1
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Li D, Haldar S, Heinze S. Proposal for All-Electrical Skyrmion Detection in van der Waals Tunnel Junctions. NANO LETTERS 2024; 24:2496-2502. [PMID: 38350134 DOI: 10.1021/acs.nanolett.3c04238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2024]
Abstract
A major challenge for magnetic skyrmions in atomically thin van der Waals (vdW) materials is reliable skyrmion detection. Here, based on rigorous first-principles calculations, we show that all-electrical skyrmion detection is feasible in two-dimensional vdW magnets via scanning tunneling microscopy (STM) and in planar tunnel junctions. We use the nonequilibrium Green's function method for quantum transport in planar junctions, including self-energy due to electrodes and working conditions, going beyond the standard Tersoff-Hamann approximation. We obtain a very large tunneling anisotropic magnetoresistance (TAMR) around the Fermi energy for a graphite/Fe3GeTe2/germanene/graphite vdW tunnel junction. For atomic-scale skyrmions, the noncollinear magnetoresistance (NCMR) reaches giant values. We trace the origin of the NCMR to spin mixing between spin-up and -down states of pz and dz2 character at the surface atoms. Both TAMR and NCMR are drastically enhanced in tunnel junctions with respect to STM geometry due to orbital symmetry matching at the interface.
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Affiliation(s)
- Dongzhe Li
- CEMES, Université de Toulouse, CNRS, 29 rue Jeanne Marvig, F-31055 Toulouse, France
| | - Soumyajyoti Haldar
- Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstrasse 15, 24098 Kiel, Germany
| | - Stefan Heinze
- Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstrasse 15, 24098 Kiel, Germany
- Kiel Nano, Surface and Interface Science (KiNSIS), University of Kiel, 24118 Kiel, Germany
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2
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Bera S. Role of isotropic and anisotropic Dzyaloshinskii-Moriya interaction on skyrmions, merons and antiskyrmions in the Cnvsymmetric system. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2024; 36:195805. [PMID: 38316047 DOI: 10.1088/1361-648x/ad266f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Accepted: 02/05/2024] [Indexed: 02/07/2024]
Abstract
The lattice Hamiltonian with the presence of a chiral magnetic isotropic Dzyaloshinskii-Moriya interaction (DMI) in a square and hexagonal lattice is numerically solved to give the full phase diagram consisting of skyrmions and merons in different parameter planes. The phase diagram provides the actual regions of analytically unresolved asymmetric skyrmions and merons, and it is found that these regions are substantially larger than those of symmetric skyrmions and merons. With magnetic field, a change from meron or spin spiral (SS) to skyrmion is seen. The complete phase diagram for theCnvsymmetric system with anisotropic DMI is drawn and it is shown that this DMI helps to change the SS propagation direction. Finally, the well-defined region of a thermodynamically stable antiskyrmion phase in theCnvsymmetric system is shown.
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Affiliation(s)
- Sandip Bera
- Department of Physics, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7, Canada
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3
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Castell-Queralt J, Abad-López G, González-Gómez L, Del-Valle N, Navau C. Survival of skyrmions along granular racetracks at room temperature. NANOSCALE ADVANCES 2023; 5:4728-4734. [PMID: 37705781 PMCID: PMC10496888 DOI: 10.1039/d3na00464c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 07/27/2023] [Indexed: 09/15/2023]
Abstract
Skyrmions can be envisioned as bits of information that can be transported along nanoracetracks. However, temperature, defects, and/or granularity can produce diffusion, pinning, and, in general, modification in their dynamics. These effects may cause undesired errors in information transport. We present simulations of a realistic system where both the (room) temperature and sample granularity are taken into account. Key feasibility magnitudes, such as the success probability of a skyrmion traveling a given distance along the racetrack, are calculated. The results are evaluated in terms of the eventual loss of skyrmions by pinning, destruction at the edges, or excessive delay due to granularity. The model proposed is based on the Fokker-Planck equation resulting from Thiele's rigid model for skyrmions. The results could serve to establish error detection criteria and, in general, to discern the dynamics of skyrmions in realistic situations.
