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

TL;DR

This study investigates magnetic fluctuations in filled skutterudites near the transition between singlet and triplet states, revealing persistent magnetic fluctuations even in singlet ground states due to itinerant and localized electron states.

Contribution

It introduces a detailed analysis of the Anderson model with multiple orbitals to explain magnetic properties in filled skutterudites, highlighting the coexistence of itinerant and localized f-electron states.

Findings

Magnetic fluctuations persist in singlet ground states due to low-energy triplet states.

The distinction between itinerant and localized f-electron states explains complex magnetic susceptibility and entropy behaviors.

Results apply broadly across different electron counts in filled skutterudites.

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.