quadrupole moment, edge dipole moments, and corner charges.
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Affiliation(s)
- Tomoki Hirosawa
- Department of Physics, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
| | - Sebastián A Díaz
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
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29
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Chai K, Li ZA, Liu R, Zou B, Farle M, Li J. Dynamics of chiral state transitions and relaxations in an FeGe thin plate via in situ Lorentz microscopy. NANOSCALE 2020; 12:14919-14925. [PMID: 32638795 DOI: 10.1039/d0nr03278f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Studying the magnetic transition between different topological spin textures in noncentrosymmetric magnets under external stimuli is an important topic in chiral magnetism. Here, using in situ Lorentz transmission electron microscopy (LTEM) we directly visualize the thermal-driven magnetic transitions and dynamic characteristics in FeGe thin plates. A novel protocol-dependent phase diagram of FeGe thin plates was obtained via pulsed laser excitation. Moreover, by setting the appropriate specimen temperature, the relaxation of chiral magnetic states in FeGe specimens was recorded and analyzed with an Arrhenius-type relaxation mechanism. We present the field-dependent activation energy barriers for chiral state transitions and the magnetic transition pathways of these spin textures for FeGe thin plates. Our results unveil the effects of thermal excitation on the topological spin texture transitions and provide useful information about magnetic dynamics of chiral magnetic state relaxation.
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Affiliation(s)
- Ke Chai
- Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China. and Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences, Beijing 100190, China
| | - Zi-An Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences, Beijing 100190, China
| | - Ruibin Liu
- Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China.
| | - Bingsuo Zou
- Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic Systems, School of Physics, Beijing Institute of Technology, Beijing 100081, China. and Center on Nano-energy Research, School of Physical Science and Technology, Guangxi University, Nanning, 530004, China
| | - Michael Farle
- Faculty of Physics and Center for Nanointegration (CENIDE), University of Duisburg-Essen, 47057 Duisburg, Germany
| | - Jianqi Li
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences, Beijing 100190, China and Yangtze River Delta Physics Research Center Co., Ltd. - Liyang, Jiangsu, 213300, China and Songshan Lake Materials Laboratory - Dongguan, Guangdong, 523808, China
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30
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Štefančič A, Holt SJR, Lees MR, Ritter C, Gutmann MJ, Lancaster T, Balakrishnan G. Establishing magneto-structural relationships in the solid solutions of the skyrmion hosting family of materials: GaV 4S 8-ySe y. Sci Rep 2020; 10:9813. [PMID: 32555354 PMCID: PMC7299962 DOI: 10.1038/s41598-020-65676-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 04/30/2020] [Indexed: 11/09/2022] Open
Abstract
The GaV4S8-ySey (y = 0 to 8) family of materials have been synthesized in both polycrystalline and single crystal form, and their structural and magnetic properties thoroughly investigated. Each of these materials crystallizes in the F[Formula: see text][Formula: see text]3m space group at ambient temperature. However, in contrast to the end members GaV4S8 and GaV4Se8, that undergo a structural transition to the R3m space group at 42 and 41 K respectively, the solid solutions (y = 1 to 7) retain cubic symmetry down to 1.5 K. In zero applied field the end members of the family order ferromagnetically at 13 K (GaV4S8) and 18 K (GaV4Se8), while the intermediate compounds exhibit a spin-glass-like ground state. We demonstrate that the magnetic structure of GaV4S8 shows localization of spins on the V cations, indicating that a charge ordering mechanism drives the structural phase transition. We conclude that the observation of both structural and ferromagnetic transitions in the end members of the series in zero field is a prerequisite for the stabilization of a skyrmion phase, and discuss how the absence of these transitions in the y = 1 to 7 materials can be explained by their structural properties.
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Affiliation(s)
- Aleš Štefančič
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom.
| | - Samuel J R Holt
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom
| | - Martin R Lees
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom
| | | | - Matthias J Gutmann
- ISIS Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, United Kingdom
| | - Tom Lancaster
- Durham University, Department of Physics, South Road, Durham, DH1 3LE, United Kingdom
| | - Geetha Balakrishnan
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom.
