Magnetoacoustic Absorption and the Fermi Surface in Potassium

Abstract

Magnetoacoustic measurements in zone-refined and oriented single crystals of potassium have yielded detailed information on the relative attenuation, the Fermi surface, and the phase factors in this metal for magnetic-field directions lying near the , , and axes. The longitudinal ultrasonic wave was propagated along the axis, perpendicular to the magnetic field. The data show that the Fermi surface in potassium is only slightly distorted relative to its free-electron value, bulging by about 0.3% in the direction and pushed in by about 0.4 and 0.5%, respectively, in the and directions. The deviation in $k_f$ from the average value, $k_f=(7.44\mathrm{}\pm 0.06)\times {10}^7$ ${\mathrm{cm}}^{-1\mathrm{}}$, is found to be about 0.8%. The average value of the phase factor for potassium is found to lie rather close to the free-electron value of 0.375.