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Miao Y, Sun J, Gao C, Xue D, Wang XR. Anisotropic Galvanomagnetic Effects in Single Cubic Crystals: A Theory and Its Verification. PHYSICAL REVIEW LETTERS 2024; 132:206701. [PMID: 38829066 DOI: 10.1103/physrevlett.132.206701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Revised: 01/22/2024] [Accepted: 04/12/2024] [Indexed: 06/05/2024]
Abstract
A theory of anisotropic galvanomagnetic effects in single cubic crystals and its experimental verifications are presented for the current in the (001) plane. In contrast to the general belief that galvanomagnetic effects in single crystals are highly sensitive to many internal and external effects and have no universal features, the theory predicts universal angular dependencies of longitudinal and transverse resistivity and various characteristics when magnetization rotates in the (001) plane, the plane perpendicular to the current, and the plane containing the current and [001] direction. The universal angular dependencies are verified by experiments on Fe_{30}Co_{70} single cubic crystal film. The findings provide new avenues for fundamental research and applications of galvanomagnetic effects, because single crystals offer advantages over polycrystalline materials for band structure and crystallographic orientation engineering.
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Affiliation(s)
- Yu Miao
- Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China
| | - Junwen Sun
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
- Department of Physics, Nanjing Normal University, Nanjing, China
| | - Cunxu Gao
- Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China
| | - Desheng Xue
- Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University, Lanzhou 730000, China
| | - X R Wang
- Department of Physics, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
- HKUST Shenzhen Research Institute, Shenzhen 518057, China
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2
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Ritzinger P, Výborný K. Anisotropic magnetoresistance: materials, models and applications. ROYAL SOCIETY OPEN SCIENCE 2023; 10:230564. [PMID: 37859834 PMCID: PMC10582618 DOI: 10.1098/rsos.230564] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 09/07/2023] [Indexed: 10/21/2023]
Abstract
Resistance of certain (conductive and otherwise isotropic) ferromagnets turns out to exhibit anisotropy with respect to the direction of magnetization: R ∥ for magnetization parallel to the electric current direction is different from R⊥ for magnetization perpendicular to the electric current direction. In this review, this century-old phenomenon is reviewed both from the perspective of materials and physical mechanisms involved. More recently, this effect has also been identified and studied in antiferromagnets. To date, sensors based on the anisotropic magnetoresistance (AMR) effect are widely used in different fields, such as the automotive industry, aerospace or in biomedical imaging.
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Affiliation(s)
- Philipp Ritzinger
- FZU—Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, Praha 6 16253, Czech Republic
- MFF—Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, Praha 2 12000, Czech Republic
| | - Karel Výborný
- FZU—Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, Praha 6 16253, Czech Republic
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3
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Liu Q, Lin X, Zhu L. Absence of Spin-Orbit Torque and Discovery of Anisotropic Planar Nernst Effect in CoFe Single Crystal. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2301409. [PMID: 37485640 PMCID: PMC10520638 DOI: 10.1002/advs.202301409] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 06/29/2023] [Indexed: 07/25/2023]
Abstract
Exploration of exotic spin polarizations in single crystals is of increasing interest. A current of longitudinal spins, the so-called "Dresselhaus-like" spin current, which is forbidden in materials lacking certain inversion asymmetries, is implied to be generated by a charge current at the interface of single-crystal CoFe. This work reports unambiguous evidence that there is no indication of spin current of any spin polarizations from the interface or bulk of single-crystalline CoFe and that the sin2φ second harmonic Hall voltage, which is previously assumed to signify Dresselhaus-like spin current, is not related to any spin currents but rather a planar Nernst voltage induced by a longitudinal temperature gradient within the sample. Such sin2φ signal is independent of large applied magnetic fields and interfacial spin-orbit coupling, inversely correlated to the heat capacity of the substrates and overlayers, quadratic in charge current, and appears also in polycrystalline ferromagnets. Strikingly, the planar Nernst effect (PNE) in the CoFe single crystal has a strong fourfold anisotropy and varies with the crystalline orientation. Such strong, anisotropic PNE has widespread impacts on the analyses of a variety of spintronic experiments and opens a new avenue for the development of PNE-based thermoelectric battery and sensor applications.