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31
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Khanh ND, Nakajima T, Yu X, Gao S, Shibata K, Hirschberger M, Yamasaki Y, Sagayama H, Nakao H, Peng L, Nakajima K, Takagi R, Arima TH, Tokura Y, Seki S. Nanometric square skyrmion lattice in a centrosymmetric tetragonal magnet. NATURE NANOTECHNOLOGY 2020; 15:444-449. [PMID: 32424341 DOI: 10.1038/s41565-020-0684-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 03/19/2020] [Indexed: 06/11/2023]
Abstract
Magnetic skyrmions are topologically stable spin swirls with a particle-like character and are potentially suitable for the design of high-density information bits. Although most known skyrmion systems arise in non-centrosymmetric systems with a Dzyaloshinskii-Moriya interaction, centrosymmetric magnets with a triangular lattice can also give rise to skyrmion formation, with a geometrically frustrated lattice being considered essential in this case. Until now, it remains an open question if skyrmions can also exist in the absence of both geometrically frustrated lattice and inversion symmetry breaking. Here we discover a square skyrmion lattice state with 1.9 nm diameter skyrmions in the centrosymmetric tetragonal magnet GdRu2Si2 without a geometrically frustrated lattice by means of resonant X-ray scattering and Lorentz transmission electron microscopy experiments. A plausible origin of the observed skyrmion formation is four-spin interactions mediated by itinerant electrons in the presence of easy-axis anisotropy. Our results suggest that rare-earth intermetallics with highly symmetric crystal lattices may ubiquitously host nanometric skyrmions of exotic origins.
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Affiliation(s)
- Nguyen Duy Khanh
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan.
- Institute for Solid State Physics (ISSP), The University of Tokyo, Chiba, Japan.
| | - Taro Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Institute for Solid State Physics (ISSP), The University of Tokyo, Chiba, Japan
| | - Xiuzhen Yu
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
| | - Shang Gao
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
- Neutron Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA
| | - Kiyou Shibata
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Institute of Industrial Science, The University of Tokyo, Meguro, Japan
| | - Max Hirschberger
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo, Japan
- Quantum-Phase Electronics Center, The University of Tokyo, Tokyo, Japan
| | - Yuichi Yamasaki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Research and Services Division of Materials Data and Integrated System (MaDIS), National Institute for Materials Science (NIMS), Tsukuba, Japan
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Japan
| | - Hajime Sagayama
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Tsukuba, Japan
| | - Hironori Nakao
- Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba, Tsukuba, Japan
| | - Licong Peng
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
| | - Kiyomi Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
| | - Rina Takagi
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo, Japan
- Institute of Engineering Innovation, The University of Tokyo, Tokyo, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan
- Department of Applied Physics, The University of Tokyo, Tokyo, Japan
- Tokyo College, The University of Tokyo, Tokyo, Japan
| | - Shinichiro Seki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Japan.
- Department of Applied Physics, The University of Tokyo, Tokyo, Japan.
- PRESTO, Japan Science and Technology Agency (JST), Kawaguchi, Japan.
- Institute of Engineering Innovation, The University of Tokyo, Tokyo, Japan.
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32
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Zhang X, Zhou Y, Mee Song K, Park TE, Xia J, Ezawa M, Liu X, Zhao W, Zhao G, Woo S. Skyrmion-electronics: writing, deleting, reading and processing magnetic skyrmions toward spintronic applications. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:143001. [PMID: 31689688 DOI: 10.1088/1361-648x/ab5488] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The field of magnetic skyrmions has been actively investigated across a wide range of topics during the last decades. In this topical review, we mainly review and discuss key results and findings in skyrmion research since the first experimental observation of magnetic skyrmions in 2009. We particularly focus on the theoretical, computational and experimental findings and advances that are directly relevant to the spintronic applications based on magnetic skyrmions, i.e. their writing, deleting, reading and processing driven by magnetic field, electric current and thermal energy. We then review several potential applications including information storage, logic computing gates and non-conventional devices such as neuromorphic computing devices. Finally, we discuss possible future research directions on magnetic skyrmions, which also cover rich topics on other topological textures such as antiskyrmions and bimerons in antiferromagnets and frustrated magnets.
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Affiliation(s)
- Xichao Zhang
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, People's Republic of China
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33
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Han MG, Garlow JA, Kharkov Y, Camacho L, Rov R, Sauceda J, Vats G, Kisslinger K, Kato T, Sushkov O, Zhu Y, Ulrich C, Söhnel T, Seidel J. Scaling, rotation, and channeling behavior of helical and skyrmion spin textures in thin films of Te-doped Cu 2OSeO 3. SCIENCE ADVANCES 2020; 6:eaax2138. [PMID: 32258389 PMCID: PMC7101222 DOI: 10.1126/sciadv.aax2138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 01/03/2020] [Indexed: 06/11/2023]
Abstract
Topologically nontrivial spin textures such as vortices, skyrmions, and monopoles are promising candidates as information carriers for future quantum information science. Their controlled manipulation including creation and annihilation remains an important challenge toward practical applications and further exploration of their emergent phenomena. Here, we report controlled evolution of the helical and skyrmion phases in thin films of multiferroic Te-doped Cu2OSeO3 as a function of material thickness, dopant, temperature, and magnetic field using in situ Lorentz phase microscopy. We report two previously unknown phenomena in chiral spin textures in multiferroic Cu2OSeO3: anisotropic scaling and channeling with a fixed-Q state. The skyrmion channeling effectively suppresses the recently reported second skyrmion phase formation at low temperature. Our study provides a viable way toward controlled manipulation of skyrmion lattices, envisaging chirality-controlled skyrmion flow circuits and enabling precise measurement of emergent electromagnetic induction and topological Hall effects in skyrmion lattices.
