1
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Okumura S, Kravchuk VP, Garst M. Instability of Magnetic Skyrmion Strings Induced by Longitudinal Spin Currents. PHYSICAL REVIEW LETTERS 2023; 131:066702. [PMID: 37625063 DOI: 10.1103/physrevlett.131.066702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 06/13/2023] [Accepted: 07/11/2023] [Indexed: 08/27/2023]
Abstract
It is well established that spin-transfer torques exerted by in-plane spin currents give rise to a motion of magnetic skyrmions resulting in a skyrmion Hall effect. In films of finite thickness or in three-dimensional bulk samples the skyrmions extend in the third direction forming a string. We demonstrate that a spin current flowing longitudinally along the skyrmion string instead induces a Goldstone spin wave instability. Our analytical results are confirmed by micromagnetic simulations of both a single string as well as string lattices, suggesting that the instability eventually breaks the strings. A longitudinal current is thus able to melt the skyrmion string lattice via a nonequilibrium phase transition. For films of finite thickness or in the presence of disorder a threshold current will be required, and we estimate the latter assuming weak collective pinning.
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Affiliation(s)
- Shun Okumura
- Department of Applied Physics, the University of Tokyo, Tokyo 113-8656, Japan
| | - Volodymyr P Kravchuk
- Institut für Theoretische Festkörperphysik, Karlsruher Institut für Technologie, D-76131 Karlsruhe, Germany
- Bogolyubov Institute for Theoretical Physics of National Academy of Sciences of Ukraine, 03143 Kyiv, Ukraine
| | - Markus Garst
- Institut für Theoretische Festkörperphysik, Karlsruher Institut für Technologie, D-76131 Karlsruhe, Germany
- Institute for Quantum Materials and Technology, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
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2
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Dash A, Ojha B, Mohanty S, Moharana AK, Bedanta S. Device geometry dependent deterministic skyrmion generation from a skyrmionium. NANOTECHNOLOGY 2023; 34:185001. [PMID: 36716477 DOI: 10.1088/1361-6528/acb714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Accepted: 01/30/2023] [Indexed: 06/18/2023]
Abstract
A magnetic skyrmionium can be perceived as an association of two magnetic skyrmions with opposite topological charges. In this work, we have investigated the transformation of skyrmionium into multi-skyrmionic states via domain wall pairs in three different devices with variable geometric configurations. The same device geometries are considered for single ferromagnetic layer and synthetic antiferromagnetic system. It is observed that by tuning the current density, deterministic generation of skyrmions is possible via the spin transfer torque. The proposed device is efficiently adjustable to change the number of skyrmions also at room temperature. The results may lead to development of skyrmion-based devices for neuromorphic and unconventional computing.
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Affiliation(s)
- Adyashakti Dash
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni, Odisha 752050, India
| | - Brindaban Ojha
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni, Odisha 752050, India
| | - Shaktiranjan Mohanty
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni, Odisha 752050, India
| | - Ashish Kumar Moharana
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni, Odisha 752050, India
| | - Subhankar Bedanta
- Laboratory for Nanomagnetism and Magnetic Materials (LNMM), School of Physical Sciences, National Institute of Science Education and Research (NISER), An OCC of Homi Bhabha National Institute (HBNI), Jatni, Odisha 752050, India
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3
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Vizarim NP, Bellizotti Souza JC, Reichhardt C, Reichhardt CJO, Venegas PA. Directional locking and the influence of obstacle density on skyrmion dynamics in triangular and honeycomb arrays. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:305801. [PMID: 33979789 DOI: 10.1088/1361-648x/ac0081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/12/2021] [Indexed: 06/12/2023]
Abstract
We numerically examine the dynamics of a single skyrmion driven over triangular and honeycomb obstacle arrays at zero temperature. The skyrmion Hall angleθsk, defined as the angle between the applied external drive and the direction of the skyrmion motion, increases in quantized steps or continuously as a function of the applied drive. For the obstacle arrays studied in this work, the skyrmion exhibits two main directional locking angles ofθsk= -30° and -60°. We show that these directions are privileged due to the obstacle landscape symmetry, and coincide with channels along which the skyrmion may move with few or no obstacle collisions. Here we investigate how changes in the obstacle density can modify the skyrmion Hall angles and cause some dynamic phases to appear or grow while other phases vanish. This interesting behavior can be used to guide skyrmions along designated trajectories via regions with different obstacle densities. For fixed obstacle densities, we investigate the evolution of the lockedθsk= -30° and -60° phases as a function of the Magnus force, and discuss possibilities for switching between these phases using topological selection.
