Magnetoelastic Coupling Modulation at Ferromagnetic Resonance in Garnet Ferrite Films

Low-field ferromagnetic resonance in garnet ferrite epitaxial films of different composition with easy-plane anisotropy has been investigated. In ferromagnetic resonance spectra obtained by frequency sweeping, the modulation of the spectral line intensity by a set of narrow (about 100 kHz wide) lines equidistant in frequency has been observed. The lines are spaced in accordance with the resonance of the standing modes of transverse elastic vibrations along the thickness of the film–substrate structure. The modulation depth decreases with rising frequency, since the magnetoelastic coupling depends on the frequency of the elastic vibration mode. In some samples, the modulation depth drops monotonically, whereas in others it oscillates. Such behavior is explained by strong and weak spin pinning on the surface, respectively. The influence of the film–substrate interface and the hybridization of spin-wave and elastic vibration modes under magnetoacoustic resonance conditions have been discussed.