J. Phys. Soc. Jpn. 80, 054704 (2011) [7 Pages]
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f-Electron-Nuclear Hyperfine-Coupled Multiplets in the Unconventional Charge Order Phase of Filled Skutterudite PrRu4P12

Kazuaki Iwasa
JPSJ News Comments 8,  07 (2011).

Yuji Aoki1, Takahiro Namiki1, Shanta R. Saha1, Takashi Tayama2, Toshiro Sakakibara3, Ryousuke Shiina4, Hiroyuki Shiba5, Hitoshi Sugawara6, and Hideyuki Sato1
+ Affiliations
1Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan2Department of Physics, Toyama University, Toyama 930-8555, Japan3Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan4Department of Materials Science and Technology, Niigata University, Niigata 950-2181, Japan5Department of Physics, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan6Department of Physics, Kobe University, Kobe 657-8501, Japan
Received December 21, 2010; Accepted February 21, 2011; Published April 25, 2011

The filled skutterudite PrRu 4 P 12 is known to undergo an unconventional charge order phase transition at 63 K, below which two sublattices with distinct f -electron crystalline-electric-field ground states are formed. In this paper, we study experimentally and theoretically the properties of the charge order phase at very low temperature, particularly focusing on the nature of the degenerate triplet ground state on one of the sublattices. First, we present experimental results of specific heat and magnetization measured with high quality single crystals. In spite of the absence of any symmetry breaking, the specific heat shows a peak structure at T p =0.30 K in zero field; it shifts to higher temperatures as the magnetic field is applied. In addition, the magnetization curve has a remarkable rounding below 1 T. Then, we study the origin of these experimental findings by considering the hyperfine interaction between 4 f electron and nuclear spin. We demonstrate that the puzzling behaviors at low temperatures can be well accounted for by the formation of 4f-electron-nuclear hyperfine-coupled multiplets , the first thermodynamical observation of its kind.

©2011 The Author(s)
This article is published by the Physical Society of Japan under the terms of the Creative Commons Attribution 4.0 License. Any further distribution of this work must maintain attribution to the author(s) and the title of the article, journal citation, and DOI.
https://doi.org/10.1143/JPSJ.80.054704
KEYWORDS: 4f-electron-nuclear hyperfine-coupled multiplets, PrRu4P12, charge ordering, filled skutterudite, crystalline electric field

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