Magnetic and electrical properties of filled skutterudite compound (Sm1−xRx)Ru4P12 (R=La, Y)

Abstract

Sm-site substitution effect on filled skutterudite compound SmRu4P12, which shows an intriguing metal-insulator (MI) transition, has been studied by electrical resistivity, magnetic susceptibility and specific heat measurements. Single-phase polycrystalline (Sm1−xLax)Ru4P12 (x=0.1, 0.2, 0.3) and (Sm1−xYx)Ru4P12 (x=0.1, 0.2, 0.3) have been prepared at high temperature and high pressure. Both La and Y substitutions cause a large suppression of the semiconductor-like behavior at low temperature. The MI transition temperature (TMI) shifts to lower temperature with increasing La concentration. This change is qualitatively consistent with external pressure experiments. It could be due to a negative chemical pressure effect induced by La substitution. However, TMI also shifts to lower temperature with increasing Y concentration, which is expected for a positive chemical pressure effect. The results suggest that introducing a disorder into the periodicity of Sm affects sensitively the MI transition in this system.