1
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Amin OJ, Poole SF, Reimers S, Barton LX, Dal Din A, Maccherozzi F, Dhesi SS, Novák V, Krizek F, Chauhan JS, Campion RP, Rushforth AW, Jungwirth T, Tretiakov OA, Edmonds KW, Wadley P. Antiferromagnetic half-skyrmions electrically generated and controlled at room temperature. Nat Nanotechnol 2023; 18:849-853. [PMID: 37157021 PMCID: PMC10427425 DOI: 10.1038/s41565-023-01386-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Accepted: 03/24/2023] [Indexed: 05/10/2023]
Abstract
Topologically protected magnetic textures are promising candidates for information carriers in future memory devices, as they can be efficiently propelled at very high velocities using current-induced spin torques. These textures-nanoscale whirls in the magnetic order-include skyrmions, half-skyrmions (merons) and their antiparticles. Antiferromagnets have been shown to host versions of these textures that have high potential for terahertz dynamics, deflection-free motion and improved size scaling due to the absence of stray field. Here we show that topological spin textures, merons and antimerons, can be generated at room temperature and reversibly moved using electrical pulses in thin-film CuMnAs, a semimetallic antiferromagnet that is a testbed system for spintronic applications. The merons and antimerons are localized on 180° domain walls, and move in the direction of the current pulses. The electrical generation and manipulation of antiferromagnetic merons is a crucial step towards realizing the full potential of antiferromagnetic thin films as active components in high-density, high-speed magnetic memory devices.
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Affiliation(s)
- O J Amin
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK.
| | - S F Poole
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - S Reimers
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
- Diamond Light Source, Chilton, UK
- Institut für Physik, Johannes Gutenberg Universität Mainz, Mainz, Germany
| | - L X Barton
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - A Dal Din
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | | | | | - V Novák
- Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic
| | - F Krizek
- Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic
| | - J S Chauhan
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - R P Campion
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - T Jungwirth
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
- Institute of Physics, Czech Academy of Sciences, Prague, Czech Republic
| | - O A Tretiakov
- School of Physics, The University of New South Wales, Sydney, New South Wales, Australia
| | - K W Edmonds
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
| | - P Wadley
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
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2
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Pattnaik DP, Beardsley RP, Love C, Cavill SA, Edmonds KW, Rushforth AW. Multilevel information storage using magnetoelastic layer stacks. Sci Rep 2019; 9:3156. [PMID: 30816265 PMCID: PMC6395634 DOI: 10.1038/s41598-019-39775-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 02/04/2019] [Indexed: 11/09/2022] Open
Abstract
The use of voltages to control magnetisation via the inverse magnetostriction effect in piezoelectric/ferromagnet heterostructures holds promise for ultra-low energy information storage technologies. Epitaxial galfenol, an alloy of iron and gallium, has been shown to be a highly suitable material for such devices because it possesses biaxial anisotropy and large magnetostriction. Here we experimentally investigate the properties of galfenol/spacer/galfenol structures in which the compositions of the galfenol layers are varied in order to produce different strengths of the magnetic anisotropy and magnetostriction constants. Based upon these layers, we propose and simulate the operation of an information storage device that can operate as an energy efficient multilevel memory cell.
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Affiliation(s)
- D P Pattnaik
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - R P Beardsley
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - C Love
- Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom
| | - S A Cavill
- Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom
| | - K W Edmonds
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom.
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3
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Beardsley RP, Parkes DE, Zemen J, Bowe S, Edmonds KW, Reardon C, Maccherozzi F, Isakov I, Warburton PA, Campion RP, Gallagher BL, Cavill SA, Rushforth AW. Effect of lithographically-induced strain relaxation on the magnetic domain configuration in microfabricated epitaxially grown Fe 81Ga 19. Sci Rep 2017; 7:42107. [PMID: 28186114 PMCID: PMC5301210 DOI: 10.1038/srep42107] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/05/2017] [Indexed: 11/27/2022] Open
Abstract
We investigate the role of lithographically-induced strain relaxation in a micron-scaled device fabricated from epitaxial thin films of the magnetostrictive alloy Fe81Ga19. The strain relaxation due to lithographic patterning induces a magnetic anisotropy that competes with the magnetocrystalline and shape induced anisotropies to play a crucial role in stabilising a flux-closing domain pattern. We use magnetic imaging, micromagnetic calculations and linear elastic modelling to investigate a region close to the edges of an etched structure. This highly-strained edge region has a significant influence on the magnetic domain configuration due to an induced magnetic anisotropy resulting from the inverse magnetostriction effect. We investigate the competition between the strain-induced and shape-induced anisotropy energies, and the resultant stable domain configurations, as the width of the bar is reduced to the nanoscale range. Understanding this behaviour will be important when designing hybrid magneto-electric spintronic devices based on highly magnetostrictive materials.
