Magnetoresistivity tensor of arsenic (25.5 at. %) – Antimony alloy single crystals.

Abstract

An experimental investigation of the galvanomagnetic effects in a particular A7 structure material and a theoretical study of the symmetry properties of the transport tensors are presented. For the experimental study, arsenic-antimony alloy single crystals have been grown at the minimum melting point composition (25.5 at. % A8) where the solidus and liquids touch on the phase diagram. Dislocation etch pit studies have been made on the (111) cleavage faces. Measurements have been made between 1.5K and 300K of the twelve components that define the low-field magnetoresistivity tensor and of the orientation dependence of the tensor components P (_11) (B (_1), B (_2), 0), P (_11) (B (_1), 0 B (_3)) and P (_21) (B (_1), 0, B (_3)). A least-mean-squares fit to the data has been used to obtain the model parameters for a two band, multivalley, ellipsoidal Fermi surface. The alloy model parameters are compared and contrasted with those of the parent elements. The alloy is semi metallic. In the theoretical work, the forms of the magnetic field dependent transport tensors are established for all 32 crystallographic point groups. A formulation of galvanomagnetic and thermomagnetic effects based on the separation of the tensor components into “even” and “odd” functions of the applied magnetic field is given. It is shown that the Umkehr effect is a natural result of the anisotropy of crystals.