Magnon transmission by an atomic interface in Ni-Fe and Fe-Ni systems

This work describes spin wave localized states and coherent magnon transport in ferromagnetic systems. The model system, A-B, consists of a semi-infinite bcc ferromagnetically ordered lead B joined to another fcc semi-infinite ferromagnetically ordered lead A, oriented in the same direction. It is applied to the systems Ni-Fe and the inverse Fe-Ni. The magnon transmission, scattering coherently at the interface boundary, and the localized density of spin states are calculated and analyzed. Transmission and reflection scattering cross sections are determined from elements of a Landauer-type scattering matrix. The theoretical calculations are carried out using the matching procedure. The results highlight the localized spin states on the interface domain and their interactions with incident magnons. The calculated properties are presented for arbitrary incidence angles of the magnons on the boundary, for all accessible frequencies in the propagating bands, and for the interatomic magnetic exchange of the A and B subsystems, and their spin intensity, with no externally applied magnetic field. The spin waves associated with the surface and the interface, in layered magnetic structures, interact with each other leading to interesting magnetic behaviors and give symmetry properties of spin layers at a microscopic scale.