Acoustic measurements of the electronic structure of zinc and cadmium

Abstract

Measurements have been made on both zinc and cadmium of the variation of the attenuation of acoustic waves (frequencies 20–150 Mc sec^-1) with temperature and magnetic field strength. The data can be divided into two regions. First, when ql < 1, where q is the acoustic wave vector and l the mean free path of the conduction electrons. Here average parameters such as τ the relaxation time and v _F, the Fermi velocity, were calculated from the data and compared with independent measurements in order to test the validity of the theories of the acoustic attenuation. Second, the region ql > 1. In this region the geometrical resonances were observed and in addition de Haas–Schubnikov type oscillations were also observed when the magnetic field was greater than approximately 40 koe. These two types of measurements allowed us to calculate the ‘caliper’ dimensions, k _c, of the Fermi surface in a given direction and the extremal cross-sectional areas of the Fermi surface perpendicular to the magnetic field respectively. These data are assigned to particular sections of a free electron surface. In the case of zinc the distortions from the free electron model are discussed and these are compared with an existing band calculation. No such band calculation exists for cadmium; however, our data suggest that the horizontal arms of the ‘monster’ are pinched off, i.e. the Σ level is depressed below the Fermi energy. The data which corroborate these conclusions are discussed.