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Affiliation(s)
- Qianbiao Liu
- State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of SciencesBeijing100083China
| | - Xin Lin
- State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of SciencesBeijing100083China
- College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of SciencesBeijing100049China
| | - Lijun Zhu
- State Key Laboratory for Superlattices and MicrostructuresInstitute of SemiconductorsChinese Academy of SciencesBeijing100083China
- College of Materials Science and Opto‐Electronic TechnologyUniversity of Chinese Academy of SciencesBeijing100049China
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Dai Y, Zhao YW, Ma L, Tang M, Qiu XP, Liu Y, Yuan Z, Zhou SM. Fourfold Anisotropic Magnetoresistance of L1_{0} FePt Due to Relaxation Time Anisotropy. PHYSICAL REVIEW LETTERS 2022; 128:247202. [PMID: 35776447 DOI: 10.1103/physrevlett.128.247202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Revised: 04/06/2022] [Accepted: 05/25/2022] [Indexed: 06/15/2023]
Abstract
Experimental measurements show that the angular dependence of the anisotropic magnetoresistance (AMR) in L1_{0} ordered FePt epitaxial films on the current orientation and magnetization direction is a superposition of the corresponding dependences of twofold and fourfold symmetries. The twofold AMR exhibits a strong dependence on the current orientation, whereas the fourfold term only depends on the magnetization direction in the crystal and is independent of the current orientation. First-principles calculations reveal that the fourfold AMR arises from the relaxation time anisotropy due to the variation of the density of states near the Fermi energy under rotation of the magnetization. This relaxation time anisotropy is a universal property in ferromagnetic metals and determines other anisotropic physical properties that are observable in experiment.
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Affiliation(s)
- Y Dai
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Y W Zhao
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
| | - L Ma
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - M Tang
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - X P Qiu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
| | - Y Liu
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Z Yuan
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
| | - S M Zhou
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology and Pohl Institute of Solid State Physics and School of Physics Science and Engineering, Tongji University, Shanghai 200092, China
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5
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Temperature dependence of intrinsic and extrinsic contributions to anisotropic magnetoresistance. Sci Rep 2021; 11:20884. [PMID: 34686705 PMCID: PMC8536661 DOI: 10.1038/s41598-021-00374-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2021] [Accepted: 10/11/2021] [Indexed: 11/21/2022] Open
Abstract
Electrical conduction in magnetic materials depends on their magnetization configuration, resulting in various magnetoresistances (MRs). The microscopic mechanisms of MR have so far been attributed to either an intrinsic or extrinsic origin, yet the contribution and temperature dependence of either origin has remained elusive due to experimental limitations. In this study, we independently probed the intrinsic and extrinsic contributions to the anisotropic MR (AMR) of a permalloy film at varying temperatures using temperature-variable terahertz time-domain spectroscopy. The AMR induced by the scattering-independent intrinsic origin was observed to be approximately 1.5% at T = 16 K and is virtually independent of temperature. In contrast, the AMR induced by the scattering-dependent extrinsic contribution was approximately 3% at T = 16 K but decreased to 1.5% at T = 155 K, which is the maximum temperature at which the AMR can be resolved using THz measurements. Our results experimentally quantify the temperature-dependent intrinsic and extrinsic contributions to AMR, which can stimulate further theoretical research to aid the fundamental understanding of AMR.
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Zeng FL, Ren ZY, Li Y, Zeng JY, Jia MW, Miao J, Hoffmann A, Zhang W, Wu YZ, Yuan Z. Intrinsic Mechanism for Anisotropic Magnetoresistance and Experimental Confirmation in Co_{x}Fe_{1-x} Single-Crystal Films. PHYSICAL REVIEW LETTERS 2020; 125:097201. [PMID: 32915598 DOI: 10.1103/physrevlett.125.097201] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 07/13/2020] [Accepted: 07/31/2020] [Indexed: 06/11/2023]
Abstract
Using first-principles transport calculations, we predict that the anisotropic magnetoresistance (AMR) of single-crystal Co_{x}Fe_{1-x} alloys is strongly dependent on the current orientation and alloy concentration. An intrinsic mechanism for AMR is found to arise from the band crossing due to magnetization-dependent symmetry protection. These special k points can be shifted towards or away from the Fermi energy by varying the alloy composition and hence the exchange splitting, thus allowing AMR tunability. The prediction is confirmed by delicate transport measurements, which further reveal a reciprocal relationship of the longitudinal and transverse resistivities along different crystal axes.
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Affiliation(s)
- F L Zeng
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - Z Y Ren
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
| | - Y Li
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - J Y Zeng
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - M W Jia
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
| | - J Miao
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - A Hoffmann
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - W Zhang
- Department of Physics, Oakland University, Rochester, Michigan 48309, USA
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, USA
| | - Y Z Wu
- Department of Physics, State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
- Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
| | - Z Yuan
- Center for Advanced Quantum Studies and Department of Physics, Beijing Normal University, Beijing 100875, China
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7
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Avci CO, Mendil J, Beach GSD, Gambardella P. Origins of the Unidirectional Spin Hall Magnetoresistance in Metallic Bilayers. PHYSICAL REVIEW LETTERS 2018; 121:087207. [PMID: 30192570 DOI: 10.1103/physrevlett.121.087207] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2018] [Indexed: 06/08/2023]
Abstract
Recent studies evidenced the emergence of asymmetric electron transport in layered conductors owing to the interplay between electrical conductivity, magnetization, and the spin Hall or Rashba-Edelstein effects. Here, we investigate the unidirectional magnetoresistance (UMR) caused by the current-induced spin accumulation in Co/Pt and CoCr/Pt bilayers. We identify three competing mechanisms underpinning the resistance asymmetry, namely, interface and bulk spin-dependent electron scattering and electron-magnon scattering. Our measurements provide a consistent description of the current, magnetic field, and temperature dependence of the UMR and show that both positive and negative UMR can be obtained by tuning the interface and bulk spin-dependent scattering.
