METAL-INSULATOR-TRANSITION OF CUIR2(S,SE)(4) UNDER HIGH-PRESSURE

We have studied the transport and structural properties of CuIr2(S1-xS ex)(4) spinel compound up to 10 GPa using a cubic-anvils-type press. F or CuIr2S4, the insulating phase was found to become stable above 4 GP a at room temperature. Resistivities of all samples increased with inc reasing pressure even for the metallic samples with x > 0.8 at ambient pressure. When pressure (P < 4GPa) was applied to the samples with x = 0.9 and 1.0, an anomalous peak appeared below 100 K in the temperatu re dependence of the resistivity. The resistivity was metallic like on the low-temperature side of the peak while a semiconducting behavior emerged on the high-temperature side. In this pressure range, no struc tural phase transition was observed. One possible explanation for thes e results is due to the change in the local arrangement of constituent in this spinel structure. (C) 1998 Elsevier Science B.V. All rights r eserved.