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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 Trans Magn 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] [What about the content of this article? (0)] [Affiliation(s)] [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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Ryu J, Lee S, Lee KJ, Park BG. Current-Induced Spin-Orbit Torques for Spintronic Applications. Adv Mater 2020; 32:e1907148. [PMID: 32141681 DOI: 10.1002/adma.201907148] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 12/13/2019] [Indexed: 06/10/2023]
Abstract
Control of magnetization in magnetic nanostructures is essential for development of spintronic devices because it governs fundamental device characteristics such as energy consumption, areal density, and operation speed. In this respect, spin-orbit torque (SOT), which originates from the spin-orbit interaction, has been widely investigated due to its efficient manipulation of the magnetization using in-plane current. SOT spearheads novel spintronic applications including high-speed magnetic memories, reconfigurable logics, and neuromorphic computing. Herein, recent advances in SOT research, highlighting the considerable benefits and challenges of SOT-based spintronic devices, are reviewed. First, the materials and structural engineering that enhances SOT efficiency are discussed. Then major experimental results for field-free SOT switching of perpendicular magnetization are summarized, which includes the introduction of an internal effective magnetic field and the generation of a distinct spin current with out-of-plane spin polarization. Finally, advanced SOT functionalities are presented, focusing on the demonstration of reconfigurable and complementary operation in spin logic devices.
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Affiliation(s)
- Jeongchun Ryu
- Department of Materials Science and Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Soogil Lee
- Department of Materials Science and Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
| | - Kyung-Jin Lee
- Department of Materials Science and Engineering and KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Anam-dong, Seongbuk-gu, Seoul, 02841, Republic of Korea
| | - Byong-Guk Park
- Department of Materials Science and Engineering, KAIST, 291 Daehak-ro, Yuseong-gu, Daejeon, 34141, Republic of Korea
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Okabayashi J, Miura Y, Kota Y, Z Suzuki K, Sakuma A, Mizukami S. Detecting quadrupole: a hidden source of magnetic anisotropy for Manganese alloys. Sci Rep 2020; 10:9744. [PMID: 32546779 PMCID: PMC7297735 DOI: 10.1038/s41598-020-66432-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 05/07/2020] [Indexed: 11/25/2022] Open
Abstract
Mn-based alloys exhibit unique properties in the spintronics materials possessing perpendicular magnetic anisotropy (PMA) beyond the Fe and Co-based alloys. It is desired to figure out the quantum physics of PMA inherent to Mn-based alloys, which have never been reported. Here, the origin of PMA in ferrimagnetic Mn3− δ Ga ordered alloys is investigated to resolve antiparallel-coupled Mn sites using x-ray magnetic circular and linear dichroism (XMCD/XMLD) and a first-principles calculation. We found that the contribution of orbital magnetic moments in PMA is small from XMCD and that the finite quadrupole-like orbital distortion through spin-flipped electron hopping is dominant from XMLD and theoretical calculations. These findings suggest that the spin-flipped orbital quadrupole formations originate from the PMA in Mn3− δ Ga and bring the paradigm shift in the researches of PMA materials using x-ray magnetic spectroscopies.
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Affiliation(s)
- Jun Okabayashi
- Research Center for Spectrochemistry, The University of Tokyo, 113-0033, Tokyo, Japan.
| | - Yoshio Miura
- Research Center for Magnetic and Spintronic Materials, National Institute for Materials Science (NIMS), Tsukuba, 305-0047, Japan
| | - Yohei Kota
- National Institute of Technology, Fukushima College, Iwaki, Fukushima, 970-8034, Japan
| | - Kazuya Z Suzuki
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan
| | - Akimasa Sakuma
- Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan.,Department of Applied Physics, Tohoku University, Sendai, 980-8579, Japan.,Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan
| | - Shigemi Mizukami
- WPI-Advanced Institute for Materials Research, Tohoku University, Sendai, 980-8577, Japan.,Center for Spintronics Research Network (CSRN), Tohoku University, Sendai, 980-8579, Japan.,Center for Science and Innovation in Spintronics (CSIS), Tohoku University, Sendai, 980-8577, Japan
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Li H, Wang G, Li D, Hu P, Zhou W, Dang S, Ma X, Dai T, Kang S, Yu F, Zhou X, Wu S, Li S. Field-Free Deterministic Magnetization Switching with Ultralow Current Density in Epitaxial Au/Fe 4N Bilayer Films. ACS Appl Mater Interfaces 2019; 11:16965-16971. [PMID: 30977629 DOI: 10.1021/acsami.9b00129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Current-induced magnetization switching was investigated in Au/Fe4N bilayer films grown by a plasma-assisted molecular beam epitaxy (PA-MBE) system. Depending on lattice distortion and interfacial coupling induced by substrates, the Fe4N layer could be divided into two sublayers having different magnetic anisotropies. The bottom sublayer shows perpendicular magnetic anisotropy (PMA), while the top one has in-plane magnetic anisotropy (IMA). Coupling between the two sublayers provides an extra in-plane effective field and enables a field-free magnetization switching in the bilayer films. By summarizing a series of Hall measurements, a switching phase diagram was obtained. Temperature-dependent switching behaviors demonstrate that the threshold current density for the field-free magnetization switching, which is much smaller than that of pervious reports, increases with decreasing temperature and shows similar temperature dependences to those of coercivity.
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Affiliation(s)
- Hongwei Li
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Gaili Wang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Dan Li
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Ping Hu
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Wenqi Zhou
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Shuai Dang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Xingyuan Ma
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Tian Dai
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Songdan Kang
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Fengmei Yu
- Automation College , Zhongkai University of Agriculture and Engineering , Guangzhou 510225 , People's Republic of China
| | - Xiang Zhou
- School of Physics and Astronomy , Sun Yat-sen University Zhuhai campus , Zhuhai 519082 , People's Republic of China
| | - Shuxiang Wu
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
| | - Shuwei Li
- State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics, School of Materials Science and Engineering , Sun Yat-Sen University , Guangzhou 510275 , People's Republic of China
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