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Affiliation(s)
- Josep Castell-Queralt
- Departament de Física, Universitat Autònoma de Barcelona 08193 Bellaterra Barcelona Catalonia Spain
| | - Guillermo Abad-López
- Departament de Física, Universitat Autònoma de Barcelona 08193 Bellaterra Barcelona Catalonia Spain
| | - Leonardo González-Gómez
- Departament de Física, Universitat Autònoma de Barcelona 08193 Bellaterra Barcelona Catalonia Spain
| | - Nuria Del-Valle
- Departament de Física, Universitat Autònoma de Barcelona 08193 Bellaterra Barcelona Catalonia Spain
| | - Carles Navau
- Departament de Física, Universitat Autònoma de Barcelona 08193 Bellaterra Barcelona Catalonia Spain
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4
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Graham JN, Qureshi N, Ritter C, Manuel P, Wildes AR, Clark L. Experimental Evidence for the Spiral Spin Liquid in LiYbO_{2}. PHYSICAL REVIEW LETTERS 2023; 130:166703. [PMID: 37154642 DOI: 10.1103/physrevlett.130.166703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2023] [Accepted: 03/20/2023] [Indexed: 05/10/2023]
Abstract
Spiral spin liquids are an exotic class of correlated paramagnets with an enigmatic magnetic ground state composed of a degenerate manifold of fluctuating spin spirals. Experimental realizations of the spiral spin liquid are scarce, mainly due to the prominence of structural distortions in candidate materials that can trigger order-by-disorder transitions to more conventionally ordered magnetic ground states. Expanding the pool of candidate materials that may host a spiral spin liquid is therefore crucial to realizing this novel magnetic ground state and understanding its robustness against perturbations that arise in real materials. Here, we show that the material LiYbO_{2} is the first experimental realization of a spiral spin liquid predicted to emerge from the J_{1}-J_{2} Heisenberg model on an elongated diamond lattice. Through a complementary combination of high-resolution and diffuse neutron magnetic scattering studies on a polycrystalline sample, we demonstrate that LiYbO_{2} fulfills the requirements for the experimental realization of the spiral spin liquid and reconstruct single-crystal diffuse neutron magnetic scattering maps that reveal continuous spiral spin contours-a characteristic experimental hallmark of this exotic magnetic phase.
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Affiliation(s)
- J N Graham
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
- Institut Laue-Langevin, 71 avenue des Martyrs, CS20156, 38042 Grenoble Cédex 9, France
| | - N Qureshi
- Institut Laue-Langevin, 71 avenue des Martyrs, CS20156, 38042 Grenoble Cédex 9, France
| | - C Ritter
- Institut Laue-Langevin, 71 avenue des Martyrs, CS20156, 38042 Grenoble Cédex 9, France
| | - P Manuel
- ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, United Kingdom
| | - A R Wildes
- Institut Laue-Langevin, 71 avenue des Martyrs, CS20156, 38042 Grenoble Cédex 9, France
| | - L Clark
- School of Chemistry, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom
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5
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Ruiz-Gómez S, Pérez L, Mascaraque A, Santos B, El Gabaly F, Schmid AK, de la Figuera J. Stacking influence on the in-plane magnetic anisotropy in a 2D magnetic system. NANOSCALE 2023; 15:8313-8319. [PMID: 37083943 DOI: 10.1039/d3nr00348e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The magnetization patterns on three atomic layers thick islands of Co on Ru(0001) are studied by spin-polarized low-energy electron microscopy (SPLEEM). In-plane magnetized micrometer wide triangular Co islands are grown on Ru(0001). They present two different orientations correlated with two different stacking sequences which differ only in the last layer position. The stacking sequence determines the type of magnetization pattern observed: the hcp islands present very wide domain walls, while the fcc islands present domains separated by much narrower domain walls. The former is an extremely low in-plane anisotropy system. We estimate the in-plane magnetic anisotropy of the fcc regions to be 1.96 × 104 J m-3 and of the hcp ones to be 2.5 × 102 J m-3.
