Superconductivity and crystalline electric field effects in the filled skutterudite series Pr(Os1-xRux)4Sb12 -: art. no. 024523

X-ray powder-diffraction, magnetic-susceptibility chi(T), and electrical resistivity rho(T) measurements were made on single crystals of the filled skutterudite series Pr(Os1-xRux)(4)Sb-12. One end of the series (x=0) is a heavy fermion superconductor with a superconducting critical temperature T-c=1.85 K, while the other end (x=1) is a conventional superconductor with T(c)approximate to1 K. The lattice constant a decreases approximately linearly with increasing Ru concentration x. As Ru (Os) is substituted for Os (Ru), T-c decreases nearly linearly with substituent concentration and exhibits a minimum with a value of T-c=0.75 K at x=0.6, suggesting that the two types of superconductivity compete with one another. Crystalline electric field effects in chi(dc)(T) and rho(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 chi(dc)(T) and rho(T) data are consistent with a Gamma(3) doublet ground state for all values of x, although reasonable fits can be obtained for a Gamma(1) ground state for x values near the end member compounds (x=0 or x=1).