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Affiliation(s)
- M.-G. Han
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - J. A. Garlow
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Y. Kharkov
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - L. Camacho
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
| | - R. Rov
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
- MacDiarmid Institute of Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington, New Zealand
| | - J. Sauceda
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - G. Vats
- School of Materials Science and Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
| | - K. Kisslinger
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - T. Kato
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, Japan
| | - O. Sushkov
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Y. Zhu
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - C. Ulrich
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - T. Söhnel
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
- MacDiarmid Institute of Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington, New Zealand
| | - J. Seidel
- School of Materials Science and Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
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34
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Ding B, Li Z, Xu G, Li H, Hou Z, Liu E, Xi X, Xu F, Yao Y, Wang W. Observation of Magnetic Skyrmion Bubbles in a van der Waals Ferromagnet Fe 3GeTe 2. NANO LETTERS 2020; 20:868-873. [PMID: 31869236 DOI: 10.1021/acs.nanolett.9b03453] [Citation(s) in RCA: 75] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Two-dimensional (2D) van der Waals (vdW) magnetic materials have recently been introduced as a new horizon in materials science, and they enable potential applications for next-generation spintronic devices. Here, in this communication, the observations of stable Bloch-type magnetic skyrmions in single crystals of 2D vdW Fe3GeTe2 (FGT) are reported by using in situ Lorentz transmission electron microscopy (TEM). We find the ground-state magnetic stripe domains in FGT transform into skyrmion bubbles when an external magnetic field is applied perpendicularly to the (001) thin plate with temperatures below the Curie temperature TC. Most interestingly, a hexagonal lattice of skyrmion bubbles is obtained via field-cooling manipulation with magnetic field applied along the [001] direction. Owing to their topological stability, the skyrmion bubble lattices are stable to large field-cooling tilted angles and further reproduced by utilizing the micromagnetic simulations. These observations directly demonstrate that the 2D vdW FGT possesses a rich variety of topological spin textures, being of great promise for future applications in the field of spintronics.
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Affiliation(s)
- Bei Ding
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Zefang Li
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Guizhou Xu
- School of Materials Science and Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - Hang Li
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
- University of Chinese Academy of Sciences , Beijing 100049 , China
| | - Zhipeng Hou
- South China Academy of Advanced Optoelectronics , South China Normal University , Guangzhou 510006 , China
| | - Enke Liu
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
| | - Xuekui Xi
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
| | - Feng Xu
- School of Materials Science and Engineering , Nanjing University of Science and Technology , Nanjing 210094 , China
| | - Yuan Yao
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
| | - Wenhong Wang
- Beijing National Laboratory for Condensed Matter Physics , Institute of Physics, Chinese Academy of Sciences , Beijing 100190 , China
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35
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Puphal P, Pomjakushin V, Kanazawa N, Ukleev V, Gawryluk DJ, Ma J, Naamneh M, Plumb NC, Keller L, Cubitt R, Pomjakushina E, White JS. Topological Magnetic Phase in the Candidate Weyl Semimetal CeAlGe. PHYSICAL REVIEW LETTERS 2020; 124:017202. [PMID: 31976692 DOI: 10.1103/physrevlett.124.017202] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Revised: 11/01/2019] [Indexed: 06/10/2023]
Abstract
We report the discovery of topological magnetism in the candidate magnetic Weyl semimetal CeAlGe. Using neutron scattering we find this system to host several incommensurate, square-coordinated multi-k[over →] magnetic phases below T_{N}. The topological properties of a phase stable at intermediate magnetic fields parallel to the c axis are suggested by observation of a topological Hall effect. Our findings highlight CeAlGe as an exceptional system for exploiting the interplay between the nontrivial topologies of the magnetization in real space and Weyl nodes in momentum space.
