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Impact of interface structure on magnetic exchange coupling in MnBi/FexCo1−x bilayers

Sabet, S. and Moradabadi, A. and Gorji, S. and Yi, M. and Gong, Q. and Fawey, M. H. and Hildebrandt, E. and Wang, D. and Zhang, H. and Xu, B.-X. and Kübel, C. and Alff, L. (2018):
Impact of interface structure on magnetic exchange coupling in MnBi/FexCo1−x bilayers.
In: Physical Review B, American Physical Society, 98, (17), ISSN 2469-9950, DOI: 10.1103/PhysRevB.98.174440, [Online-Edition: https://doi.org/10.1103/PhysRevB.98.174440],
[Article]

Abstract

Magnetic exchange coupling behavior was investigated in MnBi/FeCo bilayer system at the hard/soft magnetic interface. We performed a combined study of cross-sectional high resolution transmission electron microscopy (HR-TEM), DFT calculations, and micromagnetic simulations to elucidate effect of interface structure on exchange coupling. Exchange spring MnBi/FexCo1−x(x=0.65 and 0.35) bilayers with various thicknesses of the soft magnetic layer were deposited in a dc magnetron sputtering unit from alloy targets. According to magnetic measurements, using a Co-rich layer leads to a more coherent exchange coupling with optimum soft layer thickness of about 1 nm. Our DFT calculations predicted formation of a polycrystalline FeCo layer with coexisting crystalline and disordered (110) phases. The indexed FFTs from HR-TEM images confirmed a crystalline FeCo(110) layer, with slight misorientation in some areas, and a disordered region close to the interface which deteriorates interface exchange coupling. Moreover, our micromagnetic simulations showed how the thickness of the FeCo layer and the interface roughness both control the effectiveness of exchange coupling in MnBi/FeCo bilayer.

Item Type: Article
Erschienen: 2018
Creators: Sabet, S. and Moradabadi, A. and Gorji, S. and Yi, M. and Gong, Q. and Fawey, M. H. and Hildebrandt, E. and Wang, D. and Zhang, H. and Xu, B.-X. and Kübel, C. and Alff, L.
Title: Impact of interface structure on magnetic exchange coupling in MnBi/FexCo1−x bilayers
Language: English
Abstract:

Magnetic exchange coupling behavior was investigated in MnBi/FeCo bilayer system at the hard/soft magnetic interface. We performed a combined study of cross-sectional high resolution transmission electron microscopy (HR-TEM), DFT calculations, and micromagnetic simulations to elucidate effect of interface structure on exchange coupling. Exchange spring MnBi/FexCo1−x(x=0.65 and 0.35) bilayers with various thicknesses of the soft magnetic layer were deposited in a dc magnetron sputtering unit from alloy targets. According to magnetic measurements, using a Co-rich layer leads to a more coherent exchange coupling with optimum soft layer thickness of about 1 nm. Our DFT calculations predicted formation of a polycrystalline FeCo layer with coexisting crystalline and disordered (110) phases. The indexed FFTs from HR-TEM images confirmed a crystalline FeCo(110) layer, with slight misorientation in some areas, and a disordered region close to the interface which deteriorates interface exchange coupling. Moreover, our micromagnetic simulations showed how the thickness of the FeCo layer and the interface roughness both control the effectiveness of exchange coupling in MnBi/FeCo bilayer.

Journal or Publication Title: Physical Review B
Volume: 98
Number: 17
Publisher: American Physical Society
Divisions: 11 Department of Materials and Earth Sciences
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences > Material Science > Advanced Thin Film Technology
11 Department of Materials and Earth Sciences > Material Science > Theory of Magnetic Materials
Date Deposited: 17 Jan 2019 08:48
DOI: 10.1103/PhysRevB.98.174440
Official URL: https://doi.org/10.1103/PhysRevB.98.174440
Funders: The authors thank the LOEWE project RESPONSE funded by the Ministry of Higher Education, Research and the Arts (HMWK) of the state of Hessen, Germany., We also acknowl- edge the computing time by the high performance computer center of Hessen (Lichtenberg), and K. Albe from Technische Universität Darmstadt.
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