1
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Sánchez C, Caso D, Aliev FG. Artificial Neuron Based on the Bloch-Point Domain Wall in Ferromagnetic Nanowires. MATERIALS (BASEL, SWITZERLAND) 2024; 17:2425. [PMID: 38793491 PMCID: PMC11123237 DOI: 10.3390/ma17102425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/10/2024] [Accepted: 05/13/2024] [Indexed: 05/26/2024]
Abstract
Nanomagnetism and spintronics are currently active areas of research, with one of the main goals being the creation of low-energy-consuming magnetic memories based on nanomagnet switching. These types of devices could also be implemented in neuromorphic computing by crafting artificial neurons (ANs) that emulate the characteristics of biological neurons through the implementation of neuron models such as the widely used leaky integrate-and-fire (LIF) with a refractory period. In this study, we have carried out numerical simulations of a 120 nm diameter, 250 nm length ferromagnetic nanowire (NW) with the aim of exploring the design of an artificial neuron based on the creation and destruction of a Bloch-point domain wall. To replicate signal integration, we applied pulsed trains of spin currents to the opposite faces of the ferromagnetic NW. These pulsed currents (previously studied only in the continuous form) are responsible for inducing transitions between the stable single vortex (SV) state and the metastable Bloch point domain wall (BP-DW) state. To ensure the system exhibits leak and refractory properties, the NW was placed in a homogeneous magnetic field of the order of mT in the axial direction. The suggested configuration fulfills the requirements and characteristics of a biological neuron, potentially leading to the future creation of artificial neural networks (ANNs) based on reversible changes in the topology of magnetic NWs.
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Affiliation(s)
- Carlos Sánchez
- Departamento de Física de la Materia Condensada C03, Universidad Autónoma de Madrid, 28049 Madrid, Spain; (C.S.); (D.C.)
| | - Diego Caso
- Departamento de Física de la Materia Condensada C03, Universidad Autónoma de Madrid, 28049 Madrid, Spain; (C.S.); (D.C.)
| | - Farkhad G. Aliev
- Departamento de Física de la Materia Condensada C03, Universidad Autónoma de Madrid, 28049 Madrid, Spain; (C.S.); (D.C.)
- Instituto Nicolás Cabrera (INC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
- Condensed Matter Physics Institute (IFIMAC), Universidad Autónoma de Madrid, 28049 Madrid, Spain
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2
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Zhu L. Switching of Perpendicular Magnetization by Spin-Orbit Torque. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2300853. [PMID: 37004142 DOI: 10.1002/adma.202300853] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 03/16/2023] [Indexed: 06/19/2023]
Abstract
Magnetic materials with strong perpendicular magnetic anisotropy are of great interest for the development of nonvolatile magnetic memory and computing technologies due to their high stabilities at the nanoscale. However, electrical switching of such perpendicular magnetization in an energy-efficient, deterministic, scalable manner has remained a big challenge. This problem has recently attracted enormous efforts in the field of spintronics. Here, recent advances and challenges in the understanding of the electrical generation of spin currents, the switching mechanisms and the switching strategies of perpendicular magnetization, the switching current density by spin-orbit torque of transverse spins, the choice of perpendicular magnetic materials are reviewed, and the progress in prototype perpendicular SOT memory and logic devices toward the goal of energy-efficient, dense, fast perpendicular spin-orbit torque applications is summarized.
