Magnetoacoustic Studies of the Fermi Surface of Aluminium

Magnetoacoustic measurements are made on very pure aluminium single crystals (R293 °K/R4.2 °K up to 26 500) in the frequency range 70 to 150 MHz. The directions of acoustic propagation are 〈100〉, 〈110〉, 〈111〉, 〈112〉, and 16° from 〈120〉 towards the nearest 〈100〉. In all cases a large number of oscillations are observed. The deduced Fermi surface dimensions for the second zone are in general agreement with Harrison's free‐electron model. The data obtained with the direction of propagation along the three principal crystallographic directions agree with earlier investigations by KAMM and BOHM, and BEZUGLYI et al. Third zone dimensions are obtained which are in agreement with Ashcroft's calculations. The conditions for magnetoacoustic oscillations are discussed. Large‐angle intersection between the plane of the electron orbit and the contour at the point of interaction with the Fermi surface seem to be a fundamental requirement for pronounced oscillations. With wave vector along 〈110〉 orbits are reported which are probably due to magnetic breakthrough at a field strength of 370 Gauss.