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Affiliation(s)
- Sandra Ruiz-Gómez
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
| | - Lucas Pérez
- Dept. Física de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- "Surface Science and Magnetism of Low Dimensional Systems", UCM, Unidad Asociada al IQFR-CSIC, 28040 Madrid, Spain
- IMDEA Nanociencia, 28049 Madrid, Spain
| | - Arantzazu Mascaraque
- Dept. Física de Materiales, Universidad Complutense de Madrid, 28040 Madrid, Spain
- "Surface Science and Magnetism of Low Dimensional Systems", UCM, Unidad Asociada al IQFR-CSIC, 28040 Madrid, Spain
| | - Benito Santos
- Instituto Regional de Investigación Científica Aplicada (IRICA), 13005 Ciudad Real, Spain
- Dept. Física Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
| | - Farid El Gabaly
- Sandia National Laboratories, Livermore, California 94550, USA
| | - Andreas K Schmid
- Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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6
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Ahrens V, Kiesselbach C, Gnoli L, Giuliano D, Mendisch S, Kiechle M, Riente F, Becherer M. Skyrmions Under Control-FIB Irradiation as a Versatile Tool for Skyrmion Circuits. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2023; 35:e2207321. [PMID: 36255142 DOI: 10.1002/adma.202207321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Magnetic data storage and processing offer certain advances over conventional technologies, amongst which nonvolatility and low power operation are the most outstanding ones. Skyrmions are a promising candidate as a magnetic data carrier. However, the sputtering of skyrmion films and the control of the skyrmion nucleation, motion, and annihilation remains challenging. This work demonstrates that using optimized focused ion beam irradiation and annealing protocols enables the skyrmion phase in W/CoFeB/MgO thin films to be accessed easily. By analyzing ion-beam-engineered skyrmion hosting wires, excited by sub-100 ns current pulses, possibilities to control skyrmion nucleation, guide their motion, and control their annihilation unfold. Overall, the key elements needed to develop extensive skyrmion networks are presented.
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Affiliation(s)
- Valentin Ahrens
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Clara Kiesselbach
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Luca Gnoli
- Department of Electronics and Telecommunications, Politecnico di Torino, Torino, 10129, Italy
| | - Domenico Giuliano
- Department of Electronics and Telecommunications, Politecnico di Torino, Torino, 10129, Italy
| | - Simon Mendisch
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Martina Kiechle
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
| | - Fabrizio Riente
- Department of Electronics and Telecommunications, Politecnico di Torino, Torino, 10129, Italy
| | - Markus Becherer
- Department of Electrical and Computer Engineering, Technical University of Munich, 85748, Garching, Germany
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7
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Lu Q, Liu Z, Yang Q, Cao H, Balakrishnan P, Wang Q, Cheng L, Lu Y, Zuo JM, Zhou H, Quarterman P, Muramoto S, Grutter AJ, Chen H, Zhai X. Engineering Magnetic Anisotropy and Emergent Multidirectional Soft Ferromagnetism in Ultrathin Freestanding LaMnO 3 Films. ACS NANO 2022; 16:7580-7588. [PMID: 35446560 DOI: 10.1021/acsnano.1c11065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The combination of small coercive fields and weak magnetic anisotropy makes soft ferromagnetic films extremely useful for nanoscale devices that need to easily switch spin directions. However, soft ferromagnets are relatively rare, particularly in ultrathin films with thicknesses of a few nanometers or less. We have synthesized large-area, high-quality, ultrathin freestanding LaMnO3 films on Si and found unexpected soft ferromagnetism along both the in-plane and out-of-plane directions when the film thickness was reduced to 4 nm. We argue that the vanishing magnetic anisotropy between the two directions is a consequence of two coexisting magnetic easy axes in different atomic layers of the LaMnO3 film. Spectroscopy measurements reveal a change in Mn valence from 3+ in the film interior to approximately 2+ at the surfaces where considerable hydrogen infiltration occurs due to the water dissolving process. First-principles calculations show that protonation of LaMnO3 decreases the Mn valence and switches the magnetic easy axis from in-plane to out-of-plane as the Mn valence approaches 2+ from its 3+ bulk value. Our work demonstrates that ultrathin freestanding films can exhibit functional properties that are absent in homogeneous materials, concomitant with their convenient compatibility with Si-based devices.
