Two-dimensional magnetostatic resonances in a thin film disk containing a magnetic bubble

Abstract

We have recently discussed magnetostatic modes in a normally-magnetized, thin-film disk that are bound to ’’virtual-surfaces’’ created by the presence of a radial dc-field gradient; the frequency and polarization of such modes was found to be sensitive function of the gradient. We now employ a similar method of analysis to study two-dimensional resonance modes in a thin film contaning a single magnetic bubble. When the thickness of the bubble domain wall is ignored, and there is no applied gradient, the spectrum, as expected, contains single bubble resonances coupled to disk resonances. However, actual domain walls contain large magnetic anisotropy field gradients due to the often complex spin reversal pattern. Such gradients will affect the mode polarization within the wall and the effective boundary conditions acting across the wall may be significantly altered for those resonances coupled to exchange modes within the domain wall. The related but simpler problem of rf exchange modes generated at a plane ’’virtual-surface’’ within a single domain region is studied in detail.