Disordered magnetic multilayers: Electron transport within the coherent potential approximation

We develop an efficient technique for ab initio calculations of the current-perpendicular-to-plane (CPP) electron transport in disordered magnetic multilayers. The method is based on the tight-binding linear muffin-tin orbital theory and the coherent potential approximation (CPA) to treat the substitutional randomness in an effective-medium approach. A formulation of the CPA vertex corrections, giving rise to an incoherent part of the CPP conductance, is described in detail and the numerical implementation is discussed. The developed approach is illustrated on several disordered systems derived from fcc Co-Cu-Co trilayers and its results are compared to those of a supercell technique simulating the randomness in terms of two-dimensional lateral supercells. The overall good agreement of the two techniques proves reliability of the CPA for a number of specific features encountered in disordered multilayers. As another example, results for layered diluted ferromagnetic (Ga, Mn)As semiconductors are reported, including a brief discussion of spin-resolved and incoherent CPP conductances and a comparison to bulk residual resistivities.