Anomalous Hall effect and magnetoresistance in Ge1−x−yPbxMnyTe cluster-glass system

Abstract

We present studies of magnetotransport properties of Ge1−x−yPbxMnyTe bulk crystals with chemical composition changing from 0.180 < x < 0.311 to 0.019 < y < 0.136. Our samples show the presence of the cluster-glass-like transition accompanied with magnetic irreversibility at temperatures TSG around 90 K. The presence of strong anomalous Hall effect (AHE) with hysteresis is observed at T < TSG. The data analysis allowed calculation of a correction to the Hall constant RH for T < TSG and the AHE constant, RS. RS is around 10−6 m3/C. RS and RH do not change strongly with temperature. The scaling law analysis has proved that the AHE in this system is due to the extrinsic mechanisms dominated by the skew scattering with relatively small contribution of the side jump process. Strong localization occurs in our system at T < TSG and causes a presence of a minimum in the resistivity vs. temperature dependence. The magnetoresistance of our samples shows complex behavior at T < TSG. The negative magnetoresistance is observed at T < 20 K and interpreted as spin-dependent scattering of conducting carriers on localized magnetic moments. At higher T nearly linear positive magnetoresistance is observed at temperatures from 20 K up to T ≈ TSG, where it reaches maximum. Positive linear magnetoresistance is related to the granular nature of our samples while the maximum near TSG is related to the giant spin-splitting of the valence band.