4f electronic states of the filled skutterudite compound PrFe4Sb12 synthesized under high pressure

Crystals of the filled skutterudite PrFe4Sb12 with the 73~87% Pr-site filling fractions prepared under ambient pressure show some magnetic ordering around 5 K and their crystal-field (CF) ground state are reported to be a magnetic triplet. In the crystal with 97% filling fraction synthesized under high pressure, on the other hand, absence of the magnetic transition has been confirmed and its bulk properties clearly evidence that the CF ground state is a singlet. Such drastic effect of the filling fraction on the magnetic properties may be related to the 3d-electrons with the large density of states at the Fermi energy. Therefore, in order to clarify the correlation between the itinerant 3d-electrons and the CF states of 4f-electrons, first of all, we would like to microscopically determine the CF level scheme of PrFe4Sb12 with high filling fraction synthesized under high pressure.