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Affiliation(s)
- Lijun Zhu
- State Key Laboratory of Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing, 100083, China
- College of Materials Science and Opto-Electronic Technology, University of Chinese Academy of Sciences, Beijing, 100049, China
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3
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Li X, Singh H, Bao Y, Luo Q, Li S, Chatterjee J, Goiriena-Goikoetxea M, Xiao Z, Tamura N, Candler RN, You L, Bokor J, Hong J. Energy Efficient All-Electric-Field-Controlled Multiferroic Magnetic Domain-Wall Logic. NANO LETTERS 2023; 23:6845-6851. [PMID: 37467358 PMCID: PMC10416346 DOI: 10.1021/acs.nanolett.3c00707] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 07/03/2023] [Indexed: 07/21/2023]
Abstract
Magnetic domain wall (DW)-based logic devices offer numerous opportunities for emerging electronics applications allowing superior performance characteristics such as fast motion, high density, and nonvolatility to process information. However, these devices rely on an external magnetic field, which limits their implementation; this is particularly problematic in large-scale applications. Multiferroic systems consisting of a piezoelectric substrate coupled with ferromagnets provide a potential solution that provides the possibility of controlling magnetization through an electric field via magnetoelastic coupling. Strain-induced magnetization anisotropy tilting can influence the DW motion in a controllable way. We demonstrate a method to perform all-electrical logic operations using such a system. Ferromagnetic coupling between neighboring magnetic domains induced by the electric-field-controlled strain has been exploited to promote noncollinear spin alignment, which is used for realizing essential building blocks, including DW generation, propagation, and pinning, in all implementations of Boolean logic, which will pave the way for scalable memory-in-logic applications.
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Affiliation(s)
- Xin Li
- School
of Integrated Circuits, Huazhong University
of Science and Technology, Wuhan 430074, China
| | - Hanuman Singh
- School
of Sciences, Hubei University of Technology, Wuhan 430068, China
- EECS, UC Berkeley, Berkeley, California 94720, United States
| | - Yi Bao
- School
of Integrated Circuits, Huazhong University
of Science and Technology, Wuhan 430074, China
| | - Qiang Luo
- School
of Integrated Circuits, Huazhong University
of Science and Technology, Wuhan 430074, China
| | - Shihao Li
- School
of Integrated Circuits, Huazhong University
of Science and Technology, Wuhan 430074, China
| | | | - Maite Goiriena-Goikoetxea
- Department
of Electricity and Electronics, University
of the Basque Country (UPV/EHU), Leioa 48940, Spain
| | - Zhuyun Xiao
- Department
of Electrical and Computer Engineering, UCLA, Los Angeles, California 90095, United States
| | - Nobumichi Tamura
- Advanced
Light Source, Lawrence Berkeley National
Lab, Berkeley, California 94720, United States
| | - Rob N. Candler
- Department
of Electrical and Computer Engineering, UCLA, Los Angeles, California 90095, United States
| | - Long You
- School
of Integrated Circuits, Huazhong University
of Science and Technology, Wuhan 430074, China
| | - Jeff Bokor
- EECS, UC Berkeley, Berkeley, California 94720, United States
| | - Jeongmin Hong
- School
of Sciences, Hubei University of Technology, Wuhan 430068, China
- EECS, UC Berkeley, Berkeley, California 94720, United States
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4
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Kaushik D, Sharda J, Bhowmik D. Synapse cell optimization and back-propagation algorithm implementation in a domain wall synapse based crossbar neural network for scalable on-chip learning. NANOTECHNOLOGY 2020; 31:364004. [PMID: 32454478 DOI: 10.1088/1361-6528/ab967d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
On-chip learning in spin orbit torque driven domain wall synapse based crossbar fully connected neural network (FCNN) has been shown to be extremely efficient in terms of speed and energy, when compared to training on a conventional computing unit or even on a crossbar FCNN based on other non-volatile memory devices. However there are issues with respect to scalability of the on-chip learning scheme in the domain wall synapse based FCNN. Unless the scheme is scalable, it will not be competitive with respect to training a neural network on a conventional computing unit for real applications. In this paper, we have proposed a modification in the standard gradient descent algorithm, used for training such FCNN, by including appropriate thresholding units. This leads to optimization of the synapse cell at each intersection of the crossbars and makes the system scalable. In order for the system to approximate a wide range of functions for data classification, hidden layers must be present and the backpropagation algorithm (extension of gradient descent algorithm for multi-layered FCNN) for training must be implemented on hardware. We have carried this out in this paper by employing an extra crossbar. Through a combination of micromagnetic simulations and SPICE circuit simulations, we hence show highly improved accuracy for domain wall syanpse based FCNN with a hidden layer compared to that without a hidden layer for different machine learning datasets.
