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Ding S, Kang MG, Legrand W, Gambardella P. Orbital Torque in Rare-Earth Transition-Metal Ferrimagnets. PHYSICAL REVIEW LETTERS 2024; 132:236702. [PMID: 38905652 DOI: 10.1103/physrevlett.132.236702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 01/13/2024] [Accepted: 05/08/2024] [Indexed: 06/23/2024]
Abstract
Orbital currents have recently emerged as a promising tool to achieve electrical control of the magnetization in thin-film ferromagnets. Efficient orbital-to-spin conversion is required in order to torque the magnetization. Here, we show that the injection of an orbital current in a ferrimagnetic Gd_{y}Co_{100-y} alloy generates strong orbital torques whose sign and magnitude can be tuned by changing the Gd content and temperature. The effective spin-orbital Hall angle reaches up to -0.25 in a Gd_{y}Co_{100-y}/CuO_{x} bilayer compared to +0.03 in Co/CuO_{x} and +0.13 in Gd_{y}Co_{100-y}/Pt. This behavior is attributed to the local orbital-to-spin conversion taking place at the Gd sites, which is about 5 times stronger and of the opposite sign relative to Co. Furthermore, we observe a manyfold increase in the net orbital torque at low temperature, which we attribute to the improved conversion efficiency following the magnetic ordering of the Gd and Co sublattices.
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2
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Gao T, Qaiumzadeh A, Troncoso RE, Haku S, An H, Nakayama H, Tazaki Y, Zhang S, Tu R, Asami A, Brataas A, Ando K. Impact of inherent energy barrier on spin-orbit torques in magnetic-metal/semimetal heterojunctions. Nat Commun 2023; 14:5187. [PMID: 37626028 PMCID: PMC10457350 DOI: 10.1038/s41467-023-40876-9] [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: 09/03/2022] [Accepted: 08/15/2023] [Indexed: 08/27/2023] Open
Abstract
Spintronic devices are based on heterojunctions of two materials with different magnetic and electronic properties. Although an energy barrier is naturally formed even at the interface of metallic heterojunctions, its impact on spin transport has been overlooked. Here, using diffusive spin Hall currents, we provide evidence that the inherent energy barrier governs the spin transport even in metallic systems. We find a sizable field-like torque, much larger than the damping-like counterpart, in Ni81Fe19/Bi0.1Sb0.9 bilayers. This is a distinct signature of barrier-mediated spin-orbit torques, which is consistent with our theory that predicts a strong modification of the spin mixing conductance induced by the energy barrier. Our results suggest that the spin mixing conductance and the corresponding spin-orbit torques are strongly altered by minimizing the work function difference in the heterostructure. These findings provide a new mechanism to control spin transport and spin torque phenomena by interfacial engineering of metallic heterostructures.
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Affiliation(s)
- Tenghua Gao
- Keio Institute of Pure and Applied Science, Keio University, Yokohama, 223-8522, Japan
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, 223-8522, Japan
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China
| | - Alireza Qaiumzadeh
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway
| | - Roberto E Troncoso
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway
- School of Engineering and Sciences, Universidad Adolfo Ibáñez, Santiago, Chile
| | - Satoshi Haku
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, 223-8522, Japan
| | - Hongyu An
- College of New Materials and New Energies, Shenzhen Technology University, Shenzhen, 518118, China
| | - Hiroki Nakayama
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, 223-8522, Japan
| | - Yuya Tazaki
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, 223-8522, Japan
| | - Song Zhang
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China
| | - Rong Tu
- State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, China
| | - Akio Asami
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, 223-8522, Japan
| | - Arne Brataas
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491, Trondheim, Norway
| | - Kazuya Ando
- Keio Institute of Pure and Applied Science, Keio University, Yokohama, 223-8522, Japan.
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, 223-8522, Japan.
- Center for Spintronics Research Network, Keio University, Yokohama, 223-8522, Japan.