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Affiliation(s)
- Pascal Puphal
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Vladimir Pomjakushin
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
| | - Victor Ukleev
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Dariusz J Gawryluk
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Junzhang Ma
- Swiss Light Source (SLS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Muntaser Naamneh
- Swiss Light Source (SLS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Nicholas C Plumb
- Swiss Light Source (SLS), Paul Scherrer Institute (PSI), CH-5232 Villigen PSI, Switzerland
| | - Lukas Keller
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Robert Cubitt
- Institut Laue-Langevin (ILL), 71 avenue des Martyrs, CS 20156, 38042 Grenoble cedex 9, France
| | - Ekaterina Pomjakushina
- Laboratory for Multiscale Materials Experiments (LMX), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
| | - Jonathan S White
- Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland
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36
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Jena J, Stinshoff R, Saha R, Srivastava AK, Ma T, Deniz H, Werner P, Felser C, Parkin SSP. Observation of Magnetic Antiskyrmions in the Low Magnetization Ferrimagnet Mn 2Rh 0.95Ir 0.05Sn. NANO LETTERS 2020; 20:59-65. [PMID: 31809059 PMCID: PMC6953472 DOI: 10.1021/acs.nanolett.9b02973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2019] [Revised: 12/04/2019] [Indexed: 06/10/2023]
Abstract
Recently, magnetic antiskyrmions were discovered in Mn1.4Pt0.9Pd0.1Sn, an inverse tetragonal Heusler compound that is nominally a ferrimagnet, but which can only be formed with substantial Mn vacancies. The vacancies reduce considerably the compensation of the moments between the two expected antiferromagnetically coupled Mn sub-lattices so that the overall magnetization is very high and the compound is almost a "ferromagnet". Here, we report the observation of antiskyrmions in a second inverse tetragonal Heusler compound, Mn2Rh0.95Ir0.05Sn, which can be formed stoichiometrically without any Mn vacancies and which thus exhibits a much smaller magnetization. Individual and lattices of antiskyrmions can be stabilized over a wide range of temperature from near room temperature to 100 K, the base temperature of the Lorentz transmission electron microscope used to image them. In low magnetic fields helical spin textures are found which evolve into antiskyrmion structures in the presence of small magnetic fields. A weaker Dzyaloshinskii-Moriya interaction (DMI), that stabilizes the antiskyrmions, is expected for the 4d element Rh as compared to the 5d element Pt, so that the observation of antiskyrmions in Mn2Rh0.95Ir0.05Sn establishes the intrinsic stability of antiskyrmions in these Heusler compounds. Moreover, the finding of antiskyrmions with substantially lower magnetization promises, via chemical tuning, even zero moment antiskyrmions with important technological import.
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Affiliation(s)
- Jagannath Jena
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
| | - Rolf Stinshoff
- Max
Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Rana Saha
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
| | - Abhay K. Srivastava
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
- Institute
of Physics, Martin Luther University, Halle-Wittenberg, 06120 Halle (Saale), Germany
| | - Tianping Ma
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
| | - Hakan Deniz
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
| | - Peter Werner
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
| | - Claudia Felser
- Max
Planck Institute for Chemical Physics of Solids, Nöthnitzer Strasse 40, 01187 Dresden, Germany
| | - Stuart S. P. Parkin
- Max Planck
Institute of Microstructure Physics, Weinberg 2, 06120 Halle (Saale), Germany
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37
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Cheng Y, Yu S, Zhu M, Hwang J, Yang F. Evidence of the Topological Hall Effect in Pt/Antiferromagnetic Insulator Bilayers. PHYSICAL REVIEW LETTERS 2019; 123:237206. [PMID: 31868464 DOI: 10.1103/physrevlett.123.237206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Revised: 11/04/2019] [Indexed: 06/10/2023]
Abstract
The topological Hall effect has been a primary indicator of nontrivial spin textures in magnetic materials. We observe the evidence of the topological Hall effect in Pt/Cr_{2}O_{3} bilayers grown on Al_{2}O_{3}(0001) and Al_{2}O_{3}(112[over ¯]0), where the Cr_{2}O_{3} epitaxial film is an antiferromagnetic insulator. The Pt/Cr_{2}O_{3} bilayers exhibit topological Hall resistivity for Cr_{2}O_{3} thicknesses below 6 nm near and above room temperature, which is above the Néel temperature of Cr_{2}O_{3}, revealing the key role of thermal fluctuations in the formation of spin textures. The similarity of topological Hall signals in (0001)- and (112[over ¯]0)-oriented Cr_{2}O_{3} films indicates that the emergence of spin textures is insensitive to crystalline orientation.
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Affiliation(s)
- Yang Cheng
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Sisheng Yu
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Menglin Zhu
- Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43212, USA
| | - Jinwoo Hwang
- Department of Materials Science and Engineering, The Ohio State University, Columbus, Ohio 43212, USA
| | - Fengyuan Yang
- Department of Physics, The Ohio State University, Columbus, Ohio 43210, USA
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38
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Bornemann M, Grytsiuk S, Baumeister PF, Dos Santos Dias M, Zeller R, Lounis S, Blügel S. Complex magnetism of B20-MnGe: from spin-spirals, hedgehogs to monopoles. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:485801. [PMID: 31382246 DOI: 10.1088/1361-648x/ab38a0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
B20 compounds are the playground for various non-trivial magnetic textures such as skyrmions, which are topologically protected states. Recent measurements on B20-MnGe indicate no clear consensus on its magnetic behavior, which is characterized by the presence of either spin-spirals or three-dimensional objects interpreted to be a cubic lattice of hedgehogs and anti-hedgehogs. Utilizing a massively parallel linear scaling all-electron density functional algorithm, we find from full first-principles simulations on cells containing thousands of atoms that upon increase of the compound volume, the state with lowest energy switches across different magnetic phases: ferromagnetic, spin-spiral, hedgehog and monopole.