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Affiliation(s)
- Divya Kaushik
- Department of Electrical Engineering, Indian Institute of Technology Delhi, New Delhi, Delhi-110016 India
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5
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Blachowicz T, Ehrmann A. Magnetic Elements for Neuromorphic Computing. Molecules 2020; 25:E2550. [PMID: 32486173 PMCID: PMC7321415 DOI: 10.3390/molecules25112550] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2020] [Revised: 05/18/2020] [Accepted: 05/28/2020] [Indexed: 01/02/2023] Open
Abstract
Neuromorphic computing is assumed to be significantly more energy efficient than, and at the same time expected to outperform, conventional computers in several applications, such as data classification, since it overcomes the so-called von Neumann bottleneck. Artificial synapses and neurons can be implemented into conventional hardware using new software, but also be created by diverse spintronic devices and other elements to completely avoid the disadvantages of recent hardware architecture. Here, we report on diverse approaches to implement neuromorphic functionalities in novel hardware using magnetic elements, published during the last years. Magnetic elements play an important role in neuromorphic computing. While other approaches, such as optical and conductive elements, are also under investigation in many groups, magnetic nanostructures and generally magnetic materials offer large advantages, especially in terms of data storage, but they can also unambiguously be used for data transport, e.g., by propagation of skyrmions or domain walls. This review underlines the possible applications of magnetic materials and nanostructures in neuromorphic systems.
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Affiliation(s)
- Tomasz Blachowicz
- Institute of Physics–Center for Science and Education, Silesian University of Technology, 44-100 Gliwice, Poland;
| | - Andrea Ehrmann
- Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, 33619 Bielefeld, Germany
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6
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Azam MA, Bhattacharya D, Querlioz D, Ross CA, Atulasimha J. Voltage control of domain walls in magnetic nanowires for energy-efficient neuromorphic devices. NANOTECHNOLOGY 2020; 31:145201. [PMID: 31842010 DOI: 10.1088/1361-6528/ab6234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
An energy-efficient voltage-controlled domain wall (DW) device for implementing an artificial neuron and synapse is analyzed using micromagnetic modeling in the presence of room temperature thermal noise. By controlling the DW motion utilizing spin transfer or spin-orbit torques in association with voltage generated strain control of perpendicular magnetic anisotropy in the presence of Dzyaloshinskii-Moriya interaction, different positions of the DW are realized in the free layer of a magnetic tunnel junction to program different synaptic weights. The feasibility of scaling of such devices is assessed in the presence of thermal perturbations that compromise controllability. Additionally, an artificial neuron can be realized by combining this DW device with a CMOS buffer. This provides a possible pathway to realize energy-efficient voltage-controlled nanomagnetic deep neural networks that can learn in real time.
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Affiliation(s)
- Md Ali Azam
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth Univ., Richmond, VA, United States of America
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7
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Pathak S, Youm C, Hong J. Impact of Spin-Orbit Torque on Spin-Transfer Torque Switching in Magnetic Tunnel Junctions. Sci Rep 2020; 10:2799. [PMID: 32071322 PMCID: PMC7029010 DOI: 10.1038/s41598-020-59533-y] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 01/24/2020] [Indexed: 11/17/2022] Open
Abstract
The paper presents our simulated results showing the substantial improvement of both switching speed and energy consumption in a perpendicular magnetic tunnel junction (p-MTJ), a core unit of Spin-Transfer-Torque Magnetic Random Access Memory (STT-MRAM), by the help of additional Spin-Orbit-Torque (SOT) write pulse current (WPSOT). An STT-SOT hybrid torque module for OOMMF simulation is implemented to investigate the switching behavior of a 20 nm cell in the p-MTJ. We found that the assistance of WPSOT to STT write pulse current (WPSTT) have a huge influence on the switching behavior of the free layer in the p-MTJ. For example, we could dramatically reduce the switching time (tSW) by 80% and thereby reduce the write energy over 70% as compared to those in the absence of the WPSOT. Even a very tiny amplitude of WPSOT (JSOT of the order of 102 A/m2) substantially assists to reduce the critical current density for switching of the free layer and thereby decreases the energy consumption as well. It is worth to be pointed out that the energy can be saved further by tuning the WPSOT parameters, i.e., amplitude and duration along at the threshold WPSTT. Our findings show that the proposed STT-SOT hybrid switching scheme has a great impact on the MRAM technology seeking the high speed and low energy consumption.
