Effect of High Pressure on the Fermi Surface of Aluminum

The effect of pressures up to 7 kbar on portions of the third-zone Fermi surface of aluminum has been determined by using the field-modulation technique to detect de Haas-van Alphen oscillations and by using solid helium as a pressure medium. The $\gamma$-[110] cross section decreased (0.47±0.06)% per kbar while the $\beta$-[100] cross section increased (1.2±0.15)% per kbar. The nearly-free-electron model would predict an increase of 0.074% per kbar for both of these cross sections. The departure of the observed effects from this value is attributed to changes in the finite band gaps of aluminum, which the nearly-free-electron model does not take into account. A simple model is described which utilizes the pressure dependence of the pseudopotential coefficients to predict changes in the Fermi-surface cross sections with pressure. The effects predicted by this model are of the correct order of magnitude and sign to explain the experimental results.