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Affiliation(s)
- R P Beardsley
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - D E Parkes
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - J Zemen
- Department of Physics, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK
| | - S Bowe
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.,Diamond Light Source Chilton, Didcot, Oxfordshire OX11 0DE UK
| | - K W Edmonds
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - C Reardon
- Department of Physics, University of York, Heslington, York, YO10 5DD, UK
| | - F Maccherozzi
- Diamond Light Source Chilton, Didcot, Oxfordshire OX11 0DE UK
| | - I Isakov
- Department of Physics, Blackett Laboratory, Imperial College, Prince Consort Road, London SW7 2AZ, UK.,London Centre of Nanotechnology, University College London, London, WC1H 0AH, UK
| | - P A Warburton
- London Centre of Nanotechnology, University College London, London, WC1H 0AH, UK
| | - R P Campion
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - B L Gallagher
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - S A Cavill
- Diamond Light Source Chilton, Didcot, Oxfordshire OX11 0DE UK.,Department of Physics, University of York, Heslington, York, YO10 5DD, UK
| | - A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
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4
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Wadley P, Howells B, Železný J, Andrews C, Hills V, Campion RP, Novák V, Olejník K, Maccherozzi F, Dhesi SS, Martin SY, Wagner T, Wunderlich J, Freimuth F, Mokrousov Y, Kuneš J, Chauhan JS, Grzybowski MJ, Rushforth AW, Edmonds KW, Gallagher BL, Jungwirth T. Electrical switching of an antiferromagnet. Science 2016; 351:587-90. [PMID: 26841431 DOI: 10.1126/science.aab1031] [Citation(s) in RCA: 294] [Impact Index Per Article: 36.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Accepted: 01/04/2016] [Indexed: 11/02/2022]
Abstract
Antiferromagnets are hard to control by external magnetic fields because of the alternating directions of magnetic moments on individual atoms and the resulting zero net magnetization. However, relativistic quantum mechanics allows for generating current-induced internal fields whose sign alternates with the periodicity of the antiferromagnetic lattice. Using these fields, which couple strongly to the antiferromagnetic order, we demonstrate room-temperature electrical switching between stable configurations in antiferromagnetic CuMnAs thin-film devices by applied current with magnitudes of order 10(6) ampere per square centimeter. Electrical writing is combined in our solid-state memory with electrical readout and the stored magnetic state is insensitive to and produces no external magnetic field perturbations, which illustrates the unique merits of antiferromagnets for spintronics.
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Affiliation(s)
- P Wadley
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK.
| | - B Howells
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - J Železný
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic. Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16 Prague 2, Czech Republic
| | - C Andrews
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - V Hills
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - R P Campion
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - V Novák
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic
| | - K Olejník
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic
| | - F Maccherozzi
- Diamond Light Source, Chilton, Didcot, Oxfordshire, OX11 0DE, UK
| | - S S Dhesi
- Diamond Light Source, Chilton, Didcot, Oxfordshire, OX11 0DE, UK
| | - S Y Martin
- Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - T Wagner
- Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK. Department of Materials Science and Metallurgy, University of Cambridge, Cambridge CB3 0HE, UK
| | - J Wunderlich
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic. Hitachi Cambridge Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE, UK
| | - F Freimuth
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - Y Mokrousov
- Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany
| | - J Kuneš
- Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Praha 8, Czech Republic
| | - J S Chauhan
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - M J Grzybowski
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK. Institute of Physics, Polish Academy of Sciences, al. Lotnikow 32/46, PL-02-668 Warsaw, Poland
| | - A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - K W Edmonds
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - B L Gallagher
- School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
| | - T Jungwirth
- Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnická 10, 162 00 Praha 6, Czech Republic. School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
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5
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Wadley P, Hills V, Shahedkhah MR, Edmonds KW, Campion RP, Novák V, Ouladdiaf B, Khalyavin D, Langridge S, Saidl V, Nemec P, Rushforth AW, Gallagher BL, Dhesi SS, Maccherozzi F, Železný J, Jungwirth T. Antiferromagnetic structure in tetragonal CuMnAs thin films. Sci Rep 2015; 5:17079. [PMID: 26602978 PMCID: PMC4658521 DOI: 10.1038/srep17079] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 10/26/2015] [Indexed: 12/03/2022] Open
Abstract
Tetragonal CuMnAs is an antiferromagnetic material with favourable properties for applications in spintronics. Using a combination of neutron diffraction and x-ray magnetic linear dichroism, we determine the spin axis and magnetic structure in tetragonal CuMnAs, and reveal the presence of an interfacial uniaxial magnetic anisotropy. From the temperature-dependence of the neutron diffraction intensities, the Néel temperature is shown to be (480 ± 5) K. Ab initio calculations indicate a weak anisotropy in the (ab) plane for bulk crystals, with a large anisotropy energy barrier between in-plane and perpendicular-to-plane directions.
