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Araki T, Takagi R, Kurumaji T, Tokura Y, Mochizuki M, Seki S. Exotic Spin Excitations in a Polar Magnet VOSe_{2}O_{5}. PHYSICAL REVIEW LETTERS 2024; 133:136702. [PMID: 39392995 DOI: 10.1103/physrevlett.133.136702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2024] [Revised: 07/18/2024] [Accepted: 08/22/2024] [Indexed: 10/13/2024]
Abstract
Magnetic resonance dynamics has been studied for a polar magnet VOSe_{2}O_{5}, which hosts several nontrivial magnetic phases including Néel-type skyrmion lattice (SkL). In both cycloidal and SkL spin states, two excitation modes active to oscillating magnetic field B_{ν}⊥c and one mode active to B_{ν}∥c are identified. The subsequent micromagnetic simulations well reproduce the observed selection rules and relative resonance frequencies, which allows the unambiguous assignment of the spin oscillation manner for each mode. Interestingly, the IC-2 phase with a potential double-q character was found to host similar excitation modes as the SkL state. We also discovered the existence of the novel B' phase with four modes active to B_{ν}⊥c. The present results provide a fundamental basis for the comprehensive understanding of resonant spin dynamics in polar magnets, and highlight VOSe_{2}O_{5} as a unique material platform to host a rich variety of nontrivial spin excitations.
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2
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Magnaterra M, Attig J, Peterlini L, Hermanns M, Upton MH, Kim J, Prodan L, Tsurkan V, Kézsmárki I, van Loosdrecht PHM, Grüninger M. Quasimolecular J_{tet}=3/2 Moments in the Cluster Mott Insulator GaTa_{4}Se_{8}. PHYSICAL REVIEW LETTERS 2024; 133:046501. [PMID: 39121433 DOI: 10.1103/physrevlett.133.046501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Revised: 04/16/2024] [Accepted: 06/07/2024] [Indexed: 08/11/2024]
Abstract
Quasimolecular orbitals in cluster Mott insulators provide a route to tailor exchange interactions, which may yield novel quantum phases of matter. We demonstrate the cluster Mott character of the lacunar spinel GaTa_{4}Se_{8} using resonant inelastic x-ray scattering (RIXS) at the Ta L_{3} edge. Electrons are fully delocalized over Ta_{4} tetrahedra, forming quasimolecular J_{tet}=3/2 moments. The modulation of the RIXS intensity as function of the transferred momentum q allows us to determine the cluster wave function, which depends on competing intracluster hopping terms that mix states with different character. This mixed wave function is decisive for the macroscopic properties since it affects intercluster hopping and exchange interactions and furthermore renormalizes the effective spin-orbit coupling constant. The versatile wave function, tunable via intracluster hopping, opens a new perspective on the large family of lacunar spinels and cluster Mott insulators in general.
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Shi S, Zhao Y, Sun J, Yu G, Zhou H, Wang J. Strain-mediated multistate skyrmion for neuron devices. NANOSCALE 2024; 16:12013-12020. [PMID: 38805240 DOI: 10.1039/d4nr01464b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2024]
Abstract
Magnetic skyrmions are potential candidates for neuromorphic computing because of their inherent topological stability, low drive current density and nanoscale size. However, an artificial neuron device based on current-driven skyrmion motion cannot satisfy the requirement of energy efficiency and integration density due to hundreds of millions of interconnected neurons and synapses present in the deep networks. Here, we present a compact and energy efficient skyrmion-based artificial neuron consisting of ferromagnetic/heavy metal/ferroelectric layers which uses strain-mediated voltage manipulation of skyrmion states to mimic the Integrate-and-Fire (IF) function of biological neurons. By implementation of a spiking neural network (SNN) based on the proposed skyrmionic neuronal devices, it can achieve a high accuracy of 95.08% on a modified National Institute of Standards and Technology (MNIST) handwritten digit dataset, as well as a low power consumption of ∼46.8 fJ per epoch per neuron. The present work suggests a novel way to realize energy-efficient and high-density neuromorphic computing.
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Affiliation(s)
- Shengbin Shi
- Department of Engineering Mechanics, Zhejiang University, Zheda Road 38, Hangzhou, Zhejiang 310027, China.
| | - Yunhong Zhao
- Zhejiang Laboratory, Hangzhou 311100, Zhejiang, China
| | - Jiajun Sun
- Department of Engineering Mechanics, Zhejiang University, Zheda Road 38, Hangzhou, Zhejiang 310027, China.
| | - Guoliang Yu
- Key Laboratory of Electromagnetic Wave Information Technology and Metrology of Zhejiang Province, College of Information Engineering, China Jiliang University, Hangzhou 310018, People's Republic of China
| | - Haomiao Zhou
- Key Laboratory of Electromagnetic Wave Information Technology and Metrology of Zhejiang Province, College of Information Engineering, China Jiliang University, Hangzhou 310018, People's Republic of China
| | - Jie Wang
- Department of Engineering Mechanics, Zhejiang University, Zheda Road 38, Hangzhou, Zhejiang 310027, China.
- Zhejiang Laboratory, Hangzhou 311100, Zhejiang, China
- Key Laboratory of Soft Machines and Smart Devices of Zhejiang Province, Zhejiang University, Zheda Road 38, Hangzhou, Zhejiang 310027, China
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4
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Wang Y, Shen Z, Zhang D, Wang L, Tsurkan V, Prodan L, Loidl A, Dumre BB, Khare SV. Pressure-Induced Changes in the Crystal Structure and Electrical Conductivity of GeV 4S 8. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2024; 36:3128-3137. [PMID: 38617806 PMCID: PMC11008103 DOI: 10.1021/acs.chemmater.3c02488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/02/2023] [Revised: 03/10/2024] [Accepted: 03/11/2024] [Indexed: 04/16/2024]
Abstract
Lacunar spinels, represented by AM4X8 compounds (A = Ga or Ge; M = V, Mo, Nb, or Ta; X = S or Se), form a unique group of ternary chalcogenide compounds. Among them, GeV4S8 has garnered significant attention due to its distinctive electrical and magnetic properties. While previous research efforts have primarily focused on studying how this material behaves under cooling conditions, pressure is another factor that determines the state and characteristics of solid matter. In this study, we employed a diamond anvil cell in conjunction with high-energy synchrotron X-ray diffraction, Raman spectroscopy, four-point probes, and theoretical computation to thoroughly investigate this material. We found that the structural transformation from cubic to orthorhombic was initiated at 34 GPa and completed at 54 GPa. Through data fitting of volume vs pressure, we determined the bulk moduli to be 105 ± 4 GPa for the cubic phase and 111 ± 12 GPa for the orthorhombic phase. Concurrently, electrical resistance measurements indicated a semiconductor-to-nonmetallic conductor transition at ∼15 GPa. Moreover, we experimentally assessed the band gaps at different pressures to validate the occurrence of the electrical phase transition. We infer that the electrical phase transition correlates with the valence electrons in the V4 cluster rather than the crystal structure transformation. Furthermore, the computational results, electronic density of states, and band structure verified the experimental observation and facilitated the understanding of the mechanism governing the electrical phase transition in GeV4S8.
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Affiliation(s)
- Yuejian Wang
- Physics
Department, Oakland University, Rochester, Michigan 48309, United States
| | - Zhiwei Shen
- Center
for
High-Pressure Science (CHiPS), State Key Laboratory of Metastable
Materials Science and Technology, Yanshan
University, Qinhuangdao, Hebei 066004, China
| | - Dongzhou Zhang
- Partnership
for Extreme Crystallography, University
of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Lin Wang
- Center
for
High-Pressure Science (CHiPS), State Key Laboratory of Metastable
Materials Science and Technology, Yanshan
University, Qinhuangdao, Hebei 066004, China
| | - Vladimir Tsurkan
- Experimental
Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Institute
of Applied Physics, Moldova State University, MD-2028 Chisinau, Republic of Moldova
| | - Lilian Prodan
- Experimental
Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
- Institute
of Applied Physics, Moldova State University, MD-2028 Chisinau, Republic of Moldova
| | - Alois Loidl
- Experimental
Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg 86135, Germany
| | - Bishal B. Dumre
- Department
of Physics and Astronomy, and Wright Center for Photovoltaics Innovation
and Commercialization (PVIC), University
of Toledo, Toledo, Ohio 43606, United States
| | - Sanjay V. Khare
- Department
of Physics and Astronomy, and Wright Center for Photovoltaics Innovation
and Commercialization (PVIC), University
of Toledo, Toledo, Ohio 43606, United States
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5
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Sekiguchi F, Budzinauskas K, Padmanabhan P, Versteeg RB, Tsurkan V, Kézsmárki I, Foggetti F, Artyukhin S, van Loosdrecht PHM. Slowdown of photoexcited spin dynamics in the non-collinear spin-ordered phases in skyrmion host GaV 4S 8. Nat Commun 2022; 13:3212. [PMID: 35680864 PMCID: PMC9184521 DOI: 10.1038/s41467-022-30829-z] [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: 08/10/2021] [Accepted: 05/20/2022] [Indexed: 11/10/2022] Open
Abstract
Formation of magnetic order alters the character of spin excitations, which then affects transport properties. We investigate the photoexcited ultrafast spin dynamics in different magnetic phases in Néel-type skyrmion host GaV4S8 with time-resolved magneto-optical Kerr effect experiments. The coherent spin precession, whose amplitude is enhanced in the skyrmion-lattice phase, shows a signature of phase coexistence across the magnetic phase transitions. The incoherent spin relaxation dynamics slows down by a factor of two in the skyrmion-lattice/cycloid phases, indicating significant decrease in thermal conductivity triggered by a small change of magnetic field. The slow heat diffusion in the skyrmion-lattice/cycloid phases is attributed to the stronger magnon scattering off the domain walls formed in abundance in the skyrmion-lattice/cycloid phase. These results highlight the impact of spatial spin structure on the ultrafast heat transport in spin systems, providing a useful insight for the step toward ultrafast photocontrol of the magnets with novel spin orders. Skyrmions are a topological magnetic texture that have garnered considerable interest for various technological applications. Here, Sekiguchi et al. investigate the ultrafast optical response of GaV4S6, and find a significant reduction in the thermal conductivity in the skyrmion phase.
