Magnetic Breakdown Effects in the Galvanomagnetic Properties of Zinc

Abstract

The galvanomagnetic properties of several single-crystal specimens of high-purity zinc have been investigated. The results of this investigation are presented and a Fermi-surface topology consistent with the data is discussed. Many of the detailed features of the galvanomagnetic properties are found to result from the effects of magnetic breakdown. The open orbit parallel to the hexagonal axis is modified but not eliminated by magnetic breakdown at fields of about 17.5 kG. A "giant orbit" of the type previously observed in magnesium is found in zinc. This orbit results from magnetic breakdown across the energy gap near $K$ which separates the second-band hole sheet from portions of the third-band electron sheets. Magnetic breakdown across this same energy gap gives rise to discrete bands of open trajectories in the basal plane when the direction of the magnetic field is tilted away from the hexagonal axis in the ($10\overline{1}0$) and ($11\overline{2}0$) crystallographic planes. The transition region of the magnetic breakdown which gives rise to the giant orbit is investigated in detail, and the large quantum oscillations which have been previously observed in the transport properties of zinc are shown to be a transition-region phenomenon. The oscillations appear to result from an oscillatory breakdown probability which, in turn, arises from oscillations in the density of states associated with the Landau levels of the needle-shaped portion of the Fermi surface of zinc. An analysis of the detailed shape of the oscillations indicates that the Landau levels of the needle are split into discrete spin levels with a very large effective $g$ factor. The three values of the effective $g$ factor which are compatible with the present data are $g^{*}=90\mathrm{}$, $g^{*}=180\mathrm{}$, and $g^{*}=360\mathrm{}$, but an investigation with higher magnetic-field strengths will allow a unique choice to be made. No evidence has yet been obtained that yields a direct confirmation of the quasi-particle states predicted by Pippard.