Novel electronic states realized in the filled skutterudites containing rare earth elements with more than one 4f-electrons

• Published in: Journal of magnetism and magnetic materials Vol. 310; no. 2; pp. 188 - 194
• Main Authors: Sato, H., Kikuchi, D., Tanaka, K., Aoki, H., Kuwahara, K., Aoki, Y., Kohgi, M., Sugawara, H., Iwasa, K.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 01.03.2007; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystal field effect; Electronic structure; Exact sciences and technology; Heavy fermion; Heavy-fermion superconductors; Kondo effect; Multipolar interaction; Physics; Properties of type I and type II superconductors; Skutterudite; Superconducting materials (excluding high-tc compounds); Superconductivity; 71.27.+a; 72.15.Qm; Multipolar interaction; Kondo effect; Skutterudite; 75.20.Hr; Heavy fermion; Crystal field effect; Degrees of freedom; Metal-insulator transition; Crystal field; Hybridization; Electronic density of states; Electronic structure; Skutterudites; Heavy fermion superconductors; Strongly correlated electron systems; Crystal structure
• ISSN: 0304-8853
• DOI: 10.1016/j.jmmm.2006.10.006

In the filled skutterudite compounds (RT 4X 12: R rare earth, T=Fe, Ru, Os, and X=pnictogen-ions), various attractive features have been found by replacing the constituent elements, e.g., metal–insulator transition in PrRu 4P 12, competing heavy fermion and multipolar ordered states in PrFe 4P 12, heavy fermion superconductivity in PrOs 4Sb 12, etc. Most of these features are realized probably by the unique crystal structure; R is embedded in the cage made of 12X and eight T ions, so that the strong c–f hybridization becomes a common feature irrespective of the constituent elements. The strong c–f hybridization in skutterudites enables the strongly correlated electron behaviors even in the systems containing rare-earth elements with more than one 4f-electron. The effect of X-replacement appears most apparently as a change in c–f hybridization, as is naturally inferred from the large difference in lattice constant. In addition to the c–f hybridization effect, it was recognized that f-electron's multipolar degrees of freedom and relatively small crystalline electric field splitting are important factors to understand the aforementioned novel phenomena.