Spin-mixing conductances of metallic and half-metallic magnetic layers

Abstract

The spin-mixing conductance of a thin ferromagnetic layer attached epitaxially to twosemi-infinite non-magnetic metallic leads is formulated in terms of non-equilibrium Green’sfunctions. The spin-mixing conductance is obtained as a response of the spin torque actingon the ferromagnet with respect to the spin accumulation in one of the leads, while the spintorque is defined as a time derivative of the spin magnetic moment. The equivalence of thederived formula with a previous expression of the Landauer–Büttiker scatteringtheory is sketched and an implementation within the ab initio tight-binding linearmuffin-tin orbital method is briefly described. Applications are made for metallicCo- and Ni-based slabs embedded between Cu(111) leads and for half-metallicCo2MnSi films sandwiched by Cr(001) leads. The calculated results throw serious doubts on thegeneral validity of two features: fast convergence of the spin-mixing conductance withincreasing thickness of the magnetic layer and negligible values of the imaginary part of thespin-mixing conductance as compared to the real part.