Longitudinal magnetoresistance

Abstract

De Haas-van Alphen oscillations of magnetization in single crystals of potassium have been studied by means of a sensitive recording system (Lee 1966) based on the second harmonic modulation technique. From the observed variation of the de Haas-van Alphen phase as the crystal is rotated m a constant magnetic field, the amsotropy of the cross sectional area of the Fermi surface is deduced. The radial distortions of the Fermi surface of potassium are computed by inverting a least squares cubic harmonic fit to the experimental data. The results are found to be in good general agreement with those of Shoenberg & Stiles (1964). It is shown that the experimental data cannot be explained in detail in terms of a local pseudopotential. The coefficients of a nonlocal pseudopotential scheme are adjusted to fit the data, and the d noulocality in potassium is deduced. The back scattering matrix elements of the pseudopotential are evaluated, and are compared with the model potential form factor of Animalu & Heine (1965). The lowest band gap at the symmetry point N is deduced and compared with the results of recent band structure calculations.