Thermally activated phase-slip in high-temperature cuprates

Gd1-x-zPrxCazBa2Cu3O7-delta (GdPrCa-123) high-temperature superconductor cu prate (HTSC) samples with 0.0 less than or equal to x less than or equal to 0.3 and 0.0 less than or equal to z less than or equal to 0.35 were prepar ed by standard solid-state reaction and characterized by XRD technique. The magnetoresistance of the samples were measured and analysed. The supercond ucting transition region broadened by the application of a magnetic held. T he resistive transition showed two distinct parts. (1) A steep part near th e onset of superconductivity, where the onset transition temperature remain ed unchanged. For the Gd0.85Ca0.15-123 sample, the steep part was more sens itive to the application of magnetic fields. (2) A transition tail part. Th e experimental data in this region were fitted with an Ambegakor and Halper in (AH) phase-slip model. The AH parameter, gamma (H), was used to estimate the critical current density at zero temperature of samples at various mag netic fields. It was observed that the critical current density decreased w ith Pr substitution and increased with Ca substitution in Gd-123. An optima l value of the Ca doping concentration for increasing the critical current density was determined. We suggest that the Pr ion probably acts to enhance the weak link and the Ca ion acts as a flux pinning centre in the GdPrCa-1 23 system. Moreover, we observed that the AH parameter, gamma, and activati on energy, U-0, depend not only on temperature and magnetic field, but also on the Pr and Ca ion concentrations.