Magnetic properties and spin polarization of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mi>Co</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>MnSi</mml:mi></mml:mrow></mml:math>Heusler alloy thin films epitaxially grown on GaAs(001)

Wang, W. H.; Przybylski, M.; Kuch, W.; Chelaru, Li; Wang, J.; Lu, Yafeng; Barthel, J.; Meyerheim, H. L.; Kirschner, J.

doi:10.1103/physrevb.71.144416

Cited by 198 publications

(158 citation statements)

References 58 publications

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“…Uniaxial-type magnetic anisotropy similar to that shown in Fig. 1 has been reported in several previous studies, [11][12][13][14][15][16][17][18] in particular for Fe ͑Ref. 11͒ or Co-based Heusler alloy thin films 12-18 grown on GaAs.…”

supporting

confidence: 65%

“…There have been several theoretical models for the symmetry of the GaAs substrate, such as a surface reconstruction of GaAs, formation of an interface alloy, or anisotropic interfacial bonds. 16 Although these models based on the structural asymmetry of the GaAs substrate might be able to explain the nonequivalent tunnel resistance between R 110 and R 110 , they cannot explain the results for the bias voltage dependence of the MR, in particular the switching behavior between the positive and negative MR ratios depending on the bias voltage, as shown in Fig. 4.…”

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confidence: 92%

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Tunneling anisotropic magnetoresistance in epitaxial CoFe/n-GaAs junctions

Uemura

Imai

Harada

et al. 2009

Applied Physics Letters

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Magnetic and transport properties of a fully epitaxial CoFe/n-GaAs junction were investigated. The CoFe film grown on the GaAs showed strong magnetic anisotropy in which uniaxial anisotropy with an easy axis of ͓110͔ dominated with a slight cubic anisotropy having easy axes of ͓110͔ and ͓110͔ superimposed. Tunneling anisotropic magnetoresistance ͑TAMR͒ was observed at 4.2 K in the CoFe/n-GaAs junction. Angular dependence of the tunnel resistance showed uniaxial-type anisotropic tunnel resistance between the ͓110͔ and ͓110͔ directions in the ͑001͒ plane that varied strongly with a bias voltage. The observed TAMR effect can be explained by the anisotropic electronic structure due to Rashba and Dresselhaus spin-orbit interactions.

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confidence: 65%

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confidence: 92%

Tunneling anisotropic magnetoresistance in epitaxial CoFe/n-GaAs junctions

Uemura

Imai

Harada

et al. 2009

Applied Physics Letters

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“…This can be explained by a model in which ͑i͒ uniaxial anisotropy imposed by the GaAs symmetry with an easy axis of either the GaAs͓110͔ or ͓1−10͔ direction and ͑ii͒ cubic anisotropy imposed by the Co 2 YZ with easy axes of Co 2 YZ͗110͘ are superimposed. [14][15][16] In our case, the easy axis direction of the uniaxial anisotropy was along the GaAs͓1−10͔ direction. When the MgO interlayer was inserted, the uniaxial anisotropy was weakened ͓Fig.…”

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confidence: 99%

Structural, magnetic, and electrical properties of Co2MnSi∕MgO∕n-GaAs tunnel junctions

Kawagishi

Uemura

Imai

et al. 2008

Journal of Applied Physics

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The structural, magnetic, and electrical properties of Co 2 MnSi ͑CMS͒/MgO ͑0 -3.0 nm͒ / n-GaAs tunnel junctions were investigated. CMS films with L2 1 -ordered structures were grown epitaxially on GaAs. The crystallographic relations were CMS͑001͓͒100͔ ʈ GaAs͑001͓͒110͔ when a thin MgO interlayer was inserted between the CMS and the GaAs, and CMS͑001͓͒110͔ ʈ GaAs͑001͓͒110͔ when the CMS film was directly grown on GaAs without a MgO interlayer. The CMS film without a MgO interlayer showed strong magnetic anisotropy consisting of uniaxial anisotropy with an easy axis of CMS͓1−10͔ ͑GaAs͓1−10͔͒ direction and cubic anisotropy with easy axes of CMS͗110͘ directions. The uniaxial anisotropy was weakened in the samples with a MgO interlayer. The magnetization value of the CMS film with a 3.0-nm-thick MgO layer was approximately 820 emu/ cm 3 ͑3.9 B / f.u.͒ at room temperature ͑RT͒, a value slightly higher ͑ϳ7%͒ than that of the sample without MgO. The resistance value of the CMS/MgO ͑3.0 nm͒ / n-GaAs junction was approximately two to three orders of magnitude higher than that of the CMS/ n-GaAs junction at RT. The potential height and width of the tunnel barrier in the CMS/ MgO / n-GaAs junction were estimated to be 0.6 eV and 3.3 nm, respectively.