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Affiliation(s)
- N P Vizarim
- POSMAT-Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Faculdade de Ciências, Universidade Estadual Paulista-UNESP, Bauru, SP, CP 473, 17033-360, Brazil
| | - J C Bellizotti Souza
- Departamento de Física, Faculdade de Ciências, Universidade Estadual Paulista-UNESP, Bauru, SP, CP 473, 17033-360, Brazil
| | - C Reichhardt
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States of America
| | - C J O Reichhardt
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States of America
| | - P A Venegas
- Departamento de Física, Faculdade de Ciências, Universidade Estadual Paulista-UNESP, Bauru, SP, CP 473, 17033-360, Brazil
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Zheng D, Fang YW, Zhang S, Li P, Wen Y, Fang B, He X, Li Y, Zhang C, Tong W, Mi W, Bai H, Alshareef HN, Qiu ZQ, Zhang X. Berry Phase Engineering in SrRuO 3/SrIrO 3/SrTiO 3 Superlattices Induced by Band Structure Reconstruction. ACS NANO 2021; 15:5086-5095. [PMID: 33606942 DOI: 10.1021/acsnano.0c10200] [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
The Berry phase, which reveals the intimate geometrical structure underlying quantum mechanics, plays a central role in the anomalous Hall effect. In this work, we observed a sign change of Berry curvatures at the interface between the ferromagnet SrRuO3 (SRO) layer and the SrIrO3 (SIO) layer with strong spin-orbit coupling. The negative Berry curvature at the interface, induced by the strongly spin-orbit-coupled Ir 5d bands near the Fermi level, makes the SRO/SIO interface different from the SRO layer that has a positive Berry curvature. These opposite Berry curvatures led to two anomalous Hall effect (AHE) channels with opposite signs at the SRO/SIO interface and in the SRO layer, respectively, resulting in a hump-like feature in the Hall resistivity loop. This observation offers a straightforward explanation of the hump-like feature that is usually associated with the chiral magnetic structure or magnetic skyrmions. Hence, this study provides evidence to oppose the widely accepted claim that magnetic skyrmions induce the hump-like feature.
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Affiliation(s)
- Dongxing Zheng
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Processing Technology, Institute of Advanced Materials Physics, Faculty of Science, Tianjin University, Tianjin 300072, China
| | - Yue-Wen Fang
- Laboratory for Materials and Structures & Tokyo Tech World Research Hub Initiative (WRHI), Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8503, Japan
- NYU-ECNU Institute of Physics, New York University Shanghai, Shanghai 200122, China
| | - Senfu Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Peng Li
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Yan Wen
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Bin Fang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Xin He
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Yan Li
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Chenhui Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Wenyi Tong
- Theoretical Materials Physics, Q-MAT, CESAM, Université de Liège, B-4000 Liège, Belgium
| | - Wenbo Mi
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Processing Technology, Institute of Advanced Materials Physics, Faculty of Science, Tianjin University, Tianjin 300072, China
| | - Haili Bai
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Processing Technology, Institute of Advanced Materials Physics, Faculty of Science, Tianjin University, Tianjin 300072, China
| | - Husam N Alshareef
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
| | - Zi Qiang Qiu
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
| | - Xixiang Zhang
- Physical Science and Engineering Division (PSE), King Abdullah University of Science and Technology (KAUST), Thuwal 23955-6900, Saudi Arabia
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Je SG, Thian D, Chen X, Huang L, Jung DH, Chao W, Lee KS, Hong JI, Soumyanarayanan A, Im MY. Targeted Writing and Deleting of Magnetic Skyrmions in Two-Terminal Nanowire Devices. NANO LETTERS 2021; 21:1253-1259. [PMID: 33481614 DOI: 10.1021/acs.nanolett.0c03686] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Controllable writing and deleting of nanoscale magnetic skyrmions are key requirements for their use as information carriers for next-generation memory and computing technologies. While several schemes have been proposed, they require complex fabrication techniques or precisely tailored electrical inputs, which limits their long-term scalability. Here, we demonstrate an alternative approach for writing and deleting skyrmions using conventional electrical pulses within a simple, two-terminal wire geometry. X-ray microscopy experiments and micromagnetic simulations establish the observed skyrmion creation and annihilation as arising from Joule heating and Oersted field effects of the current pulses, respectively. The unique characteristics of these writing and deleting schemes, such as spatial and temporal selectivity, together with the simplicity of the two-terminal device architecture, provide a flexible and scalable route to the viable applications of skyrmions.
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Affiliation(s)
- Soong-Geun Je
- Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
- Department of Physics, Chonnam National University, Gwangju 61186, Korea
| | - Dickson Thian
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research, 138634 Singapore
| | - Xiaoye Chen
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research, 138634 Singapore
- Data Storage Institute, Agency for Science, Technology, and Research, 138634 Singapore
| | - Lisen Huang
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research, 138634 Singapore
- Data Storage Institute, Agency for Science, Technology, and Research, 138634 Singapore
| | - Dae-Han Jung
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Weilun Chao
- Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ki-Suk Lee
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea
| | - Jung-Il Hong
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Anjan Soumyanarayanan
- Institute of Materials Research and Engineering, Agency for Science, Technology, and Research, 138634 Singapore
- Data Storage Institute, Agency for Science, Technology, and Research, 138634 Singapore
- Department of Physics, National University of Singapore, 117551 Singapore
| | - Mi-Young Im
- Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
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6
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Chen K, Lott D, Philippi-Kobs A, Weigand M, Luo C, Radu F. Observation of compact ferrimagnetic skyrmions in DyCo 3 film. NANOSCALE 2020; 12:18137-18143. [PMID: 32852506 DOI: 10.1039/d0nr02947e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Owing to the experimental discovery of magnetic skyrmions stabilized by the Dzyaloshinskii-Moriya and/or dipolar interactions in thin films, there is a recent upsurge of interest in magnetic skyrmions with antiferromagnetic spins in order to overcome the fundamental limitations inherent with skyrmions in ferromagnetic materials. Here, we report on the observation of compact ferrimagnetic skyrmions for the class of amorphous alloys consisting of 4f rare-earth and 3d transition-metal elements with perpendicular magnetic anisotropy, using a DyCo3 film, that are identified by combining X-ray magnetic scattering, scanning transmission X-ray microscopy, and Hall transport technique. These skyrmions, with antiparallel aligned Dy and Co magnetic moments and a characteristic core radius of about 40 nm, are formed during the nucleation and annihilation of the magnetic maze-like domain pattern exhibiting a topological Hall effect contribution. Our findings provide a promising route for fundamental research in the field of ferrimagnetic/antiferromagnetic spintronics towards practical applications.
