Anisotropy of the Ultrasonic Attenuation in Metals

Abstract

The anisotropy of ultrasonic attenuation is calculated by using Pippard’s formula for a model in which the Fermi surface consists of a single prolate spheroidal surface. For longitudinal ultrasounds the attenuation coefficient α shows two maxima in the regions δ=35°∼45° and 145°∼135°, but for transverse ultrasounds α shows a maximum at δ=90°, where δ is the angle between the major axis of the spheroid and the direction of propagation. Next, the method is applied to bismuth for longitudinal sound waves. In this case, however, because of a large deformation potential, the general features of the anisotropy are very different from the former case. Moreover, in this case the anisotropy of the deformation potential itself seems to play a very important role.