1
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Urrestarazu Larrañaga J, Sisodia N, Guedas R, Pham VT, Di Manici I, Masseboeuf A, Garello K, Disdier F, Fernandez B, Wintz S, Weigand M, Belmeguenai M, Pizzini S, Sousa RC, Buda-Prejbeanu LD, Gaudin G, Boulle O. Electrical Detection and Nucleation of a Magnetic Skyrmion in a Magnetic Tunnel Junction Observed via Operando Magnetic Microscopy. NANO LETTERS 2024; 24:3557-3565. [PMID: 38499397 DOI: 10.1021/acs.nanolett.4c00316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Magnetic skyrmions are topological spin textures which are envisioned as nanometer scale information carriers in magnetic memory and logic devices. The recent demonstrations of room temperature skyrmions and their current induced manipulation in ultrathin films were first steps toward the realization of such devices. However, important challenges remain regarding the electrical detection and the low-power nucleation of skyrmions, which are required for the read and write operations. Here, we demonstrate, using operando magnetic microscopy experiments, the electrical detection of a single magnetic skyrmion in a magnetic tunnel junction (MTJ) and its nucleation and annihilation by gate voltage via voltage control of magnetic anisotropy. The nucleated skyrmion can be manipulated by both gate voltages and external magnetic fields, leading to tunable intermediate resistance states. Our results unambiguously demonstrate the readout and voltage controlled write operations in a single MTJ device, which is a major milestone for low power skyrmion based technologies.
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Affiliation(s)
| | - Naveen Sisodia
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Rodrigo Guedas
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Van Tuong Pham
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
- Univ. Grenoble Alpes, CNRS, Institut Néel, 38042 Grenoble, France
| | - Ilaria Di Manici
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Aurélien Masseboeuf
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Kevin Garello
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Florian Disdier
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Bruno Fernandez
- Univ. Grenoble Alpes, CNRS, Institut Néel, 38042 Grenoble, France
| | - Sebastian Wintz
- Max Planck Institute for Intelligent Systems, Heisenbergstraße 3, 70569 Stuttgart, Germany
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, D-14109 Berlin, Germany
| | - Markus Weigand
- Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, D-14109 Berlin, Germany
| | - Mohamed Belmeguenai
- LSPM (CNRS-UPR 3407), Université Paris 13, Sorbonne Paris Cité, 99 Avenue Jean-Baptiste Clément, 93430 Villetaneuse, France
| | - Stefania Pizzini
- Univ. Grenoble Alpes, CNRS, Institut Néel, 38042 Grenoble, France
| | - Ricardo C Sousa
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | | | - Gilles Gaudin
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
| | - Olivier Boulle
- Univ. Grenoble Alpes, CNRS, CEA, Grenoble INP, SPINTEC, 38000 Grenoble, France
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2
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Chen S, Lourembam J, Ho P, Toh AKJ, Huang J, Chen X, Tan HK, Yap SLK, Lim RJJ, Tan HR, Suraj TS, Sim MI, Toh YT, Lim I, Lim NCB, Zhou J, Chung HJ, Lim ST, Soumyanarayanan A. All-electrical skyrmionic magnetic tunnel junction. Nature 2024; 627:522-527. [PMID: 38509277 DOI: 10.1038/s41586-024-07131-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2023] [Accepted: 01/25/2024] [Indexed: 03/22/2024]
Abstract
Topological whirls or 'textures' of spins such as magnetic skyrmions represent the smallest realizable emergent magnetic entities1-5. They hold considerable promise as robust, nanometre-scale, mobile bits for sustainable computing6-8. A longstanding roadblock to unleashing their potential is the absence of a device enabling deterministic electrical readout of individual spin textures9,10. Here we present the wafer-scale realization of a nanoscale chiral magnetic tunnel junction (MTJ) hosting a single, ambient skyrmion. Using a suite of electrical and multimodal imaging techniques, we show that the MTJ nucleates skyrmions of fixed polarity, whose large readout signal-20-70% relative to uniformly magnetized states-corresponds directly to skyrmion size. The MTJ exploits complementary nucleation mechanisms to stabilize distinctly sized skyrmions at zero field, thereby realizing three non-volatile electrical states. Crucially, it can electrically write and delete skyrmions to both uniform states with switching energies 1,000 times lower than the state of the art. Here, the applied voltage emulates a magnetic field and, in contrast to conventional MTJs, it reshapes both the energetics and kinetics of the switching transition, enabling deterministic bidirectional switching. Our stack platform enables large readout and efficient switching, and is compatible with lateral manipulation of skyrmionic bits, providing the much-anticipated backbone for all-electrical skyrmionic device architectures9,10. Its wafer-scale realizability provides a springboard to harness chiral spin textures for multibit memory and unconventional computing8,11.
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Affiliation(s)
- Shaohai Chen
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - James Lourembam
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Pin Ho
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Alexander K J Toh
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Jifei Huang
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Xiaoye Chen
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Hang Khume Tan
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Sherry L K Yap
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Royston J J Lim
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Hui Ru Tan
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - T S Suraj
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - May Inn Sim
- Department of Physics, National University of Singapore, Singapore, Singapore
| | - Yeow Teck Toh
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Idayu Lim
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Nelson C B Lim
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Jing Zhou
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Hong Jing Chung
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Sze Ter Lim
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore
| | - Anjan Soumyanarayanan
- Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Singapore, Singapore.
- Department of Physics, National University of Singapore, Singapore, Singapore.