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Affiliation(s)
- K Chen
- Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Str. 15, 12489 Berlin, Germany.
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7
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Jiang Y, Yuan HY, Li ZX, Wang Z, Zhang HW, Cao Y, Yan P. Twisted Magnon as a Magnetic Tweezer. PHYSICAL REVIEW LETTERS 2020; 124:217204. [PMID: 32530668 DOI: 10.1103/physrevlett.124.217204] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2019] [Accepted: 04/30/2020] [Indexed: 06/11/2023]
Abstract
Wave fields with spiral phase dislocations carrying orbital angular momentum (OAM) have been realized in many branches of physics, such as for photons, sound waves, electron beams, and neutrons. However, the OAM states of magnons (spin waves)-the building block of modern magnetism-and particularly their implications have yet to be addressed. Here, we theoretically investigate the twisted spin-wave generation and propagation in magnetic nanocylinders. The OAM nature of magnons is uncovered by showing that the spin-wave eigenmode is also the eigenstate of the OAM operator in the confined geometry. Inspired by optical tweezers, we predict an exotic "magnetic tweezer" effect by showing skyrmion gyrations under twisted magnons in the exchange-coupled nanocylinder-nanodisk heterostructure, as a practical demonstration of magnonic OAM transfer to manipulate topological spin defects. Our study paves the way for the emerging magnetic manipulations by harnessing the OAM degree of freedom of magnons.
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Affiliation(s)
- Yuanyuan Jiang
- School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - H Y Yuan
- Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China
| | - Z-X Li
- School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Zhenyu Wang
- School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - H W Zhang
- School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Yunshan Cao
- School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
| | - Peng Yan
- School of Electronic Science and Engineering and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
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Bai C, Chen J, Zhang Y, Zhang D, Zhan Q. Dynamic tailoring of an optical skyrmion lattice in surface plasmon polaritons. OPTICS EXPRESS 2020; 28:10320-10328. [PMID: 32225619 DOI: 10.1364/oe.384718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 03/11/2020] [Indexed: 06/10/2023]
Abstract
A skyrmion is a topologically protected soliton with a spin structure on the micro/nano scale that has promising applications in magnetic information storage and spintronics devices. This study focuses on the optical skyrmion lattice structures created in the surface plasmon polaritons (SPPs) field. Both the Néel-type optical skyrmion lattice formed by the electric field vector and Bloch-type optical skyrmion lattice formed by the magnetic field vector are generated via exciting a hexagonal grating structure on the metal surface with six Gaussian optical spots. Such a multiple-spot excitation can be realized through tightly focusing a specially designed complex field with a high NA lens. Through introducing the phase difference of the excitation beams to shift the SPP standing waves, the shape and position of the optical skyrmion lattice can be dynamically controlled. Both the electric field vector and magnetic field vector are evaluated quantitatively based on the electric and magnetic field obtained by finite difference time domain (FDTD) simulation to demonstrate the validity and capability of the proposed technique.
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Skyrmion Crystals and Phase Transitions in Magneto-Ferroelectric Superlattices: Dzyaloshinskii–Moriya Interaction in a Frustrated J1 − J2 Model. Symmetry (Basel) 2019. [DOI: 10.3390/sym12010026] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The formation of a skyrmion crystal and its phase transition are studied, taking into account the Dzyaloshinskii–Moriya (DM) interaction at the interface between a ferroelectric layer and a magnetic layer in a superlattice. Frustration is introduced in both magnetic and ferroelectric films. The films have a simple cubic lattice structure. The spins inside the magnetic layers are Heisenberg spins interacting with each other via nearest-neighbor (NN) exchange J m and next-nearest-neighbor (NNN) exchange J 2 m . The polarizations in the ferroelectric layers are assumed to be of Ising type with NN and NNN interactions J f and J 2 f . At the magnetoelectric interface, a DM interaction J m f between spins and polarizations is supposed. The spin configuration in the ground state is calculated by the steepest descent method. In an applied magnetic field H perpendicular to the layers, we show that the formation of skyrmions at the magnetoelectric interface is strongly enhanced by the frustration brought about by the NNN antiferromagnetic interactions J 2 m and J 2 f . Various physical quantities at finite temperatures are obtained by Monte Carlo simulations. We show the critical temperature, the order parameters of magnetic and ferroelectric layers as functions of the interface DM coupling, the applied magnetic field, and J 2 m and J 2 f . The phase transition to the disordered phase is studied in detail.
