Weak localization effects on the upper critical field of bulk superconductors

Weak localization effects on bulk superconductivity are investigated by measuring upper critical field Hc2 and heat capacity on the same sample of a given alloy composition. Systems studied include rapidly solidified glassy Zr(70)Ni(30), Zr(75)Rh(25), and body-centered cubic Hf(90)Mo(10). The homogeneity of samples are examined. Without including quantum corrections, very good fits to the Hc2 curves predicted by the classical theory of dirty superconductors are obtained by varying the Pauli paramagnetic limiting and spin-orbit scattering parameters. However, the initial gradients obtained from fitting the Hc2 data are approx. 10-30% higher than those determined by the products of the electrical resistivity and the density of states obtained from heat capacity measurements). These relative enhancements of upper critical fields are attributed to field-induced delocalization effects. The results are analysed in the framework of Fukuyama, Ebisawa and Maekawa (FEM) theory and weak localizat ion. (IPM