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3
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He B, Tomasello R, Luo X, Zhang R, Nie Z, Carpentieri M, Han X, Finocchio G, Yu G. All-Electrical 9-Bit Skyrmion-Based Racetrack Memory Designed with Laser Irradiation. NANO LETTERS 2023; 23:9482-9490. [PMID: 37818857 DOI: 10.1021/acs.nanolett.3c02978] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/13/2023]
Abstract
Racetrack memories with magnetic skyrmions have recently been proposed as a promising storage technology. To be appealing, several challenges must still be faced for the deterministic generation of skyrmions, their high-fidelity transfer, and accurate reading. Here, we realize the first proof-of-concept of a 9-bit skyrmion racetrack memory with all-electrical controllable functionalities implemented in the same device. The key ingredient is the generation of a tailored nonuniform distribution of magnetic anisotropy via laser irradiation in order to (i) create a well-defined skyrmion nucleation center, (ii) define the memory cells hosting the information coded as the presence/absence of skyrmions, and (iii) improve the signal-to-noise ratio of anomalous Hall resistance measurements. This work introduces a strategy to unify previous findings and predictions for the development of a generation of racetrack memories with robust control of skyrmion nucleation and position, as well as effective skyrmion electrical detection.
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Affiliation(s)
- Bin He
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Riccardo Tomasello
- Department of Electrical and Information Engineering, Politecnico of Bari, Bari 70125, Italy
| | - Xuming Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Ran Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Zhuyang Nie
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Mario Carpentieri
- Department of Electrical and Information Engineering, Politecnico of Bari, Bari 70125, Italy
| | - Xiufeng Han
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
| | - Giovanni Finocchio
- Department of Mathematical and Computer Sciences, Physical Sciences and Earth Sciences, University of Messina, Messina 98166, Italy
| | - Guoqiang Yu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China
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4
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Yu D, Ga Y, Liang J, Jia C, Yang H. Voltage-Controlled Dzyaloshinskii-Moriya Interaction Torque Switching of Perpendicular Magnetization. PHYSICAL REVIEW LETTERS 2023; 130:056701. [PMID: 36800473 DOI: 10.1103/physrevlett.130.056701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 09/30/2022] [Accepted: 12/20/2022] [Indexed: 06/18/2023]
Abstract
Magnetization switching is the most important operation in spintronic devices. In modern nonvolatile magnetic random-access memory (MRAM), it is usually realized by spin-transfer torque (STT) or spin-orbit torque (SOT). However, both STT and SOT MRAM require current to drive magnetization switching, which will cause Joule heating. Here, we report an alternative mechanism, Dzyaloshinskii-Moriya interaction (DMI) torque, that can realize magnetization switching fully controlled by voltage pulses. We find that a consequential voltage-controlled reversal of DMI chirality in multiferroics can lead to continued expansion of a skyrmion thanks to the DMI torque. Enough DMI torque will eventually make the skyrmion burst into a quasiuniform ferromagnetic state with reversed magnetization, thus realizing the switching of a perpendicular magnet. The discovery is demonstrated in two-dimensional multiferroics, CuCrP_{2}Se_{6} and CrN, using first-principles calculations and micromagnetic simulations. As an example, we applied the DMI torque for simulating leaky-integrate-fire functionality of biological neurons. Our discovery of DMI torque switching of perpendicular magnetization provides tremendous potential toward magnetic-field-free and current-free spintronic devices, and neuromorphic computing as well.
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Affiliation(s)
- Dongxing Yu
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Yonglong Ga
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Jinghua Liang
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
| | - Chenglong Jia
- Key Laboratory for Magnetism and Magnetic Materials of MOE and Lanzhou Center for Theoretical Physics, Lanzhou University, Lanzhou 730000, China
| | - Hongxin Yang
- National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
- Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China
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5
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Xue F, Zhang C, Ma Y, Wen Y, He X, Yu B, Zhang X. Integrated Memory Devices Based on 2D Materials. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2022; 34:e2201880. [PMID: 35557021 DOI: 10.1002/adma.202201880] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2022] [Revised: 05/07/2022] [Indexed: 06/15/2023]
Abstract
With the advent of the Internet of Things and big data, massive data must be rapidly processed and stored within a short timeframe. This imposes stringent requirements on memory hardware implementation in terms of operation speed, energy consumption, and integration density. To fulfill these demands, 2D materials, which are excellent electronic building blocks, provide numerous possibilities for developing advanced memory device arrays with high performance, smart computing architectures, and desirable downscaling. Over the past few years, 2D-material-based memory-device arrays with different working mechanisms, including defects, filaments, charges, ferroelectricity, and spins, have been increasingly developed. These arrays can be used to implement brain-inspired computing or sensing with extraordinary performance, architectures, and functionalities. Here, recent research into integrated, state-of-the-art memory devices made from 2D materials, as well as their implications for brain-inspired computing are surveyed. The existing challenges at the array level are discussed, and the scope for future research is presented.
