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  • Küçük Resim
    Öğe
    Investigation of superconducting and normal-state properties of the filled-skutterudite system PrPt4Ge12-xSbx
    (Amer Physical Assoc, 2016) Jeon, Inho; Huang, Kevin; Yazıcı, Duygu; Kanchanavatee, Noravee; White, B. D.; Ho, Pei-Chun; Jang, Sooyoung; Pouse, Naveen; Maple, M. Brian
    We report a study of the superconducting and normal-state properties of the filled-skutterudite system PrPt4Ge12-xSbx. Polycrystalline samples with Sb concentrations up to x = 5 were synthesized and investigated by means of x-ray diffraction, electrical resistivity, magnetic susceptibility, and specific heat measurements. We observed a suppression of superconductivity with increasing Sb substitution up to x = 4, above which no signature of superconductivity was observed down to 140 mK. The Sommerfeld coefficient, gamma, of superconducting specimens decreases with increasing x up to x = 3, suggesting that superconductivity may depend on the density of electronic states in this system. The specific heat for x = 0.5 exhibits an exponential temperature dependence in the superconducting state, reminiscent of a nodeless superconducting energy gap. We observed evidence for a weak "rattling" mode associated with the Pr ions, characterized by an Einstein temperature Theta(E) similar to 60 K for 0 <= x <= 5; however, the rattling mode may not play any role in suppressing superconductivity.
  • Küçük Resim
    Öğe
    Superconducting and normal state properties of the systems La1-xMxPt4Ge12 (M = Ce, Th)
    (Amer Physical Soc, 2016) Huang, Kevin; Yazıcı, Duygu; White, Bryan D.; Jeon, Inho; Breindel, Alexander J.; Pouse, Naveen; Maple, M. Brian
    Electrical resistivity, magnetization, and specific heat measurements were performed on polycrystalline samples of the filled-skutterudite systems La1?xMxPt4Ge12 (M = Ce, Th). Superconductivity in LaPt4Ge12 was quickly suppressed with Ce substitution and no evidence for superconductivity was found down to 1.1 K for x > 0.2. Temperature-dependent specific heat data at low temperatures for La1?xCexPt4Ge12 show a change from power-law to exponential behavior, which may be an indication for multi-band superconductivity in LaPt4Ge12. A similar crossover was observed in the Pr1?xCexPt4Ge12 system. However, the suppression rates of the superconducting transition temperatures, Tc(x), in the two systems are quite disparate, indicating a difference in the nature of superconductivity, which is conventional in LaPt4Ge12 and unconventional in PrPt4Ge12. In comparison, a nearly linear and smooth evolution of Tc with increasing Th was observed in the La1?xThxPt4Ge12 system, with no change of the superconducting energy gap in the temperature dependence of the specific heat, suggesting similar types of superconductivity in both the LaPt4Ge12 and ThPt4Ge12 compounds.