Generation of spin waves via spin-phonon interaction in a buried dielectric thin film

Abstract

In this paper, we investigate the magnetic, optical, and lattice responses of a $\mathrm{Pt}/\mathrm{Cu}/{\mathrm{Bi}}_{1}{\mathrm{Y}}_{2}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}/{\mathrm{Gd}}_{3}{\mathrm{Ga}}_{5}{\mathrm{O}}_{12}$ heterostructure to femtosecond laser excitation of the opaque Pt/Cu metallic bilayer. The electronic excitation generates coherent and incoherent phonons, which trigger high-frequency standing spin waves (SWs) in the dielectric ${\mathrm{Bi}}_{1}{\mathrm{Y}}_{2}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ layer via a phonon-induced change of magnetic anisotropy. We find that the incoherent phonons (heat) can induce a fast $(<1\mathrm{ps})$ and slow $(>1000\phantom{\rule{0.16em}{0ex}}\mathrm{ps})$ decrease of the magnetic order by different spin-phonon interaction scenarios. These results open perspectives for generating high-frequency SWs in buried magnetic garnets.