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Affiliation(s)
- P. Wadley
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - V. Hills
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - M. R. Shahedkhah
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - K. W. Edmonds
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - R. P. Campion
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - V. Novák
- Institute of Physics ASCR, v. v. i., Cukrovarnicka 10, 16253 Prague 6, Czech Republic
| | - B. Ouladdiaf
- Institut Laue-Langevin, 6 Rue Jules Horowitz, 38042 Grenoble, France
| | - D. Khalyavin
- ISIS, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Science and Technology Facilities Council, Oxon OX11 0QX, United Kingdom
| | - S. Langridge
- ISIS, Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Science and Technology Facilities Council, Oxon OX11 0QX, United Kingdom
| | - V. Saidl
- Faculty of Mathematics and Physics, Charles University in Prague, 121 16 Prague, Czech Republic
| | - P. Nemec
- Faculty of Mathematics and Physics, Charles University in Prague, 121 16 Prague, Czech Republic
| | - A. W. Rushforth
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - B. L. Gallagher
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
| | - S. S. Dhesi
- Diamond Light Source, Chilton, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - F. Maccherozzi
- Diamond Light Source, Chilton, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - J. Železný
- Institute of Physics ASCR, v. v. i., Cukrovarnicka 10, 16253 Prague 6, Czech Republic
- Faculty of Mathematics and Physics, Charles University in Prague, 121 16 Prague, Czech Republic
| | - T. Jungwirth
- School of Physics and Astronomy, University of Nottingham, NG7 2RD, United Kingdom
- Institute of Physics ASCR, v. v. i., Cukrovarnicka 10, 16253 Prague 6, Czech Republic
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6
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Ostler TA, Cuadrado R, Chantrell RW, Rushforth AW, Cavill SA. Strain Induced Vortex Core Switching in Planar Magnetostrictive Nanostructures. Phys Rev Lett 2015; 115:067202. [PMID: 26296129 DOI: 10.1103/physrevlett.115.067202] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Indexed: 06/04/2023]
Abstract
The dynamics of magnetic vortex cores is of great interest because the gyrotropic mode has applications in spin torque driven magnetic microwave oscillators, and also provides a means to flip the direction of the core for use in magnetic storage devices. Here, we propose a new means of stimulating magnetization reversal of the vortex core by applying a time-varying strain gradient to planar structures of the magnetostrictive material Fe(81)Ga(19) (Galfenol), coupled to an underlying piezoelectric layer. Using micromagnetic simulations we have shown that the vortex core state can be deterministically reversed by electric field control of the time-dependent strain-induced anisotropy.
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Affiliation(s)
- T A Ostler
- Department of Physics, The University of York, York YO10 5DD, United Kingdom
| | - R Cuadrado
- Department of Physics, The University of York, York YO10 5DD, United Kingdom
| | - R W Chantrell
- Department of Physics, The University of York, York YO10 5DD, United Kingdom
| | - A W Rushforth
- School of Physics and Astronomy, The University of Nottingham, Nottingham NG7 2RD, United Kingdom
| | - S A Cavill
- Department of Physics, The University of York, York YO10 5DD, United Kingdom
- Diamond Light Source, Harwell Science and Innovation Campus, Chilton, Didcot OX11 0DE, United Kingdom
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7
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Shepley PM, Rushforth AW, Wang M, Burnell G, Moore TA. Modification of perpendicular magnetic anisotropy and domain wall velocity in Pt/Co/Pt by voltage-induced strain. Sci Rep 2015; 5:7921. [PMID: 25605499 PMCID: PMC4300497 DOI: 10.1038/srep07921] [Citation(s) in RCA: 68] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 12/10/2014] [Indexed: 11/09/2022] Open
Abstract
The perpendicular magnetic anisotropy Keff, magnetization reversal, and field-driven domain wall velocity in the creep regime are modified in Pt/Co(0.85–1.0 nm)/Pt thin films by strain applied via piezoelectric transducers. Keff, measured by the extraordinary Hall effect, is reduced by 10 kJ/m3 by tensile strain out-of-plane εz = 9 × 10−4, independently of the film thickness, indicating a dominant volume contribution to the magnetostriction. The same strain reduces the coercive field by 2–4 Oe, and increases the domain wall velocity measured by wide-field Kerr microscopy by 30-100%, with larger changes observed for thicker Co layers. We consider how strain-induced changes in the perpendicular magnetic anisotropy can modify the coercive field and domain wall velocity.