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Affiliation(s)
- Marcel Bornemann
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich & JARA, 52425 Jülich, Germany
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39
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Ahmed AS, Lee AJ, Bagués N, McCullian BA, Thabt AMA, Perrine A, Wu PK, Rowland JR, Randeria M, Hammel PC, McComb DW, Yang F. Spin-Hall Topological Hall Effect in Highly Tunable Pt/Ferrimagnetic-Insulator Bilayers. NANO LETTERS 2019; 19:5683-5688. [PMID: 31310542 DOI: 10.1021/acs.nanolett.9b02265] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Electrical detection of topological magnetic textures such as skyrmions is currently limited to conducting materials. Although magnetic insulators offer key advantages for skyrmion technologies with high speed and low loss, they have not yet been explored electrically. Here, we report a prominent topological Hall effect in Pt/Tm3Fe5O12 bilayers, where the pristine Tm3Fe5O12 epitaxial films down to 1.25 unit cell thickness allow for tuning of topological Hall stability over a broad range from 200 to 465 K through atomic-scale thickness control. Although Tm3Fe5O12 is insulating, we demonstrate the detection of topological magnetic textures through a novel phenomenon: "spin-Hall topological Hall effect" (SH-THE), where the interfacial spin-orbit torques allow spin-Hall-effect generated spins in Pt to experience the unique topology of the underlying skyrmions in Tm3Fe5O12. This novel electrical detection phenomenon paves a new path for utilizing a large family of magnetic insulators in future skyrmion technologies.
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40
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Kurumaji T, Nakajima T, Hirschberger M, Kikkawa A, Yamasaki Y, Sagayama H, Nakao H, Taguchi Y, Arima TH, Tokura Y. Skyrmion lattice with a giant topological Hall effect in a frustrated triangular-lattice magnet. Science 2019; 365:914-918. [DOI: 10.1126/science.aau0968] [Citation(s) in RCA: 262] [Impact Index Per Article: 52.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 07/30/2019] [Indexed: 11/02/2022]
Abstract
Geometrically frustrated magnets can host complex spin textures, leading to unconventional electromagnetic responses. Magnetic frustration may also promote topologically nontrivial spin states such as magnetic skyrmions. Experimentally, however, skyrmions have largely been observed in noncentrosymmetric lattice structures or interfacial symmetry-breaking heterostructures. Here, we report the emergence of a Bloch-type skyrmion state in the frustrated centrosymmetric triangular-lattice magnet Gd2PdSi3. We observed a giant topological Hall response, indicating a field-induced skyrmion phase, which is further corroborated by the observation of in-plane spin modulation probed by resonant x-ray scattering. Our results may lead to further discoveries of emergent electrodynamics in magnetically frustrated centrosymmetric materials.
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41
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Meng KY, Ahmed AS, Baćani M, Mandru AO, Zhao X, Bagués N, Esser BD, Flores J, McComb DW, Hug HJ, Yang F. Observation of Nanoscale Skyrmions in SrIrO 3/SrRuO 3 Bilayers. NANO LETTERS 2019; 19:3169-3175. [PMID: 30935207 DOI: 10.1021/acs.nanolett.9b00596] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Skyrmion imaging and electrical detection via topological Hall (TH) effect are two primary techniques for probing magnetic skyrmions, which hold promise for next-generation magnetic storage. However, these two kinds of complementary techniques have rarely been employed to investigate the same samples. We report the observation of nanoscale skyrmions in SrIrO3/SrRuO3 (SIO/SRO) bilayers in a wide temperature range from 10 to 100 K. The SIO/SRO bilayers exhibit a remarkable TH effect, which is up to 200% larger than the anomalous Hall (AH) effect at 5 K, and zero-field TH effect at 90 K. Using variable-temperature, high-field magnetic force microscopy (MFM), we imaged skyrmions as small as 10 nm, which emerge in the same field ranges as the TH effect. These results reveal a rich space for skyrmion exploration and tunability in oxide heterostructures.
