Brillouin Light Scattering Spectroscopy of Magneto-Acoustic Resonances In a Thin-Film Garnet Resonator

We used Brillouin light scattering to measure the local excitations of magneto-acoustic resonance at high spatial resolution in a laterally confined magnetic structure. We prepared a polished yttrium-iron garnet (YIG)/gadolinium-gallium garnet (GGG) square film resonator with highly efficient magneto-acoustic coupling. The structure was placed in a constant magnetic field and excited by a microwave current. The magneto-acoustic resonance had a high quality factor (Q ≃ 10⁵-10⁶). The acoustic resonance was confined to the center of the excited magnetic resonant mode. By exciting the resonant modes in the YIG layer, one can control the area of acoustic resonance excitation in the GGG substrate.