Bilayer ferromagnetic film with tensorial interface exchange coupling. Localized modes

Abstract

We present some results of a new theory of standing spin-wave excitations in bilayer magnetic film with exchange coupling across the interface between two ferromagnetic layers. The model Hamiltonian includes exchange and Zeeman energies, as well as anisotropy terms at the free surfaces and at the interface. Exchange coupling across the interface is assumed in tensorial form with (two) in-plane J | int and out-of-plane J ± int exchange integral components. We discuss the interface effects using the concept of effective pinning parameters and dynamical coupling parameters for the spin-waves at the interface. It is found that for certain values of the ratio of the inteface exchange intergral components ϵ = J ± int/ J | int the constituent magnetic sublayers may be considered as effectively decoupled as regards the spin-wave properties. When studying the existence conditions of localized modes in the bilayer magnetic film one comes upon quite novel features that do not occur in the analysis of the respective existence conditions for a single film.