Magnetic Fluctuations of Filled Skutterudites Emerging in the Transition Region between Singlet and Triplet States

Abstract

In order to clarify magnetic properties of filled skutterudites, we analyze the Anderson model including seven $f$ orbitals hybridized with an $a_{\rm u}$ conduction band using a numerical technique. For $n$=2 corresponding to Pr-based filled skutterudites, where $n$ is the local $f$-electron number, even if the ground state is a singlet, there remain significant magnetic fluctuations from a triplet state with a small excitation energy. This result can be understood by the fact that $f$-electron states are clearly distinguished as itinerant and localized ones in the filled skutterudite structure. This picture also explains the complex results for $f$-electron magnetic susceptibility and entropy for $n$=1$\sim$13.