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Affiliation(s)
- Keng-Yuan Meng
- Department of Physics , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Adam S Ahmed
- Department of Physics , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Mirko Baćani
- Empa , Swiss Federal Laboratories for Materials Science and Technology , Dübendorf CH-8600 , Switzerland
| | - Andrada-Oana Mandru
- Empa , Swiss Federal Laboratories for Materials Science and Technology , Dübendorf CH-8600 , Switzerland
| | - Xue Zhao
- Empa , Swiss Federal Laboratories for Materials Science and Technology , Dübendorf CH-8600 , Switzerland
| | - Núria Bagués
- Center for Electron Microscopy and Analysis , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Bryan D Esser
- Center for Electron Microscopy and Analysis , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Jose Flores
- Department of Physics , The Ohio State University , Columbus , Ohio 43210 , United States
| | - David W McComb
- Center for Electron Microscopy and Analysis , The Ohio State University , Columbus , Ohio 43210 , United States
| | - Hans J Hug
- Empa , Swiss Federal Laboratories for Materials Science and Technology , Dübendorf CH-8600 , Switzerland
- Department of Physics , University of Basel , Basel CH-4056 , Switzerland
| | - Fengyuan Yang
- Department of Physics , The Ohio State University , Columbus , Ohio 43210 , United States
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42
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Dynamics of skyrmion in disordered chiral magnet of thin film form. Sci Rep 2019; 9:5111. [PMID: 30911022 PMCID: PMC6434043 DOI: 10.1038/s41598-019-41441-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Accepted: 03/05/2019] [Indexed: 11/16/2022] Open
Abstract
Magnetic skyrmion is a topological spin texture characterized by the mapping from the two dimensional real space to the unit sphere. It is realized in chiral magnets under an external magnetic field in the plane perpendicular to it. In thin film samples, which are most relevant to the applications, the thickness of the system parallel to the magnetic field is finite, and a skyrmion turns into a skyrmion string, which is often assumed to be a straight rod. There are phenomena related to the internal degrees of freedom along the string, e.g., the monopole and anti-monopole creation/annihilation, corresponding to the change in the skyrmion number. However, the role of this finite thickness in the topological stability and dynamics has not been explored yet. Here we study theoretically the current-driven dynamics of a skyrmion string under disorder potential by systematically changing the thickness of the sample to reveal the dynamical phase diagram in the plane of current density and thickness. We found the three regions, i.e., (i) pinned skyrmion string, (ii) moving depinned skyrmion string, and (iii) annihilation of skyrmion string, for thin and thick limits while (iii) is missing in the intermediate case. This indicates that there is the optimal range of thickness for the topological stability of skyrmion string enhanced compared with a two-dimensional skyrmion. This result provides a way to design and control skyrmions in thin films and interfaces of finite thickness.
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43
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Fujishiro Y, Kanazawa N, Nakajima T, Yu XZ, Ohishi K, Kawamura Y, Kakurai K, Arima T, Mitamura H, Miyake A, Akiba K, Tokunaga M, Matsuo A, Kindo K, Koretsune T, Arita R, Tokura Y. Topological transitions among skyrmion- and hedgehog-lattice states in cubic chiral magnets. Nat Commun 2019; 10:1059. [PMID: 30837479 PMCID: PMC6401095 DOI: 10.1038/s41467-019-08985-6] [Citation(s) in RCA: 83] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2018] [Accepted: 02/11/2019] [Indexed: 11/09/2022] Open
Abstract
Manipulating topological spin textures is a key for exploring unprecedented emergent electromagnetic phenomena. Whereas switching control of magnetic skyrmions, e.g., the transitions between a skyrmion-lattice phase and conventional magnetic orders, is intensively studied towards development of future memory device concepts, transitions among spin textures with different topological orders remain largely unexplored. Here we develop a series of chiral magnets MnSi1-xGex, serving as a platform for transitions among skyrmion- and hedgehog-lattice states. By neutron scattering, Lorentz transmission electron microscopy and high-field transport measurements, we observe three different topological spin textures with variation of the lattice constant controlled by Si/Ge substitution: two-dimensional skyrmion lattice in x = 0-0.25 and two distinct three-dimensional hedgehog lattices in x = 0.3-0.6 and x = 0.7-1. The emergence of various topological spin states in the chemical-pressure-controlled materials suggests a new route for direct manipulation of the spin-texture topology by facile mechanical methods.
