Magnetotransport in the insulating regime of Mn doped GaAs

Abstract

We consider transport in the insulating regime of GaMnAs. We calculate the resistance, magnetoresitance and Hall effect, assuming that the Fermi energy is in the region of localized states above the valence band mobility edge. Both hopping and activated band transport contributions are included. The anomalous Hall current from band states is very different from the hopping Hall current and has extrinsic (skew) and intrinsic (Luttinger) contributions. Comparison with experiment allows us to assess the degree to which band and hopping contribution determine each of the three transport coefficients in a particular temperature range. There are strong indications that the insulating state transport in GaMnAs is controlled primarily by extended state, band edge, transport rather than by variable range hopping, as reported in the literature.