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Affiliation(s)
- Fei Xue
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310020, P. R. China
- School of Micro-Nano Electronics, Zhejiang University, Hangzhou, 311200, P. R. China
| | - Chenhui Zhang
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Yinchang Ma
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Yan Wen
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Xin He
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
| | - Bin Yu
- ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou, 310020, P. R. China
- School of Micro-Nano Electronics, Zhejiang University, Hangzhou, 311200, P. R. China
| | - Xixiang Zhang
- Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia
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6
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Yang S, Ju TS, Kim C, Kim HJ, An K, Moon KW, Park S, Hwang C. Magnetic Field Magnitudes Needed for Skyrmion Generation in a General Perpendicularly Magnetized Film. NANO LETTERS 2022; 22:8430-8436. [PMID: 36282733 PMCID: PMC9650724 DOI: 10.1021/acs.nanolett.2c02268] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 10/08/2022] [Indexed: 06/16/2023]
Abstract
Due to its topological protection, the magnetic skyrmion has been intensively studied for both fundamental aspects and spintronics applications. However, despite recent advancements in skyrmion research, the deterministic creation of isolated skyrmions in a generic perpendicularly magnetized film is still one of the most essential and challenging techniques. Here, we present a method to create magnetic skyrmions in typical perpendicular magnetic anisotropy (PMA) films by applying a magnetic field pulse and a method to determine the magnitude of the required external magnetic fields. Furthermore, to demonstrate the usefulness of this result for future skyrmion research, we also experimentally study the PMA dependence on the minimum size of skyrmions. Although field-driven skyrmion generation is unsuitable for device application, this result can provide an easier approach for obtaining isolated skyrmions, making skyrmion-based research more accessible.
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Affiliation(s)
- Seungmo Yang
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
| | - Tae-Seong Ju
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
- Department
of Physics, Pusan National University, Busan46241, Republic of Korea
| | - Changsoo Kim
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
| | - Hyun-Joong Kim
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
| | - Kyongmo An
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
| | - Kyoung-Woong Moon
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
| | - Sungkyun Park
- Department
of Physics, Pusan National University, Busan46241, Republic of Korea
| | - Chanyong Hwang
- Quantum
Spin Team, Korea Research Institute of Standards
and Science, Daejeon34113, Republic of Korea
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7
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MacKinnon CR, Zeissler K, Finizio S, Raabe J, Marrows CH, Mercer T, Bissell PR, Lepadatu S. Collective skyrmion motion under the influence of an additional interfacial spin-transfer torque. Sci Rep 2022; 12:10786. [PMID: 35750744 PMCID: PMC9232533 DOI: 10.1038/s41598-022-14969-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/15/2022] [Indexed: 11/26/2022] Open
Abstract
Here we study the effect of an additional interfacial spin-transfer torque, as well as the well-established spin–orbit torque and bulk spin-transfer torque, on skyrmion collections—group of skyrmions dense enough that they are not isolated from one another—in ultrathin heavy metal/ferromagnetic multilayers, by comparing modelling with experimental results. Using a skyrmion collection with a range of skyrmion diameters and landscape disorder, we study the dependence of the skyrmion Hall angle on diameter and velocity, as well as the velocity as a function of diameter. We show that inclusion of the interfacial spin-transfer torque results in reduced skyrmion Hall angles, with values close to experimental results. We also show that for skyrmion collections the velocity is approximately independent of diameter, in marked contrast to the motion of isolated skyrmions, as the group of skyrmions move together at an average group velocity. Moreover, the calculated skyrmion velocities are comparable to those obtained in experiments when the interfacial spin-transfer torque is included. Our results thus show the significance of the interfacial spin-transfer torque in ultrathin magnetic multilayers, which helps to explain the low skyrmion Hall angles and velocities observed in experiment. We conclude that the interfacial spin-transfer torque should be considered in numerical modelling for reproduction of experimental results.
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Affiliation(s)
- Callum R MacKinnon
- Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston, PR1 2HE, UK.
| | - Katharina Zeissler
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK.,Bragg Center for Materials Research, University of Leeds, Leeds, LS2 9JT, UK
| | - Simone Finizio
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen, Switzerland
| | - Jörg Raabe
- Swiss Light Source, Paul Scherrer Institut, 5232, Villigen, Switzerland
| | - Christopher H Marrows
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK.,Bragg Center for Materials Research, University of Leeds, Leeds, LS2 9JT, UK
| | - Tim Mercer
- Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston, PR1 2HE, UK
| | - Philip R Bissell
- Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston, PR1 2HE, UK
| | - Serban Lepadatu
- Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston, PR1 2HE, UK.
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8
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Spin-orbit enabled all-electrical readout of chiral spin-textures. Nat Commun 2022; 13:1576. [PMID: 35332149 PMCID: PMC8948229 DOI: 10.1038/s41467-022-29237-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Accepted: 03/01/2022] [Indexed: 11/22/2022] Open
Abstract
Chirality and topology are intimately related fundamental concepts, which are heavily explored to establish spin-textures as potential magnetic bits in information technology. However, this ambition is inhibited since the electrical reading of chiral attributes is highly non-trivial with conventional current perpendicular-to-plane (CPP) sensing devices. Here we demonstrate from extensive first-principles simulations and multiple scattering expansion the emergence of the chiral spin-mixing magnetoresistance (C-XMR) enabling highly efficient all-electrical readout of the chirality and helicity of respectively one- and two-dimensional magnetic states of matter. It is linear with spin-orbit coupling in contrast to the quadratic dependence associated with the unveiled non-local spin-mixing anisotropic MR (X-AMR). Such transport effects are systematized on various non-collinear magnetic states – spin-spirals and skyrmions – and compared to the uncovered spin-orbit-independent multi-site magnetoresistances. Owing to their simple implementation in readily available reading devices, the proposed magnetoresistances offer exciting and decisive ingredients to explore with all-electrical means the rich physics of topological and chiral magnetic objects. One challenge for encoding information in chiral spin textures is how to read the information electrically. Here, Lima Fernandes et al. show that chiral spin textures exhibit a magnetoresistance signature which could allow for efficient electric readout of the chirality and helicity.
