Temperature and magnetic field dependence of electrical resistivity in indium-doped CdCr2Se4 single crystals. Temperature-driven metal–semiconductor transition

The electrical resistivity ρ of single crystals of Cd1−xInxCr2Se4 (0.012 ≤ x ≤ 0.051) and Cd0.957Ga0.043Cr2Se4 is studied over the temperature range T = 2−200°K in magnetic fields of up to 50 kOe. Three characteristic types of ρ(T) curves were observed, all of which have a peak near 150°K, the position and size of which are strongly affected by the magnetic field. For weakly doped specimens, a minimum was found near 50°K which is followed by a sharp increase in ρ with decrease in temperature. For specimens with x = 0.051 and for Cd0.957Ga0.043Cr2Se4 no such minimum was observed: in these cases below 12°K there was a sharp drop in ρ, while in the first composition a metal–semiconductor transition took place. The transition may be explained by formation of collective ferron states above the transition point.