Effect of rare earth filling on unfilled skutterudite compound CoSb3

We have succeeded in synthesizing the filled skutterudite compound Pr_xCo₄Sb₁₂ under high pressures. Pr site filling factor was estimated to be about 50 ±10% by powder X-ray diffraction and chemical composition analysis using field emission electron microscope. Apparent expansion of lattice constant 9.09 Å compared to that of CoSb₃9.03 Å is also indirect evidence of successful filling of Pr-ions. In the magnetization and specific heat measurements, no anomaly suggesting phase transition has been found down to 2 K.