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9
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Experimental demonstration of skyrmionic magnetic tunnel junction at room temperature. Sci Bull (Beijing) 2022; 67:691-699. [DOI: 10.1016/j.scib.2022.01.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2021] [Revised: 01/07/2022] [Accepted: 01/12/2022] [Indexed: 11/24/2022]
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10
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Raju M, Petrović AP, Yagil A, Denisov KS, Duong NK, Göbel B, Şaşıoğlu E, Auslaender OM, Mertig I, Rozhansky IV, Panagopoulos C. Colossal topological Hall effect at the transition between isolated and lattice-phase interfacial skyrmions. Nat Commun 2021; 12:2758. [PMID: 33980841 PMCID: PMC8115237 DOI: 10.1038/s41467-021-22976-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Accepted: 04/07/2021] [Indexed: 11/16/2022] Open
Abstract
The topological Hall effect is used extensively to study chiral spin textures in various materials. However, the factors controlling its magnitude in technologically-relevant thin films remain uncertain. Using variable-temperature magnetotransport and real-space magnetic imaging in a series of Ir/Fe/Co/Pt heterostructures, here we report that the chiral spin fluctuations at the phase boundary between isolated skyrmions and a disordered skyrmion lattice result in a power-law enhancement of the topological Hall resistivity by up to three orders of magnitude. Our work reveals the dominant role of skyrmion stability and configuration in determining the magnitude of the topological Hall effect. Previous studies of skyrmions in thin film architectures have shown widely-varying magnitudes of the topological Hall effect. Here, Raju et al. show that this variation follows a power-law behaviour driven by chiral spin fluctuations at the phase transition between isolated and lattice skyrmions.
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Affiliation(s)
- M Raju
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore. .,Institute for Quantum Matter and Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, USA.
| | - A P Petrović
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - A Yagil
- Department of Physics, Technion, Haifa, Israel
| | | | - N K Duong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - B Göbel
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany
| | - E Şaşıoğlu
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany
| | - O M Auslaender
- Department of Physics, Technion, Haifa, Israel.,Neuroscience Institute and Tech4Health Institute, NYU Langone Health, New York, NY, USA
| | - I Mertig
- Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany
| | | | - C Panagopoulos
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
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11
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Satywali B, Kravchuk VP, Pan L, Raju M, He S, Ma F, Petrović AP, Garst M, Panagopoulos C. Microwave resonances of magnetic skyrmions in thin film multilayers. Nat Commun 2021; 12:1909. [PMID: 33772026 PMCID: PMC7998029 DOI: 10.1038/s41467-021-22220-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Accepted: 03/03/2021] [Indexed: 11/09/2022] Open
Abstract
Non-collinear magnets exhibit a rich array of dynamic properties at microwave frequencies. They can host nanometre-scale topological textures known as skyrmions, whose spin resonances are expected to be highly sensitive to their local magnetic environment. Here, we report a magnetic resonance study of an [Ir/Fe/Co/Pt] multilayer hosting Néel skyrmions at room temperature. Experiments reveal two distinct resonances of the skyrmion phase during in-plane ac excitation, with frequencies between 6-12 GHz. Complementary micromagnetic simulations indicate that the net magnetic dipole moment rotates counterclockwise (CCW) during both resonances. The magnon probability distribution for the lower-frequency resonance is localised within isolated skyrmions, unlike the higher-frequency mode which principally originates from areas between skyrmions. However, the properties of both modes depend sensitively on the out-of-plane dipolar coupling, which is controlled via the ferromagnetic layer spacing in our heterostructures. The gyrations of stable isolated skyrmions reported in this room temperature study encourage the development of new material platforms and applications based on skyrmion resonances. Moreover, our material architecture enables the resonance spectra to be tuned, thus extending the functionality of such applications over a broadband frequency range.
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Affiliation(s)
- Bhartendu Satywali
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Volodymyr P Kravchuk
- Bogolyubov Institute for Theoretical Physics of National Academy of Sciences of Ukraine, Kyiv, Ukraine
- Institute for Theoretical Solid State Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Liqing Pan
- Research Institute for Magnetoelectronics and Weak Magnetic Field Detection, College of Science, China Three Gorges University, Yichang, China
| | - M Raju
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Shikun He
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - Fusheng Ma
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore
| | - A P Petrović
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
| | - Markus Garst
- Institute for Theoretical Solid State Physics, Karlsruhe Institute of Technology, Karlsruhe, Germany
- Institut für Theoretische Physik, TU Dresden, Dresden, Germany
- Institute for Quantum Materials and Technologies, Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - Christos Panagopoulos
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
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12
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Abstract
Skyrmion, a concept originally proposed in particle physics half a century ago, can now find the most fertile field for its applicability, that is, the magnetic skyrmion realized in helimagnetic materials. The spin swirling vortex-like texture of the magnetic skyrmion can define the particle nature by topology; that is, all the constituent spin moments within the two-dimensional sheet wrap the sphere just one time. Such a topological nature of the magnetic skyrmion can lead to extraordinary metastability via topological protection and the driven motion with low electric-current excitation, which may promise future application to spintronics. The skyrmions in the magnetic materials frequently show up as the crystal lattice form, e.g., hexagonal lattice, but sometimes as isolated or independent particles. These skyrmions in magnets were initially found in acentric magnets, such as chiral, polar, and bilayered magnets endowed with antisymmetric spin exchange interaction, while the skyrmion host materials have been explored in a broader family of compounds including centrosymmetric magnets. This review describes the materials science and materials chemistry of magnetic skyrmions using the classification scheme of the skyrmion forming microscopic mechanisms. The emergent phenomena and functions mediated by skyrmions are described, including the generation of emergent magnetic and electric field by statics and dynamics of skrymions and the inherent magnetoelectric effect. The other important magnetic topological defects in two or three dimensions, such as biskyrmions, antiskyrmions, merons, and hedgehogs, are also reviewed in light of their interplay with the skyrmions.
