Specific heat and magnetization measurements have been performed on high-quality single crystals of filled-skutterudite PrFe_4P_{12} in order to study the high-field heavy-fermion state (HFS) and low-field ordered state (ODS). From a broad hump observed in C/T vs T in HFS for magnetic fields applied along the <100> direction, the Kondo temperature of ~ 9 K and the existence of ferromagnetic Pr-Pr interactions are deduced. The {141}-Pr nuclear Schottky contribution, which works as a highly-sensitive on-site probe for the Pr magnetic moment, sets an upper bound for the ordered moment as ~ 0.03 \mu_B/Pr-ion. This fact strongly indicates that the primary order parameter in the ODS is nonmagnetic and most probably of quadrupolar origin, combined with other experimental facts. Significantly suppressed heavy-fermion behavior in the ODS suggests a possibility that the quadrupolar degrees of freedom is essential for the heavy quasiparticle band formation in the HFS. Possible crystalline-electric-field level schemes estimated from the anisotropy in the magnetization are consistent with this conjecture.
@article{arxiv.cond-mat/0201046,
title = {Anomalous heavy-fermion and ordered states in the filled skutterudite PrFe4P12},
author = {Y. Aoki and T. Namiki and T. D. Matsuda and K. Abe and H. Sugawara and H. Sato},
journal= {arXiv preprint arXiv:cond-mat/0201046},
year = {2009}
}
Comments
7 pages and 7 figures. Accepted for publication in Phys. Rev. B