Magnetic Bragg peak enhancement under ultrasound injection

Ultrasound injection effect on a magnetic Bragg peak of yttrium iron garnet has been studied by quasielastic neutron scattering. The magnetic Bragg peak is vastly enhanced with decreasing temperature. The energy width increases proportionally to the square root of the sample temperature increase induced by the ultrasound injection. Based on a liquid model, the estimated effective mass becomes light when magnetic domain walls are removed under a magnetic field. Because the magnetic Bragg peak is enhanced by the lattice vibration, the enhancement is expected to closely relate to the spin-lattice coupling. The sharp drop is observed above 100 K for the longitudinal mode, indicating the degradation of the spin-lattice coupling. It is consistent with the suppression of the spin Seebeck effect when the temperature rises above 100 K, demonstrating the spin-lattice coupling as the degradation mechanism.