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Affiliation(s)
- Sachin Pathak
- Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea
- Physics, University of Petroleum and Energy Studies, Dehradun, 248007, India
| | - Chanyoung Youm
- Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea
| | - Jongill Hong
- Materials Science and Engineering, Yonsei University, Seoul, 03722, Korea.
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8
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Ren Z, Liu S, Jin L, Wen T, Liao Y, Tang X, Zhang H, Zhong Z. Reconfigurable nanoscale spin-wave directional coupler using spin-orbit torque. Sci Rep 2019; 9:7093. [PMID: 31068649 PMCID: PMC6506528 DOI: 10.1038/s41598-019-43597-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 04/26/2019] [Indexed: 11/24/2022] Open
Abstract
We present a reconfigurable nanoscale spin-wave directional coupler based on spin-orbit torque (SOT). By micromagnetic simulations, it is demonstrated that the functionality and operating frequency of proposed device can be dynamically switched by inverting the whole or part of the relative magnetic configuration of the dipolar-coupled waveguides using SOT. Utilizing the effect of sudden change in coupling length, the functionality of power divider can be realized. The proposed reconfigurable spin-wave directional coupler opens a way for two-dimensional planar magnonic integrated circuits.
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Affiliation(s)
- Zhiwei Ren
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Shuang Liu
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Lichuan Jin
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Tianlong Wen
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Yulong Liao
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Xiaoli Tang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Huaiwu Zhang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China
| | - Zhiyong Zhong
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 611731, China.
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9
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Deb S, Vatwani T, Chattopadhyay A, Basu A, Fong X. Domain Wall Motion-Based Dual-Threshold Activation Unit for Low-Power Classification of Non-Linearly Separable Functions. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2018; 12:1410-1421. [PMID: 30176604 DOI: 10.1109/tbcas.2018.2867038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Recently, a great deal of scientific endeavour has been devoted to developing spin-based neuromorphic platforms owing to the ultra-low-power benefits offered by spin devices and the inherent correspondence between spintronic phenomena and the desired neuronal, synaptic behavior. While domain wall motion-based threshold activation unit has previously been demonstrated for neuromorphic circuits, it remains well known that neurons with threshold activation cannot completely learn nonlinearly separable functions. This paper addresses this fundamental limitation by proposing a novel domain wall motion-based dual-threshold activation unit with additional nonlinearity in its function. Furthermore, a new learning algorithm is formulated for a neuron with this activation function. We perform 100 trials of tenfold training and testing of our neural networks on real-world datasets taken from the UCI machine learning repository. On an average, the proposed algorithm achieves [Formula: see text] lower misclassification rate (MCR) than the traditional perceptron learning algorithm. In a circuit-level simulation, the neural networks with the proposed activation unit are observed to outperform the perceptron networks by as much as [Formula: see text] MCR. The energy consumption of a neuron having the proposed domain wall motion-based activation unit averages to [Formula: see text] approximately.
