Ultrasonic Quantum Oscillations in Chromium

Abstract

Measurements of quantum oscillations in the ultrasonic attenuation have been made to investigate the Fermi surface of chromium in the "single-$\stackrel{\ensuremath{\rightarrow}}{\mathrm{Q}}$" state. Several frequency branches were followed over the entire Fermi surface and many of these data agree with earlier de Haas-van Alphen and ultrasonic results. Three branches display harmonic behavior which is exact when the measuring field is in the basal plane, but which deviates smoothly from exactness as the field is rotated toward $\stackrel{\ensuremath{\rightarrow}}{\mathrm{Q}}$. The most likely explanation of this feature is that of magnetic breakdown among nonextremal orbits on the Fermi surface. The lack of degeneracy of the branches at certain symmetry axes prevented identifying the data with the location of sections of the Fermi surface. The data in one family of branches agree point by point with the de Haas-van Alphen results when the measuring field is near the basal plane, but differ as the field approaches $\stackrel{\ensuremath{\rightarrow}}{\mathrm{Q}}$. For the remaining data, symmetry arguments may not be applicable because of changes in the topology caused by magnetic breakdown.