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Affiliation(s)
- Yoshinori Tokura
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan.,RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan.,Tokyo College, University of Tokyo, Tokyo 113-8656, Japan
| | - Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan
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13
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Fernández Scarioni A, Barton C, Corte-León H, Sievers S, Hu X, Ajejas F, Legrand W, Reyren N, Cros V, Kazakova O, Schumacher HW. Thermoelectric Signature of Individual Skyrmions. PHYSICAL REVIEW LETTERS 2021; 126:077202. [PMID: 33666484 DOI: 10.1103/physrevlett.126.077202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 06/26/2020] [Accepted: 11/02/2020] [Indexed: 06/12/2023]
Abstract
We experimentally study the thermoelectrical signature of individual skyrmions in chiral Pt/Co/Ru multilayers. Using a combination of controlled nucleation, single skyrmion annihilation, and magnetic field dependent measurements the thermoelectric signature of individual skyrmions is characterized. The observed signature is explained by the anomalous Nernst effect of the skyrmion's spin structure. Possible topological contributions to the observed thermoelectrical signature are discussed. Such thermoelectrical characterization allows for noninvasive detection and counting of skyrmions and enables fundamental studies of topological thermoelectric effects on the nanoscale.
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Affiliation(s)
| | - Craig Barton
- National Physical Laboratory, Teddington TW110LW, United Kingdom
| | | | - Sibylle Sievers
- Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
| | - Xiukun Hu
- Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
| | - Fernando Ajejas
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - William Legrand
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Nicolas Reyren
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Vincent Cros
- Unité Mixte de Physique, CNRS, Thales, Université Paris-Saclay, 91767 Palaiseau, France
| | - Olga Kazakova
- National Physical Laboratory, Teddington TW110LW, United Kingdom
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14
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Stenning KD, Gartside JC, Dion T, Vanstone A, Arroo DM, Branford WR. Magnonic Bending, Phase Shifting and Interferometry in a 2D Reconfigurable Nanodisk Crystal. ACS NANO 2021; 15:674-685. [PMID: 33320533 DOI: 10.1021/acsnano.0c06894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Strongly interacting nanomagnetic systems are pivotal across next-generation technologies including reconfigurable magnonics and neuromorphic computation. Controlling magnetization states and local coupling between neighboring nanoelements allows vast reconfigurability and a host of associated functionalities. However, existing designs typically suffer from an inability to tailor interelement coupling post-fabrication and nanoelements restricted to a pair of Ising-like magnetization states. Here, we propose a class of reconfigurable magnonic crystals incorporating nanodisks as the functional element. Ferromagnetic nanodisks are crucially bistable in macrospin and vortex states, allowing interelement coupling to be selectively activated (macrospin) or deactivated (vortex). Through microstate engineering, we leverage the distinct coupling behaviors and magnonic band structures of bistable nanodisks to achieve reprogrammable magnonic waveguiding, bending, gating, and phase-shifting across a 2D network. The potential of nanodisk-based magnonics for wave-based computation is demonstrated via an all-magnon interferometer exhibiting XNOR logic functionality. Local microstate control is achieved here via topological magnetic writing using a magnetic force microscope tip.
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Affiliation(s)
- Kilian D Stenning
- Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
| | - Jack C Gartside
- Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
| | - Troy Dion
- Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
- London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom
| | - Alexander Vanstone
- Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
| | - Daan M Arroo
- London Centre for Nanotechnology, University College London, London WC1H 0AH, United Kingdom
| | - Will R Branford
- Blackett Laboratory, Imperial College London, London SW7 2AZ, United Kingdom
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15
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Denisov KS. Theory of an electron asymmetric scattering on skyrmion textures in two-dimensional systems. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:415302. [PMID: 32454477 DOI: 10.1088/1361-648x/ab966e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2020] [Accepted: 05/26/2020] [Indexed: 06/11/2023]
Abstract
We discuss in detail the electron scattering pattern on skyrmion-like magnetic textures in two-dimensional geometry. The special attention is focused on analyzing the scattering asymmetry, which is a precursor of the topological Hall effect. We present analytical results valid in the limiting regimes of strong and weak coupling, we analyze analytically the conditions when the transverse response acquires a quantized character determined by the topological charge of a magnetic texture, we also derive the numerical scheme that gives access to the exact solution of the scattering problem. We describe how the electron scattering asymmetry is modified due to an additional short-range impurity located inside a magnetic skyrmion. Based on the numerical computations we investigate the properties of the asymmetric scattering for an arbitrary magnitude of the interaction strength and the topology of a magnetic texture, we also account for the presence or absence of a scalar impurity.
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Affiliation(s)
- K S Denisov
- Ioffe Institute, 194021 St. Petersburg, Russia
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16
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Zhang X, Zhou Y, Mee Song K, Park TE, Xia J, Ezawa M, Liu X, Zhao W, Zhao G, Woo S. Skyrmion-electronics: writing, deleting, reading and processing magnetic skyrmions toward spintronic applications. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:143001. [PMID: 31689688 DOI: 10.1088/1361-648x/ab5488] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The field of magnetic skyrmions has been actively investigated across a wide range of topics during the last decades. In this topical review, we mainly review and discuss key results and findings in skyrmion research since the first experimental observation of magnetic skyrmions in 2009. We particularly focus on the theoretical, computational and experimental findings and advances that are directly relevant to the spintronic applications based on magnetic skyrmions, i.e. their writing, deleting, reading and processing driven by magnetic field, electric current and thermal energy. We then review several potential applications including information storage, logic computing gates and non-conventional devices such as neuromorphic computing devices. Finally, we discuss possible future research directions on magnetic skyrmions, which also cover rich topics on other topological textures such as antiskyrmions and bimerons in antiferromagnets and frustrated magnets.
