Ultrasound and magnetic domain structure in polycrystalline material

Ultrasound magnetostrictively stimulates vibrations of Bloch walls and periodic rotations of the magnetic moments of the domains. If the stress amplitudes are small the domain configuration remains unaltered. When compared with the measured reversible susceptibility, measurements of the attenuation and the velocity of sound as functions of magnetization provide information about some aspects such as domain width and the occurrence of different elementary processes during magnetization. Using sound waves with propagation direction normal to the external magnetic field, one gets as a new variable the angle between the field and the oscillation direction. The results of these measurements cannot be discussed without contradicting classical ideas concerning te magnetostrictive excitation process.