Electrical Transport in FeCr2S4-CuCr2S4 Spinels

Thermoelectric power α, electrical conductivity σ, and Hall effect have been studied for single crystals of the Fe1−xCuxCr2S4 system. While FeCr2S4 is a p-type semiconductor, substitution of Fe by Cu causes n-type conduction between x∼0.2 and x∼0.5 in the temperature range 4.2°–550°K. For x>0.5, p-type conductivity is observed. An explanation of the experiments is given on the basis of a three-band model.