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Affiliation(s)
- Y Fujishiro
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - N Kanazawa
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
| | - T Nakajima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - X Z Yu
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - K Ohishi
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Naka, Ibaraki, 319-1106, Japan
| | - Y Kawamura
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Naka, Ibaraki, 319-1106, Japan
| | - K Kakurai
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
- Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society (CROSS), Tokai, Naka, Ibaraki, 319-1106, Japan
| | - T Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa, Chiba, 277-8561, Japan
| | - H Mitamura
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - A Miyake
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - K Akiba
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - M Tokunaga
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - A Matsuo
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - K Kindo
- The Institute for Solid State Physics (ISSP), The University of Tokyo, Kashiwa, Chiba, 277-8581, Japan
| | - T Koretsune
- Department of Physics, Tohoku University, Aoba-ku, Sendai, Miyagi, 980-8578, Japan
| | - R Arita
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
| | - Y Tokura
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama, 351-0198, Japan
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Yokouchi T, Hoshino S, Kanazawa N, Kikkawa A, Morikawa D, Shibata K, Arima TH, Taguchi Y, Kagawa F, Nagaosa N, Tokura Y. Current-induced dynamics of skyrmion strings. SCIENCE ADVANCES 2018; 4:eaat1115. [PMID: 30105304 PMCID: PMC6086615 DOI: 10.1126/sciadv.aat1115] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 06/29/2018] [Indexed: 05/29/2023]
Abstract
Dynamics of string-like objects is an important issue in a broad range of physical systems, including vortex lines in superconductors, viscoelastic polymers, and superstrings in elementary particle physics. In noncentrosymmetric magnets, string forms of magnetic skyrmions are present as topological spin objects, and their current-induced dynamics has recently attracted intense interest. We show in the chiral magnet MnSi that the current-induced deformation dynamics of skyrmion strings results in transport response associated with the real-space Berry phase. Prominent nonlinear Hall signals emerge above the threshold current only in the skyrmion phase. We clarify the mechanism for these nonlinear Hall signals by adopting spin density wave picture to describe the moving skyrmion lattice; deformation of skyrmion strings occurs in an asymmetric manner due to the Dzyaloshinskii-Moriya interaction, which leads to the nonreciprocal nonlinear Hall response originating from an emergent electromagnetic field. This finding reveals the dynamical nature of string-like objects and consequent transport outcomes in noncentrosymmetric systems.
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Affiliation(s)
- Tomoyuki Yokouchi
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | | | - Naoya Kanazawa
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
| | - Akiko Kikkawa
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | | | - Kiyou Shibata
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Taka-hisa Arima
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
- Department of Advanced Materials Science, The University of Tokyo, Kashiwa 277-8561, Japan
| | | | - Fumitaka Kagawa
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Naoto Nagaosa
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
| | - Yoshinori Tokura
- Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
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45
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Zheng F, Rybakov FN, Borisov AB, Song D, Wang S, Li ZA, Du H, Kiselev NS, Caron J, Kovács A, Tian M, Zhang Y, Blügel S, Dunin-Borkowski RE. Experimental observation of chiral magnetic bobbers in B20-type FeGe. NATURE NANOTECHNOLOGY 2018; 13:451-455. [PMID: 29632400 DOI: 10.1038/s41565-018-0093-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 02/14/2018] [Indexed: 05/12/2023]
Abstract
Chiral magnetic skyrmions1,2 are nanoscale vortex-like spin textures that form in the presence of an applied magnetic field in ferromagnets that support the Dzyaloshinskii-Moriya interaction (DMI) because of strong spin-orbit coupling and broken inversion symmetry of the crystal3,4. In sharp contrast to other systems5,6 that allow for the formation of a variety of two-dimensional (2D) skyrmions, in chiral magnets the presence of the DMI commonly prevents the stability and coexistence of topological excitations of different types 7 . Recently, a new type of localized particle-like object-the chiral bobber (ChB)-was predicted theoretically in such materials 8 . However, its existence has not yet been verified experimentally. Here, we report the direct observation of ChBs in thin films of B20-type FeGe by means of quantitative off-axis electron holography (EH). We identify the part of the temperature-magnetic field phase diagram in which ChBs exist and distinguish two mechanisms for their nucleation. Furthermore, we show that ChBs are able to coexist with skyrmions over a wide range of parameters, which suggests their possible practical applications in novel magnetic solid-state memory devices, in which a stream of binary data bits can be encoded by a sequence of skyrmions and bobbers.
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Affiliation(s)
- Fengshan Zheng
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
| | - Filipp N Rybakov
- Department of Physics, KTH-Royal Institute of Technology, Stockholm, Sweden
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia
- Ural Federal University, Ekaterinburg, Russia
| | - Aleksandr B Borisov
- M.N. Miheev Institute of Metal Physics of Ural Branch of Russian Academy of Sciences, Ekaterinburg, Russia
- Ural Federal University, Ekaterinburg, Russia
| | - Dongsheng Song
- National Center for Electron Microscopy in Beijing, School of Materials Science and Engineering, Tsinghua University, Beijing, China
| | - Shasha Wang
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory and University of Science and Technology of China, Chinese Academy of Science (CAS), Hefei, Anhui Province, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province, China
| | - Zi-An Li
- Institute of Physics, Chinese Academy of Sciences, Beijing, China
| | - Haifeng Du
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory and University of Science and Technology of China, Chinese Academy of Science (CAS), Hefei, Anhui Province, China.