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10
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D'Souza N, Biswas A, Ahmad H, Fashami MS, Al-Rashid MM, Sampath V, Bhattacharya D, Abeed MA, Atulasimha J, Bandyopadhyay S. Energy-efficient switching of nanomagnets for computing: straintronics and other methodologies. NANOTECHNOLOGY 2018; 29:442001. [PMID: 30052200 DOI: 10.1088/1361-6528/aad65d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The need for increasingly powerful computing hardware has spawned many ideas stipulating, primarily, the replacement of traditional transistors with alternate 'switches' that dissipate miniscule amounts of energy when they switch and provide additional functionality that are beneficial for information processing. An interesting idea that has emerged recently is the notion of using two-phase (piezoelectric/magnetostrictive) multiferroic nanomagnets with bistable (or multi-stable) magnetization states to encode digital information (bits), and switching the magnetization between these states with small voltages (that strain the nanomagnets) to carry out digital information processing. The switching delay is ∼1 ns and the energy dissipated in the switching operation can be few to tens of aJ, which is comparable to, or smaller than, the energy dissipated in switching a modern-day transistor. Unlike a transistor, a nanomagnet is 'non-volatile', so a nanomagnetic processing unit can store the result of a computation locally without refresh cycles, thereby allowing it to double as both logic and memory. These dual-role elements promise new, robust, energy-efficient, high-speed computing and signal processing architectures (usually non-Boolean and often non-von-Neumann) that can be more powerful, architecturally superior (fewer circuit elements needed to implement a given function) and sometimes faster than their traditional transistor-based counterparts. This topical review covers the important advances in computing and information processing with nanomagnets, with emphasis on strain-switched multiferroic nanomagnets acting as non-volatile and energy-efficient switches-a field known as 'straintronics'. It also outlines key challenges in straintronics.
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Affiliation(s)
- Noel D'Souza
- Department of Mechanical and Nuclear Engineering, Virginia Commonwealth University, Richmond VA 23284, United States of America
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11
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Moon KW, Kim C, Yoon J, Choi JW, Kim DO, Song KM, Kim D, Chun BS, Hwang C. A spin torque meter with magnetic facet domains. Nat Commun 2018; 9:3788. [PMID: 30224700 PMCID: PMC6141574 DOI: 10.1038/s41467-018-06223-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 08/24/2018] [Indexed: 11/23/2022] Open
Abstract
Current-induced magnetic domain wall (DW) motion is an important operating principle of spintronic devices. Injected current generates spin torques (STs) on the DWs in two ways. One is the spin transfer from magnetic domains to the walls by the current flowing in the magnet. Current flow in attached heavy metals also generates another ST because of the spin-Hall effect. Both phenomena explain the wall motions well; therefore, their respective contribution is an important issue. Here, we show the simultaneous measurement of both torques by using magnetic facet domains that form mountain-shaped domains with straight walls. When the STs and the external magnetic field push the walls in opposite directions, the walls should have equilibrium angles to create balanced states. Such angles can be modulated by an additional in-plane magnetic field. Angle measurements distinguish the STs because each torque has a distinct mechanism related to the DW structure.
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Affiliation(s)
- Kyoung-Woong Moon
- Spin Convergence Research Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Changsoo Kim
- Spin Convergence Research Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Jungbum Yoon
- Spin Convergence Research Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Jun Woo Choi
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
| | - Dong-Ok Kim
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
- Department of Physics, Soongsil University, Seoul, 06978, Republic of Korea
| | - Kyung Mee Song
- Center for Spintronics, Korea Institute of Science and Technology, Seoul, 02792, Republic of Korea
- Department of Physics, Sookmyung Women's University, Seoul, 04130, Republic of Korea
| | - Dongseuk Kim
- Spin Convergence Research Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Byong Sun Chun
- Spin Convergence Research Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea
| | - Chanyong Hwang
- Spin Convergence Research Team, Korea Research Institute of Standards and Science, Daejeon, 34113, Republic of Korea.