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Affiliation(s)
- Qinwen Lu
- Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Zhiwei Liu
- Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Science, East China Normal University, Shanghai 200241, China
- NYU-ECNU Institute of Physics, NYU Shanghai, Shanghai 200122, China
| | - Qun Yang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Hui Cao
- Materials Science Division, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Purnima Balakrishnan
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Qing Wang
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Long Cheng
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
| | - Yalin Lu
- Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026, China
| | - Jian-Min Zuo
- Department of Materials Science and Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
- Materials Research Laboratory, University of Illinois Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Hua Zhou
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States
| | - Patrick Quarterman
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Shin Muramoto
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Alexander J Grutter
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
| | - Hanghui Chen
- NYU-ECNU Institute of Physics, NYU Shanghai, Shanghai 200122, China
- Department of Physics, New York University, New York, New York 10012, United States
| | - Xiaofang Zhai
- School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China
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8
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Huang C, Jiang LZ, Zhu Y, Pan YF, Fan JY, Ma CL, Hu J, Shi DN. Tuning Dzyaloshinskii-Moriya interaction via an electric field at the Co/h-BN interface. Phys Chem Chem Phys 2021; 23:22246-22250. [PMID: 34586123 DOI: 10.1039/d1cp02554f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Dzyaloshinsky-Moriya interaction (DMI) at the Co/h-BN interface can emerge and be enhanced by applying a downward electric field. The height of the Co atom relative to the h-BN layer with the electric field determines the variation of DMI. One half reduction of J1 is beneficial to generate skyrmions. Tuning the DMI by an electric field sheds new light for research on skyrmions.
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Affiliation(s)
- C Huang
- College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. .,MIIT Key Laboratory of Aerospace Information Materials and Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China.
| | - L Z Jiang
- College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. .,MIIT Key Laboratory of Aerospace Information Materials and Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China.
| | - Y Zhu
- College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. .,MIIT Key Laboratory of Aerospace Information Materials and Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China.
| | - Y F Pan
- College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. .,MIIT Key Laboratory of Aerospace Information Materials and Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China.
| | - J Y Fan
- College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. .,MIIT Key Laboratory of Aerospace Information Materials and Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China.
| | - C L Ma
- Jiangsu Key Laboratory of Micro and Nano Heat Fluid Flow Technology and Energy Application, School of Physical Science and Technology, Suzhou University of Science and Technology, Suzhou, 215009, China
| | - J Hu
- School of Physical Science and Technology, Ningbo University, Ningbo 315211, China.
| | - D N Shi
- College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China. .,MIIT Key Laboratory of Aerospace Information Materials and Physics, Nanjing University of Aeronautics and Astronautics, Nanjing 211106, China.
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9
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Ukpong AM. Emergence of Nontrivial Spin Textures in Frustrated Van Der Waals Ferromagnets. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:1770. [PMID: 34361155 PMCID: PMC8308132 DOI: 10.3390/nano11071770] [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: 04/27/2021] [Revised: 06/11/2021] [Accepted: 06/12/2021] [Indexed: 11/16/2022]
Abstract
In this work, first principles ground state calculations are combined with the dynamic evolution of a classical spin Hamiltonian to study the metamagnetic transitions associated with the field dependence of magnetic properties in frustrated van der Waals ferromagnets. Dynamically stabilized spin textures are obtained relative to the direction of spin quantization as stochastic solutions of the Landau-Lifshitz-Gilbert-Slonczewski equation under the flow of the spin current. By explicitly considering the spin signatures that arise from geometrical frustrations at interfaces, we may observe the emergence of a magnetic skyrmion spin texture and characterize the formation under competing internal fields. The analysis of coercivity and magnetic hysteresis reveals a dynamic switch from a soft to hard magnetic configuration when considering the spin Hall effect on the skyrmion. It is found that heavy metals in capped multilayer heterostructure stacks host field-tunable spiral skyrmions that could serve as unique channels for carrier transport. The results are discussed to show the possibility of using dynamically switchable magnetic bits to read and write data without the need for a spin transfer torque. These results offer insight to the spin transport signatures that dynamically arise from metamagnetic transitions in spintronic devices.
