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

Abstract A normal thiospinel CuIr 2 S 4 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, CuCr 2 S 4 has the same normal spinel structure without the structural transformation. CuCr 2 S 4 has been found to be metallic and ferromagnetic with the Curie temperature T c ~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(Ir 1− x Cr x ) 2 S 4 . 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.