Electrical and magnetic properties of n-Cd(_1-x)Mn(_x) Te close to the metal-insulator transition

Abstract

Electrical transport and magnetic measurements have been made on n-Cd(_1-x)Mn(_x) Te (0.047 50 mT) Efros-Shklovskii variable range hopping is observed in the insulating phase. These results are attributed to the formation of a hard gap in the density of states, having a magnetic origin. At higher fields an insulator-metal phase transition occurs. In the metallic phase the conductivity can be described by a quantum correction to the zero temperature conductivity due to the effect of electron-electron interactions. Results obtained before and after illumination are consistent with scaling theory of electron localisation, having a critical exponent close to unity, indicative of the importance of electron-electron interactions. A reduction in the value of the critical field is seen after increasing the carrier density (B(_c) = 2.0 and 1.3 T for n = 3.3 xl0(^17)cm(^-3) and 3.8 x10(^17) cm(^-3) respectively).At low temperatures an anisotropy in the resistivity has been measured for samples in the spin glass phase. Magnetoresistance measurements have shown results consistent with previous measurements, in addition to a large, low field component that is attributed to the effect of magnetic field on electrons in the variable range hopping regime