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Psaroudaki C, Loss D. Skyrmions Driven by Intrinsic Magnons. PHYSICAL REVIEW LETTERS 2018; 120:237203. [PMID: 29932693 DOI: 10.1103/physrevlett.120.237203] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2018] [Indexed: 05/10/2023]
Abstract
We study the dynamics of a Skyrmion in a magnetic insulating nanowire in the presence of time-dependent oscillating magnetic field gradients. These ac fields act as a net driving force on the Skyrmion via its own intrinsic magnetic excitations. In a microscopic quantum field theory approach, we include the unavoidable coupling of the external field to the magnons, which gives rise to time-dependent dissipation for the Skyrmion. We demonstrate that the magnetic ac field induces a super-Ohmic to Ohmic crossover behavior for the Skyrmion dissipation kernels with time-dependent Ohmic terms. The ac driving of the magnon bath at resonance results in a unidirectional helical propagation of the Skyrmion in addition to the otherwise periodic bounded motion.
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Affiliation(s)
- Christina Psaroudaki
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, 4056 Basel, Switzerland
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11
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Duzgun A, Selinger JV, Saxena A. Comparing skyrmions and merons in chiral liquid crystals and magnets. Phys Rev E 2018; 97:062706. [PMID: 30011572 DOI: 10.1103/physreve.97.062706] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Indexed: 06/08/2023]
Abstract
When chiral liquid crystals or magnets are subjected to applied fields or other anisotropic environments, the competition between favored twist and anisotropy leads to the formation of complex defect structures. In some cases, the defects are skyrmions, which have 180^{∘} double twist going outward from the center, and hence can pack together without singularities in the orientational order. In other cases, the defects are merons, which have 90^{∘} double twist going outward from the center; packing such merons requires singularities in the orientational order. In the liquid crystal context, a lattice of merons is equivalent to a blue phase. Here we perform theoretical and computational studies of skyrmions and merons in chiral liquid crystals and magnets. Through these studies, we calculate the phase diagrams for liquid crystals and magnets in terms of dimensionless ratios of energetic parameters. We also predict the range of metastability for liquid crystal skyrmions and show that these skyrmions can move and interact as effective particles. The results show how the properties of skyrmions and merons depend on the vector or tensor nature of the order parameter.
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Affiliation(s)
- Ayhan Duzgun
- Department of Physics and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - Jonathan V Selinger
- Department of Physics and Liquid Crystal Institute, Kent State University, Kent, Ohio 44242, USA
| | - Avadh Saxena
- Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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12
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Zhang X, Cai W, Zhang X, Wang Z, Li Z, Zhang Y, Cao K, Lei N, Kang W, Zhang Y, Yu H, Zhou Y, Zhao W. Skyrmions in Magnetic Tunnel Junctions. ACS APPLIED MATERIALS & INTERFACES 2018; 10:16887-16892. [PMID: 29682962 DOI: 10.1021/acsami.8b03812] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
In this work, we demonstrate that skyrmions can be nucleated in the free layer of a magnetic tunnel junction (MTJ) with Dzyaloshinskii-Moriya interactions (DMIs) by a spin-polarized current with the assistance of stray fields from the pinned layer. The size, stability, and number of created skyrmions can be tuned by either the DMI strength or the stray field distribution. The interaction between the stray field and the DMI effective field is discussed. A device with multilevel tunneling magnetoresistance is proposed, which could pave the ways for skyrmion-MTJ-based multibit storage and artificial neural network computation. Our results may facilitate the efficient nucleation and electrical detection of skyrmions.
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Affiliation(s)
- Xueying Zhang
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute , Beihang University , Qingdao 266101 , China
| | - Wenlong Cai
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Xichao Zhang
- School of Science and Engineering , The Chinese University of Hong Kong , Shenzhen 518172 , China
| | - Zilu Wang
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Zhi Li
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute , Beihang University , Qingdao 266101 , China
| | - Yu Zhang
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Kaihua Cao
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Na Lei
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute , Beihang University , Qingdao 266101 , China
| | - Wang Kang
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Yue Zhang
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Haiming Yu
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
| | - Yan Zhou
- School of Science and Engineering , The Chinese University of Hong Kong , Shenzhen 518172 , China
| | - Weisheng Zhao
- Fert Beijing Institute, BDBC, School of Electronic and Information Engineering , Beihang University , Beijing 100191 , China
- Beihang-Goertek Joint Microelectronics Institute, Qingdao Research Institute , Beihang University , Qingdao 266101 , China
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13
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Yang W, Yang H, Cao Y, Yan P. Photonic orbital angular momentum transfer and magnetic skyrmion rotation. OPTICS EXPRESS 2018; 26:8778-8790. [PMID: 29715841 DOI: 10.1364/oe.26.008778] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 03/19/2018] [Indexed: 06/08/2023]
Abstract
Magnetic skyrmions are chiral quasiparticles that show promise for future spintronic applications such as skyrmion racetrack memories and logic devices because of their topological stability, small size (typically ∼ 3 - 500 nm), and ultralow threshold force to drive their motion. On the other hand, the ability of light to carry and deliver orbital angular momentum (OAM) in the form of optical vortices has attracted a lot of interest. In this work, we predict a photonic OAM transfer effect, by studying the dynamics of magnetic skyrmions subject to Laguerre-Gaussian optical vortices, which manifests a rotational motion of the skyrmionic quasiparticle around the beam axis. The topological charge of the optical vortex determines both the magnitude and the handedness of the rotation velocity of skyrmions. In our proposal, the twisted light beam acts as an optical tweezer to enable us displacing skyrmions over large-scale defects in magnetic films to avoid being captured.
