Pressure Dependence of Superconductivity in Filled-Skutterudite YOs4P12

We have studied the magnetization on YOs4P12 under pressure up to similar to 4 GPa. Pure polycrystalline YOs4P12 was prepared by the high-pressure high -temperature method and was evaluated by the X-ray diffraction measurement. YOs4P12 shows superconducting transition at Tsc 3 K at ambient pressure. We have investigated the pressure dependence of Tsc by means of DC magnetization measurements with incorporating opposed ceramic anvil pressure apparatus into MPMS. Tsc of YOs4P12 slightly decreases with pressure at a rate of dTsc/dP = -0.11 K/GPa. This is quite contrary to the Tsc of related compounds YFe4P12, which rapidly increases with pressure at a rate of 1.0 K/GPa. The dTsc/dPs relationship of YFe4P12 and YOs4P12 are similar with that of LaFe4P12 and LaPs(4)P(12). Tsc of LaFe4P12 increases rapidly with pressure at a rate of dTsc/dP 0.72 K/GPa below 2 GPa and that of LaOs4P12 decreases gradually with pressure at a rate of -0.095 K/GPa. Considering these similarity, we can assume that the origin of dTsc/dP of these compounds are the same and are attributed to the density of states at Fermi level and to the Hopfield parameter.