Spin wave modes in inhomogeneous ferromagnetic film at arbitrary magnetic field direction

Abstract

A generalization of the Portis model for the case of arbitrary direction of magnetization is presented, which gives the separation of linear positioned modes decreasing with θ as δ(H)(θ)/δH(0) = [12(3 cos2θ − 1)]12 till θ ≥ θc, at which all modes collapse into one single line or convert to modes following a quadratic law, and the intensities increase rapidly when θ approaches θc. We explain such behavior using spin wave modes in thin film with parabolic dependence of magnetization. A good agreement of this theory with the experiments on the reduced Ca-rich CaGe : YIG film has been obtained.