Physical Properties Of Lu1-Xybxni2b2c

The Lu1-xYbxNi2B2C system exhibits superconductivity at low Yb concentrations (0 <= x <= 0: 1), Kondo behaviour at low and moderate Yb concentrations (0 <= x <= 0: 34), and heavy fermion behaviour with a non-magnetic ground state at high Yb concentrations. In order to characterize the evolution of these phenomena with x, we have performed dc magnetic susceptibility, electrical resistivity, thermoelectric power, and specific heat measurements on single crystals of Lu1-xYbxNi2B2C with various values of x between 0 and 1. The enhanced suppression of T-c by Yb substitution, compared to other rare earth substitutions, is consistent with the behaviour of superconducting Kondo systems with T-K >> T-c when T-K decreases with increasing x. The electronic specific heat coefficient gamma increases from similar to 11 mJ/mol K-2 for x = 0 to similar to 530 mJ/mol K-2 for x = 1. The curve of the reduced specific heat jump Delta C/Delta C-0 versus T-c/T-c0, where Delta C-0 and T-c0 refer to the LuNi2B2C matrix, does not conform to the BCS theory, but is consistent with the magnetic pair breaking theory of Abrikosov and Gor'kov or the theory of Muller-Hartmann and Zittartz for superconductivity in the presence of the Kondo effect for T-K/T-c0 similar to 10(3). This is in agreement with the evolution of the upper critical field H-c2 with x, where the slope dH(c2)/dT vertical bar(T = Tc) decreases with increasing x.