Spectrum and lineshape of bubble-lattice resonance

Spectral analysis of photometrically detected bubble-lattice oscillations reveal resonance frequencies of 45 and 66 MHz in a 6.2μm film of (Gd,Y)3(Fe,Ga)5O12. Similar results are obtained for stripe lattices. Existing theory explains the dependence of the lower-frequency resonance on bias field and lattice parameter. To explain the higher resonance, a theory of flexural wall vibration for plane walls associates the resonances with wave functions having zero and two nodal lines lying parallel to the film, respectively. We conclude that the amplitude of the main mode is greater at the surfaces than within the interior of the film. Characteristic fold-over and clipping of resonance line shapes are noted and discussed.