Spin-dependent lifetimes and nondegenerate spin-orbit driven hybridization points in Heusler compounds

We present an ab initio calculation of the (k) over right arrow- and spin-resolved electronic lifetimes in the half-metallic Heusler compounds Co2MnSi and Co2FeSi. We determine the spin-flip and spin-conserving contributions to the lifetimes and study in detail the behavior of the lifetimes around states that are strongly spin mixed by spin-orbit coupling. We find that for nondegenerate bands the spin mixing alone does not determine the energy dependence of the (spin-flip) lifetimes. Qualitatively, the lifetimes reflect the lineup of electron and hole bands. We predict that different excitation conditions lead to drastically different spin-flip dynamics of excited electrons and may even give rise to an enhancement of the nonequilibrium spin polarization.