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Yang H, Ormaza M, Chi Z, Dolan E, Ingla-Aynés J, Safeer CK, Herling F, Ontoso N, Gobbi M, Martín-García B, Schiller F, Hueso LE, Casanova F. Gate-Tunable Spin Hall Effect in an All-Light-Element Heterostructure: Graphene with Copper Oxide. NANO LETTERS 2023; 23:4406-4414. [PMID: 37140909 DOI: 10.1021/acs.nanolett.3c00687] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Graphene is a light material for long-distance spin transport due to its low spin-orbit coupling, which at the same time is the main drawback for exhibiting a sizable spin Hall effect. Decoration by light atoms has been predicted to enhance the spin Hall angle in graphene while retaining a long spin diffusion length. Here, we combine a light metal oxide (oxidized Cu) with graphene to induce the spin Hall effect. Its efficiency, given by the product of the spin Hall angle and the spin diffusion length, can be tuned with the Fermi level position, exhibiting a maximum (1.8 ± 0.6 nm at 100 K) around the charge neutrality point. This all-light-element heterostructure shows a larger efficiency than conventional spin Hall materials. The gate-tunable spin Hall effect is observed up to room temperature. Our experimental demonstration provides an efficient spin-to-charge conversion system free from heavy metals and compatible with large-scale fabrication.
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Affiliation(s)
- Haozhe Yang
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Maider Ormaza
- Departamento de Polímeros y Materiales Avanzados: Física Química y Tecnología Facultad de Químicas, UPV/EHU, 20080 Donostia-San Sebastián, Basque Country, Spain
| | - Zhendong Chi
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Eoin Dolan
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Josep Ingla-Aynés
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - C K Safeer
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Franz Herling
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Nerea Ontoso
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Marco Gobbi
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
- Centro de Física de Materiales (CSIC-EHU/UPV) and Materials Physics Center (MPC), 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Beatriz Martín-García
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
| | - Frederik Schiller
- Centro de Física de Materiales (CSIC-EHU/UPV) and Materials Physics Center (MPC), 20018 Donostia-San Sebastian, Basque Country, Spain
- Donostia International Physics Center, 20018 Donostia-San Sebastian, Basque Country, Spain
| | - Luis E Hueso
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
| | - Fèlix Casanova
- CIC nanoGUNE BRTA, 20018 Donostia-San Sebastian, Basque Country, Spain
- IKERBASQUE, Basque Foundation for Science, 48009 Bilbao, Basque Country, Spain
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4
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An T, Cui B, Liu L, Zhang M, Liu F, Liu W, Xie J, Ren X, Chu R, Cheng B, Jiang C, Hu J. Enhanced Spin Current in Ni 81 Fe 19 /Cu-CuO x Bilayer with Top and Sideways Oxidization. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2207988. [PMID: 36630709 DOI: 10.1002/adma.202207988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Revised: 01/06/2023] [Indexed: 06/17/2023]
Abstract
Generation and manipulation of spin current are the cores of spintronic devices, which are intensely pursued. Heavy metals with strong spin-orbit coupling are commonly used for the generation of spin current, but are incompatible with the mass production of devices, and the polarization of spin current is limited to be in-plane. Here, it is shown that the spin current with strong out-of-plane polarization component can be generated and transmitted in Ni81 Fe19 /Cu-CuOx bilayer with sideways and top oxidizations. The charge-to-spin current conversion efficiency can be enhanced through the spin currents consisting of both out-of-plane polarization (σz ) and in-plane polarization (σy ) induced by spin-vorticity coupling. Such a spin current is demonstrated to be closely related to the lateral oxidization gradient and can be controlled by changing the temperatures and times of annealing. The finding here provides a novel degree of freedom to produce and control the spin current in spintronic devices.
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Affiliation(s)
- Taiyu An
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Bin Cui
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Liang Liu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Mingfang Zhang
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Fufu Liu
- Key Laboratory for Magnetism and Magnetic Materials, Ministry of Education, Lanzhou University, Lanzhou, 730000, China
- Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou, 730000, China
| | - Weikang Liu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Jihao Xie
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Xue Ren
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Ruiyue Chu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Bin Cheng
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
| | - Changjun Jiang
- Key Laboratory for Magnetism and Magnetic Materials, Ministry of Education, Lanzhou University, Lanzhou, 730000, China
- Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou, 730000, China
| | - Jifan Hu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, China
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An T, Cui B, Zhang M, Liu F, Cheng S, Zhang K, Ren X, Liu L, Cheng B, Jiang C, Hu J. Electrical Manipulation of Orbital Current Via Oxygen Migration in Ni 81 Fe 19 /CuO x /TaN Heterostructure. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023:e2300858. [PMID: 36976522 DOI: 10.1002/adma.202300858] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 03/23/2023] [Indexed: 06/18/2023]
Abstract
The orbital Hall effect and the interfacial Rashba effect provide new approaches to generate orbital current and spin-orbit torque (SOT) efficiently without the use of heavy metals. However, achieving efficient dynamic control of orbital current and SOT in light metal oxides has proven challenging. In this study, it is demonstrated that a sizable magnetoresistance effect related to orbital current and SOT can be observed in Ni81 Fe19 /CuOx /TaN heterostructures with various CuOx oxidization concentrations. The ionic liquid gating induces the migration of oxygen ions, which modulates the oxygen concentration at the Ni81 Fe19 /CuOx interface, leading to reversible manipulation of the magnetoresistance effect and SOT. The existence of a thick TaN capping layer allows for sophisticated internal oxygen ion reconstruction in the CuOx layer, rather than conventional external ion exchange. These results provide a method for the reversible and dynamic manipulation of the orbital current and SOT generation efficiency, thereby advancing the development of spin-orbitronic devices through ionic engineering.