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Affiliation(s)
- Fumiya Sekiguchi
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany.
| | - Kestutis Budzinauskas
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany
| | - Prashant Padmanabhan
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany
| | - Rolf B Versteeg
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany
| | - Vladimir Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany.,Institute of Applied Physics, MD 2028, Chișinău, Republic of Moldova
| | - István Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159, Augsburg, Germany
| | - Francesco Foggetti
- Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy.,Dipartimento di Fisica, Università di Genova, Via Dodecaneso, 33, 16146, Genova, Italy
| | - Sergey Artyukhin
- Istituto Italiano di Tecnologia, Via Morego 30, 16163, Genova, Italy
| | - Paul H M van Loosdrecht
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937, Köln, Germany.
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Jiang L, Huang C, Zhu Y, Pan Y, Fan J, Zhang K, Ma C, Shi D, Zhang H. Tuning the size of skyrmion by strain at the Co/Pt3 Interfaces. iScience 2022; 25:104039. [PMID: 35330683 PMCID: PMC8938285 DOI: 10.1016/j.isci.2022.104039] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Revised: 02/09/2022] [Accepted: 03/03/2022] [Indexed: 11/25/2022] Open
Abstract
Based on density functional theory calculations, we elucidated the tunability of the atomic structures and magnetic interactions of Co/Pt3 interface (one layer of hcp(0001) Co and three layers of fcc(111) Pt) and thus the skyrmion sizes using strain. The dispersion relations of the spin spiral in the opposite directions, E(q) and E(-q), were evaluated based on generalized Bloch equations. Effective exchange coupling (EC) and Dzyaloshinsky-Moriya interaction (DMI) parameters between different neighbors Ji and di at different lattice constants were derived by fitting the resulting spin spiral dispersion E(q) to EC model with DMI and E(q)-E(-q) formula, respectively. We observed an increase in DMI and a significant decrease in EC with an increase in strain. Hence, the size of Néel-type skyrmions determined by the ratio of EC/DMI can be controlled by applying strain, leading to an effective approach to tailor the formation of skyrmion lattices by inducing slight structural modifications on the magnetic thin films. Calculate the EC and DMI of multi-nearest neighbors in the VASP program Show detailed changes of multi-nearest neighboring EC and DMI with deformation The size of skyrmion does decrease as the lattice constant increases Distance between Co and Pt layer determines the size of DMI
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Hirosawa T, Klinovaja J, Loss D, Díaz SA. Laser-Controlled Real- and Reciprocal-Space Topology in Multiferroic Insulators. PHYSICAL REVIEW LETTERS 2022; 128:037201. [PMID: 35119897 DOI: 10.1103/physrevlett.128.037201] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2021] [Revised: 12/02/2021] [Accepted: 12/17/2021] [Indexed: 06/14/2023]
Abstract
Magnetic materials in which it is possible to control the topology of their magnetic order in real space or the topology of their magnetic excitations in reciprocal space are highly sought after as platforms for alternative data storage and computing architectures. Here we show that multiferroic insulators, owing to their magnetoelectric coupling, offer a natural and advantageous way to address these two different topologies using laser fields. We demonstrate that via a delicate balance between the energy injection from a high-frequency laser and dissipation, single skyrmions-archetypical topological magnetic textures-can be set into motion with a velocity and propagation direction that can be tuned by the laser field amplitude and polarization, respectively. Moreover, we uncover an ultrafast Floquet magnonic topological phase transition in a laser-driven skyrmion crystal and we propose a new diagnostic tool to reveal it using the magnonic thermal Hall conductivity.
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Affiliation(s)
- Tomoki Hirosawa
- Department of Physics, University of Tokyo, Bunkyo, Tokyo 113-0033, Japan
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Jelena Klinovaja
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Daniel Loss
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
| | - Sebastián A Díaz
- Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland
- Faculty of Physics, University of Duisburg-Essen, 47057 Duisburg, Germany
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8
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Oyeka EE, Winiarski MJ, Tran TT. Study of Integer Spin S = 1 in the Polar Magnet β-Ni(IO 3) 2. Molecules 2021; 26:molecules26237210. [PMID: 34885793 PMCID: PMC8658994 DOI: 10.3390/molecules26237210] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 11/23/2021] [Accepted: 11/26/2021] [Indexed: 11/16/2022] Open
Abstract
Polar magnetic materials exhibiting appreciable asymmetric exchange interactions can potentially host new topological states of matter such as vortex-like spin textures; however, realizations have been mostly limited to half-integer spins due to rare numbers of integer spin systems with broken spatial inversion lattice symmetries. Here, we studied the structure and magnetic properties of the S = 1 integer spin polar magnet β-Ni(IO3)2 (Ni2+, d8, 3F). We synthesized single crystals and bulk polycrystalline samples of β-Ni(IO3)2 by combining low-temperature chemistry techniques and thermal analysis and characterized its crystal structure and physical properties. Single crystal X-ray and powder X-ray diffraction measurements demonstrated that β-Ni(IO3)2 crystallizes in the noncentrosymmetric polar monoclinic structure with space group P21. The combination of the macroscopic electric polarization driven by the coalignment of the (IO3)− trigonal pyramids along the b axis and the S = 1 state of the Ni2+ cation was chosen to investigate integer spin and lattice dynamics in magnetism. The effective magnetic moment of Ni2+ was extracted from magnetization measurements to be 3.2(1) µB, confirming the S = 1 integer spin state of Ni2+ with some orbital contribution. β-Ni(IO3)2 undergoes a magnetic ordering at T = 3 K at a low magnetic field, μ0H = 0.1 T; the phase transition, nevertheless, is suppressed at a higher field, μ0H = 3 T. An anomaly resembling a phase transition is observed at T ≈ 2.7 K in the Cp/T vs. T plot, which is the approximate temperature of the magnetic phase transition of the material, indicating that the transition is magnetically driven. This work offers a useful route for exploring integer spin noncentrosymmetric materials, broadening the phase space of polar magnet candidates, which can harbor new topological spin physics.
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Affiliation(s)
- Ebube E. Oyeka
- Department of Chemistry, Clemson University, Clemson, SC 29634, USA;
| | - Michał J. Winiarski
- Advanced Materials Center, Faculty of Applied Physics and Mathematics, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland;
| | - Thao T. Tran
- Department of Chemistry, Clemson University, Clemson, SC 29634, USA;
- Correspondence:
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9
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Oyeka EE, Winiarski MJ, Sorolla Ii M, Taddei KM, Scheie A, Tran TT. Spin and Orbital Effects on Asymmetric Exchange Interaction in Polar Magnets: M(IO 3) 2 (M = Cu and Mn). Inorg Chem 2021; 60:16544-16557. [PMID: 34637293 DOI: 10.1021/acs.inorgchem.1c02432] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Magnetic polar materials feature an astonishing range of physical properties, such as magnetoelectric coupling, chiral spin textures, and related new spin topology physics. This is primarily attributable to their lack of space inversion symmetry in conjunction with unpaired electrons, potentially facilitating an asymmetric Dzyaloshinskii-Moriya (DM) exchange interaction supported by spin-orbital and electron-lattice coupling. However, engineering the appropriate ensemble of coupled degrees of freedom necessary for enhanced DM exchange has remained elusive for polar magnets. Here, we study how spin and orbital components influence the capability of promoting the magnetic interaction by studying two magnetic polar materials, α-Cu(IO3)2 (2D) and Mn(IO3)2 (6S), and connecting their electronic and magnetic properties with their structures. The chemically controlled low-temperature synthesis of these complexes resulted in pure polycrystalline samples, providing a viable pathway to prepare bulk forms of transition-metal iodates. Rietveld refinements of the powder synchrotron X-ray diffraction data reveal that these materials exhibit different crystal structures but crystallize in the same polar and chiral P21 space group, giving rise to an electric polarization along the b-axis direction. The presence and absence of an evident phase transition to a possible topologically distinct state observed in α-Cu(IO3)2 and Mn(IO3)2, respectively, imply the important role of spin-orbit coupling. Neutron diffraction experiments reveal helpful insights into the magnetic ground state of these materials. While the long-wavelength incommensurability of α-Cu(IO3)2 is in harmony with sizable asymmetric DM interaction and low dimensionality of the electronic structure, the commensurate stripe AFM ground state of Mn(IO3)2 is attributed to negligible DM exchange and isotropic orbital overlapping. The work demonstrates connections between combined spin and orbital effects, magnetic coupling dimensionality, and DM exchange, providing a worthwhile approach for tuning asymmetric interaction, which promotes evolution of topologically distinct spin phases.