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province, China.
| | - Nikolai S Kiselev
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich, Germany.
| | - Jan Caron
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
| | - András Kovács
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
| | - Mingliang Tian
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory and University of Science and Technology of China, Chinese Academy of Science (CAS), Hefei, Anhui Province, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province, China
| | - Yuheng Zhang
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory and University of Science and Technology of China, Chinese Academy of Science (CAS), Hefei, Anhui Province, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province, China
| | - Stefan Blügel
- Peter Grünberg Institute and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, Jülich, Germany
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, Jülich, Germany
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46
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Schneider S, Wolf D, Stolt MJ, Jin S, Pohl D, Rellinghaus B, Schmidt M, Büchner B, Goennenwein STB, Nielsch K, Lubk A. Induction Mapping of the 3D-Modulated Spin Texture of Skyrmions in Thin Helimagnets. PHYSICAL REVIEW LETTERS 2018; 120:217201. [PMID: 29883134 DOI: 10.1103/physrevlett.120.217201] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Revised: 03/29/2018] [Indexed: 06/08/2023]
Abstract
Envisaged applications of Skyrmions in magnetic memory and logic devices crucially depend on the stability and mobility of these topologically nontrivial magnetic textures in thin films. We present for the first time quantitative maps of the magnetic induction that provide evidence for a 3D modulation of the Skyrmionic spin texture. The projected in-plane magnetic induction maps as determined from in-line and off-axis electron holography carry the clear signature of Bloch Skyrmions. However, the magnitude of this induction is much smaller than the values expected for homogeneous Bloch Skyrmions that extend throughout the thickness of the film. This finding can only be understood if the underlying spin textures are modulated along the out-of-plane z direction. The projection of (the in-plane magnetic induction of) helices is further found to exhibit thickness-dependent lateral shifts, which show that this z modulation is accompanied by an (in-plane) modulation along the x and y directions.
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Affiliation(s)
- S Schneider
- Institute for Metallic Materials, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
| | - D Wolf
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - M J Stolt
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA
| | - S Jin
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, USA
| | - D Pohl
- Institute for Metallic Materials, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
- Dresden Center for Nanoanalysis, Technische Universität Dresden, 01062 Dresden, Germany
| | - B Rellinghaus
- Institute for Metallic Materials, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
- Dresden Center for Nanoanalysis, Technische Universität Dresden, 01062 Dresden, Germany
| | - M Schmidt
- Department Chemical Metal Science, Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany
| | - B Büchner
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
| | - S T B Goennenwein
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
- Center for Transport and Devices of Emergent Materials, Technische Universität Dresden, 01062 Dresden, Germany
| | - K Nielsch
- Institute for Metallic Materials, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
- Institute of Materials Science, Technische Universität Dresden, Helmholtzstr. 7, 01069 Dresden, Germany
| | - A Lubk
- Institute for Solid State Research, IFW Dresden, Helmholtzstr. 20, 01069 Dresden, Germany
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47
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Zheng F, Li H, Wang S, Song D, Jin C, Wei W, Kovács A, Zang J, Tian M, Zhang Y, Du H, Dunin-Borkowski RE. Direct Imaging of a Zero-Field Target Skyrmion and Its Polarity Switch in a Chiral Magnetic Nanodisk. PHYSICAL REVIEW LETTERS 2017; 119:197205. [PMID: 29219505 DOI: 10.1103/physrevlett.119.197205] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2017] [Indexed: 05/10/2023]
Abstract
A target Skyrmion is a flux-closed spin texture that has twofold degeneracy and is promising as a binary state in next generation universal memories. Although its formation in nanopatterned chiral magnets has been predicted, its observation has remained challenging. Here, we use off-axis electron holography to record images of target Skyrmions in a 160-nm-diameter nanodisk of the chiral magnet FeGe. We compare experimental measurements with numerical simulations, demonstrate switching between two stable degenerate target Skyrmion ground states that have opposite polarities and rotation senses, and discuss the observed switching mechanism.
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Affiliation(s)
- Fengshan Zheng
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Hang Li
- Department of Physics, University of New Hampshire, Durham, New Hampshire 03824, USA
| | - Shasha Wang
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province 210093, China
| | - Dongsheng Song
- National Center for Electron Microscopy in Beijing, Key Laboratory of Advanced Materials (MOE) and the State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
| | - Chiming Jin
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province 210093, China
| | - Wenshen Wei
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province 210093, China
| | - András Kovács
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
| | - Jiadong Zang
- Department of Physics, University of New Hampshire, Durham, New Hampshire 03824, USA
| | - Mingliang Tian
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province 210093, China
| | - Yuheng Zhang
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province 210093, China
| | - Haifeng Du
- The Anhui Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences and University of Science and Technology of China, Hefei 230026, China
- Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Jiangsu Province 210093, China
| | - Rafal E Dunin-Borkowski
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, 52425 Jülich, Germany
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