Multiple Ferromagnetic Resonance in Ferrite Spheres

Ferromagnetic resonance experiments have been performed on single crystal spheres of manganese and manganese-zinc ferrites placed in field configurations having large gradients in the rf magnetic field at the sample site. Five major and several minor resonant absorptions are observed extending over a region of 700 oersteds at room temperature. The line spacings are essentially independent of sphere size. The absorptions are shown to be attributable to modes of precession of the bulk magnetization of the sample which are more complicated than the spatially uniform precession contemplated by the usual ferromagnetic resonance theory. The lowest order modes are identified and their dynamical properties shown to be consistent with the prediction of an idealized magnetically-coupled-oscillator model.