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Affiliation(s)
- Ebube E Oyeka
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Michał J Winiarski
- Faculty of Applied Physics and Mathematics and Advanced Materials Center, Gdansk University of Technology, ul. Narutowicza 11/12, 80-233 Gdansk, Poland
| | - Maurice Sorolla Ii
- Department of Chemical Engineering, University of the Philippines Diliman, Quezon City 1101, Philippines
| | - Keith M Taddei
- Neutron Scattering Division, Oak Ridge National Laboratory, 9500 Spallation Dr, Oak Ridge, Tennessee 37830, United States
| | - Allen Scheie
- Neutron Scattering Division, Oak Ridge National Laboratory, 9500 Spallation Dr, Oak Ridge, Tennessee 37830, United States
| | - Thao T Tran
- Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
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10
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Solovyev I, Ono R, Nikolaev S. Magnetically Induced Polarization in Centrosymmetric Bonds. PHYSICAL REVIEW LETTERS 2021; 127:187601. [PMID: 34767415 DOI: 10.1103/physrevlett.127.187601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 09/27/2021] [Indexed: 06/13/2023]
Abstract
We reveal the microscopic origin of electric polarization P[over →] induced by noncollinear magnetic order. We show that in Mott insulators, such P[over →] is given by all possible combinations of position operators r[over →][over ^]_{ij}=(r[over →]_{ij}^{0},r[over →]_{ij}) and transfer integrals t[over ^]_{ij}=(t_{ij}^{0},t_{ij}) in the bonds, where r[over →]_{ij}^{0} and t_{ij}^{0} are spin-independent contributions in the basis of Kramers doublet states, while r[over →]_{ij} and t_{ij} stem solely from the spin-orbit interaction. Among them, the combination t_{ij}^{0}r[over →]_{ij}, which couples to the spin current, remains finite in the centrosymmetric bonds, thus yielding finite P[over →] in the case of noncollinear arrangement of spins. The form of the magnetoelectric coupling, which is controlled by r[over →]_{ij}, appears to be rich and is not limited to the phenomenological law P[over →]∼ε_{ij}×[e_{i}×e_{j}] with ε_{ij} being the bond vector connecting the spins e_{i} and e_{j}. Using density-functional theory, we illustrate how the proposed mechanism works in the spiral magnets CuCl_{2}, CuBr_{2}, CuO, and α-Li_{2}IrO_{3}, providing a consistent explanation for the available experimental data.
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Affiliation(s)
- Igor Solovyev
- National Institute for Materials Science, MANA, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
- Department of Theoretical Physics and Applied Mathematics, Ural Federal University, Mira Street 19, 620002 Ekaterinburg, Russia
- Institute of Metal Physics, S. Kovalevskaya Street 18, 620108 Ekaterinburg, Russia
| | - Ryota Ono
- Graduate School of Science and Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba-shi 265-8522, Japan
| | - Sergey Nikolaev
- National Institute for Materials Science, MANA, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
- Tokyo Tech World Research Hub Initiative (WRHI), Institute of Innovative Research, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-Ku, Yokohama, Kanagawa 226-8503, Japan
- Laboratory for Materials and Structures, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-Ku, Yokohama, Kanagawa 226-8503, Japan
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11
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Jandieri V, Khomeriki R, Chotorlishvili L, Watanabe K, Erni D, Werner DH, Berakdar J. Photonic Signatures of Spin-Driven Ferroelectricity in Multiferroic Dielectric Oxides. PHYSICAL REVIEW LETTERS 2021; 127:127601. [PMID: 34597074 DOI: 10.1103/physrevlett.127.127601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 08/17/2021] [Indexed: 06/13/2023]
Abstract
We study the dispersion and scattering properties of electromagnetic modes coupled to a helically ordered spin lattice hosted by a dielectric oxide with a ferroelectric polarization driven by vector spin chirality. Quasianalytical approaches and full-fledged numerics evidence the formation of a chiral magnonic photonic band gap and the presence of gate-voltage dependent circular dichroism in the scattering of electromagnetic waves from the lattice. Gating couples to the emergent ferroelectric polarization and hence, to the underlying vector-spin chirality. The theory relies on solving simultaneously Maxwell's equations coupled to the driven localized spins taking into account their spatial topology and spatial anisotropic interactions. The developed approach is applicable to various settings involving noncollinear spins and multiferroic systems with potential applications in noncollinear magnetophotonics.
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Affiliation(s)
- Vakhtang Jandieri
- General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen and CENIDE - Center for Nanointegration Duisburg-Essen, D-47048 Duisburg, Germany
| | - Ramaz Khomeriki
- Physics Department, Tbilisi State University, 3 Chavchavadze, 0128 Tbilisi, Georgia
| | - Levan Chotorlishvili
- Institut für Physik, Martin-Luther-Universität, Halle-Wittenberg, D-06099 Halle/Saale, Germany
- Department of Physics and Medical Engineering, Rzeszow University of Technology, 35-959 Rzeszow, Poland
| | - Koki Watanabe
- Department of Information and Communication Engineering, Fukuoka Institute of Technology, 3-30-1 Wajirohigashi, Higashi-ku, Fukuoka 811-0295, Japan
| | - Daniel Erni
- General and Theoretical Electrical Engineering (ATE), Faculty of Engineering, University of Duisburg-Essen and CENIDE - Center for Nanointegration Duisburg-Essen, D-47048 Duisburg, Germany
| | - Douglas H Werner
- Department of Electrical Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
| | - Jamal Berakdar
- Institut für Physik, Martin-Luther-Universität, Halle-Wittenberg, D-06099 Halle/Saale, Germany
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12
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Zhang C, Zhang J, Liu C, Zhang S, Yuan Y, Li P, Wen Y, Jiang Z, Zhou B, Lei Y, Zheng D, Song C, Hou Z, Mi W, Schwingenschlögl U, Manchon A, Qiu ZQ, Alshareef HN, Peng Y, Zhang X. Chiral Helimagnetism and One-Dimensional Magnetic Solitons in a Cr-Intercalated Transition Metal Dichalcogenide. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2101131. [PMID: 34302387 PMCID: PMC11468724 DOI: 10.1002/adma.202101131] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 04/25/2021] [Indexed: 06/13/2023]
Abstract
Chiral magnets endowed with topological spin textures are expected to have promising applications in next-generation magnetic memories. In contrast to the well-studied 2D or 3D magnetic skyrmions, the authors report the discovery of 1D nontrivial magnetic solitons in a transition metal dichalcogenide 2H-TaS2 via precise intercalation of Cr elements. In the synthetic Cr1/3 TaS2 (CTS) single crystal, the coupling of the strong spin-orbit interaction from TaS2 and the chiral arrangement of the magnetic Cr ions evoke a robust Dzyaloshinskii-Moriya interaction. A magnetic helix having a short spatial period of ≈25 nm is observed in CTS via Lorentz transmission electron microscopy. In a magnetic field perpendicular to the helical axis, the helical spin structure transforms into a chiral soliton lattice (CSL) with the spin structure evolution being consistent with the chiral sine-Gordon theory, which opens promising perspectives for the application of CSL to fast-speed nonvolatile magnetic memories. This work introduces a new paradigm to soliton physics and provides an effective strategy for seeking novel 2D magnets.
