Investigation of the temperature dependence of the critical state in melt processed YBa2Cu3O7−∂ thick films

Abstract

The inter- and intra-grain critical current densities of melt processed YBa2Cu3O7−∂ (YBCO) thick films have been measured as a function of temperature using vibrating sample magnetometry. The width of the M-H hysteresis curve has been observed to scale with the cube of the sample width for temperatures up to ∼70 K and applied fields of greater than 1 T which implies that current flows on the length scale of the sample over this temperature and field regime. An exponential decrease of magnetic moment hysteresis with temperature up to ∼70 K and between ∼80 K and Tc has been observed and attributed to the dominance of inter- and intra-granular current, respectively. An empirical model is presented to account for the observed dependence of the critical current density on temperature, based upon weak link behavior within the ‘‘Hub and Spoke’’ like morphology characteristic of melt processed YBCO thick films.