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12
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Spin orbit torques induced magnetization reversal through asymmetric domain wall propagation in Ta/CoFeB/MgO structures. Sci Rep 2018; 8:1355. [PMID: 29358598 PMCID: PMC5777997 DOI: 10.1038/s41598-018-19927-5] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Accepted: 01/09/2018] [Indexed: 11/08/2022] Open
Abstract
The magnetization reversal induced by spin orbit torques in the presence of Dzyaloshinskii-Moriya interaction (DMI) in perpendicularly magnetized Ta/CoFeB/MgO structures were investigated by using a combination of Anomalous Hall effect measurement and Kerr effect microscopy techniques. By analyzing the in-plane field dependent spin torque efficiency measurements, an effective field value for the DMI of ~300 Oe was obtained, which plays a key role to stabilize Néel walls in the film stack. Kerr imaging reveals that the current-induced reversal under small and medium in-plane field was mediated by domain nucleation at the edge of the Hall bar, followed by asymmetric domain wall (DW) propagation. However, as the in-plane field strength increases, an isotropic DW expansion was observed before reaching complete reversal. Micromagnetic simulations of the DW structure in the CoFeB layer suggest that the DW configuration under the combined effect of the DMI and the external field is responsible for the various DW propagation behaviors.
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13
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Cai K, Yang M, Ju H, Wang S, Ji Y, Li B, Edmonds KW, Sheng Y, Zhang B, Zhang N, Liu S, Zheng H, Wang K. Electric field control of deterministic current-induced magnetization switching in a hybrid ferromagnetic/ferroelectric structure. NATURE MATERIALS 2017; 16:712-716. [PMID: 28369053 DOI: 10.1038/nmat4886] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2016] [Accepted: 03/01/2017] [Indexed: 05/22/2023]
Abstract
All-electrical and programmable manipulations of ferromagnetic bits are highly pursued for the aim of high integration and low energy consumption in modern information technology. Methods based on the spin-orbit torque switching in heavy metal/ferromagnet structures have been proposed with magnetic field, and are heading toward deterministic switching without external magnetic field. Here we demonstrate that an in-plane effective magnetic field can be induced by an electric field without breaking the symmetry of the structure of the thin film, and realize the deterministic magnetization switching in a hybrid ferromagnetic/ferroelectric structure with Pt/Co/Ni/Co/Pt layers on PMN-PT substrate. The effective magnetic field can be reversed by changing the direction of the applied electric field on the PMN-PT substrate, which fully replaces the controllability function of the external magnetic field. The electric field is found to generate an additional spin-orbit torque on the CoNiCo magnets, which is confirmed by macrospin calculations and micromagnetic simulations.
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Affiliation(s)
- Kaiming Cai
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Meiyin Yang
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Hailang Ju
- Department of Physics, School of Sciences, Beijing Technology and Business University, Beijing 100048, China
| | - Sumei Wang
- ICAC, Institute of Microelectronics of CAS, University of Chinese Academy of Sciences, Beijing 100029, China
| | - Yang Ji
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Baohe Li
- Department of Physics, School of Sciences, Beijing Technology and Business University, Beijing 100048, China
| | | | - Yu Sheng
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Bao Zhang
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Nan Zhang
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Shuai Liu
- Department of Physics, School of Sciences, Beijing Technology and Business University, Beijing 100048, China
| | - Houzhi Zheng
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
| | - Kaiyou Wang
- SKLSM, Institute of Semiconductors, CAS, PO Box 912, Beijing 100083, China
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14
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Deterministic Spin-Orbit Torque Induced Magnetization Reversal In Pt/[Co/Ni] n /Co/Ta Multilayer Hall Bars. Sci Rep 2017; 7:972. [PMID: 28428617 PMCID: PMC5430536 DOI: 10.1038/s41598-017-01079-7] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Accepted: 03/27/2017] [Indexed: 11/26/2022] Open
Abstract
Spin-orbit torque (SOT) induced by electric current has attracted extensive attention as an efficient method of controlling the magnetization in nanomagnetic structures. SOT-induced magnetization reversal is usually achieved with the aid of an in-plane bias magnetic field. In this paper, we show that by selecting a film stack with weak out-of-plane magnetic anisotropy, field-free SOT-induced switching can be achieved in micron sized multilayers. Using direct current, deterministic bipolar magnetization reversal is obtained in Pt/[Co/Ni]2/Co/Ta structures. Kerr imaging reveals that the SOT-induced magnetization switching process is completed via the nucleation of reverse domain and propagation of domain wall in the system.