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Affiliation(s)
- Chenhui Zhang
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Junwei Zhang
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of EducationSchool of Physical Science and Technology and Electron Microscopy Centre of Lanzhou UniversityLanzhou UniversityLanzhouGansu Province730000China
| | - Chen Liu
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Senfu Zhang
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Ye Yuan
- Songshan Lake Materials LaboratoryDongguanGuangdong523808China
| | - Peng Li
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Yan Wen
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Ze Jiang
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of EducationSchool of Physical Science and Technology and Electron Microscopy Centre of Lanzhou UniversityLanzhou UniversityLanzhouGansu Province730000China
| | - Bojian Zhou
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of EducationSchool of Physical Science and Technology and Electron Microscopy Centre of Lanzhou UniversityLanzhou UniversityLanzhouGansu Province730000China
| | - Yongjiu Lei
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Dongxing Zheng
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Chengkun Song
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of EducationSchool of Physical Science and Technology and Electron Microscopy Centre of Lanzhou UniversityLanzhou UniversityLanzhouGansu Province730000China
| | - Zhipeng Hou
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute for Advanced MaterialsSouth China Academy of Advanced OptoelectronicsSouth China Normal UniversityGuangzhouGuangdong Province510006China
- National Center for International Research on Green OptoelectronicsSouth China Normal UniversityGuangzhouGuangdong Province510006China
| | - Wenbo Mi
- Tianjin Key Laboratory of Low Dimensional Materials Physics and Processing TechnologyInstitute of Advanced Materials PhysicsFaculty of ScienceTianjin UniversityTianjinTianjin Municipality300354China
| | - Udo Schwingenschlögl
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | | | - Zi Qiang Qiu
- Department of PhysicsUniversity of CaliforniaBerkeleyCA94720USA
| | - Husam N. Alshareef
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
| | - Yong Peng
- Key Laboratory for Magnetism and Magnetic Materials of Ministry of EducationSchool of Physical Science and Technology and Electron Microscopy Centre of Lanzhou UniversityLanzhou UniversityLanzhouGansu Province730000China
| | - Xi‐Xiang Zhang
- Physical Science and Engineering Division (PSE)King Abdullah University of Science and Technology (KAUST)Thuwal23955‐6900Saudi Arabia
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13
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Henderson ME, Beare J, Sharma S, Bleuel M, Clancy P, Cory DG, Huber MG, Marjerrison CA, Pula M, Sarenac D, Smith EM, Zhernenkov K, Luke GM, Pushin DA. Characterization of a Disordered above Room Temperature Skyrmion Material Co 8Zn 8Mn 4. MATERIALS (BASEL, SWITZERLAND) 2021; 14:4689. [PMID: 34443211 PMCID: PMC8399547 DOI: 10.3390/ma14164689] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 08/06/2021] [Accepted: 08/10/2021] [Indexed: 11/16/2022]
Abstract
Topologically nontrivial spin textures host great promise for future spintronic applications. Skyrmions in particular are of burgeoning interest owing to their nanometric size, topological protection, and high mobility via ultra-low current densities. It has been previously reported through magnetic susceptibility, microscopy, and scattering techniques that Co8Zn8Mn4 forms an above room temperature triangular skyrmion lattice. Here, we report the synthesis procedure and characterization of a polycrystalline Co8Zn8Mn4 disordered bulk sample. We employ powder X-ray diffraction and backscatter Laue diffraction as characterization tools of the crystallinity of the samples, while magnetic susceptibility and Small Angle Neutron Scattering (SANS) measurements are performed to study the skyrmion phase. Magnetic susceptibility measurements show a dip anomaly in the magnetization curves, which persists over a range of approximately 305 K-315 K. SANS measurements reveal a rotationally disordered polydomain skyrmion lattice. Applying a symmetry-breaking magnetic field sequence, we were able to orient and order the previously jammed state to yield the prototypical hexagonal diffraction patterns with secondary diffraction rings. This emergence of the skyrmion order serves as a unique demonstration of the fundamental interplay of structural disorder and anisotropy in stabilizing the thermal equilibrium phase.
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Affiliation(s)
- Melissa E. Henderson
- Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (D.G.C.); (D.S.); (K.Z.); (D.A.P.)
- Department of Physics & Astronomy, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - James Beare
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (J.B.); (S.S.); (M.P.); (E.M.S.); (G.M.L.)
| | - Sudarshan Sharma
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (J.B.); (S.S.); (M.P.); (E.M.S.); (G.M.L.)
| | - Markus Bleuel
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (M.B.); (M.G.H.)
- Department of Materials Science and Engineering, University of Maryland, College Park, MD 20742, USA
| | - Pat Clancy
- Brockhouse Institute for Materials Research, Hamilton, ON L8S 4M1, Canada; (P.C.); (C.A.M.)
| | - David G. Cory
- Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (D.G.C.); (D.S.); (K.Z.); (D.A.P.)
- Department of Chemistry, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Michael G. Huber
- National Institute of Standards and Technology, Gaithersburg, MD 20899, USA; (M.B.); (M.G.H.)
| | - Casey A. Marjerrison
- Brockhouse Institute for Materials Research, Hamilton, ON L8S 4M1, Canada; (P.C.); (C.A.M.)
| | - Mathew Pula
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (J.B.); (S.S.); (M.P.); (E.M.S.); (G.M.L.)
| | - Dusan Sarenac
- Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (D.G.C.); (D.S.); (K.Z.); (D.A.P.)
| | - Evan M. Smith
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (J.B.); (S.S.); (M.P.); (E.M.S.); (G.M.L.)
| | - Kirill Zhernenkov
- Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (D.G.C.); (D.S.); (K.Z.); (D.A.P.)
- Jülich Centre for Neutron Science at Heinz Maier-Leibnitz Zentrum, Forschungszentrum Jülich GmbH, 85748 Garching, Germany
| | - Graeme M. Luke
- Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1, Canada; (J.B.); (S.S.); (M.P.); (E.M.S.); (G.M.L.)
- Brockhouse Institute for Materials Research, Hamilton, ON L8S 4M1, Canada; (P.C.); (C.A.M.)
| | - Dmitry A. Pushin
- Institute for Quantum Computing, University of Waterloo, Waterloo, ON N2L 3G1, Canada; (D.G.C.); (D.S.); (K.Z.); (D.A.P.)
- Department of Physics & Astronomy, University of Waterloo, Waterloo, ON N2L 3G1, Canada
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14
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Aguilar-Maldonado C, Mentré O, Tsirlin AA, Ritter C, Missiul A, Fauth F, Arévalo-López AM. Hybrid electrons in the trimerized GaV 4O 8. MATERIALS HORIZONS 2021; 8:2325-2329. [PMID: 34846437 DOI: 10.1039/d1mh00390a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Mixed-valent transition-metal compounds display complex structural, electronic and magnetic properties, which often intricately coexist. Here, we report the new ternary oxide GaV4O8, a structural sibling of skyrmion-hosting lacunar spinels. GaV4O8 contains a vanadium trimer and an original spin-orbital-charge texture that forms upon the structural phase transition at TS = 68 K followed by the magnetic transition at TN = 35 K. The texture arises from the coexistence of orbital molecules on the vanadium trimers and localized electrons on the remaining vanadium atoms. Such hybrid electrons create opportunities for novel types of spin, charge, and orbital order in mixed-valent transition-metal compounds.
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Affiliation(s)
- Cintli Aguilar-Maldonado
- Université Lille Nord de France, UMR 8181 CNRS, Unité de Catalyse et de Chimie du Solide (UCCS USTL), Villeneuve d'Ascq F-59655, France.
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15
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Routledge K, Vir P, Cook N, Murgatroyd PAE, Ahmed SJ, Savvin SN, Claridge JB, Alaria J. Mode Crystallography Analysis through the Structural Phase Transition and Magnetic Critical Behavior of the Lacunar Spinel GaMo 4Se 8. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2021; 33:5718-5729. [PMID: 34475635 PMCID: PMC8382239 DOI: 10.1021/acs.chemmater.1c01448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 06/17/2021] [Indexed: 06/13/2023]
Abstract
In the lacunar spinels, with the formula AB4X8, transition-metal ions form tightly bound B4 clusters resulting in exotic physical properties such as the stabilization of Néel-type skyrmion lattices, which hold great promise for energy-efficient switching devices. These properties are governed by the symmetry of these compounds with distortion of the parent noncentrosymmetric F4̅3m space group to the polar R3m, with recent observation of a coexisting Imm2 low-temperature phase. In this study, through powder neutron diffraction, we further confirm that a metastable Imm2 coexists with the R3m phase in GaMo4Se8 and we present its structure. By applying the mode crystallography approach to the distortions together with anisotropic microstrain broadening analysis, we postulate that the formation origin of the minority Imm2 phase stems from the high compressive stress observed in the R3m phase. Bond valence sum analysis also suggests a change in electronic configuration in the transition to Imm2 which could have implications on the electrical properties of the compound. We further establish the nature of the magnetic phase transition using critical exponent analysis obtained from single-crystal magnetization measurements which shows a mixture of tricritical mean-field and 3D Heisenberg behavior [β = 0.22(4), γ = 1.19(1), and δ = 6.42(1)]. Magnetoentropic mapping performed on a single crystal reveals the signature of a positive entropy region near the magnetic phase transition which corresponds to the skyrmion phase field observed in a polycrystalline sample.
