Metal-insulator transition in the spinel-type Cu(Ir1−xCrx)2S4 system Original Research Article

A normal thiospinel CuIr2S4 exhibits a temperature-induced metal-insulator (M–I) transition around 230 K with structural transformation, showing hysteresis on heating and cooling. On the other hand, CuCr2S4 has the same normal spinel structure without the structural transformation. CuCr2S4 has been found to be metallic and ferromagnetic with the Curie temperature Tc~377 K. In order to see the effect of substituting Cr for Ir on the M–I transition, we have carried out a systematic experimental study of electrical and magnetic properties of Cu(Ir1−xCrx)2S4. The M–I transition temperature shifts to lower temperature with increasing Cr-concentration x and this transition is not detected above x~0.05. The ferromagnetic transition temperature decreases as x is decreased and the transition does not occur below x~0.20.