Ferromagnetic resonance of thin yttrium iron garnet films near a ground plane: Parallel field

Parallel field ferromagnetic resonance spectra of an yttrium iron garnet film in the vicinity of a metallic ground plane are presented. The evolution of the spectra with changing film-ground distance is traced continuously over a wide range. The following effects are found to occur at distances of less than about 500 μm: Large shifts of the resonance fields, disappearance and subsequent reappearance of lines, appearance of "forbidden" lines, and crossing of lines. All of these effects are confirmed by a theoretical calculation which relies on the mechanism of excitation of waves which are circulating around the sample.