High pressure synthesis and magnetic properties of heavy-rare-earth filled skutterudite compounds R Os 4 P 12 ( R  =Gd, Tb, Dy and Ho)

Filled skutterudite compounds have attracted attention due to their excellent thermoelectric properties and various anomalous properties specific to strongly correlated electron systems such as metal-nonmetal transition, multipole ordering, and heavy electron state. Filled skutterudite compounds containing heavy rare-earth elements are extremely difficult to synthesize at ambient pressure. However, we have succeeded in synthesizing new filled skutterudite compounds containing heavy rare-earth elements by high pressure synthesis methods. We report high pressure synthesis and magnetic properties of ROs4P12 (R = Gd, Tb, Dy, and Ho), which are difficult to obtain at ambient pressure. We discuss the crystal field ground states, magnetic phase diagrams and the role of multipole degree of freedom, in these compounds.