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Affiliation(s)
- Kieran Routledge
- Department
of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, U.K.
| | - Praveen Vir
- Diffraction
Group, Institut Laue-Langevin, 71 Avenue des Martyrs, Grenoble 38000, France
| | - Nicholas Cook
- Department
of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, U.K.
| | | | - Sheikh J. Ahmed
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
| | - Stanislav N. Savvin
- Diffraction
Group, Institut Laue-Langevin, 71 Avenue des Martyrs, Grenoble 38000, France
| | - John B. Claridge
- Department
of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K.
| | - Jonathan Alaria
- Department
of Physics, University of Liverpool, Oxford Street, Liverpool L69 7ZE, U.K.
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16
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Ghara S, Geirhos K, Kuerten L, Lunkenheimer P, Tsurkan V, Fiebig M, Kézsmárki I. Giant conductivity of mobile non-oxide domain walls. Nat Commun 2021; 12:3975. [PMID: 34172747 PMCID: PMC8233373 DOI: 10.1038/s41467-021-24160-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 05/31/2021] [Indexed: 02/06/2023] Open
Abstract
Atomically sharp domain walls in ferroelectrics are considered as an ideal platform to realize easy-to-reconfigure nanoelectronic building blocks, created, manipulated and erased by external fields. However, conductive domain walls have been exclusively observed in oxides, where domain wall mobility and conductivity is largely influenced by stoichiometry and defects. Here, we report on giant conductivity of domain walls in the non-oxide ferroelectric GaV4S8. We observe conductive domain walls forming in zig-zagging structures, that are composed of head-to-head and tail-to-tail domain wall segments alternating on the nanoscale. Remarkably, both types of segments possess high conductivity, unimaginable in oxide ferroelectrics. These effectively 2D domain walls, dominating the 3D conductance, can be mobilized by magnetic fields, triggering abrupt conductance changes as large as eight orders of magnitude. These unique properties demonstrate that non-oxide ferroelectrics can be the source of novel phenomena beyond the realm of oxide electronics.
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Affiliation(s)
- S. Ghara
- grid.7307.30000 0001 2108 9006Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany
| | - K. Geirhos
- grid.7307.30000 0001 2108 9006Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany
| | - L. Kuerten
- grid.5801.c0000 0001 2156 2780Department of Materials, ETH Zurich, Zurich, Switzerland
| | - P. Lunkenheimer
- grid.7307.30000 0001 2108 9006Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany
| | - V. Tsurkan
- grid.7307.30000 0001 2108 9006Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany ,grid.450974.bInstitute of Applied Physics, Chisinau, Republic of Moldova
| | - M. Fiebig
- grid.5801.c0000 0001 2156 2780Department of Materials, ETH Zurich, Zurich, Switzerland
| | - I. Kézsmárki
- grid.7307.30000 0001 2108 9006Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, Augsburg, Germany
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17
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Geirhos K, Langmann J, Prodan L, Tsirlin AA, Missiul A, Eickerling G, Jesche A, Tsurkan V, Lunkenheimer P, Scherer W, Kézsmárki I. Cooperative Cluster Jahn-Teller Effect as a Possible Route to Antiferroelectricity. PHYSICAL REVIEW LETTERS 2021; 126:187601. [PMID: 34018769 DOI: 10.1103/physrevlett.126.187601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 03/02/2021] [Accepted: 04/08/2021] [Indexed: 06/12/2023]
Abstract
We report the observation of an antipolar phase in cubic GaNb_{4}S_{8} driven by an unconventional microscopic mechanism, the cooperative Jahn-Teller effect of Nb_{4}S_{4} molecular clusters. The assignment of the antipolar nature is based on sudden changes in the crystal structure and a strong drop of the dielectric constant at T_{JT}=31 K, also indicating the first-order nature of the transition. In addition, we found that local symmetry lowering precedes long-range orbital ordering, implying the presence of a dynamic Jahn-Teller effect in the cubic phase above T_{JT}. Based on the variety of structural polymorphs reported in lacunar spinels, also including ferroelectric phases, we argue that GaNb_{4}S_{8} may be transformable to a ferroelectric state, which would further classify the observed antipolar phase as antiferroelectric.
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Affiliation(s)
- K Geirhos
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - J Langmann
- CPM, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - L Prodan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
- Institute of Applied Physics, MD 2028, Chisinau, Republic of Moldova
| | - A A Tsirlin
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - A Missiul
- CELLS-ALBA Synchrotron, Cerdanyola del Valles, E-08290 Barcelona, Spain
| | - G Eickerling
- CPM, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - A Jesche
- Experimental Physics VI, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
- Institute of Applied Physics, MD 2028, Chisinau, Republic of Moldova
| | - P Lunkenheimer
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
| | - W Scherer
- CPM, Institute of Physics, University of Augsburg, 86135 Augsburg, Germany
| | - I Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135 Augsburg, Germany
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18
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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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19
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Khomskii DI, Streltsov SV. Orbital Effects in Solids: Basics, Recent Progress, and Opportunities. Chem Rev 2020; 121:2992-3030. [PMID: 33314912 DOI: 10.1021/acs.chemrev.0c00579] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The properties of transition metal compounds are largely determined by nontrivial interplay of different degrees of freedom: charge, spin, lattice, and also orbital ones. Especially rich and interesting effects occur in systems with orbital degeneracy. For example, they result in the famous Jahn-Teller effect, leading to a plethora of consequences for static and dynamic properties, including nontrivial quantum effects. In the present review, we discuss the main phenomena in the physics of such systems, paying central attention to the novel manifestations of those. After shortly summarizing the basic phenomena and their descriptions, we concentrate on several specific directions in this field. One of them is the reduction of effective dimensionality in many systems with orbital degrees of freedom due to the directional character of orbitals, with the concomitant appearance of some instabilities that lead in particular to the formation of dimers, trimers, and similar clusters in a material. The properties of such cluster systems, which are largely determined by their orbital structure, are discussed in detail, and many specific examples of those in different materials are presented. Another big field that has acquired special significance relatively recently is the role of the relativistic spin-orbit interaction. The mutual influence of this interaction and the more traditional Jahn-Teller physics is treated in detail in the second part of the review. In discussing all of these questions, special attention is paid to novel quantum effects.
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Affiliation(s)
- Daniel I Khomskii
- II. Physikalisches Institut, Universität zu Köln, Zülpicher Straße 77, D-50937 Köln, Germany
| | - Sergey V Streltsov
- Institute of Metal Physics, S. Kovalevskoy St. 18, 620990 Ekaterinburg, Russia.,Department of Theoretical Physics and Applied Mathematics, Ural Federal University, Mira St. 19, 620002 Ekaterinburg, Russia
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20
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Mokdad J, Knebel G, Marin C, Brison JP, Matei I, Braithwaite D. Probing insulators under pressure. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:093902. [PMID: 33003814 DOI: 10.1063/5.0016465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 08/16/2020] [Indexed: 06/11/2023]
Abstract
Applying pressure on a material can reveal many physical properties and is a very efficient tool to understand its physics. Resistivity measurements have been the ideal probe to study metals under pressure. However, in the case of insulators, resistivity, or conductivity, it is often not the appropriate quantity characterizing the material. In this work, we present a newly developed in situ pressure tuning system that can be used over a wide temperature range (2 K-300 K) and allows changing the pressure at any temperature. We also present AC calorimetry and capacitance/loss measurements under pressure and demonstrate how this combination can be used to characterize a material that is too insulating for standard resistivity techniques.
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Affiliation(s)
- J Mokdad
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - G Knebel
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - C Marin
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - J-P Brison
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - I Matei
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
| | - D Braithwaite
- Université Grenoble Alpes, CEA, IRIG-Pheliqs, 38000 Grenoble, France
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21
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Štefančič A, Holt SJR, Lees MR, Ritter C, Gutmann MJ, Lancaster T, Balakrishnan G. Establishing magneto-structural relationships in the solid solutions of the skyrmion hosting family of materials: GaV 4S 8-ySe y. Sci Rep 2020; 10:9813. [PMID: 32555354 PMCID: PMC7299962 DOI: 10.1038/s41598-020-65676-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2019] [Accepted: 04/30/2020] [Indexed: 11/09/2022] Open
Abstract
The GaV4S8-ySey (y = 0 to 8) family of materials have been synthesized in both polycrystalline and single crystal form, and their structural and magnetic properties thoroughly investigated. Each of these materials crystallizes in the F[Formula: see text][Formula: see text]3m space group at ambient temperature. However, in contrast to the end members GaV4S8 and GaV4Se8, that undergo a structural transition to the R3m space group at 42 and 41 K respectively, the solid solutions (y = 1 to 7) retain cubic symmetry down to 1.5 K. In zero applied field the end members of the family order ferromagnetically at 13 K (GaV4S8) and 18 K (GaV4Se8), while the intermediate compounds exhibit a spin-glass-like ground state. We demonstrate that the magnetic structure of GaV4S8 shows localization of spins on the V cations, indicating that a charge ordering mechanism drives the structural phase transition. We conclude that the observation of both structural and ferromagnetic transitions in the end members of the series in zero field is a prerequisite for the stabilization of a skyrmion phase, and discuss how the absence of these transitions in the y = 1 to 7 materials can be explained by their structural properties.
