Superconductivity and crystalline electric field effects in the filled skutterudite series Pr(Os1−xRux)4Sb12

Abstract

X-ray powder-diffraction, magnetic-susceptibility χ(T), and electrical resistivity ρ(T) measurements were made on single crystals of the filled skutterudite series Pr(Os1−xRux)4Sb12. One end of the series (x=0) is a heavy fermion superconductor with a superconducting critical temperature Tc=1.85K, while the other end (x=1) is a conventional superconductor with Tc≈1K. The lattice constant a decreases approximately linearly with increasing Ru concentration x. As Ru (Os) is substituted for Os (Ru), Tc decreases nearly linearly with substituent concentration and exhibits a minimum with a value of Tc=0.75K at x=0.6, suggesting that the two types of superconductivity compete with one another. Crystalline electric field effects in χdc(T) and ρ(T) due to the splitting of the Pr3+ ninefold degenerate Hund’s rule J=4 multiplet are observed throughout the series, with the splitting between the ground state and the first excited state increasing monotonically as x increases. The fits to the χdc(T) and ρ(T) data are consistent with a Γ3 doublet ground state for all values of x, although reasonable fits can be obtained for a Γ1 ground state for x values near the end member compounds (x=0 or x=1).

Source-reported materials — not catalogue approval

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