f-Electron-Nuclear Hyperfine-Coupled Multiplets in the Unconventional   Charge Order Phase of Filled Skutterudite PrRu4P12
  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. 
Yuji Aoki, Takahiro Namiki, Shanta R. Saha, Takashi Tayama, Toshiro   Sakakibara, Ryousuke Shiina, Hiroyuki Shiba, Hitoshi S...
cond-mat.str-el cond-mat.mtrl-sci physics.atom-ph