Nearest neighbor hopping in Cd_0.83Mn_0.17Te:In, controlled by persistent photoconductivity

We have measured the temperature dependence of the electrical resistivity of a sample of the dilute magnetic persistent photoconductor Cd_1-xMn_xTe:In (x = 0.17) as a function of persistent photocarrier concentration. We observe a resistivity with the form ρ = ρ₃ exp(E₃/k_BT) over the temperature range investigated (20-4 K), where E₃ and ρ₃ vary with the carrier density in a manner that suggests a nearest neighbor hopping transport mechanism. Magnetotransport measurements have also been made and we observe an anisotropic negative magnetoresistance (MR) at higher temperatures, which crosses over to a MR that is positive, and essentially isotropic, at low temperatures. We interpret this behavior as a cross over from a mechanism that is sensitive to the length of the nearest neighbor hop (an `orbital' effect) to a situation where the interaction between the localized electron and the magnetic ions of the host becomes important.