Direct Imaging of Resonant Phonon-Magnon Coupling
Chenbo Zhao, Zhizhi Zhang, Yi Li, Wei Zhang, John E. Pearson, Ralu Divan, Qingfang Liu, Valentine Novosad, Jianbo Wang, Axel Hoffmann
Abstract
Detection of phonons is critical for research on the interconversion between resonantly coupled magnons and phonons. Here we report the direct visualization of the resonant coupling of magnons and phonons by microfocused Brillouin light scattering on the $\mathrm{Ni}/{\mathrm{Li}\mathrm{Nb}\mathrm{O}}_{3}$ hybrid heterostructure. The static patterns of surface acoustic wave phonons, originating from the interference between the incident wave ${\ensuremath{\psi}}_{0}({A}_{0},\mathbf{k},{\ensuremath{\varphi}}_{0})$ and reflected wave ${\ensuremath{\psi}}_{1}({A}_{1},\ensuremath{-}\mathbf{k},\phantom{\rule{0.25em}{0ex}}{\ensuremath{\varphi}}_{1})$, can be modulated by magnetic field due to the magnon-phonon coupling. By analyzing the information of phonons obtained from Brillouin spectroscopy, the properties of the magnon system (Ni film), e.g., ferromagnetic resonance field and resonance linewidth, can be determined. The results provide spatially resolved information about phonon manipulation and detection in a coupled magnon-phonon system.