Specific features of Bragg resonances in a magnonic crystal with two periods

Specific features of Bragg resonances in a magnonic crystal with a metallic grating on the surface with two periods have been revealed. A theoretical model describing the spectral characteristics of magnetostatic waves has been constructed by matching the permeabilities of the metal layer and the ferromagnetic film at the interface between them and using the coupled-wave analysis. The distribution of the magnetization amplitude at each Bragg resonance frequency has been calculated by the finite-element method. It has been shown that three Bragg resonances in the first Brillouin zone for the grating with a smaller period and one resonance in the first Brillouin zone for the grating with a larger period are formed in this structure. Resonance frequencies are determined by the ratio of the large and small periods.