Ab initio theory of spin-transfer torques

Abstract

We develop an ab initio material-specific theory of current induced magnetization switching. The formulation is based on non-equilibrium Green's functions (NEGF) formalism applied to the so-called spin-mixing conductance, i.e., the linear response of the spin torque exerted on a magnetic layer to a spin accumulation in an adjacent non-magnetic layer. The numerical implementation employs the local spin density approximation (LSDA) and the linear muffin-tin orbital (LMTO) method. Possible substitutional disorder is treated using the coherent potential approximation (CPA) that allows for evaluation of the coherent (ballistic) and incoherent (diffusive) parts of the spin-mixing conductance. The developed scheme is applied to a few selected magnetic layers including systems containing diluted magnetic semiconductors and Heusler alloys. Their halfmetallic character leads to enhanced spin-mixing conductances with respect to charge conductances.