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Affiliation(s)
- Taiyu An
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
| | - Bin Cui
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
| | - Mingfang Zhang
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
| | - Fufu Liu
- Key Laboratory for Magnetism and Magnetic Materials, Ministry of Education, Lanzhou University, Lanzhou, 730000, P. R. China
- Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Shaobo Cheng
- Henan Key Laboratory of Diamond Optoelectronic Materials and Devices, Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, 450052, P. R. China
| | - Kuikui Zhang
- Henan Key Laboratory of Diamond Optoelectronic Materials and Devices, Key Laboratory of Material Physics, Ministry of Education, School of Physics and Microelectronics, Zhengzhou University, Zhengzhou, 450052, P. R. China
| | - Xue Ren
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
| | - Liang Liu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
| | - Bin Cheng
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
| | - Changjun Jiang
- Key Laboratory for Magnetism and Magnetic Materials, Ministry of Education, Lanzhou University, Lanzhou, 730000, P. R. China
- Key Laboratory of Special Function Materials and Structure Design, Ministry of Education, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Jifan Hu
- School of Physics, State Key Laboratory for Crystal Materials, Shandong University, Jinan, 250100, P. R. China
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6
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ANDO K. Generation and manipulation of current-induced spin-orbit torques. PROCEEDINGS OF THE JAPAN ACADEMY. SERIES B, PHYSICAL AND BIOLOGICAL SCIENCES 2021; 97:499-519. [PMID: 34759072 PMCID: PMC8610784 DOI: 10.2183/pjab.97.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 08/12/2021] [Indexed: 06/13/2023]
Abstract
An emerging field of spintronics, spin-orbitronics, aims to discover novel phenomena and functionalities originating from spin-orbit coupling in solid-state devices. The development of spin-orbitronics promises a fundamental understanding of spin physics in condensed matter, as well as smaller, faster, and far-more energy-efficient spin-based devices. Of particular importance in this field is current-induced spin-orbit torques, which trigger magnetic dynamics by the transfer of angular momentum from an atomic lattice to local magnetization through the spin-orbit coupling. The spin-orbit torque has attracted extensive attention for its fascinating relativistic and quantum mechanical nature, as well as prospective nanoelectronic applications. In this article, we review our studies on the generation and manipulation of current-induced spin-orbit torques.
