Anomalous Hall effect in ferromagnetic semiconductors with hopping transport

We use high-field magnetotransport to examine the relation between the Hall effects and the longitudinal resistance, R-xx, in digitally doped (Ga,Mn)As structures with hopping transport. The ordinary and anomalous Hall resistances, R-OH and R-AH, display sublinear dependences on R-xx, a behavior inconsistent with theories used to interpret data from metallic semiconductor ferromagnets. None of the resistances are simply activated. While R-OH is consistently holelike, R-AH can have either sign. These results agree qualitatively with aspects of a recently developed model for the Hall effects in the hopping regime.