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“…It has recently been shown that x-ray absorption spectroscopy ͑XAS͒ and x-ray magnetic circular dichroism ͑XMCD͒ measurements are powerful techniques for obtaining microscopic information about the element-specific electronic and magnetic states in the interfacial region of MTJs. [6][7][8][9] Our purpose of the present study is to clarify the electronic and magnetic states of the interfacial region of Co 2 YZ thin films facing a MgO barrier. For this study, we fabricated epitaxial CMS ultrathin films as typical Co 2 YZ films with an epitaxial MgO barrier and performed XAS and XMCD measurements at the Mn-L 2,3 and Co-L 2,3 edges.…”

mentioning

confidence: 99%

X-ray absorption spectroscopy and x-ray magnetic circular dichroism of epitaxially grown Heusler alloy Co2MnSi ultrathin films facing a MgO barrier

Saito

Katayama

Ishikawa

et al. 2007

Applied Physics Letters

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We element specifically studied the electronic and magnetic states of epitaxially grown full-Heusler alloy Co 2 MnSi ͑CMS͒ 1.1 nm ͑4 ML͒ thick ultrathin films facing an epitaxial MgO͑001͒ tunnel barrier by means of x-ray absorption spectroscopy ͑XAS͒ and x-ray magnetic circular dichroism ͑XMCD͒. In situ reflection high-energy electron-diffraction observations indicated that the CMS films grew into the L2 1 structure. The observed XAS and XMCD spectra revealed that the CMS ultrathin film was not oxidized. The ratio of Mn and Co spin magnetic moments obtained by applying the sum rules was about 2.7, close to a theoretical value of 2.8 for CMS with the L2 1 structure. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2824856͔Co-based full-Heusler alloys ͑Co 2 YZ͒ have attracted much interest as a desirable ferromagnetic electrode material for spintronic devices. [1][2][3][4][5] This is because of their potentially high spin polarization arising from the half-metallic ferromagnetic nature theoretically predicted for some of these alloys, and because of their high Curie temperatures, which are well above room temperature ͑RT͒. Some of the present authors recently developed fully epitaxial magnetic tunnel junctions ͑MTJs͒ with a Co 2 YZ thin film of Co 2 Cr 0.6 Fe 0.4 Al ͑CCFA͒, Co 2 MnSi ͑CMS͒, or Co 2 MnGe as a lower electrode and a MgO͑001͒ tunnel barrier, 3-5 and demonstrated relatively high tunnel magnetoresistance ͑TMR͒ ratios of 109% at RT ͑317% at 4.2 K͒ for CCFA/ MgO / Co 50 Fe 50 MTJs ͑Ref. 4͒ and 90% at RT ͑192% at 4.2 K͒ for CMS/ MgO / Co 50 Fe 50 MTJs. 3 The electronic and magnetic states of the interfacial region of ferromagnetic electrodes with a tunnel barrier play an essential role in the spindependent tunneling characteristics in MTJs. It has recently been shown that x-ray absorption spectroscopy ͑XAS͒ and x-ray magnetic circular dichroism ͑XMCD͒ measurements are powerful techniques for obtaining microscopic information about the element-specific electronic and magnetic states in the interfacial region of MTJs. [6][7][8][9] Our purpose of the present study is to clarify the electronic and magnetic states of the interfacial region of Co 2 YZ thin films facing a MgO barrier. For this study, we fabricated epitaxial CMS ultrathin films as typical Co 2 YZ films with an epitaxial MgO barrier and performed XAS and XMCD measurements at the Mn-L 2,3 and Co-L 2,3 edges. To investigate the interfacial region selectively, we fabricated CMS ultrathin films with a 4 ML thickness ͑=1.1 nm͒. The fabricated sample layer structure ͑from the substrate side͒ was as follows: MgO buffer ͑10 nm͒ / Fe underlayer ͑50 nm͒ / CMS ultrathin film ͑1.1 nm= 4 ML͒/MgO barrier ͑2 nm͒ / Ru cap ͑2 nm͒ ͑hereafter called Fe/CMS ͑4 ML͒/MgO͒, grown on a MgO͑001͒ single-crystal substrate. The monolayer of Co 2 MnSi consists of a Co plane and a Mn-Si plane, and a unit cell of CMS, whose lattice parameter is 0.5654 nm ͑Ref. 10͒, corresponds to 2 ML of CMS. To stabilize the ferromagnetism of ultrathin CMS films at RT, we grew them on the ...

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Magnetic properties and spin polarization ofCo2MnSiHeusler alloy thin films epitaxially grown on GaAs(001)

Cited by 198 publications

References 58 publications

Tunneling anisotropic magnetoresistance in epitaxial CoFe/n-GaAs junctions

Tunneling anisotropic magnetoresistance in epitaxial CoFe/n-GaAs junctions

Structural, magnetic, and electrical properties of Co2MnSi∕MgO∕n-GaAs tunnel junctions

X-ray absorption spectroscopy and x-ray magnetic circular dichroism of epitaxially grown Heusler alloy Co2MnSi ultrathin films facing a MgO barrier

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