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14
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Hou Z, Ren W, Ding B, Xu G, Wang Y, Yang B, Zhang Q, Zhang Y, Liu E, Xu F, Wang W, Wu G, Zhang X, Shen B, Zhang Z. Observation of Various and Spontaneous Magnetic Skyrmionic Bubbles at Room Temperature in a Frustrated Kagome Magnet with Uniaxial Magnetic Anisotropy. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1701144. [PMID: 28589629 DOI: 10.1002/adma.201701144] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 04/23/2017] [Indexed: 06/07/2023]
Abstract
The quest for materials hosting topologically protected skyrmionic spin textures continues to be fueled by the promise of novel devices. Although many materials have demonstrated the existence of such spin textures, major challenges remain to be addressed before devices based on magnetic skyrmions can be realized. For example, being able to create and manipulate skyrmionic spin textures at room temperature is of great importance for further technological applications because they can adapt to various external stimuli acting as information carriers in spintronic devices. Here, the first observation of skyrmionic magnetic bubbles with variable topological spin textures formed at room temperature in a frustrated kagome Fe3 Sn2 magnet with uniaxial magnetic anisotropy is reported. The magnetization dynamics are investigated using in situ Lorentz transmission electron microscopy, revealing that the transformation between different magnetic bubbles and domains is via the motion of Bloch lines driven by an applied external magnetic field. These results demonstrate that Fe3 Sn2 facilitates a unique magnetic control of topological spin textures at room temperature, making it a promising candidate for further skyrmion-based spintronic devices.
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Affiliation(s)
- Zhipeng Hou
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Weijun Ren
- Shenyang Materials Science National Laboratory, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016, China
| | - Bei Ding
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Guizhou Xu
- School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Yue Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Bing Yang
- Shenyang Materials Science National Laboratory, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016, China
| | - Qiang Zhang
- King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering (PSE), Thuwal, 23955-6900, Saudi Arabia
| | - Ying Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Enke Liu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Feng Xu
- School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing, 210094, China
| | - Wenhong Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Guangheng Wu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Xixiang Zhang
- King Abdullah University of Science and Technology (KAUST), Physical Science and Engineering (PSE), Thuwal, 23955-6900, Saudi Arabia
| | - Baogen Shen
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, China
| | - Zhidong Zhang
- Shenyang Materials Science National Laboratory, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang, 110016, China
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15
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Yu X, Morikawa D, Tokunaga Y, Kubota M, Kurumaji T, Oike H, Nakamura M, Kagawa F, Taguchi Y, Arima TH, Kawasaki M, Tokura Y. Current-Induced Nucleation and Annihilation of Magnetic Skyrmions at Room Temperature in a Chiral Magnet. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1606178. [PMID: 28370455 DOI: 10.1002/adma.201606178] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2016] [Revised: 02/20/2017] [Indexed: 06/07/2023]
Abstract
A magnetic skyrmion is a nanometer-scale magnetic vortex carrying an integer topological charge. Skyrmions show a promise for potential application in low-power-consumption and high-density memory devices. To promote their use in applications, it is attempted to control the existence of skyrmions using low electric currents at room temperature (RT). This study presents real-space observations for the current-induced formation and annihilation of a skyrmion lattice (SkL) as well as isolated skyrmions in a microdevice composed of a thin chiral magnet Co8 Zn9 Mn3 with a Curie temperature, TC ≈ 325 K, above RT. It is found that the critical current for the manipulation of Bloch-type skyrmions is on the order of 108 A m-2 , approximately three orders of magnitude lower than that needed for the creation and drive of ferromagnetic (FM) domain walls in thin FM films. The in situ real-space imaging also demonstrates the dynamical topological transition from a helical or conical structure to a SkL induced by the flow of DC current, thus paving the way for the electrical control of magnetic skyrmions.