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Affiliation(s)
- Xichao Zhang
- School of Science and Engineering, The Chinese University of Hong Kong, Shenzhen, Guangdong 518172, People's Republic of China
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17
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Fallon K, Hughes S, Zeissler K, Legrand W, Ajejas F, Maccariello D, McFadzean S, Smith W, McGrouther D, Collin S, Reyren N, Cros V, Marrows CH, McVitie S. Controlled Individual Skyrmion Nucleation at Artificial Defects Formed by Ion Irradiation. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2020; 16:e1907450. [PMID: 32141234 DOI: 10.1002/smll.201907450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 02/14/2020] [Accepted: 02/17/2020] [Indexed: 06/10/2023]
Abstract
Magnetic skyrmions are particle-like deformations in a magnetic texture. They have great potential as information carriers in spintronic devices because of their interesting topological properties and favorable motion under spin currents. A new method of nucleating skyrmions at nanoscale defect sites, created in a controlled manner with focused ion beam irradiation, in polycrystalline magnetic multilayer samples with an interfacial Dzyaloshinskii-Moriya interaction, is reported. This new method has three notable advantages: 1) localization of nucleation; 2) stability over a larger range of external field strengths, including stability at zero field; and 3) existence of skyrmions in material systems where, prior to defect fabrication, skyrmions were not previously obtained by field cycling. Additionally, it is observed that the size of defect nucleated skyrmions is uninfluenced by the defect itself-provided that the artificial defects are controlled to be smaller than the inherent skyrmion size. All of these characteristics are expected to be useful toward the goal of realizing a skyrmion-based spintronic device. This phenomenon is studied with a range of transmission electron microscopy techniques to probe quantitatively the magnetic behavior at the defects with applied field and correlate this with the structural impact of the defects.
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Affiliation(s)
- Kayla Fallon
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Sean Hughes
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Katharina Zeissler
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, 91767, France
| | - William Legrand
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | - Fernando Ajejas
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | | | - Samuel McFadzean
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - William Smith
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Damien McGrouther
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
| | - Sophie Collin
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | - Nicolas Reyren
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | - Vincent Cros
- National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, UK
| | | | - Stephen McVitie
- SUPA School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK
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18
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Lux FR, Freimuth F, Blügel S, Mokrousov Y. Chiral Hall Effect in Noncollinear Magnets from a Cyclic Cohomology Approach. PHYSICAL REVIEW LETTERS 2020; 124:096602. [PMID: 32202897 DOI: 10.1103/physrevlett.124.096602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Revised: 12/22/2019] [Accepted: 02/06/2020] [Indexed: 06/10/2023]
Abstract
We demonstrate the emergence of an anomalous Hall effect in chiral magnetic textures which is neither proportional to the net magnetization nor to the well-known emergent magnetic field that is responsible for the topological Hall effect. Instead, it appears already at linear order in the gradients of the magnetization texture and exists for one-dimensional magnetic textures such as domain walls and spin spirals. It receives a natural interpretation in the language of Alain Connes' noncommutative geometry. We show that this chiral Hall effect resembles the familiar topological Hall effect in essential properties while its phenomenology is distinctly different. Our findings make the reinterpretation of experimental data necessary, and offer an exciting twist in engineering the electrical transport through magnetic skyrmions.
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Affiliation(s)
- Fabian R Lux
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Department of Physics, RWTH Aachen University, 52056 Aachen, Germany
| | - Frank Freimuth
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Stefan Blügel
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Yuriy Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
- Institute of Physics, Johannes Gutenberg University Mainz, 55099 Mainz, Germany
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19
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Diameter-independent skyrmion Hall angle observed in chiral magnetic multilayers. Nat Commun 2020; 11:428. [PMID: 31969569 PMCID: PMC6976618 DOI: 10.1038/s41467-019-14232-9] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 12/13/2019] [Indexed: 11/24/2022] Open
Abstract
Magnetic skyrmions are topologically non-trivial nanoscale objects. Their topology, which originates in their chiral domain wall winding, governs their unique response to a motion-inducing force. When subjected to an electrical current, the chiral winding of the spin texture leads to a deflection of the skyrmion trajectory, characterised by an angle with respect to the applied force direction. This skyrmion Hall angle is predicted to be skyrmion diameter-dependent. In contrast, our experimental study finds that the skyrmion Hall angle is diameter-independent for skyrmions with diameters ranging from 35 to 825 nm. At an average velocity of 6 ± 1 ms−1, the average skyrmion Hall angle was measured to be 9° ± 2°. In fact, the skyrmion dynamics is dominated by the local energy landscape such as materials defects and the local magnetic configuration. Magnetic skyrmions are promising objects for future spintronic devices. However, a better understanding of their dynamics is required. Here, the authors show that in contrast to predictions the skyrmion Hall angle is independent of their diameter and motion is dominated by disorder and skyrmion-skyrmion interactions in the system.