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Affiliation(s)
- Aleš Štefančič
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom.
| | - Samuel J R Holt
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom
| | - Martin R Lees
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom
| | | | - Matthias J Gutmann
- ISIS Facility, Rutherford Appleton Laboratory, Oxfordshire, OX11 0QX, United Kingdom
| | - Tom Lancaster
- Durham University, Department of Physics, South Road, Durham, DH1 3LE, United Kingdom
| | - Geetha Balakrishnan
- University of Warwick, Department of Physics, Coventry, CV4 7AL, United Kingdom.
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22
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Wyżga P, Veremchuk I, Bobnar M, Koželj P, Klenner S, Pöttgen R, Leithe‐Jasper A, Gumeniuk R. Structural Peculiarities and Thermoelectric Study of Iron Indium Thiospinel. Chemistry 2020; 26:5245-5256. [PMID: 31943404 PMCID: PMC7216953 DOI: 10.1002/chem.201905665] [Citation(s) in RCA: 8] [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: 12/16/2019] [Revised: 01/14/2020] [Indexed: 11/07/2022]
Abstract
The homogeneity range of ternary iron indium thiospinel at 873 K was investigated. A detailed study was focused on two distinct series (y=z): 1) a previously reported charge-balanced (In0.67+0.33y □0.33-0.33y )tetr [In2-z Fez ]oct S4 (A1-series; □ stands for vacancy; the abbreviations "tetr" and "oct" indicate atoms occupying tetrahedral 8a and octahedral 16d sites, respectively) and 2) a new charge-unbalanced (In0.67+y □0.33-y )tetr [In2-z Fez ]oct S4 (A2-series). Fe atoms were confirmed to exclusively occupy an octahedral position in both series. An unusual reduction of the unit cell parameter with increasing Fe content is explained by differences in the ionic radii between Fe and In, as well as by an additional electrostatic attraction originating from charge imbalance (latter only in A2-series). The studied compound is an n-type semiconductor, and its charge carrier concentration increases or decreases for larger Fe content within the A1- and A2-series, respectively. The thermal conductivity κtot is significantly reduced upon increasing vacancy concentration, whereas the change of power factor is insufficient to drastically improve the thermoelectric figure of merit.
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Affiliation(s)
- Paweł Wyżga
- Institut für Experimentelle PhysikTU Bergakademie FreibergLeipziger Strasse 2309599FreibergGermany
- Max-Planck-Institut für Chemische Physik fester StoffeNöthnitzer Strasse 4001187DresdenGermany
| | - Igor Veremchuk
- Max-Planck-Institut für Chemische Physik fester StoffeNöthnitzer Strasse 4001187DresdenGermany
| | - Matej Bobnar
- Max-Planck-Institut für Chemische Physik fester StoffeNöthnitzer Strasse 4001187DresdenGermany
| | - Primož Koželj
- Max-Planck-Institut für Chemische Physik fester StoffeNöthnitzer Strasse 4001187DresdenGermany
| | - Steffen Klenner
- Institut für Anorganische und Analytische ChemieUniversität MünsterCorrensstrasse 348149MünsterGermany
| | - Rainer Pöttgen
- Institut für Anorganische und Analytische ChemieUniversität MünsterCorrensstrasse 348149MünsterGermany
| | - Andreas Leithe‐Jasper
- Max-Planck-Institut für Chemische Physik fester StoffeNöthnitzer Strasse 4001187DresdenGermany
| | - Roman Gumeniuk
- Institut für Experimentelle PhysikTU Bergakademie FreibergLeipziger Strasse 2309599FreibergGermany
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23
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Han MG, Garlow JA, Kharkov Y, Camacho L, Rov R, Sauceda J, Vats G, Kisslinger K, Kato T, Sushkov O, Zhu Y, Ulrich C, Söhnel T, Seidel J. Scaling, rotation, and channeling behavior of helical and skyrmion spin textures in thin films of Te-doped Cu 2OSeO 3. SCIENCE ADVANCES 2020; 6:eaax2138. [PMID: 32258389 PMCID: PMC7101222 DOI: 10.1126/sciadv.aax2138] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/04/2019] [Accepted: 01/03/2020] [Indexed: 06/11/2023]
Abstract
Topologically nontrivial spin textures such as vortices, skyrmions, and monopoles are promising candidates as information carriers for future quantum information science. Their controlled manipulation including creation and annihilation remains an important challenge toward practical applications and further exploration of their emergent phenomena. Here, we report controlled evolution of the helical and skyrmion phases in thin films of multiferroic Te-doped Cu2OSeO3 as a function of material thickness, dopant, temperature, and magnetic field using in situ Lorentz phase microscopy. We report two previously unknown phenomena in chiral spin textures in multiferroic Cu2OSeO3: anisotropic scaling and channeling with a fixed-Q state. The skyrmion channeling effectively suppresses the recently reported second skyrmion phase formation at low temperature. Our study provides a viable way toward controlled manipulation of skyrmion lattices, envisaging chirality-controlled skyrmion flow circuits and enabling precise measurement of emergent electromagnetic induction and topological Hall effects in skyrmion lattices.
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Affiliation(s)
- M.-G. Han
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - J. A. Garlow
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Y. Kharkov
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - L. Camacho
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
| | - R. Rov
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
- MacDiarmid Institute of Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington, New Zealand
| | - J. Sauceda
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - G. Vats
- School of Materials Science and Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
| | - K. Kisslinger
- Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - T. Kato
- Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya, Japan
| | - O. Sushkov
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Y. Zhu
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - C. Ulrich
- School of Physics, UNSW Sydney, Sydney, NSW 2052, Australia
| | - T. Söhnel
- School of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
- MacDiarmid Institute of Advanced Materials and Nanotechnology, Victoria University of Wellington, Wellington, New Zealand
| | - J. Seidel
- School of Materials Science and Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
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24
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Mochizuki M. Dynamical magnetoelectric phenomena of skyrmions in multiferroics. PHYSICAL SCIENCES REVIEWS 2020. [DOI: 10.1515/psr-2019-0017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Magnetic skyrmions, nanoscopic spin vortices carrying a quantized topological number in chiral-lattice magnets, are recently attracting great research interest. Although magnetic skyrmions had been observed only in metallic chiral-lattice magnets such as B20 alloys in the early stage of the research, their realization was discovered in 2012 also in an insulating chiral-lattice magnet
Cu
2
OSeO
3
$\textrm{Cu}_2\textrm{OSeO}_3$
. A characteristic of the insulating skyrmions is that they can host multiferroicity, that is, the noncollinear magnetization alignment of skyrmion induces electric polarizations in insulators with a help of the relativistic spin-orbit interaction. It was experimentally confirmed that the skyrmion phase in
Cu
2
OSeO
3
$\textrm{Cu}_2\textrm{OSeO}_3$
is indeed accompanied by the spin-induced ferroelectricity. The resulting strong magnetoelectric coupling between magnetizations and electric polarizations can provide us with a means to manipulate and activate magnetic skyrmions by application of electric fields. This is in sharp contrast to skyrmions in metallic systems, which are driven through injection of electric currents. The magnetoelectric phenomena specific to the skyrmion-based multiferroics are attracting intensive research interest, and, in particular, those in dynamical regime are widely recognized as an issue of vital importance because their understanding is crucial both for fundamental science and for technical applications. In this article, we review recent studies on multiferroic properties and dynamical magnetoelectric phenomena of magnetic skyrmions in insulating chiral-lattice magnet
Cu
2
OSeO
3
$\textrm{Cu}_2\textrm{OSeO}_3$
. It is argued that the multiferroic skyrmions show unique resonant excitation modes of coupled magnetizations and polarizations, so-called electromagnon excitations, which can be activated both magnetically with a microwave magnetic field and electrically with a microwave electric field. The interference between these two activation processes gives rise to peculiar phenomena in the gigahertz regime. As its representative example, we discuss a recent theoretical prediction of unprecedentedly large nonreciprocal directional dichroism of microwaves in the skyrmion phase of
Cu
2
OSeO
3
$\textrm{Cu}_2\textrm{OSeO}_3$
. This phenomenon can be regarded as a one-way window effect on microwaves, that is, the extent of microwave absorption changes significantly when its incident direction is reversed. This dramatic effect was indeed observed by subsequent experiments. These studies demonstrated that the multiferroic skyrmions can be a promising building block for microwave devices.