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Affiliation(s)
- Can Onur Avci
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Johannes Mendil
- Department of Materials, ETH Zürich, 8093 Zürich, Switzerland
| | - Geoffrey S D Beach
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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8
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Chen L, Decker M, Kronseder M, Islinger R, Gmitra M, Schuh D, Bougeard D, Fabian J, Weiss D, Back CH. Robust spin-orbit torque and spin-galvanic effect at the Fe/GaAs (001) interface at room temperature. Nat Commun 2016; 7:13802. [PMID: 27958265 PMCID: PMC5159805 DOI: 10.1038/ncomms13802] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Accepted: 11/01/2016] [Indexed: 11/11/2022] Open
Abstract
Interfacial spin-orbit torques (SOTs) enable the manipulation of the magnetization through in-plane charge currents, which has drawn increasing attention for spintronic applications. The search for material systems providing efficient SOTs, has been focused on polycrystalline ferromagnetic metal/non-magnetic metal bilayers. In these systems, currents flowing in the non-magnetic layer generate—due to strong spin–orbit interaction—spin currents via the spin Hall effect and induce a torque at the interface to the ferromagnet. Here we report the observation of robust SOT occuring at a single crystalline Fe/GaAs (001) interface at room temperature. We find that the magnitude of the interfacial SOT, caused by the reduced symmetry at the interface, is comparably strong as in ferromagnetic metal/non-magnetic metal systems. The large spin-orbit fields at the interface also enable spin-to-charge current conversion at the interface, known as spin-galvanic effect. The results suggest that single crystalline Fe/GaAs interfaces may enable efficient electrical magnetization manipulation. Interfacial spin-orbit torque allows electrical manipulation of magnetization, but this has been shown mostly in polycrystalline metal bilayers. Here the authors show robust spin-orbit torque in single crystalline Fe/GaAs interface at room temperature, observing conversion between spin and charge current.
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Affiliation(s)
- L Chen
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M Decker
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M Kronseder
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - R Islinger
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - M Gmitra
- Institute of Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - D Schuh
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - D Bougeard
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - J Fabian
- Institute of Theoretical Physics, University of Regensburg, 93040 Regensburg, Germany
| | - D Weiss
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
| | - C H Back
- Institute of Experimental and Applied Physics, University of Regensburg, 93040 Regensburg, Germany
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9
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Buchner M, Högl P, Putz S, Gmitra M, Günther S, Schoen MAW, Kronseder M, Schuh D, Bougeard D, Fabian J, Back CH. Anisotropic Polar Magneto-Optic Kerr Effect of Ultrathin Fe/GaAs(001) Layers due to Interfacial Spin-Orbit Interaction. PHYSICAL REVIEW LETTERS 2016; 117:157202. [PMID: 27768325 DOI: 10.1103/physrevlett.117.157202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2016] [Indexed: 06/06/2023]
Abstract
We report the observation of the anisotropic polar magneto-optical Kerr effect in thin layers of epitaxial Fe/GaAs(001) at room temperature. A clear twofold symmetry of the Kerr rotation angle depending on the orientation of the linear polarization of the probing laser beam with respect to the crystallographic directions of the sample is detected for ultrathin magnetic films saturated out of the film plane. The amplitude of the anisotropy decreases with increasing Fe film thickness, suggesting that the interfacial region is the origin of the anisotropy. The twofold symmetry is fully reproduced by model calculations based on an interference of interfacial Bychkov-Rashba and Dresselhaus spin-orbit coupling.
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Affiliation(s)
- M Buchner
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - P Högl
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - S Putz
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - M Gmitra
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - S Günther
- Department of Materials, ETH Zürich, Zürich 8093, Switzerland
| | - M A W Schoen
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - M Kronseder
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - D Schuh
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - D Bougeard
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
| | - J Fabian
- Institute of Theoretical Physics, University of Regensburg, Regensburg 93040, Germany
| | - C H Back
- Institute of Experimental and Applied Physics, University of Regensburg, Regensburg 93040, Germany
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