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20
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Legrand W, Maccariello D, Ajejas F, Collin S, Vecchiola A, Bouzehouane K, Reyren N, Cros V, Fert A. Room-temperature stabilization of antiferromagnetic skyrmions in synthetic antiferromagnets. NATURE MATERIALS 2020; 19:34-42. [PMID: 31477905 DOI: 10.1038/s41563-019-0468-3] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/24/2018] [Accepted: 07/24/2019] [Indexed: 05/23/2023]
Abstract
Room-temperature skyrmions in ferromagnetic films and multilayers show promise for encoding information bits in new computing technologies. Despite recent progress, ferromagnetic order generates dipolar fields that prevent ultrasmall skyrmion sizes, and allows a transverse deflection of moving skyrmions that hinders their efficient manipulation. Antiferromagnetic skyrmions shall lift these limitations. Here we demonstrate that room-temperature antiferromagnetic skyrmions can be stabilized in synthetic antiferromagnets (SAFs), in which perpendicular magnetic anisotropy, antiferromagnetic coupling and chiral order can be adjusted concurrently. Utilizing interlayer electronic coupling to an adjacent bias layer, we demonstrate that spin-spiral states obtained in a SAF with vanishing perpendicular magnetic anisotropy can be turned into isolated antiferromagnetic skyrmions. We also provide model-based estimates of skyrmion size and stability, showing that room-temperature antiferromagnetic skyrmions below 10 nm in radius can be anticipated in further optimized SAFs. Antiferromagnetic skyrmions in SAFs may thus solve major issues associated with ferromagnetic skyrmions for low-power spintronic devices.
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Affiliation(s)
- William Legrand
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France.
| | - Davide Maccariello
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
| | - Fernando Ajejas
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
| | - Sophie Collin
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
| | - Aymeric Vecchiola
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
| | - Karim Bouzehouane
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
| | - Nicolas Reyren
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
| | - Vincent Cros
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France.
| | - Albert Fert
- Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau, France
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21
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Perini M, Meyer S, Kubetzka A, Wiesendanger R, Heinze S, von Bergmann K. Electrical Detection of Domain Walls and Skyrmions in Co Films Using Noncollinear Magnetoresistance. PHYSICAL REVIEW LETTERS 2019; 123:237205. [PMID: 31868461 DOI: 10.1103/physrevlett.123.237205] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 10/14/2019] [Indexed: 06/10/2023]
Abstract
A large noncollinear magnetoresistance (NCMR) is observed for Rh/Co atomic bilayers on Ir(111) using scanning tunneling microscopy and spectroscopy. The effect is 20% at the Fermi energy and large in a broad energy range. The NCMR can be used to electrically detect nanometer-scale domain walls and skyrmions directly in the tunnel current without the need for a differential measurement. The NCMR results from changes in the density of states of noncollinear spin textures with respect to the ferromagnetic state. Density functional theory calculations reveal that they originate from spin mixing between majority d_{xz} and minority p_{z} states.
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Affiliation(s)
- Marco Perini
- Department of Physics, University of Hamburg, 20355 Hamburg, Germany
| | - Sebastian Meyer
- Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstrasse 15, 24098 Kiel, Germany
| | - André Kubetzka
- Department of Physics, University of Hamburg, 20355 Hamburg, Germany
| | | | - Stefan Heinze
- Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstrasse 15, 24098 Kiel, Germany
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22
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Iguchi R, Kasai S, Koshikawa K, Chinone N, Suzuki S, Uchida KI. Thermoelectric microscopy of magnetic skyrmions. Sci Rep 2019; 9:18443. [PMID: 31804550 PMCID: PMC6895239 DOI: 10.1038/s41598-019-54833-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2019] [Accepted: 11/12/2019] [Indexed: 11/11/2022] Open
Abstract
The magnetic skyrmion is a nanoscale topological object characterized by the winding of magnetic moments, appearing in magnetic materials with broken inversion symmetry. Because of its low current threshold for driving the skyrmion motion, they have been intensely studied toward novel storage applications by using electron-beam, X-ray, and visible light microscopies. Here, we demonstrate another imaging method for skyrmions by using spin-caloritronic phenomena, that is, the spin Seebeck and anomalous Nernst effects, as a probe of magnetic texture. We scanned a focused heating spot on a Hall-cross shaped MgO/CoFeB/Ta/W multilayer film and mapped the magnitude as well as the direction of the resultant thermoelectric current due to the spin-caloritronic phenomena. Our experimental and calculation reveal that the characteristic patterns in the thermoelectric signal distribution reflect the skyrmions’ magnetic texture. The thermoelectric microscopy will be a complementary and useful imaging technique for the development of skyrmion devices owing to the unique symmetry of the spin-caloritronic phenomena.
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Affiliation(s)
- Ryo Iguchi
- National Institute for Materials Science, Tsukuba, 305-0047, Japan.
| | - Shinya Kasai
- National Institute for Materials Science, Tsukuba, 305-0047, Japan.,PRESTO, Japan Science and Technology Agency, Saitama, 332-0012, Japan
| | | | | | | | - Ken-Ichi Uchida
- National Institute for Materials Science, Tsukuba, 305-0047, Japan.,Department of Mechanical Engineering, The University of Tokyo, Tokyo, 113-8656, Japan.,Center for Spintronics Research Network, Tohoku University, Sendai, 980-8577, Japan
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23
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Finizio S, Zeissler K, Wintz S, Mayr S, Weßels T, Huxtable AJ, Burnell G, Marrows CH, Raabe J. Deterministic Field-Free Skyrmion Nucleation at a Nanoengineered Injector Device. NANO LETTERS 2019; 19:7246-7255. [PMID: 31525983 DOI: 10.1021/acs.nanolett.9b02840] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Magnetic skyrmions are topological solitons promising for applications as encoders for digital information. A number of different skyrmion-based memory devices have been recently proposed. In order to demonstrate a viable skyrmion-based memory device, it is necessary to reliably and reproducibly nucleate, displace, detect, and delete the magnetic skyrmions, possibly in the absence of external applied magnetic fields, which would needlessly complicate the device design. While the skyrmion displacement and detection have both been thoroughly investigated, much less attention has been dedicated to the study of the skyrmion nucleation process and its sub-nanosecond dynamics. In this study, we investigate the nucleation of magnetic skyrmions from a dedicated nanoengineered injector, demonstrating the reliable magnetic skyrmion nucleation at the remnant state. The sub-nanosecond dynamics of the skyrmion nucleation process were also investigated, allowing us to shine light on the physical processes driving the nucleation.
