The Effect of Cobalt-Sublattice Disorder on Spin Polarisation in Co₂Fe x Mn1- xSi Heusler Alloys

Philip J Hasnip; Christian H Loach; Joseph H Smith; Matthew I J Probert; Daniel Gilks; James Sizeland; Leonardo Lari; James Sagar; Kenta Yoshida; Mikihiko Oogane; Atsufumi Hirohata; Vlado K Lazarov

doi:10.3390/ma7031473

The Effect of Cobalt-Sublattice Disorder on Spin Polarisation in Co₂Fe _x Mn_{1- x}Si Heusler Alloys

Materials (Basel). 2014 Feb 25;7(3):1473-1482. doi: 10.3390/ma7031473.

Authors

Affiliations

¹ Department of Physics, University of York, York YO10 5DD, UK. phil.hasnip@york.ac.uk.
² Department of Physics, University of York, York YO10 5DD, UK. s1355587@sms.ed.ac.uk.
³ Department of Physics, University of York, York YO10 5DD, UK. js570@york.ac.uk.
⁴ Department of Physics, University of York, York YO10 5DD, UK. matt.probert@york.ac.uk.
⁵ Department of Physics, University of York, York YO10 5DD, UK. dg522@york.ac.uk.
⁶ Department of Physics, University of York, York YO10 5DD, UK. leonardo.lari@york.ac.uk.
⁷ Institute of Advanced Research, Nagoya University, Chikusa-ku, Nagoya, 464-8603, Japan. zoruda_rider03@yahoo.co.jp.
⁸ Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-05, Aramaki, Aoba-ku, Sendai 980-8579, Japan. oogane@mlab.apph.tohoku.ac.jp.
⁹ Department of Electronics, University of York, York YO10 5DD, UK. atsufumi.hirohata@york.ac.uk.
¹⁰ Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan. atsufumi.hirohata@york.ac.uk.
¹¹ Department of Physics, University of York, York YO10 5DD, UK. vlado.lazarov@york.ac.uk.

Abstract

In this work we present a theoretical study of the effect of disorder on spin polarisation at the Fermi level, and the disorder formation energies for Co₂Fe_xMn_1-xSi (CFMS) alloys. The electronic calculations are based on density functional theory with a Hubbard U term. Chemical disorders studied consist of swapping Co with Fe/Mn and Co with Si; in all cases we found these are detrimental for spin polarisation, i.e., the spin polarisation not only decreases in magnitude, but also can change sign depending on the particular disorder. Formation energy calculation shows that Co-Si disorder has higher energies of formation in CFMS compared to Co₂MnSi and Co₂FeSi, with maximum values occurring for x in the range 0.5-0.75. Cross-sectional structural studies of reference Co₂MnSi, Co₂Fe_0.5Mn_0.5Si, and Co₂FeSi by Z-contrast scanning transmission electron microscopy are in qualitative agreement with total energy calculations of the disordered structures.

Keywords: half-metals; heusler alloys; spintronics materials; thin films.

Publication types

Letter