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Hanneken C, Otte F, Kubetzka A, Dupé B, Romming N, von Bergmann K, Wiesendanger R, Heinze S. Electrical detection of magnetic skyrmions by tunnelling non-collinear magnetoresistance. NATURE NANOTECHNOLOGY 2015; 10:1039-1042. [PMID: 26436563 DOI: 10.1038/nnano.2015.218] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 08/20/2015] [Indexed: 06/05/2023]
Abstract
Magnetic skyrmions are localized non-collinear spin textures with a high potential for future spintronic applications. Skyrmion phases have been discovered in a number of materials and a focus of current research is to prepare, detect and manipulate individual skyrmions for implementation in devices. The local experimental characterization of skyrmions has been performed by, for example, Lorentz microscopy or atomic-scale tunnel magnetoresistance measurements using spin-polarized scanning tunnelling microscopy. Here we report a drastic change of the differential tunnel conductance for magnetic skyrmions that arises from their non-collinearity: mixing between the spin channels locally alters the electronic structure, which makes a skyrmion electronically distinct from its ferromagnetic environment. We propose this tunnelling non-collinear magnetoresistance as a reliable all-electrical detection scheme for skyrmions with an easy implementation into device architectures.
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Affiliation(s)
- Christian Hanneken
- Department of Physics, University of Hamburg, Jungiusstrasse 11, Hamburg 20355, Germany
| | - Fabian Otte
- Institute of Theoretical Physics and Astrophysics, Christian-Albrechts-Universität zu Kiel, Leibnizstrasse 15, Kiel 24098, Germany
| | - André Kubetzka
- Department of Physics, University of Hamburg, Jungiusstrasse 11, Hamburg 20355, Germany
| | - Bertrand Dupé
- Institute of Theoretical Physics and Astrophysics, Christian-Albrechts-Universität zu Kiel, Leibnizstrasse 15, Kiel 24098, Germany
| | - Niklas Romming
- Department of Physics, University of Hamburg, Jungiusstrasse 11, Hamburg 20355, Germany
| | - Kirsten von Bergmann
- Department of Physics, University of Hamburg, Jungiusstrasse 11, Hamburg 20355, Germany
| | - Roland Wiesendanger
- Department of Physics, University of Hamburg, Jungiusstrasse 11, Hamburg 20355, Germany
| | - Stefan Heinze
- Institute of Theoretical Physics and Astrophysics, Christian-Albrechts-Universität zu Kiel, Leibnizstrasse 15, Kiel 24098, Germany
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Le Graët C, de Vries MA, McLaren M, Brydson RMD, Loving M, Heiman D, Lewis LH, Marrows CH. Sputter growth and characterization of metamagnetic B2-ordered FeRh epilayers. J Vis Exp 2013. [PMID: 24145690 PMCID: PMC3938335 DOI: 10.3791/50603] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
Chemically ordered alloys are useful in a variety of magnetic nanotechnologies. They are most conveniently prepared at an industrial scale using sputtering techniques. Here we describe a method for preparing epitaxial thin films of B2-ordered FeRh by sputter deposition onto single crystal MgO substrates. Deposition at a slow rate onto a heated substrate allows time for the adatoms to both settle into a lattice with a well-defined epitaxial relationship with the substrate and also to find their proper places in the Fe and Rh sublattices of the B2 structure. The structure is conveniently characterized with X-ray reflectometry and diffraction and can be visualised directly using transmission electron micrograph cross-sections. B2-ordered FeRh exhibits an unusual metamagnetic phase transition: the ground state is antiferromagnetic but the alloy transforms into a ferromagnet on heating with a typical transition temperature of about 380 K. This is accompanied by a 1% volume expansion of the unit cell: isotropic in bulk, but laterally clamped in an epilayer. The presence of the antiferromagnetic ground state and the associated first order phase transition is very sensitive to the correct equiatomic stoichiometry and proper B2 ordering, and so is a convenient means to demonstrate the quality of the layers that can be deposited with this approach. We also give some examples of the various techniques by which the change in phase can be detected.
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Franken JH, Hoeijmakers M, Swagten HJM, Koopmans B. Tunable resistivity of individual magnetic domain walls. PHYSICAL REVIEW LETTERS 2012; 108:037205. [PMID: 22400781 DOI: 10.1103/physrevlett.108.037205] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2011] [Indexed: 05/31/2023]
Abstract
Despite the relevance of current-induced magnetic domain wall (DW) motion for new spintronics applications, the exact details of the current-domain wall interaction are not yet understood. A property intimately related to this interaction is the intrinsic DW resistivity. Here, we investigate experimentally how the resistivity inside a DW depends on the wall width Δ, which is tuned using focused ion beam irradiation of Pt/Co/Pt strips. We observe the nucleation of individual DWs with Kerr microscopy, and measure resistance changes in real time. A 1/Δ(2) dependence of DW resistivity is found, compatible with Levy-Zhang theory. Also quantitative agreement with theory is found by taking full account of the current flowing through each individual layer inside the multilayer stack.