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Affiliation(s)
- Simone Finizio
- Paul Scherrer Institut , 5232 Villigen PSI , Switzerland
| | - Katharina Zeissler
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Sebastian Wintz
- Paul Scherrer Institut , 5232 Villigen PSI , Switzerland
- Institute of Ion Beam Physics and Materials Research , Helmholtz-Zentrum Dresden-Rossendorf , 01328 Dresden , Germany
| | - Sina Mayr
- Paul Scherrer Institut , 5232 Villigen PSI , Switzerland
- Laboratory for Mesoscopic Systems, Department of Materials , ETH Zürich , 8093 Zürich , Switzerland
| | - Teresa Weßels
- Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute , Forschungszentrum Jülich GmbH , 52425 Jülich , Germany
| | - Alexandra J Huxtable
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Gavin Burnell
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Christopher H Marrows
- School of Physics and Astronomy , University of Leeds , Leeds LS2 9JT , United Kingdom
| | - Jörg Raabe
- Paul Scherrer Institut , 5232 Villigen PSI , Switzerland
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24
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Lepadatu S. Effect of inter-layer spin diffusion on skyrmion motion in magnetic multilayers. Sci Rep 2019; 9:9592. [PMID: 31270384 PMCID: PMC6610116 DOI: 10.1038/s41598-019-46091-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Accepted: 06/21/2019] [Indexed: 12/01/2022] Open
Abstract
It is well known that skyrmions can be driven using spin-orbit torques due to the spin-Hall effect. Here we show an additional contribution in multilayered stacks arises from vertical spin currents due to inter-layer diffusion of a spin accumulation generated at a skyrmion. This additional interfacial spin torque is similar in form to the in-plane spin transfer torque, but is significantly enhanced in ultra-thin films and acts in the opposite direction to the electron flow. The combination of this diffusive spin torque and the spin-orbit torque results in skyrmion motion which helps to explain the observation of small skyrmion Hall angles even with moderate magnetisation damping values. Further, the effect of material imperfections on threshold currents and skyrmion Hall angle is also investigated. Topographical surface roughness, as small as a single monolayer variation, is shown to be an important contributing factor in ultra-thin films, resulting in good agreement with experimental observations.
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Affiliation(s)
- Serban Lepadatu
- Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston, PR1 2HE, UK.
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The evolution of skyrmions in Ir/Fe/Co/Pt multilayers and their topological Hall signature. Nat Commun 2019; 10:696. [PMID: 30842413 PMCID: PMC6403237 DOI: 10.1038/s41467-018-08041-9] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 12/06/2018] [Indexed: 11/09/2022] Open
Abstract
The topological Hall effect (THE) is the Hall response to an emergent magnetic field, a manifestation of the skyrmion Berry-phase. As the magnitude of THE in magnetic multilayers is an open question, it is imperative to develop comprehensive understanding of skyrmions and other chiral textures, and their electrical fingerprint. Here, using Hall-transport and magnetic-imaging in a technologically viable multilayer film, we show that topological-Hall resistivity scales with the isolated-skyrmion density over a wide range of temperature and magnetic-field, confirming the impact of the skyrmion Berry-phase on electronic transport. While we establish qualitative agreement between the topological-Hall resistivity and the topological-charge density, our quantitative analysis shows much larger topological-Hall resistivity than the prevailing theory predicts for the observed skyrmion density. Our results are fundamental for the skyrmion-THE in multilayers, where interfacial interactions, multiband transport and non-adiabatic effects play an important role, and for skyrmion applications relying on THE.
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Leroux M, Stolt MJ, Jin S, Pete DV, Reichhardt C, Maiorov B. Skyrmion Lattice Topological Hall Effect near Room Temperature. Sci Rep 2018; 8:15510. [PMID: 30341339 PMCID: PMC6195581 DOI: 10.1038/s41598-018-33560-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 09/28/2018] [Indexed: 11/16/2022] Open
Abstract
Magnetic skyrmions are stable nanosized spin structures that can be displaced at low electrical current densities. Because of these properties, they have been proposed as building blocks of future electronic devices with unprecedentedly high information density and low energy consumption. The electrical detection of an ordered skyrmion lattice via the Topological Hall Effect (THE) in a bulk crystal, has so far been demonstrated only at cryogenic temperatures in the MnSi family of compounds. Here, we report the observation of a skyrmion lattice Topological Hall Effect near room temperature (276 K) in a mesoscopic lamella carved from a bulk crystal of FeGe. This region coincides with the skyrmion lattice location revealed by neutron scattering. We provide clear evidence of a re-entrant helicoid magnetic phase adjacent to the skyrmion phase, and discuss the large THE amplitude (5 nΩ.cm) in view of the ordinary Hall Effect.
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Affiliation(s)
- Maxime Leroux
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA
| | - Matthew J Stolt
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin, 53706, USA
| | - Song Jin
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin, 53706, USA
| | - Douglas V Pete
- Centre for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, New Mexico, 87185, USA
| | - Charles Reichhardt
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA
| | - Boris Maiorov
- Materials Physics and Applications Division, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, USA.
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