Pressure-induced volume anomaly of intermediate valence compound Sm 0.9La 0.1S

Abstract

Thermal expansion of intermediate valence compound Sm 0.9La 0.1S has been measured under high pressure up to 2.1 GPa in the temperature range, 4.2⩽ T⩽300 K. It is found that the thermal expansion shows a smooth variation below 0.5 GPa but an anomalously large expansion, i.e., a large negative thermal expansion coefficient is observed at low temperature above 0.5 GPa. These results are related to the pressure-induced metal–insulator transition. The negative anomaly in the thermal expansion coefficient is suggested to be due to the negative Grüneisen parameter of the energy gap.