Electrical Transport in FeCr2S4-CuCr2S4 Spinels

Thermoelectric power $\alpha$ , electrical conductivity $\sigma$ , and Hall effect have been studied for single crystals of the ${\mathrm{Fe}}_{\text{1−x}}{\mathrm{Cu}}_x{\mathrm{Cr}}_2{\mathrm{S}}_4$ system. While ${\mathrm{FeCr}}_2{\mathrm{S}}_4$ is a p‐type semiconductor, substitution of Fe by Cu causes n‐type conduction between $\text{x∼0.2}$ and $\text{x∼0.5}$ in the temperature range 4.2°–550°K. For $\text{x>0.5}$ , p‐type conductivity is observed. An explanation of the experiments is given on the basis of a three‐band model.