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Affiliation(s)
- Aniekan Magnus Ukpong
- Theoretical and Computational Condensed Matter and Materials Physics Group, School of Chemistry and Physics, University of KwaZulu-Natal, Pietermaritzburg 3201, South Africa
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10
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Bera S, Mandal SS. Skyrmions at vanishingly small Dzyaloshinskii-Moriya interaction or zero magnetic field. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:255801. [PMID: 33848984 DOI: 10.1088/1361-648x/abf783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 04/13/2021] [Indexed: 06/12/2023]
Abstract
By introducing biquadratic together with usual bilinear ferromagnetic nearest neighbor exchange interaction in a square lattice, we find that the energy of the spin-wave mode is minimized at a finite wavevector for a vanishingly small Dzyaloshinskii-Moriya interaction (DMI), supporting a ground state with spin-spiral structure whose pitch length is unusually short as found in some of the experiments. Apart from reproducing the magnetic structures that can be obtained in a canonical model with nearest neighbor exchange interaction only, a numerical simulation of this model with further introduction of magnetic anisotropy and magnetic field predicts many other magnetic structures some of which are already observed in the experiments. Among many observed structures, nanoscale skyrmion even at vanishingly small DMI is found for the first time in a model. The model provides the nanoscale skyrmions of unit topological charge at zero magnetic field as well. We obtain phase diagrams for all the magnetic structures predicted in the model.
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Affiliation(s)
- Sandip Bera
- Department of Physics, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
| | - Sudhansu S Mandal
- Department of Physics, Indian Institute of Technology, Kharagpur, West Bengal 721302, India
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11
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Petrović AP, Raju M, Tee XY, Louat A, Maggio-Aprile I, Menezes RM, Wyszyński MJ, Duong NK, Reznikov M, Renner C, Milošević MV, Panagopoulos C. Skyrmion-(Anti)Vortex Coupling in a Chiral Magnet-Superconductor Heterostructure. PHYSICAL REVIEW LETTERS 2021; 126:117205. [PMID: 33798341 DOI: 10.1103/physrevlett.126.117205] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 01/14/2021] [Indexed: 06/12/2023]
Abstract
We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ≈50 nm is sufficient to nucleate antivortices in a 25 nm Nb film, with unique signatures in the magnetization, critical current, and flux dynamics, corroborated via simulations. We also detect a thermally tunable Rashba-Edelstein exchange coupling in the isolated skyrmion phase. This realization of a strongly interacting skyrmion-(anti)vortex system opens a path toward controllable topological hybrid materials, unattainable to date.
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Affiliation(s)
- A P Petrović
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
| | - M Raju
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
| | - X Y Tee
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
| | - A Louat
- Department of Physics, Technion, Haifa 32000, Israel
| | - I Maggio-Aprile
- Department of Quantum Matter Physics, Université de Genève, 24 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - R M Menezes
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
- Departamento de Física, Universidade Federal de Pernambuco, Cidade Universitária, 50670-901 Recife-PE, Brazil
| | - M J Wyszyński
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - N K Duong
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
| | - M Reznikov
- Department of Physics, Technion, Haifa 32000, Israel
| | - Ch Renner
- Department of Quantum Matter Physics, Université de Genève, 24 Quai Ernest Ansermet, CH-1211 Geneva 4, Switzerland
| | - M V Milošević
- Department of Physics, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp, Belgium
| | - C Panagopoulos
- Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore
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12
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Meijer MJ, Lucassen J, Duine RA, Swagten HJ, Koopmans B, Lavrijsen R, Guimarães MHD. Chiral Spin Spirals at the Surface of the van der Waals Ferromagnet Fe 3GeTe 2. NANO LETTERS 2020; 20:8563-8568. [PMID: 33238096 PMCID: PMC7729936 DOI: 10.1021/acs.nanolett.0c03111] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 11/10/2020] [Indexed: 05/28/2023]
Abstract
Topologically protected magnetic structures provide a robust platform for low power consumption devices for computation and data storage. Examples of these structures are skyrmions, chiral domain walls, and spin spirals. Here, we use scanning electron microscopy with polarization analysis to unveil the presence of chiral counterclockwise Néel spin spirals at the surface of a bulk van der Waals ferromagnet Fe3GeTe2 (FGT) at zero magnetic field. These Néel spin spirals survive up to FGT's Curie temperature of TC = 220 K, with little change in the periodicity p = 300 nm of the spin spiral throughout the studied temperature range. The formation of a spin spiral showing counterclockwise rotation strongly suggests the presence of a positive Dzyaloshinskii-Moriya interaction in FGT, which provides the first steps towards the understanding of the magnetic structure of FGT. Our results additionally pave the way for chiral magnetism in van der Waals materials and their heterostructures.
