Dynamic magnetic susceptibility of a binary ordered ferromagnetic alloy. Application to spin wave stiffness constant of FeRh

Abstract
An analytical expression for the transverse susceptibility of an ordered alloy described by a tight-binding Hartree-Fock bandstructure is derived. The intra-atomic electron-electron interactions are taken into account. An exact expression for the spin wave stiffness constant is obtained which takes into account the deformations of the bands of both spin directions in the ferromagnetic structure. A simplified multi-orbital model is thoroughly examined and the computation of the FeRh ordered alloy spin wave stiffness constant is reported.