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Affiliation(s)
- Xiuzhen Yu
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Daisuke Morikawa
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Yusuke Tokunaga
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, 277-8561, Japan
| | - Masashi Kubota
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Research and Development Headquarters, ROHM Co., Ltd., Kyoto, 615-8585, Japan
| | - Takashi Kurumaji
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Hiroshi Oike
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Masao Nakamura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Fumitaka Kagawa
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Yasujiro Taguchi
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Taka-Hisa Arima
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, 277-8561, Japan
| | - Masashi Kawasaki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo, 113-8656, Japan
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
- Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Tokyo, 113-8656, Japan
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16
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Reichhardt C, Olson Reichhardt CJ. Depinning and nonequilibrium dynamic phases of particle assemblies driven over random and ordered substrates: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2017; 80:026501. [PMID: 27997373 DOI: 10.1088/1361-6633/80/2/026501] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We review the depinning and nonequilibrium phases of collectively interacting particle systems driven over random or periodic substrates. This type of system is relevant to vortices in type-II superconductors, sliding charge density waves, electron crystals, colloids, stripe and pattern forming systems, and skyrmions, and could also have connections to jamming, glassy behaviors, and active matter. These systems are also ideal for exploring the broader issues of characterizing transient and steady state nonequilibrium flow phases as well as nonequilibrium phase transitions between distinct dynamical phases, analogous to phase transitions between different equilibrium states. We discuss the differences between elastic and plastic depinning on random substrates and the different types of nonequilibrium phases which are associated with specific features in the velocity-force curves, fluctuation spectra, scaling relations, and local or global particle ordering. We describe how these quantities can change depending on the dimension, anisotropy, disorder strength, and the presence of hysteresis. Within the moving phase we discuss how there can be a transition from a liquid-like state to dynamically ordered moving crystal, smectic, or nematic states. Systems with periodic or quasiperiodic substrates can have multiple nonequilibrium second or first order transitions in the moving state between chaotic and coherent phases, and can exhibit hysteresis. We also discuss systems with competing repulsive and attractive interactions, which undergo dynamical transitions into stripes and other complex morphologies when driven over random substrates. Throughout this work we highlight open issues and future directions such as absorbing phase transitions, nonequilibrium work relations, inertia, the role of non-dissipative dynamics such as Magnus effects, and how these results could be extended to the broader issues of plasticity in crystals, amorphous solids, and jamming phenomena.
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Affiliation(s)
- C Reichhardt
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA
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17
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Generic Aspects of Skyrmion Lattices in Chiral Magnets. TOPOLOGICAL STRUCTURES IN FERROIC MATERIALS 2016. [DOI: 10.1007/978-3-319-25301-5_1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
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18
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Liang D, DeGrave JP, Stolt MJ, Tokura Y, Jin S. Current-driven dynamics of skyrmions stabilized in MnSi nanowires revealed by topological Hall effect. Nat Commun 2015; 6:8217. [PMID: 26400204 PMCID: PMC4598358 DOI: 10.1038/ncomms9217] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Accepted: 07/30/2015] [Indexed: 11/09/2022] Open
Abstract
Skyrmions hold promise for next-generation magnetic storage as their nanoscale dimensions may enable high information storage density and their low threshold for current-driven motion may enable ultra-low energy consumption. Skyrmion-hosting nanowires not only serve as a natural platform for magnetic racetrack memory devices but also stabilize skyrmions. Here we use the topological Hall effect (THE) to study phase stability and current-driven dynamics of skyrmions in MnSi nanowires. THE is observed in an extended magnetic field-temperature window (15–30 K), suggesting stabilization of skyrmions in nanowires compared with the bulk. Furthermore, we show in nanowires that under the high current density of 108–109 A m−2, the THE decreases with increasing current densities, which demonstrates the current-driven motion of skyrmions generating the emergent electric field in the extended skyrmion phase region. These results open up the exploration of skyrmions in nanowires for fundamental physics and magnetic storage technologies. Magnetic skyrmions are topologically protected magnetization textures which can arise in helical magnets and present promise for low-power nanoscale magnetic storage device applications. Here, the authors demonstrate extended phase stability and current-driven dynamics of skyrmions in nanowires of MnSi.
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Affiliation(s)
- Dong Liang
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 63706, USA
| | - John P DeGrave
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 63706, USA
| | - Matthew J Stolt
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 63706, USA
| | - Yoshinori Tokura
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.,Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Tokyo 113-8656, Japan
| | - Song Jin
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 63706, USA
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19
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Jiang W, Upadhyaya P, Zhang W, Yu G, Jungfleisch MB, Fradin FY, Pearson JE, Tserkovnyak Y, Wang KL, Heinonen O, te Velthuis SGE, Hoffmann A. Blowing magnetic skyrmion bubbles. Science 2015; 349:283-6. [DOI: 10.1126/science.aaa1442] [Citation(s) in RCA: 995] [Impact Index Per Article: 110.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2014] [Accepted: 05/28/2015] [Indexed: 11/02/2022]
Abstract
The formation of soap bubbles from thin films is accompanied by topological transitions. Here we show how a magnetic topological structure, a skyrmion bubble, can be generated in a solid-state system in a similar manner. Using an inhomogeneous in-plane current in a system with broken inversion symmetry, we experimentally “blow” magnetic skyrmion bubbles from a geometrical constriction. The presence of a spatially divergent spin-orbit torque gives rise to instabilities of the magnetic domain structures that are reminiscent of Rayleigh-Plateau instabilities in fluid flows. We determine a phase diagram for skyrmion formation and reveal the efficient manipulation of these dynamically created skyrmions, including depinning and motion. The demonstrated current-driven transformation from stripe domains to magnetic skyrmion bubbles could lead to progress in skyrmion-based spintronics.
