Coherent Potential Approximation for Alloys with Random Off‐Diagonal Elements: Heisenberg Ferromagnet

Abstract

AbstractWe use ideas of Blackman et al. [4] for the coherent potential approximation (CPA) in alloys with configuration‐dependent hopping terms. In the locator formalism the inverse self energy obeys an equation of the same form as the standard CPA equation. We first apply the formalism to the magnon spectrum of the disordered anisotropic Heisenberg ferromagnet with equal exchange constants but different spins. We calculate densities of states, the magnon dispersion relation, and the lifetime of the states, and we find regions of localized states at both ends of the spectrum at low concentrations. The formalism is then applied to the case of different exchange constants but equal spins in order to discuss recent experimental results.