Upper critical field of borocarbide superconductors

We have investigated the upper critical fields of Y1-xErxNi2B2C and Y1-xErx Pd5B3C0.4 (0 less than or equal to x less than or equal to 1) systems by th e scaling analysis of the thermal fluctuation conductivity, The experiments were done over wide magnetic field range. We are going to test the thermal fluctuation theory in the borocarbide superconducting systems. According t o the scaling analysis, the thermal fluctuation conductivity should be scal ed as sigma (f) = (T-2/H)(1/3) F[AT-T-c(H)/(TH)(2/3)]. Because the scaling function is field independent, all scaling curves obtained under various ap plied fields should converge to a universal curve if the function of T,(H) is properly chosen. We therefore obtain H-c2(T) determined by optimizing th e scaling fit, The superconducting coherence length and Ginzburg-Landau par ameter kappa in those superconductors are also estimated. We categorize the Y1-xErxNi2B2C and Y1-xErxPd5B3C0.4 systems as strong type-II superconducto rs.