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Affiliation(s)
- Wanjun Jiang
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Pramey Upadhyaya
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA
| | - Wei Zhang
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Guoqiang Yu
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA
| | | | - Frank Y. Fradin
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - John E. Pearson
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Yaroslav Tserkovnyak
- Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
| | - Kang L. Wang
- Device Research Laboratory, Department of Electrical Engineering, University of California, Los Angeles, CA 90095, USA
| | - Olle Heinonen
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
- Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
- Northwestern-Argonne Institute of Science and Engineering, Northwestern University, Evanston, IL 60208, USA
- Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | | | - Axel Hoffmann
- Materials Science Division, Argonne National Laboratory, Lemont, IL 60439, USA
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20
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Abstract
A linear array of periodically spaced and individually controllable skyrmions is introduced as a magnonic crystal. It is numerically demonstrated that skyrmion nucleation and annihilation can be accurately controlled by a nanosecond spin polarized current pulse through a nanocontact. Arranged in a periodic array, such nanocontacts allow the creation of a skyrmion lattice that causes a periodic modulation of the waveguide's magnetization, which can be dynamically controlled by changing either the strength of an applied external magnetic field or the density of the injected spin current through the nanocontacts. The skyrmion diameter is highly dependent on both the applied field and the injected current. This implies tunability of the lowest band gap as the skyrmion diameter directly affects the strength of the pinning potential. The calculated magnonic spectra thus exhibit tunable allowed frequency bands and forbidden frequency bandgaps analogous to that of conventional magnonic crystals where, in contrast, the periodicity is structurally induced and static. In the dynamic magnetic crystal studied here, it is possible to dynamically turn on and off the artificial periodic structure, which allows switching between full rejection and full transmission of spin waves in the waveguide. These findings should stimulate further research activities on multiple functionalities offered by magnonic crystals based on periodic skyrmion lattices.
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Affiliation(s)
- Fusheng Ma
- †Temasek Laboratories, National University of Singapore, 119077 Singapore
| | - Yan Zhou
- ‡Department of Physics, University of Hong Kong, Hong Kong, P. R. China
- ⊥York-Nanjing Joint Center for Spintronics and Nano Engineering (YNJC), School of Electronics Science and Engineering, Nanjing University, Nanjing 210093, China
| | - H B Braun
- §School of Physics, University College Dublin, Dublin 4, Ireland
| | - W S Lew
- ∥School of Physical and Mathematical Sciences, Nanyang Technological University, 639798 Singapore
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21
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Zhang X, Ezawa M, Xiao D, Zhao GP, Liu Y, Zhou Y. All-magnetic control of skyrmions in nanowires by a spin wave. NANOTECHNOLOGY 2015; 26:225701. [PMID: 25965121 DOI: 10.1088/0957-4484/26/22/225701] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Magnetic skyrmions are topologically protected nanoscale objects, which are promising building blocks for novel magnetic and spintronic devices. Here, we investigate the dynamics of a skyrmion driven by a spin wave in a magnetic nanowire. It is found that (i) the skyrmion is first accelerated and then decelerated exponentially; (ii) it can turn L-corners with both right and left turns; and (iii) it always turns left (right) when the skyrmion number is positive (negative) in the T- and Y-junctions. Our results will be the basis of skyrmionic devices driven by a spin wave.
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Affiliation(s)
- Xichao Zhang
- Department of Physics, The University of Hong Kong, Hong Kong, People's Republic of China
| | - Motohiko Ezawa
- Department of Applied Physics, University of Tokyo, Hongo 7-3-1, 113-8656, Japan
| | - Dun Xiao
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - G P Zhao
- College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610068, People's Republic of China
- Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Material Technology & Engineering, Chinese Academy of Sciences, Ningbo 315201, People's Republic of China
| | - Yaowen Liu
- Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology, School of Physical Science and Engineering, Tongji University, Shanghai 200092, People's Republic of China
| | - Yan Zhou
- Department of Physics, The University of Hong Kong, Hong Kong, People's Republic of China
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22
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The quantum nature of skyrmions and half-skyrmions in Cu2OSeO3. Nat Commun 2014; 5:5376. [PMID: 25367368 DOI: 10.1038/ncomms6376] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2014] [Accepted: 09/24/2014] [Indexed: 11/08/2022] Open
Abstract
The Skyrme-particle, the skyrmion, was introduced over half a century ago in the context of dense nuclear matter. But with skyrmions being mathematical objects--special types of topological solitons--they can emerge in much broader contexts. Recently skyrmions were observed in helimagnets, forming nanoscale spin-textures. Extending over length scales much larger than the interatomic spacing, they behave as large, classical objects, yet deep inside they are of quantum nature. Penetrating into their microscopic roots requires a multi-scale approach, spanning the full quantum to classical domain. Here, we achieve this for the first time in the skyrmionic Mott insulator Cu2OSeO3. We show that its magnetic building blocks are strongly fluctuating Cu4 tetrahedra, spawning a continuum theory that culminates in 51 nm large skyrmions, in striking agreement with experiment. One of the further predictions that ensues is the temperature-dependent decay of skyrmions into half-skyrmions.