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Affiliation(s)
- P M Shepley
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - M Wang
- School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, United Kingdom
| | - G Burnell
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
| | - T A Moore
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom
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8
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Piano S, Rushforth AW, Edmonds KW, Campion RP, Adesso G, Gallagher BL. Analysing surface structures on (Ga, Mn)As by atomic force microscopy. J Nanosci Nanotechnol 2012; 12:7545-7549. [PMID: 23035513 DOI: 10.1166/jnn.2012.6553] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Using atomic force microscopy, we have studied the surface structures of high quality molecular beam epitaxy grown (Ga, Mn)As compound. Several samples with different thickness and Mn concentration, as well as a few (Ga, Mn)(As, P) samples have been investigated. All these samples have shown the presence of periodic ripples aligned along the [110] direction. From a detailed Fourier analysis we have estimated the period (-50 nm) and the amplitude of these structures.
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Affiliation(s)
- S Piano
- School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom
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9
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Stolichnov I, Riester SWE, Mikheev E, Setter N, Rushforth AW, Edmonds KW, Campion RP, Foxon CT, Gallagher BL, Jungwirth T, Trodahl HJ. Ferroelectric polymer gates for non-volatile field effect control of ferromagnetism in (Ga, Mn)As layers. Nanotechnology 2011; 22:254004. [PMID: 21572188 DOI: 10.1088/0957-4484/22/25/254004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
(Ga, Mn)As and other diluted magnetic semiconductors (DMS) attract a great deal of attention for potential spintronic applications because of the possibility of controlling the magnetic properties via electrical gating. Integration of a ferroelectric gate on the DMS channel adds to the system a non-volatile memory functionality and permits nanopatterning via the polarization domain engineering. This topical review is focused on the multiferroic system, where the ferromagnetism in the (Ga, Mn)As DMS channel is controlled by the non-volatile field effect of the spontaneous polarization. Use of ferroelectric polymer gates in such heterostructures offers a viable alternative to the traditional oxide ferroelectrics generally incompatible with DMS. Here we review the proof-of-concept experiments demonstrating the ferroelectric control of ferromagnetism, analyze the performance issues of the ferroelectric gates and discuss prospects for further development of the ferroelectric/DMS heterostructures toward the multiferroic field effect transistor.
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Affiliation(s)
- I Stolichnov
- Ceramics Laboratory, EPFL-Swiss Federal Institute of Technology, Lausanne, Switzerland
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10
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Mašek J, Máca F, Kudrnovský J, Makarovsky O, Eaves L, Campion RP, Edmonds KW, Rushforth AW, Foxon CT, Gallagher BL, Novák V, Sinova J, Jungwirth T. Microscopic analysis of the valence band and impurity band theories of (Ga,Mn)As. Phys Rev Lett 2010; 105:227202. [PMID: 21231418 DOI: 10.1103/physrevlett.105.227202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Indexed: 05/30/2023]
Abstract
We analyze microscopically the valence and impurity band models of ferromagnetic (Ga,Mn)As. We find that the tight-binding Anderson approach with conventional parametrization and the full potential local-density approximation+U calculations give a very similar band structure whose microscopic spectral character is consistent with the physical premise of the k·p kinetic-exchange model. On the other hand, the various models with a band structure comprising an impurity band detached from the valence band assume mutually incompatible microscopic spectral character. By adapting the tight-binding Anderson calculations individually to each of the impurity band pictures in the single Mn impurity limit and then by exploring the entire doping range, we find that a detached impurity band does not persist in any of these models in ferromagnetic (Ga,Mn)As.