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Affiliation(s)
- Mariëlle J. Meijer
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - Juriaan Lucassen
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - Rembert A. Duine
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Institute
for Theoretical Physics, Utrecht University, Leuvenlaan 4, 3584 CE, Utrecht, The Netherlands
| | - Henk J.M. Swagten
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - Bert Koopmans
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - Reinoud Lavrijsen
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
| | - Marcos H. D. Guimarães
- Department
of Applied Physics, Eindhoven University
of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands
- Zernike
Institute for Advanced Materials, University
of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands
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Li W, Paul S, von Bergmann K, Heinze S, Wiesendanger R. Stacking-Dependent Spin Interactions in Pd/Fe Bilayers on Re(0001). PHYSICAL REVIEW LETTERS 2020; 125:227205. [PMID: 33315450 DOI: 10.1103/physrevlett.125.227205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 10/23/2020] [Indexed: 06/12/2023]
Abstract
Using spin-polarized scanning tunneling microscopy and density functional theory, we have studied the magnetic properties of Pd/Fe atomic bilayers on Re(0001). Two kinds of magnetic ground states are discovered due to different types of stacking of the Pd adlayer on Fe/Re(0001). For fcc stacking of Pd on Fe/Re(0001), it is a spin spiral propagating along the close-packed (ΓK[over ¯]) direction with a period of about 0.9 nm, driven by frustrated exchange and Dzyaloshinskii-Moriya interactions. For the hcp stacking, the four-site four-spin interaction stabilizes an up-up-down-down state propagating perpendicular to the close-packed direction (along ΓM[over ¯]) with a period of about 1.0 nm. Our work shows how higher-order exchange interactions can be tuned at interfaces.
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Affiliation(s)
- W Li
- Department of Physics, University of Hamburg, Jungiusstrasse 9-11, 20355 Hamburg, Germany
| | - S Paul
- Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstrasse 15, 24098 Kiel, Germany
| | - K von Bergmann
- Department of Physics, University of Hamburg, Jungiusstrasse 9-11, 20355 Hamburg, Germany
| | - S Heinze
- Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstrasse 15, 24098 Kiel, Germany
| | - R Wiesendanger
- Department of Physics, University of Hamburg, Jungiusstrasse 9-11, 20355 Hamburg, Germany
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Isolated zero field sub-10 nm skyrmions in ultrathin Co films. Nat Commun 2019; 10:3823. [PMID: 31444358 PMCID: PMC6707282 DOI: 10.1038/s41467-019-11831-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Accepted: 07/30/2019] [Indexed: 11/08/2022] Open
Abstract
Due to their exceptional topological and dynamical properties magnetic skyrmions—localized stable spin structures—show great promise for spintronic applications. To become technologically competitive, isolated skyrmions with diameters below 10 nm stable at zero magnetic field and at room temperature are desired. Despite finding skyrmions in a wide spectrum of materials, the quest for a material with these envisioned properties is ongoing. Here we report zero field isolated skyrmions at T = 4 K with diameters below 5 nm observed in the virgin ferromagnetic state coexisting with 1 nm thin domain walls in Rh/Co atomic bilayers on Ir(111). These spin structures are investigated by spin-polarized scanning tunneling microscopy and can also be detected using non-spin-polarized tips via the noncollinear magnetoresistance. We demonstrate that sub-10 nm skyrmions are stabilized in these ferromagnetic Co films at zero field due to strong frustration of exchange interaction, together with Dzyaloshinskii–Moriya interaction and large magnetocrystalline anisotropy. Isolated skyrmions with diameters below 10 nm stabilized at zero magnetic field are of great technological relevance to the future spintronic applications. Here the authors report stabilization of zero field isolated skyrmions with diameters smaller than 5 nm in Rh/Co atomic bilayers on the Ir(111) surface.