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15
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Modulated switching current density and spin-orbit torques in MnGa/Ta films with inserting ferromagnetic layers. Sci Rep 2016; 6:38375. [PMID: 27910938 PMCID: PMC5133548 DOI: 10.1038/srep38375] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 11/08/2016] [Indexed: 11/09/2022] Open
Abstract
We report modulated switching current density and spin-orbit torques (SOT) in MnGa/Ta films with inserting very thin Co2FeAl and Co layers. Ferromagnetic coupling has been found in MnGa/Co2FeAl/Ta, resulting in a decreased effective anisotropy field. On the contrary, in MnGa/Co/Ta, antiferromagnetic coupling plays a dominant role. The switching current density Jc in MnGa/Ta is 8.5 × 107 A/cm2. After inserting 0.8-nm-thick Co2FeAl and Co, theJc becomes 5 × 107 A/cm2 and 9 × 107 A/cm2, respectively. By performing adiabatic harmonic Hall voltage measurements, it is demonstrated that the inserted Co2FeAl layer has mainly enhanced the field-like torques, while in MnGa/Co/Ta the damping-like torques have been enhanced. Finally, the enhanced spin Hall effect (SHE) has also been studied using the spin Hall magnetoresistance measurement. The modulated Jc and SOT are ascribed to the combination of magnetic coupling, Rashba effect and SHE at the interfaces.
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Spin-orbit torque in Pt/CoNiCo/Pt symmetric devices. Sci Rep 2016; 6:20778. [PMID: 26856379 PMCID: PMC4746736 DOI: 10.1038/srep20778] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 01/12/2016] [Indexed: 11/18/2022] Open
Abstract
Current induced magnetization switching by spin-orbit torques offers an energy-efficient means of writing information in heavy metal/ferromagnet (FM) multilayer systems. The relative contributions of field-like torques and damping-like torques to the magnetization switching induced by the electrical current are still under debate. Here, we describe a device based on a symmetric Pt/FM/Pt structure, in which we demonstrate a strong damping-like torque from the spin Hall effect and unmeasurable field-like torque from Rashba effect. The spin-orbit effective fields due to the spin Hall effect were investigated quantitatively and were found to be consistent with the switching effective fields after accounting for the switching current reduction due to thermal fluctuations from the current pulse. A non-linear dependence of deterministic switching of average Mz on the in-plane magnetic field was revealed, which could be explained and understood by micromagnetic simulation.
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Sharma S, Muralidharan B, Tulapurkar A. Proposal for a Domain Wall Nano-Oscillator driven by Non-uniform Spin Currents. Sci Rep 2015; 5:14647. [PMID: 26420544 PMCID: PMC4588506 DOI: 10.1038/srep14647] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 09/02/2015] [Indexed: 11/25/2022] Open
Abstract
We propose a new mechanism and a related device concept for a robust, magnetic field tunable radio-frequency (rf) oscillator using the self oscillation of a magnetic domain wall subject to a uniform static magnetic field and a spatially non-uniform vertical dc spin current. The self oscillation of the domain wall is created as it translates periodically between two unstable positions, one being in the region where both the dc spin current and the magnetic field are present, and the other, being where only the magnetic field is present. The vertical dc spin current pushes it away from one unstable position while the magnetic field pushes it away from the other. We show that such oscillations are stable under noise and can exhibit a quality factor of over 1000. A domain wall under dynamic translation, not only being a source for rich physics, is also a promising candidate for advancements in nanoelectronics with the actively researched racetrack memory architecture, digital and analog switching paradigms as candidate examples. Devising a stable rf oscillator using a domain wall is hence another step towards the realization of an all domain wall logic scheme.
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Affiliation(s)
- Sanchar Sharma
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Bhaskaran Muralidharan
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Ashwin Tulapurkar
- Department of Electrical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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