Temperature-dependent spin polarization of Heusler <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">Co</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:mi>MnSi</mml:mi></mml:math> from the disordered local-moment approach: Effects of atomic disordering and nonstoichiometry
Kenji Nawa, Ivan Kurniawan, Keisuke Masuda, Yoshio Miura, Christopher E. Patrick, J. B. Staunton
Abstract
Half-metallic ferromagnets have been widely investigated by first-principles density-functional theory (DFT) calculations, but extending such studies to investigate spin-polarization at finite temperatures is still challenging due to the difficulty of incorporating temperature effects appropriately. We present DFT calculations, based on a Green's function formulation, which include thermal effects via the disordered local-moment method to address this issue. The calculations are carried out for Heusler ${\mathrm{Co}}_{2}\mathrm{MnSi}$ alloys in order to investigate the temperature dependence of spin polarization, where atomic-disordering and nonstoichiometric effects are taken into account. Our results show that the spin polarization strongly depends on temperature and that a Co $d$-orbital effect plays a key role in this effect. Furthermore, we find that the temperature-dependent spin polarization of ${\mathrm{Co}}_{2}\mathrm{MnSi}$ can be improved by reducing the Co content and incorporating extra Mn.