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Tunable giant magnetoresistance in a single-molecule junction. Nat Commun 2019; 10:3599. [PMID: 31399599 PMCID: PMC6689026 DOI: 10.1038/s41467-019-11587-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Accepted: 07/09/2019] [Indexed: 11/23/2022] Open
Abstract
Controlling electronic transport through a single-molecule junction is crucial for molecular electronics or spintronics. In magnetic molecular devices, the spin degree-of-freedom can be used to this end since the magnetic properties of the magnetic ion centers fundamentally impact the transport through the molecules. Here we demonstrate that the electron pathway in a single-molecule device can be selected between two molecular orbitals by varying a magnetic field, giving rise to a tunable anisotropic magnetoresistance up to 93%. The unique tunability of the electron pathways is due to the magnetic reorientation of the transition metal center, resulting in a re-hybridization of molecular orbitals. We obtain the tunneling electron pathways by Kondo effect, which manifests either as a peak or a dip line shape. The energy changes of these spin-reorientations are remarkably low and less than one millielectronvolt. The large tunable anisotropic magnetoresistance could be used to control electronic transport in molecular spintronics. Molecular electronics or spintronics relies on manipulating the electronic transport through microscopic molecule structures. Here the authors demonstrate the selective electron pathway in single-molecule device by magnetic field which enables a tunable anisotropic magnetoresistance up to 93%.
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Hervé M, Peter M, Balashov T, Wulfhekel W. Towards Laterally Resolved Ferromagnetic Resonance with Spin-Polarized Scanning Tunneling Microscopy. NANOMATERIALS 2019; 9:nano9060827. [PMID: 31159310 PMCID: PMC6630471 DOI: 10.3390/nano9060827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 05/28/2019] [Accepted: 05/29/2019] [Indexed: 11/21/2022]
Abstract
We used a homodyne detection to investigate the gyration of magnetic vortex cores in Fe islands on W(110) with spin-polarized scanning tunneling microscopy at liquid helium temperatures. The technique aims at local detection of the spin precession as a function of frequency using a radio-frequency (rf) modulation of the tunneling bias voltage. The gyration was excited by the resulting spin-polarized rf current in the tunneling junction. A theoretical analysis of different contributions to the frequency-dependent signals expected in this technique is given. These include, besides the ferromagnetic resonance signal, also signals caused by the non-linearity of the I(U) characteristics. The vortex gyration was modeled with micromagnetic finite element methods using realistic parameters for the tunneling current, its spin polarization, and the island shape, and simulations were compared with the experimental results. The observed signals are presented and critically analyzed.
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Affiliation(s)
- Marie Hervé
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany.
- Institut des Nanosciences de Paris, Sorbonne Université and CNRS-UMR7588, 75005 Paris, France.
| | - Moritz Peter
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany.
| | - Timofey Balashov
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany.
| | - Wulf Wulfhekel
- Physikalisches Institut, Karlsruhe Institute of Technology, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe, Germany.
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17
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Lemesh I, Litzius K, Böttcher M, Bassirian P, Kerber N, Heinze D, Zázvorka J, Büttner F, Caretta L, Mann M, Weigand M, Finizio S, Raabe J, Im MY, Stoll H, Schütz G, Dupé B, Kläui M, Beach GSD. Current-Induced Skyrmion Generation through Morphological Thermal Transitions in Chiral Ferromagnetic Heterostructures. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2018; 30:e1805461. [PMID: 30368960 DOI: 10.1002/adma.201805461] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/21/2018] [Indexed: 06/08/2023]
Abstract
Magnetic skyrmions promise breakthroughs in future memory and computing devices due to their inherent stability and small size. Their creation and current driven motion have been recently observed at room temperature, but the key mechanisms of their formation are not yet well-understood. Here it is shown that in heavy metal/ferromagnet heterostructures, pulsed currents can drive morphological transitions between labyrinth-like, stripe-like, and skyrmionic states. Using high-resolution X-ray microscopy, the spin texture evolution with temperature and magnetic field is imaged and it is demonstrated that with transient Joule heating, topological charges can be injected into the system, driving it across the stripe-skyrmion boundary. The observations are explained through atomistic spin dynamic and micromagnetic simulations that reveal a crossover to a global skyrmionic ground state above a threshold magnetic field, which is found to decrease with increasing temperature. It is demonstrated how by tuning the phase stability, one can reliably generate skyrmions by short current pulses and stabilize them at zero field, providing new means to create and manipulate spin textures in engineered chiral ferromagnets.