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Affiliation(s)
- J Mašek
- Institute of Physics ASCR, v.v.i., Na Slovance 2, 182 21 Praha 8, Czech Republic
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11
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Novák V, Olejník K, Wunderlich J, Cukr M, Výborný K, Rushforth AW, Edmonds KW, Campion RP, Gallagher BL, Sinova J, Jungwirth T. Curie point singularity in the temperature derivative of resistivity in (Ga,Mn)As. Phys Rev Lett 2008; 101:077201. [PMID: 18764572 DOI: 10.1103/physrevlett.101.077201] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 06/26/2008] [Indexed: 05/26/2023]
Abstract
We observe a singularity in the temperature derivative drho/dT of resistivity at the Curie point of high-quality (Ga,Mn)As ferromagnetic semiconductors with Tc's ranging from approximately 80 to 185 K. The character of the anomaly is sharply distinct from the critical contribution to transport in conventional dense-moment magnetic semiconductors and is reminiscent of the drho/dT singularity in transition metal ferromagnets. Within the critical region accessible in our experiments, the temperature dependence on the ferromagnetic side can be explained by dominant scattering from uncorrelated spin fluctuations. The singular behavior of drho/dT on the paramagnetic side points to the important role of short-range correlated spin fluctuations.
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Affiliation(s)
- V Novák
- Institute of Physics ASCR, v.v.i., Cukrovarnická 10, 162 53 Praha 6, Czech Republic
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12
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Stolichnov I, Riester SWE, Trodahl HJ, Setter N, Rushforth AW, Edmonds KW, Campion RP, Foxon CT, Gallagher BL, Jungwirth T. Non-volatile ferroelectric control of ferromagnetism in (Ga,Mn)As. Nat Mater 2008; 7:464-467. [PMID: 18454153 DOI: 10.1038/nmat2185] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Accepted: 04/04/2008] [Indexed: 05/26/2023]
Abstract
Multiferroic structures that provide coupled ferroelectric and ferromagnetic responses are of significant interest as they may be used in novel memory devices and spintronic logic elements. One approach towards this goal is the use of composites that couple ferromagnetic and ferroelectric layers through magnetostrictive and piezoelectric strain transmitted across the interfaces. However, mechanical clamping of the films to the substrate limits their response. Structures where the magnetic response is modulated directly by the electric field of the poled ferroelectric would eliminate this constraint and provide a qualitatively higher level of integration, combining the emerging field of multiferroics with conventional semiconductor microelectronics. Here, we report the realization of such a device using (Ga,Mn)As, which is an archetypical diluted magnetic semiconductor with well-understood carrier-mediated ferromagnetism, and a polymer ferroelectric gate. Polarization reversal of the gate by a single voltage pulse results in a persistent modulation of the Curie temperature of the ferromagnetic semiconductor. The non-volatile gating of (Ga,Mn)As has been made possible by applying a low-temperature copolymer deposition technique that is distinct from pre-existing technologies for ferroelectric gates on magnetic oxides. This accomplishment opens a way to nanometre-scale modulation of magnetic semiconductor properties with rewritable ferroelectric domain patterns, operating at modest voltages and subnanosecond times.
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Affiliation(s)
- I Stolichnov
- Ceramics Laboratory, EPFL-Swiss Federal Institute of Technology, Lausanne 1015, Switzerland.
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13
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Rushforth AW, Výborný K, King CS, Edmonds KW, Campion RP, Foxon CT, Wunderlich J, Irvine AC, Vasek P, Novák V, Olejník K, Sinova J, Jungwirth T, Gallagher BL. Anisotropic magnetoresistance components in (Ga,Mn)As. Phys Rev Lett 2007; 99:147207. [PMID: 17930718 DOI: 10.1103/physrevlett.99.147207] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2007] [Indexed: 05/25/2023]
Abstract
We explore the basic physical origins of the noncrystalline and crystalline components of the anisotropic magnetoresistance (AMR) in (Ga,Mn)As. The sign of the noncrystalline AMR is found to be determined by the form of spin-orbit coupling in the host band and by the relative strengths of the nonmagnetic and magnetic contributions to the Mn impurity potential. We develop experimental methods yielding directly the noncrystalline and crystalline AMR components which are then analyzed independently. We report the observation of an AMR dominated by a large uniaxial crystalline component and show that AMR can be modified by local strain relaxation. Generic implications of our findings for other dilute moment systems are discussed.
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Affiliation(s)
- A W Rushforth
- School of Physics and Astronomy, University of Nottingham, Nottingham, UK
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Rushforth AW, Giddings AD, Edmonds KW, Campion RP, Foxon CT, Gallagher BL. AMR and magnetometry studies of ultra thin GaMnAs films. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/pssc.200672836] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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