f-Electron-Nuclear Hyperfine-Coupled Multiplets in the Unconventional Charge Order Phase of Filled Skutterudite PrRu4P12

TL;DR

This study reveals the formation of hyperfine-coupled multiplets in PrRu4P12's charge order phase through specific heat and magnetization measurements, providing the first thermodynamic evidence of such phenomena in f-electron systems.

Contribution

It presents the first thermodynamic observation of Pr 4f-electron-nuclear hyperfine-coupled multiplets in a charge order phase of a filled skutterudite.

Findings

Anomalous Schottky peak at 0.30 K in specific heat.

Rounding of magnetization curve below 1 T at 0.06 K.

Evidence for hyperfine-coupled multiplet lattice formation.

Abstract

In the unconventional f-electron-associated charge order phase of filled skutterudite PrRu4P12, the low-temperature behaviors of the triplet crystalline-electric-field ground state of Pr ions have been studied by specific heat and magnetization measurements using high quality single crystals. Specific heat shows an anomalous Schottky-type peak structure at 0.30 K in zero field in spite of the absence of any symmetry breaking. Magnetization curve at 0.06 K shows a remarkable rounding below 1 T. It has been revealed that these anomalies provide compelling evidence for the formation of a lattice of Pr 4f-electron-nuclear hyperfine-coupled multiplets, the first known thermodynamical observation of its kind.