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Affiliation(s)
- Kazuya ANDO
- Department of Applied Physics and Physico-Informatics, Keio University, Yokohama, Kanagawa, Japan
- Keio Institute of Pure and Applied Science, Keio University, Yokohama, Kanagawa, Japan
- Center for Spintronics Research Network, Keio University, Yokohama, Kanagawa, Japan
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7
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Shao Q, Li P, Liu L, Yang H, Fukami S, Razavi A, Wu H, Wang K, Freimuth F, Mokrousov Y, Stiles MD, Emori S, Hoffmann A, Åkerman J, Roy K, Wang JP, Yang SH, Garello K, Zhang W. Roadmap of spin-orbit torques. IEEE TRANSACTIONS ON MAGNETICS 2021; 57:10.48550/arXiv.2104.11459. [PMID: 37057056 PMCID: PMC10091395 DOI: 10.48550/arxiv.2104.11459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Spin-orbit torque (SOT) is an emerging technology that enables the efficient manipulation of spintronic devices. The initial processes of interest in SOTs involved electric fields, spin-orbit coupling, conduction electron spins and magnetization. More recently interest has grown to include a variety of other processes that include phonons, magnons, or heat. Over the past decade, many materials have been explored to achieve a larger SOT efficiency. Recently, holistic design to maximize the performance of SOT devices has extended material research from a nonmagnetic layer to a magnetic layer. The rapid development of SOT has spurred a variety of SOT-based applications. In this Roadmap paper, we first review the theories of SOTs by introducing the various mechanisms thought to generate or control SOTs, such as the spin Hall effect, the Rashba-Edelstein effect, the orbital Hall effect, thermal gradients, magnons, and strain effects. Then, we discuss the materials that enable these effects, including metals, metallic alloys, topological insulators, two-dimensional materials, and complex oxides. We also discuss the important roles in SOT devices of different types of magnetic layers, such as magnetic insulators, antiferromagnets, and ferrimagnets. Afterward, we discuss device applications utilizing SOTs. We discuss and compare three-terminal and two-terminal SOT-magnetoresistive random-access memories (MRAMs); we mention various schemes to eliminate the need for an external field. We provide technological application considerations for SOT-MRAM and give perspectives on SOT-based neuromorphic devices and circuits. In addition to SOT-MRAM, we present SOT-based spintronic terahertz generators, nano-oscillators, and domain wall and skyrmion racetrack memories. This paper aims to achieve a comprehensive review of SOT theory, materials, and applications, guiding future SOT development in both the academic and industrial sectors.
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Affiliation(s)
- Qiming Shao
- Department of Electronic and Computer Engineering, Hong Kong University of Science and Technology
| | - Peng Li
- Department of Electrical and Computer Engineering, Auburn University
| | - Luqiao Liu
- Electrical Engineering and Computer Science, Massachusetts Institute of Technology
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore
| | - Shunsuke Fukami
- Research Institute of Electrical Communication, Tohoku University
| | - Armin Razavi
- Department of Electrical and Computer Engineering, University of California, Los Angeles
| | - Hao Wu
- Department of Electrical and Computer Engineering, University of California, Los Angeles
| | - Kang Wang
- Department of Electrical and Computer Engineering, University of California, Los Angeles
| | | | | | - Mark D Stiles
- Alternative Computing Group, National Institute of Standards and Technology
| | | | - Axel Hoffmann
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign
| | | | - Kaushik Roy
- Department of Electrical and Computer Engineering, Purdue University
| | - Jian-Ping Wang
- Electrical and Computer Engineering Department, University of Minnesota
| | | | - Kevin Garello
- IMEC, Leuven, Belgium; CEA-Spintec, Grenoble, France
| | - Wei Zhang
- Physics Department, Oakland University
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Koo HC, Kim SB, Kim H, Park TE, Choi JW, Kim KW, Go G, Oh JH, Lee DK, Park ES, Hong IS, Lee KJ. Rashba Effect in Functional Spintronic Devices. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2020; 32:e2002117. [PMID: 32930418 DOI: 10.1002/adma.202002117] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Revised: 05/28/2020] [Indexed: 06/11/2023]
Abstract
Exploiting spin transport increases the functionality of electronic devices and enables such devices to overcome physical limitations related to speed and power. Utilizing the Rashba effect at the interface of heterostructures provides promising opportunities toward the development of high-performance devices because it enables electrical control of the spin information. Herein, the focus is mainly on progress related to the two most compelling devices that exploit the Rashba effect: spin transistors and spin-orbit torque devices. For spin field-effect transistors, the gate-voltage manipulation of the Rashba effect and subsequent control of the spin precession are discussed, including for all-electric spin field-effect transistors. For spin-orbit torque devices, recent theories and experiments on interface-generated spin current are discussed. The future directions of manipulating the Rashba effect to realize fully integrated spin logic and memory devices are also discussed.
