X-ray diffraction and thermal expansion of intermediate valence compound Sm_(0.9)La_(0.1)S at high pressure

摘要

SmS is well known to show a metal-insulator transition at high pressure around 0.7GPa at room temperature. By doping La for Sm, it shows metallic conductivity at ambient pressure with intermediate valence state by the effect of chemical pressure. But a phase transition from metallic to semiconducting state is observed at low temperature by applying pressure around O.6GPa. In the present work we attempted to measure lattice spacings and the thermal expansion of Sm_(0.9)La_(0.1)S under high pressure in order to clarify the relation between the metal-insulator transition and the lattice property.