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Affiliation(s)
- J H Franken
- Department of Applied Physics, Center for NanoMaterials and COBRA Research Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
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Soh YA, Kummamuru RK. Spintronics in antiferromagnets. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2011; 369:3646-3657. [PMID: 21859727 DOI: 10.1098/rsta.2011.0186] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Magnetic domains and the walls between are the subject of great interest because of the role they play in determining the electrical properties of ferromagnetic materials and as a means of manipulating electron spin in spintronic devices. However, much less attention has been paid to these effects in antiferromagnets, primarily because there is less awareness of their existence in antiferromagnets, and in addition they are hard to probe since they exhibit no net magnetic moment. In this paper, we discuss the electrical properties of chromium, which is the only elemental antiferromagnet and how they depend on the subtle arrangement of the antiferromagnetically ordered spins. X-ray measurement of the modulation wavevector Q of the incommensurate antiferromagnetic spin-density wave shows thermal hysteresis, with the corresponding wavelength being larger during cooling than during warming. The thermal hysteresis in the Q vector is accompanied with a thermal hysteresis in both the longitudinal and Hall resistivity. During cooling, we measure a larger longitudinal and Hall resistivity compared with when warming, which indicates that a larger wavelength at a given temperature corresponds to a smaller carrier density or equivalently a larger antiferromagnetic ordering parameter compared to a smaller wavelength. This shows that the arrangement of the antiferromagnetic spins directly influences the transport properties. In thin films, the sign of the thermal hysteresis for Q is the same as in thick films, but a distinct aspect is that Q is quantized.
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Affiliation(s)
- Yeong-Ah Soh
- Department of Materials, Imperial College London, , London SW7 2AZ, UK.
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Seemann KM, Mokrousov Y, Aziz A, Miguel J, Kronast F, Kuch W, Blamire MG, Hindmarch AT, Hickey BJ, Souza I, Marrows CH. Spin-orbit strength driven crossover between intrinsic and extrinsic mechanisms of the anomalous hall effect in the epitaxial L1{0}-ordered ferromagnets FePd and FePt. PHYSICAL REVIEW LETTERS 2010; 104:076402. [PMID: 20366900 DOI: 10.1103/physrevlett.104.076402] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2009] [Indexed: 05/29/2023]
Abstract
We determine the composition of intrinsic as well as extrinsic contributions to the anomalous Hall effect (AHE) in the isoelectronic L1_{0} FePd and FePt alloys. We show that the AHE signal in our 30 nm thick epitaxially deposited films of FePd is mainly due to an extrinsic side jump, while in the epitaxial FePt films of the same thickness and degree of order the intrinsic contribution is dominating over the extrinsic mechanisms of the AHE. We relate this crossover to the difference in spin-orbit strength of Pt and Pd atoms and suggest that this phenomenon can be used for tuning the origins of the AHE in complex alloys.
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Affiliation(s)
- K M Seemann
- School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, United Kingdom.
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Boulle O, Kimling J, Warnicke P, Kläui M, Rüdiger U, Malinowski G, Swagten HJM, Koopmans B, Ulysse C, Faini G. Nonadiabatic spin transfer torque in high anisotropy magnetic nanowires with narrow domain walls. PHYSICAL REVIEW LETTERS 2008; 101:216601. [PMID: 19113434 DOI: 10.1103/physrevlett.101.216601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2008] [Indexed: 05/27/2023]
Abstract
Current induced domain wall (DW) depinning of a narrow DW in out-of-plane magnetized (Pt/Co)_{3}/Pt multilayer elements is studied by magnetotransport. We find that for conventional measurements Joule heating effects conceal the real spin torque efficiency and so we use a measurement scheme at a constant sample temperature to unambiguously extract the spin torque contribution. From the variation of the depinning magnetic field with the current pulse amplitude we directly deduce the large nonadiabaticity factor in this material and we find that its amplitude is consistent with a momentum transfer mechanism.
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Affiliation(s)
- O Boulle
- Fachbereich Physik, Universität Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany
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Kummamuru RK, Soh YA. Electrical effects of spin density wave quantization and magnetic domain walls in chromium. Nature 2008; 452:859-63. [DOI: 10.1038/nature06826] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Accepted: 01/29/2008] [Indexed: 11/09/2022]
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Aziz A, Bending SJ, Roberts HG, Crampin S, Heard PJ, Marrows CH. Angular dependence of domain wall resistivity in artificial magnetic domain structures. PHYSICAL REVIEW LETTERS 2006; 97:206602. [PMID: 17155700 DOI: 10.1103/physrevlett.97.206602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2006] [Indexed: 05/12/2023]
Abstract
We exploit the ability to precisely control the magnetic domain structure of perpendicularly magnetized Pt/Co/Pt trilayers to fabricate artificial domain wall arrays and study their transport properties. The scaling behavior of this model system confirms the intrinsic domain wall origin of the magnetoresistance, and systematic studies using domains patterned at various angles to the current flow are excellently described by an angular-dependent resistivity tensor containing perpendicular and parallel domain wall resistivities. We find that the latter are fully consistent with Levy-Zhang theory, which allows us to estimate the ratio of minority to majority spin carrier resistivities, rho downward arrow/rho upward arrow approximately 5.5, in good agreement with thin film band structure calculations.
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Affiliation(s)
- A Aziz
- Department of Physics, University of Bath, Bath BA2 7AY, UK
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Chiba D, Yamanouchi M, Matsukura F, Dietl T, Ohno H. Domain-wall resistance in ferromagnetic (Ga,Mn)As. PHYSICAL REVIEW LETTERS 2006; 96:096602. [PMID: 16606291 DOI: 10.1103/physrevlett.96.096602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2005] [Indexed: 05/08/2023]
Abstract
A series of microstructures designed to pin domain walls (DWs) in (Ga,Mn)As with perpendicular magnetic anisotropy has been employed to determine extrinsic and intrinsic contributions to DW resistance. The former is explained quantitatively as resulting from a polarity change in the Hall electric field at DW. The latter is 1 order of magnitude greater than a term brought about by anisotropic magnetoresistance and is shown to be consistent with disorder-induced mistracking of the carrier spins subject to spatially varying magnetization.
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Affiliation(s)
- D Chiba
- ERATO Semiconductor Spintronics Project, Japan Science and Technology Agency, 1-18 Kitamemachi, Aoba-ku Sendai, 980-0023, Japan
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