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Affiliation(s)
- Masahito Mochizuki
- Department of Applied Physics , Waseda University , 3-4-1 Okubo, Shinjuku-ku , Tokyo , 169-8050 , Japan
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25
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Abstract
Abstract
Multiferroic materials, showing ordering of both electrical and magnetic degrees of freedom, are promising candidates enabling the design of novel electronic devices. Various mechanisms ranging from geometrically or spin-driven improper ferroelectricity via lone-pairs, charge-order or -transfer support multiferroicity in single-phase or composite compounds. The search for materials showing these effects constitutes one of the most important research fields in solid-state physics during the last years, but scientific interest even traces back to the middle of the past century. Especially, a potentially strong coupling between spin and electric dipoles captured the interest to control via an electric field the magnetization or via a magnetic field the electric polarization. This would imply a promising route for novel electronics. Here, we provide a review about the dielectric and ferroelectric properties of various multiferroic systems ranging from type I multiferroics, in which magnetic and ferroelectric order develop almost independently of each other, to type II multiferroics, which exhibit strong coupling of magnetic and ferroelectric ordering. We thoroughly discuss the dielectric signatures of the ferroelectric polarization for BiFeO3, Fe3O4, DyMnO3 and an organic charge-transfer salt as well as show electric-field poling studies for the hexagonal manganites and a spin-spiral system LiCuVO4.
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26
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Padmanabhan P, Sekiguchi F, Versteeg RB, Slivina E, Tsurkan V, Bordács S, Kézsmárki I, van Loosdrecht PHM. Optically Driven Collective Spin Excitations and Magnetization Dynamics in the Néel-type Skyrmion Host GaV_{4}S_{8}. PHYSICAL REVIEW LETTERS 2019; 122:107203. [PMID: 30932635 DOI: 10.1103/physrevlett.122.107203] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 02/08/2019] [Indexed: 06/09/2023]
Abstract
GaV_{4}S_{8} is a multiferroic semiconductor hosting magnetic cycloid (Cyc) and Néel-type skyrmion lattice (SkL) phases with a broad region of thermal and magnetic stability. Here, we use time-resolved magneto-optical Kerr spectroscopy to show the coherent generation of collective spin excitations in the Cyc and SkL phases. Our micromagnetic simulations reveal that these are driven by an optically induced modulation of uniaxial anisotropy. Our results shed light on spin dynamics in anisotropic materials hosting skyrmions and pave a new pathway for the optical manipulation of their magnetic order.
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Affiliation(s)
- P Padmanabhan
- Physics Institute II, University of Cologne, 50937 Cologne, Germany
| | - F Sekiguchi
- Physics Institute II, University of Cologne, 50937 Cologne, Germany
| | - R B Versteeg
- Physics Institute II, University of Cologne, 50937 Cologne, Germany
| | - E Slivina
- Physics Institute II, University of Cologne, 50937 Cologne, Germany
| | - V Tsurkan
- Institute of Applied Physics, MD 2028, Chisinau, Republic of Moldova
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - S Bordács
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
- Hungarian Academy of Sciences, Premium Postdoctoral Program, 1051 Budapest, Hungary
| | - I Kézsmárki
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
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27
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Okamura Y, Seki S, Bordács S, Butykai Á, Tsurkan V, Kézsmárki I, Tokura Y. Microwave Directional Dichroism Resonant with Spin Excitations in the Polar Ferromagnet GaV_{4}S_{8}. PHYSICAL REVIEW LETTERS 2019; 122:057202. [PMID: 30822005 DOI: 10.1103/physrevlett.122.057202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Indexed: 06/09/2023]
Abstract
We have investigated the directional dichroism of magnetic resonance spectra in the polar ferromagnet GaV_{4}S_{8}. While four types of structural domains are energetically degenerated under a zero field, the magnetic resonance for each domain is well separated by applying magnetic fields due to uniaxial magnetic anisotropy. Consequently, a directional dichroism as large as 20% is clearly observed without domain cancellation. The present observation therefore demonstrates that not only magnetoelectric monodomain crystals but also magnetoelectric multidomain specimens can be used to realize microwave (optical) diodes owing to the lack of inversion domains.
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Affiliation(s)
- Y Okamura
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
| | - S Seki
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
| | - S Bordács
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendulet Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
- Hungarian Academy of Sciences, Premium Postdoctor Program, 1051 Budapest, Hungary
| | - Á Butykai
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendulet Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86159 Augsburg, Germany
| | - I Kézsmárki
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendulet Magneto-optical Spectroscopy Research Group, 1111 Budapest, Hungary
| | - Y Tokura
- Department of Applied Physics and Quantum Phase Electronics Center, University of Tokyo, Tokyo 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
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28
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Wang L, Feng Q, Kim Y, Kim R, Lee KH, Pollard SD, Shin YJ, Zhou H, Peng W, Lee D, Meng W, Yang H, Han JH, Kim M, Lu Q, Noh TW. Ferroelectrically tunable magnetic skyrmions in ultrathin oxide heterostructures. NATURE MATERIALS 2018; 17:1087-1094. [PMID: 30397313 DOI: 10.1038/s41563-018-0204-4] [Citation(s) in RCA: 95] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 09/21/2018] [Indexed: 06/08/2023]
Abstract
Magnetic skyrmions are topologically protected whirling spin texture. Their nanoscale dimensions, topologically protected stability and solitonic nature, together are promising for future spintronics applications. To translate these compelling features into practical spintronic devices, a key challenge lies in achieving effective control of skyrmion properties, such as size, density and thermodynamic stability. Here, we report the discovery of ferroelectrically tunable skyrmions in ultrathin BaTiO3/SrRuO3 bilayer heterostructures. The ferroelectric proximity effect at the BaTiO3/SrRuO3 heterointerface triggers a sizeable Dzyaloshinskii-Moriya interaction, thus stabilizing robust skyrmions with diameters less than a hundred nanometres. Moreover, by manipulating the ferroelectric polarization of the BaTiO3 layer, we achieve local, switchable and nonvolatile control of both skyrmion density and thermodynamic stability. This ferroelectrically tunable skyrmion system can simultaneously enhance the integratability and addressability of skyrmion-based functional devices.
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Affiliation(s)
- Lingfei Wang
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea.
| | - Qiyuan Feng
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China
| | - Yoonkoo Kim
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul, Republic of Korea
| | - Rokyeon Kim
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea
| | - Ki Hoon Lee
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea
| | - Shawn D Pollard
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
| | - Yeong Jae Shin
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea
| | - Haibiao Zhou
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
| | - Wei Peng
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea
| | - Daesu Lee
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea
| | - Wenjie Meng
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China
| | - Hyunsoo Yang
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
| | - Jung Hoon Han
- Department of Physics, Sungkyunkwan University, Suwon, Republic of Korea
| | - Miyoung Kim
- Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul, Republic of Korea
| | - Qingyou Lu
- Anhui Province Key Laboratory of Condensed Matter Physics at Extreme Conditions, High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, Anhui, China.
- Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei, Anhui, China.
| | - Tae Won Noh
- Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul, Republic of Korea.
- Department of Physics and Astronomy, Seoul National University, Seoul, Republic of Korea.
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29
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Neuber E, Milde P, Butykai A, Bordacs S, Nakamura H, Waki T, Tabata Y, Geirhos K, Lunkenheimer P, Kézsmárki I, Ondrejkovic P, Hlinka J, Eng LM. Architecture of nanoscale ferroelectric domains in GaMo 4S 8. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:445402. [PMID: 30255852 DOI: 10.1088/1361-648x/aae448] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Local-probe imaging of the ferroelectric domain structure and auxiliary bulk pyroelectric measurements were conducted at low temperatures with the aim to clarify the essential aspects of the orbitally driven phase transition in GaMo4S8, a lacunar spinel crystal that can be viewed as a spin-hole analogue of its GaV4S8 counterpart. We employed multiple scanning probe techniques combined with symmetry and mechanical compatibility analysis to uncover the hierarchical domain structures, developing on the 10-100 nm scale. The identified domain architecture involves a plethora of ferroelectric domain boundaries and junctions, including primary and secondary domain walls in both electrically neutral and charged configurations, and topological line defects transforming neutral secondary walls into two oppositely charged ones.
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Affiliation(s)
- Erik Neuber
- Institute of Applied Physics, Technische Universität Dresden, D-01062 Dresden, Germany
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30
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Weiler M, Aqeel A, Mostovoy M, Leonov A, Geprägs S, Gross R, Huebl H, Palstra TTM, Goennenwein STB. Helimagnon Resonances in an Intrinsic Chiral Magnonic Crystal. PHYSICAL REVIEW LETTERS 2017; 119:237204. [PMID: 29286698 DOI: 10.1103/physrevlett.119.237204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Indexed: 06/07/2023]
Abstract
We experimentally study magnetic resonances in the helical and conical magnetic phases of the chiral magnetic insulator Cu_{2}OSeO_{3} at the temperature T=5 K. Using a broadband microwave spectroscopy technique based on vector network analysis, we identify three distinct sets of helimagnon resonances in the frequency range 2 GHz≤f≤20 GHz with low magnetic damping α≤0.003. The extracted resonance frequencies are in accordance with calculations of the helimagnon band structure found in an intrinsic chiral magnonic crystal. The periodic modulation of the equilibrium spin direction that leads to the formation of the magnonic crystal is a direct consequence of the chiral magnetic ordering caused by the Dzyaloshinskii-Moriya interaction. The mode coupling in the magnonic crystal allows excitation of helimagnons with wave vectors that are multiples of the spiral wave vector.