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Affiliation(s)
- Hyun Cheol Koo
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Seong Been Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Hansung Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Tae-Eon Park
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Jun Woo Choi
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Kyoung-Whan Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
| | - Gyungchoon Go
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
| | - Jung Hyun Oh
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
| | - Dong-Kyu Lee
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
| | - Eun-Sang Park
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, South Korea
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Ik-Sun Hong
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
| | - Kyung-Jin Lee
- KU-KIST Graduate School of Converging Science and Technology, Korea University, Seoul, 02841, South Korea
- Department of Materials Science and Engineering, Korea University, Seoul, 02841, South Korea
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9
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Ding S, Ross A, Go D, Baldrati L, Ren Z, Freimuth F, Becker S, Kammerbauer F, Yang J, Jakob G, Mokrousov Y, Kläui M. Harnessing Orbital-to-Spin Conversion of Interfacial Orbital Currents for Efficient Spin-Orbit Torques. PHYSICAL REVIEW LETTERS 2020; 125:177201. [PMID: 33156648 DOI: 10.1103/physrevlett.125.177201] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 08/05/2020] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
Current-induced spin-orbit torques (SOTs) allow for the efficient electrical manipulation of magnetism in spintronic devices. Engineering the SOT efficiency is a key goal that is pursued by maximizing the active interfacial spin accumulation or modulating the nonequilibrium spin density that builds up through the spin Hall and inverse spin galvanic effects. Regardless of the origin, the fundamental requirement for the generation of the current-induced torques is a net spin accumulation. We report on the large enhancement of the SOT efficiency in thulium iron garnet (TmIG)/Pt by capping with a CuO_{x} layer. Considering the weak spin-orbit coupling (SOC) of CuO_{x}, these surprising findings likely result from an orbital current generated at the interface between CuO_{x} and Pt, which is injected into the Pt layer and converted into a spin current by strong SOC. The converted spin current decays across the Pt layer and exerts a "nonlocal" torque on TmIG. This additional torque leads to a maximum colossal enhancement of the SOT efficiency of a factor 16 for 1.5 nm of Pt at room temperature, thus opening a path to increase torques while at the same time offering insights into the underlying physics of orbital transport, which has so far been elusive.
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Affiliation(s)
- Shilei Ding
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - Andrew Ross
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - Dongwook Go
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Lorenzo Baldrati
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Zengyao Ren
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
- School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
| | - Frank Freimuth
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Sven Becker
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Fabian Kammerbauer
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
| | - Jinbo Yang
- State Key Laboratory for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
- Collaborative Innovation Center of Quantum Matter, Beijing, 100871, China
- Beijing Key Laboratory for Magnetoelectric Materials and Devices, Beijing 100871, China
| | - Gerhard Jakob
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
| | - Yuriy Mokrousov
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Mathias Kläui
- Institute of Physics, Johannes Gutenberg University Mainz, Staudingerweg 7, 55128 Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128 Mainz, Germany
- Center for Quantum Spintronics, Department of Physics, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway
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Haidar M, Awad AA, Dvornik M, Khymyn R, Houshang A, Åkerman J. A single layer spin-orbit torque nano-oscillator. Nat Commun 2019; 10:2362. [PMID: 31142758 PMCID: PMC6541614 DOI: 10.1038/s41467-019-10120-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2019] [Accepted: 04/15/2019] [Indexed: 11/23/2022] Open
Abstract
Spin torque and spin Hall effect nano-oscillators generate high intensity spin wave auto-oscillations on the nanoscale enabling novel microwave applications in spintronics, magnonics, and neuromorphic computing. For their operation, these devices require externally generated spin currents either from an additional ferromagnetic layer or a material with a high spin Hall angle. Here we demonstrate highly coherent field and current tunable microwave signals from nano-constrictions in single 15–20 nm thick permalloy layers with oxide interfaces. Using a combination of spin torque ferromagnetic resonance measurements, scanning micro-Brillouin light scattering microscopy, and micromagnetic simulations, we identify the auto-oscillations as emanating from a localized edge mode of the nano-constriction driven by spin-orbit torques. Our results pave the way for greatly simplified designs of auto-oscillating nano-magnetic systems only requiring single ferromagnetic layers with oxide interfaces. Spin torque nano-oscillatiors promise novel microwave applications but the functioning relies on the spin current from additional ferromagnetic or metal layers. The authors here achieved in a single ferromagnetic layer sandwiched by nonmagnetic insulators the spin wave auto-oscillations due to a localized edge mode of the nano-constriction.
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Affiliation(s)
- Mohammad Haidar
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden.,Physics Department, Chalmers University of Technology, 412 96, Gothenburg, Sweden
| | - Ahmad A Awad
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - Mykola Dvornik
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - Roman Khymyn
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - Afshin Houshang
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden
| | - Johan Åkerman
- Physics Department, University of Gothenburg, 412 96, Gothenburg, Sweden. .,Material Physics and Nano Physics, School of Engineering Sciences, KTH Royal Institute of Technology, Electrum 229, 164 40, Kista, Sweden.
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