Electrical, Magnetic and NMR Studies of Ge-Based Filled Skutterudites RPt4Ge12 (R=La, Ce, Pr, Nd)

Toda Masatoshi, Sugawara Hitoshi, Magishi Ko-ichi, Saito Takahito, Koyama Kuniyuki, Aoki Yuji, Sato Hideyuki

doi:10.1143/jpsj.77.124702

We have synthesized the polycrystalline samples of Ge-based filled skutterudites RPt₄Ge₁₂ (R=La, Ce, Pr, Nd) and investigated the lattice constant, electrical resistivity, magnetic susceptibility and nuclear magnetic resonance (NMR) systematically. LaPt₄Ge₁₂ 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 CePt₄Ge₁₂ shows a broad peak around 80 K, which is a typical feature of valence fluctuation systems, whereas PrPt₄Ge₁₂ and NdPt₄Ge₁₂ show the well-localized nature of 4f-electrons. The NMR measurements in CePt₄Ge₁₂ revealed that the nuclear spin–lattice relaxation rate 1⁄T₁ shows an activation-type temperature dependence 1⁄T₁∝exp(−Δ⁄k_BT) with an energy gap Δ⁄k_B=150 K above 100 K, whereas it is proportional to the temperature below 20 K. This behavior is explained by a pseudogap model originated by the c–f hybridization.

Electrical, Magnetic and NMR Studies of Ge-Based Filled Skutterudites <I>R</I>Pt<SUB>4</SUB>Ge<SUB>12</SUB> (<I>R</I>=La, Ce, Pr, Nd)

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