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Affiliation(s)
- Mathias Weiler
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
| | - Aisha Aqeel
- Zernike Institute for Advanced Materials, University of Groningen, 9700 AB Groningen, The Netherlands
| | - Maxim Mostovoy
- Zernike Institute for Advanced Materials, University of Groningen, 9700 AB Groningen, The Netherlands
| | - Andrey Leonov
- Zernike Institute for Advanced Materials, University of Groningen, 9700 AB Groningen, The Netherlands
- Center for Chiral Science, Hiroshima University, Hiroshima 739-8526, Japan
| | - Stephan Geprägs
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
| | - Rudolf Gross
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Nanosystems Initiative Munich, 80799 Munich, Germany
| | - Hans Huebl
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Nanosystems Initiative Munich, 80799 Munich, Germany
| | - Thomas T M Palstra
- Zernike Institute for Advanced Materials, University of Groningen, 9700 AB Groningen, The Netherlands
| | - Sebastian T B Goennenwein
- Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany
- Physik-Department, Technische Universität München, 85748 Garching, Germany
- Nanosystems Initiative Munich, 80799 Munich, Germany
- Institut für Festkörper- und Materialphysik, Technische Universität Dresden, 01062 Dresden, Germany
- Center for Transport and Devices of Emergent Materials, Technische Universität Dresden, 01062 Dresden, Germany
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31
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Bordács S, Butykai A, Szigeti BG, White JS, Cubitt R, Leonov AO, Widmann S, Ehlers D, von Nidda HAK, Tsurkan V, Loidl A, Kézsmárki I. Equilibrium Skyrmion Lattice Ground State in a Polar Easy-plane Magnet. Sci Rep 2017; 7:7584. [PMID: 28790441 PMCID: PMC5548730 DOI: 10.1038/s41598-017-07996-x] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2017] [Accepted: 07/04/2017] [Indexed: 11/09/2022] Open
Abstract
The skyrmion lattice state (SkL), a crystal built of mesoscopic spin vortices, gains its stability via thermal fluctuations in all bulk skyrmion host materials known to date. Therefore, its existence is limited to a narrow temperature region below the paramagnetic state. This stability range can drastically increase in systems with restricted geometries, such as thin films, interfaces and nanowires. Thermal quenching can also promote the SkL as a metastable state over extended temperature ranges. Here, we demonstrate more generally that a proper choice of material parameters alone guarantees the thermodynamic stability of the SkL over the full temperature range below the paramagnetic state down to zero kelvin. We found that GaV4Se8, a polar magnet with easy-plane anisotropy, hosts a robust Néel-type SkL even in its ground state. Our supporting theory confirms that polar magnets with weak uniaxial anisotropy are ideal candidates to realize SkLs with wide stability ranges.
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Affiliation(s)
- S Bordács
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary
| | - A Butykai
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary
| | - B G Szigeti
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary
| | - J S White
- Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institut, CH-5232, Villigen, Switzerland
| | - R Cubitt
- Institut Laue-Langevin, 6 rue Jules Horowitz, 38042, Grenoble, France
| | - A O Leonov
- Center for Chiral Science, Hiroshima University, Higashi-Hiroshima, Hiroshima, 739-8526, Japan.,Department of Chemistry, Faculty of Science, Hiroshima University Kagamiyama, Higashi Hiroshima, Hiroshima, 739-8526, Japan
| | - S Widmann
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - D Ehlers
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - H-A Krug von Nidda
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - V Tsurkan
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany.,Institute of Applied Physics, Academy of Sciences of Moldova, MD, 2028, Chisinau, Republic of Moldova
| | - A Loidl
- Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany
| | - I Kézsmárki
- Department of Physics, Budapest University of Technology and Economics and MTA-BME Lendület Magneto-optical Spectroscopy Research Group, 1111, Budapest, Hungary. .,Experimental Physics V, Center for Electronic Correlations and Magnetism, University of Augsburg, 86135, Augsburg, Germany.
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32
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Kanazawa N, Seki S, Tokura Y. Noncentrosymmetric Magnets Hosting Magnetic Skyrmions. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2017; 29:1603227. [PMID: 28306166 DOI: 10.1002/adma.201603227] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Revised: 11/30/2016] [Indexed: 06/06/2023]
Abstract
The concept of a skyrmion, which was first introduced by Tony Skyrme in the field of particle physics, has become widespread in condensed matter physics to describe various topological orders. Skyrmions in magnetic materials have recently received particular attention; they represent vortex-like spin structures with the character of nanometric particles and produce fascinating physical properties rooted in their topological nature. Here, a series of noncentrosymmetric ferromagnets hosting skyrmions is reviewed: B20 metals, Cu2 OSeO3 , Co-Zn-Mn alloys, and GaV4 S8 , where Dzyaloshinskii-Moriya interaction plays a key role in the stabilization of skyrmion spin texture. Their topological spin arrangements and consequent emergent electromagnetic fields give rise to striking features in transport and magnetoelectric properties in metals and insulators, such as the topological Hall effect, efficient electric-drive of skyrmions, and multiferroic behavior. Such electric controllability and nanometric particle natures highlight magnetic skyrmions as a potential information carrier for high-density magnetic storage devices with excellent energy efficiency.
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Affiliation(s)
- Naoya Kanazawa
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
| | - Shinichiro Seki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
| | - Yoshinori Tokura
- Department of Applied Physics, University of Tokyo, Tokyo, 113-8656, Japan
- RIKEN Center for Emergent Matter Science (CEMS), Wako, 351-0198, Japan
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33
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Characteristics of ferroelectric-ferroelastic domains in Néel-type skyrmion host GaV 4S 8. Sci Rep 2017; 7:44663. [PMID: 28294193 PMCID: PMC5353724 DOI: 10.1038/srep44663] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/13/2017] [Indexed: 11/19/2022] Open
Abstract
GaV4S8 is a multiferroic semiconductor hosting Néel-type magnetic skyrmions dressed with electric polarization. At Ts = 42 K, the compound undergoes a structural phase transition of weakly first-order, from a non-centrosymmetric cubic phase at high temperatures to a polar rhombohedral structure at low temperatures. Below Ts, ferroelectric domains are formed with the electric polarization pointing along any of the four 〈111〉 axes. Although in this material the size and the shape of the ferroelectric-ferroelastic domains may act as important limiting factors in the formation of the Néel-type skyrmion lattice emerging below TC = 13 K, the characteristics of polar domains in GaV4S8 have not been studied yet. Here, we report on the inspection of the local-scale ferroelectric domain distribution in rhombohedral GaV4S8 using low-temperature piezoresponse force microscopy. We observed mechanically and electrically compatible lamellar domain patterns, where the lamellae are aligned parallel to the (100)-type planes with a typical spacing between 100 nm–1.2 μm. Since the magnetic pattern, imaged by atomic force microscopy using a magnetically coated tip, abruptly changes at the domain boundaries, we expect that the control of ferroelectric domain size in polar skyrmion hosts can be exploited for the spatial confinement and manipulation of Néel-type skyrmions.
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Ehlers D, Stasinopoulos I, Kézsmárki I, Fehér T, Tsurkan V, von Nidda HAK, Grundler D, Loidl A. Exchange anisotropy in the skyrmion host GaV 4S 8. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:065803. [PMID: 28002048 DOI: 10.1088/1361-648x/aa4e7e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Using ferromagnetic resonance spectroscopy at 34 GHz we explored the magnetic anisotropy of single-crystalline GaV4S8 in the field-polarized magnetic state. We describe the data in terms of an easy-axis type uniaxial anisotropy with an anisotropy constant [Formula: see text] erg cm-3 at 2 K, corresponding to a relative exchange anisotropy [Formula: see text]%, and about [Formula: see text]erg cm-3 near 11 K, i.e. at temperatures where the skyrmion-lattice phase was recently discovered. The relatively large value of K 1 explains the confinement of the skyrmion tubes to the [Formula: see text] easy axes. A distinct set of resonances in the spectra is attributed to the co-existence of different rhombohedral domains. Complementary broadband spectroscopy demonstrates that non-collinear spin states may sensitively be detected by electron spin resonance techniques.
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Affiliation(s)
- D Ehlers
- Experimentalphysik V, Zentrum für elektronische Korrelationen und Magnetismus, Universität Augsburg, 86135 Augsburg, Germany
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