Magnetoacoustic Attenuation in Semimetals. III. Enhancement of Quantum Oscillations in Bismuth-Antimony Alloys forqH∼90°

Abstract
The sound attenuation in Bi 1- x Sb x alloys has been measured under the condition that the magnetic field vector H is nearly perpendicular to the sound wave vector q . Quite unlike bismuth, the quantum oscillations with very large amplitudes and with the line shape like the density of state curve were observed. Particularly, for q parallel to a bisectrix axis, the oscillations take the form of a deep dip whenever the Landau level crosses the Fermi level. These anomalies are compared with a tentative theory taking into account of an effect of random diffractions of the sound wave propagation direction due to a spatial inhomogeneity of antimony concentration. The large humps can be partially explained by the theory but the deep dips cannot be explained at all.