Anomalous Hall Effect in Variable Range Hopping Regime: Unusual Scaling   Law and Sign Reversal with Temperature
  Anomalous Hall effect (AHE) is important for understanding the topological properties of electronic states, and provides insight into the spin-polarized carriers of magnetic materials. AHE has been extensively studied in metallic, but not variable-range-hopping (VRH), regime. Here we report the experiments of both anomalous and ordinary Hall effect (OHE) in Mott and Efros VRH regimes. We found unusual scaling law of the AHE coefficient $Rah=aRxx^b$ with b>2, contrasting the OHE coefficient $Roh=cRxx^d$ with d<1. More strikingly, the sign of AHE coefficient changes with temperature with specific electron densities. 
R. M. Qiao, S. S. Yan, T. S. Xu, M. W. Zhao, Y. X. Chen, G. L. Liu, W.   L. Yang, R. K. Zheng, and L. M. Mei
cond-mat.mes-hall cond-mat.dis-nn