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Affiliation(s)
- Ivan Lemesh
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Kai Litzius
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128, Mainz, Germany
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Marie Böttcher
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Pedram Bassirian
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Nico Kerber
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Daniel Heinze
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Jakub Zázvorka
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Felix Büttner
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Lucas Caretta
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Maxwell Mann
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Markus Weigand
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Simone Finizio
- Swiss Light Source, Paul Scherrer Institut, Villigen, PSI CH-5232, Switzerland
| | - Jörg Raabe
- Swiss Light Source, Paul Scherrer Institut, Villigen, PSI CH-5232, Switzerland
| | - Mi-Young Im
- Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Emerging Materials Science, DGIST, Daegu, 42988, Republic of Korea
- School of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea
| | - Hermann Stoll
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Gisela Schütz
- Max Planck Institute for Intelligent Systems, 70569, Stuttgart, Germany
| | - Bertrand Dupé
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
| | - Mathias Kläui
- Institute of Physics, Johannes Gutenberg-University Mainz, 55099, Mainz, Germany
- Graduate School of Excellence Materials Science in Mainz, 55128, Mainz, Germany
| | - Geoffrey S D Beach
- Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
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Herklotz A, Gai Z, Sharma Y, Huon A, Rus SF, Sun L, Shen J, Rack PD, Ward TZ. Designing Magnetic Anisotropy through Strain Doping. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2018; 5:1800356. [PMID: 30479913 PMCID: PMC6247029 DOI: 10.1002/advs.201800356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 07/03/2018] [Indexed: 06/09/2023]
Abstract
The coupling between a material's lattice and its underlying spin state links structural deformation to magnetic properties; however, traditional strain engineering does not allow the continuous, post-synthesis control of lattice symmetry needed to fully utilize this fundamental coupling in device design. Uniaxial lattice expansion induced by post-synthesis low energy helium ion implantation is shown to provide a means of bypassing these limitations. Magnetocrystalline energy calculations can be used a priori to estimate the predictive design of a material's preferred magnetic spin orientation. The efficacy of this approach is experimentally confirmed in a spinel CoFe2O4 model system where the epitaxial film's magnetic easy axis is continuously manipulated between the out-of-plane (oop) and in-plane (ip) directions as lattice tetragonality moves from ip to oop with increasing strain doping. Macroscopically gradual and microscopically abrupt changes to preferential spin orientation are demonstrated by combining ion irradiation with simple beam masking and lithographic procedures. The ability to design magnetic spin orientations across multiple length scales in a single crystal wafer using only crystal symmetry considerations provides a clear path toward the rational design of spin transfer, magnetoelectric, and skyrmion-based applications where magnetocrystalline energy must be dictated across multiple length scales.
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Affiliation(s)
- Andreas Herklotz
- Materials Science and Technology DivisionOak Ridge National Laboratory1 Bethel Valley Rd.Oak RidgeTN37831USA
- Institute for PhysicsMartin‐Luther‐University Halle‐WittenbergHalle06120Germany
| | - Zheng Gai
- Center for Nanophase Materials ScienceOak Ridge National Laboratory1 Bethel Valley Rd.Oak RidgeTN37831USA
| | - Yogesh Sharma
- Materials Science and Technology DivisionOak Ridge National Laboratory1 Bethel Valley Rd.Oak RidgeTN37831USA
| | - Amanda Huon
- Materials Science and Technology DivisionOak Ridge National Laboratory1 Bethel Valley Rd.Oak RidgeTN37831USA
| | - Stefania F. Rus
- Renewable Energies – Photovoltaics LaboratoryNational Institute for Research and Development in Electrochemistry and Condensed MatterTimisoara300569Romania
| | - Lu Sun
- SISTShanghai Technology UniversityShanghai200433China
| | - Jian Shen
- Department of PhysicsFudan UniversityShanghai200433China
| | - Philip D. Rack
- Center for Nanophase Materials ScienceOak Ridge National Laboratory1 Bethel Valley Rd.Oak RidgeTN37831USA
- Materials Science and Engineering DepartmentUniversity of TennesseeKnoxvilleTN37996USA
| | - Thomas Z. Ward
- Materials Science and Technology DivisionOak Ridge National Laboratory1 Bethel Valley Rd.Oak RidgeTN37831USA
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