Electrical, Magnetic and NMR Studies of Ge-Based Filled Skutterudites RPt_4Ge_<12> (R=La, Ce, Pr, Nd)(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

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We have synthesized the polycrystalline samples of Ge-based filled skutterudites RPt_4Ge_<12> (R=La, Ce, Pr, Nd) and investigated the lattice constant, electrical resistivity, magnetic susceptibility and nuclear magnetic resonance (NMR) systematically. LaPt_4Ge_<12> is confirmed to be a conventional BCS-type superconductor by the NMR measurements. Additional contribution ascribed to the rattling motion of the La ions has been observed in the nuclear relaxation at the La site at high temperatures. Temperature dependence of the magnetic susceptibility of CePt_4Ge_<12> shows a broad peak around 80K, which is a typical feature of valence fluctuation systems, whereas PrPt_4Ge_<12> and NdPt_4Ge_<12> show the well-localized nature of 4f-electrons. The NMR measurements in CePt_4Ge_<12> revealed that the nuclear spin-lattice relaxation rate 1/T_1 shows an activation-type temperature dependence 1/T_1 ∝ exp(-Δ/k_BT) with an energy gap Δ/k_B=150K above 100K, whereas it is proportional to the temperature below 20K. This behavior is explained by a pseudogap model originated by the c-f hybridization.
社団法人日本物理学会の論文
2008-12-15