The Sound Velocity and the Attenuation of YIG and YAG Crystal under Pressure with and without an External Magnetic Field

YAG is a nonmagnetic garnet crystal and YIG is a ferromagnetic garnet crystal. The sound velocity and the attenuation of the ferromagnetic garnet and nonmagnetic garnet were studied at high pressures with or without an external magnetic field. The sound velocity was measured by Pulse echo overlap technique with Matec system model 6600. The attenuation was measured by comparison of the amplitudes of echoes. We found that both nonmagnetic garnet and ferromagnetic garnet have some similar ultrasonic behavior under pressures without magnetic field. We attribute it to their same garnet crystal structure. We also found that there exists magnonspin-phonon interaction in YIG but magnonspin-phonon interaction in YAG, even at high pressures.