SPECTRUM OF ELEMENTARY EXCITATIONS OF A SINGLE-DOMAIN WALL IN GARNET-FILMS WITH INPLANE MAGNETIZATION

Epitaxial garnet films with in-plane magnetization are studied by micr owave technique. Resonances related to different branches of domain wa ll excitations are observed: a low-frequency Goldstone branch of trans lational wall vibrations in the MHz band and a high-frequency is obser ved, if frequency Gilinskii branch in the GHz band. A strong coupling between neighbouring domain walls is observed, if their distance becom es comparable to the wall thickness. In this case each resonance is sp lit into two coupled resonant modes, their frequencies being larger at smaller wail distances. Spin wave excitations of a single wall are an alyzed by numerical solution of Landau-Lifshitz and magnetostatic equa tions for the case of a bulk orthorhombic ferromagnetic material. Unid irectional Gilinskii branch and asymmetric Goldstone branch are shown 60 exist in the spectrum of the wall excitations for the case of the p ropagation direction perpendicular to the magnetization in domains. Un expected wall excitation spectra are predicted at some values of the a nisotropy parameters when the wall becomes unstable. Such spectrum sho ws a gap in the wave number and a loop in the dispersion of the Goldst one branch.