Pressure Effect on the Structure and Superconducting Transition Temperature of Filled Skutterudites LaT4P12 (T=Fe, Ru)

We studied the effect of pressure on the superconducting transition temperature TSC of LaT4P12 (T=Fe, Ru) up to 8 GPa through electrical resistivity measurements in a cubic anvil apparatus. The TSC of LaFe4P12 was also determined through magnetization measurements up to 3.4 GPa with an opposed-anvil pressure cell. In LaFe4P12, TSC increases with pressure at a rate of 0.71 K/GPa from 0 GPa reaching its maximum at approximately 7 GPa. In contrast, the TSC of LaRu4P12 monotonically decreases with pressure. The decrease rate gradually increases from −0.07 to −0.29 K/GPa. The distinct pressure dependences of both TSC\u27s cannot be explained solely from a structural point of view. We propose that the difference between the pressure dependence of TSC for LaFe4P12 and that for LaRu4P12 can be attributed to the difference in the electronic density of states at the Fermi energy between these two compounds