The new conductive oxysulfides [(La1-xSrx)O]CuS containing a Cu-layer

We have found a metal-insulator transition in a [(La1-xSrx)O] CuS system and investigated its structural, electrical and magnetic properties. The crystal structure of (LaO) CuS is tetragonal (space group P4/nmm) and of layered type which has a sequence of -O-La-S-Cu-S-La-layers along the c-axis. The lattice parameters a and c of the compound are 0.3996 and 0.8516nm, respectively. The electrical resistivity of (LaO) CuS is similar to 10(4)Omega-cm at room temperature and its temperature dependence is semiconductive. The electrical resistivity of [(La1-xSrx)O] CuS decreased with x and that of the samples with x >= 0.04 was metallic down to 4.2 K. The magnetic susceptibilities chi of all samples were almost the same and showed a weak temperature-dependent paramagnetism on a diamagnetic background (chi(dia) = -4.1 x 10(-5) emu/ mol), chi=chi(dia) + C/T, The effective magnetic moment was 5.0 x 10(-2) mu(B) per formula unit.