B2 Atomic Disorder in Co2FeXMn1-XSi Heusler Alloys

P.J. Hasnip, C.H. Loach, J.H. Smith, M.I.J. Probert, D. Gilks, J. Sizeland, K. Yoshida, M. Oogane, A. Hirohata, V.K. Lazarov
2014 Journal of the Magnetics Society of Japan  
Co-based full Heusler alloys have attracted significant attention due to their high spin polarisation and successful integration as electrodes in magnetic tunnelling junctions and current-perpendicular-to-plane spin valves (CPP-SV). Further improvement of the CFMS based CPP-SVs requires a fundamental understanding of the effects of atomic disorder within the Heusler alloys. In this work we present a theoretical study of disorder in CFMS alloys using ab initio simulations, guided by images from
more » ... ded by images from Z-contrast scanning-TEM of sample films. The simulations are based on density functional theory plus a Hubbard U term, allowing the investigation of the effects of atomic disorder on the spin-polarisation at the Fermi level, and computation of the disorder formation energy. It is found that in order to retain the high spin-polarisation at the Fermi level the integrity of the Co-sublattice should be preserved, but that the effect of mixing between the Fe/Mn and Si sublattices (B2 phase) varies dramatically depending on the precise nature of the disorder and the chemical composition of the CFMS. Calculations of the spin-polarisation at the Fermi energy show that Co2Fe0.5Mn0.5Si is especially robust with respect to such intermixing, an observation which may explain the good performance of films in this composition range.
doi:10.3379/msjmag.1402r010 fatcat:zn4bp4d2bjcbnjh3klpemm2hle