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23
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Ozerov M, Romhányi J, Belesi M, Berger H, Ansermet JP, van den Brink J, Wosnitza J, Zvyagin SA, Rousochatzakis I. Establishing the fundamental magnetic interactions in the chiral Skyrmionic Mott insulator Cu(2)OSeO(3) by terahertz electron spin resonance. PHYSICAL REVIEW LETTERS 2014; 113:157205. [PMID: 25375739 DOI: 10.1103/physrevlett.113.157205] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Indexed: 05/26/2023]
Abstract
The recent discovery of Skyrmions in Cu(2)OSeO(3) has established a new platform to create and manipulate Skyrmionic spin textures. We use high-field electron spin resonance with a terahertz free-electron laser and pulsed magnetic fields up to 64 T to probe and quantify its microscopic spin-spin interactions. In addition to the previously observed long-wavelength Goldstone mode, this technique probes also the high-energy part of the excitation spectrum which is inaccessible by standard low-frequency electron spin resonance. Fitting the behavior of the observed modes in magnetic field to a theoretical framework establishes experimentally that the fundamental magnetic building blocks of this Skyrmionic magnet are rigid, highly entangled and weakly coupled tetrahedra.
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Affiliation(s)
- M Ozerov
- Dresden High Magnetic Field Laboratory (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Dresden D-01328, Germany
| | - J Romhányi
- Leibniz Institute for Solid State and Materials Research, IFW, Dresden D-01069, Germany
| | - M Belesi
- Leibniz Institute for Solid State and Materials Research, IFW, Dresden D-01069, Germany
| | - H Berger
- Institut de Physique de la Matiére Condensée, Ecole Polytechnique Fédérale de Lausanne, Station 3, CH-1015 Lausanne-EPFL, Switzerland
| | - J-Ph Ansermet
- Institut de Physique de la Matiére Condensée, Ecole Polytechnique Fédérale de Lausanne, Station 3, CH-1015 Lausanne-EPFL, Switzerland
| | - Jeroen van den Brink
- Leibniz Institute for Solid State and Materials Research, IFW, Dresden D-01069, Germany and Department of Physics, TU Dresden, Dresden D-01062, Germany
| | - J Wosnitza
- Dresden High Magnetic Field Laboratory (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Dresden D-01328, Germany and Department of Physics, TU Dresden, Dresden D-01062, Germany
| | - S A Zvyagin
- Dresden High Magnetic Field Laboratory (HLD), Helmholtz-Zentrum Dresden-Rossendorf, Dresden D-01328, Germany
| | - I Rousochatzakis
- Leibniz Institute for Solid State and Materials Research, IFW, Dresden D-01069, Germany
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24
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Tailoring the topology of an artificial magnetic skyrmion. Nat Commun 2014; 5:4704. [DOI: 10.1038/ncomms5704] [Citation(s) in RCA: 120] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 07/15/2014] [Indexed: 11/08/2022] Open
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25
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Zhou Y, Ezawa M. A reversible conversion between a skyrmion and a domain-wall pair in a junction geometry. Nat Commun 2014; 5:4652. [DOI: 10.1038/ncomms5652] [Citation(s) in RCA: 263] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 07/09/2014] [Indexed: 11/09/2022] Open
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26
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Lin SZ, Batista CD, Reichhardt C, Saxena A. ac current generation in chiral magnetic insulators and Skyrmion motion induced by the spin Seebeck effect. PHYSICAL REVIEW LETTERS 2014; 112:187203. [PMID: 24856718 DOI: 10.1103/physrevlett.112.187203] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Indexed: 06/03/2023]
Abstract
We show that a temperature gradient induces an ac electric current in multiferroic insulators when the sample is embedded in a circuit. We also show that a thermal gradient can be used to move magnetic Skyrmions in insulating chiral magnets: the induced magnon flow from the hot to the cold region drives the Skyrmions in the opposite direction via a magnonic spin transfer torque. Both results are combined to compute the effect of Skyrmion motion on the ac current generation and demonstrate that Skyrmions in insulators are a promising route for spin caloritronics applications.
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Affiliation(s)
- Shi-Zeng Lin
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Cristian D Batista
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Charles Reichhardt
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
| | - Avadh Saxena
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA
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27
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Nagaosa N, Tokura Y. Topological properties and dynamics of magnetic skyrmions. NATURE NANOTECHNOLOGY 2013; 8:899-911. [PMID: 24302027 DOI: 10.1038/nnano.2013.243] [Citation(s) in RCA: 823] [Impact Index Per Article: 74.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Accepted: 10/17/2013] [Indexed: 05/27/2023]
Abstract
Magnetic skyrmions are particle-like nanometre-sized spin textures of topological origin found in several magnetic materials, and are characterized by a long lifetime. Skyrmions have been observed both by means of neutron scattering in momentum space and microscopy techniques in real space, and their properties include novel Hall effects, current-driven motion with ultralow current density and multiferroic behaviour. These properties can be understood from a unified viewpoint, namely the emergent electromagnetism associated with the non-coplanar spin structure of skyrmions. From this description, potential applications of skyrmions as information carriers in magnetic information storage and processing devices are envisaged.
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Affiliation(s)
- Naoto Nagaosa
- 1] RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan [2] Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
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