Crossover of thickness dependence of critical current density Jc(T,H) in YBa2Cu3O7-δ thick films

Critical current density J(c) as a function of temperature T and magnetic field H was studied for high quality YBa2Cu3O7-delta (YBCO) films with thickness d=0.2, 1, and 3 mum by means of magnetization measurements of a circular disk in perpendicular field. We found that the thickness dependence of J(c)(H) for the YBCO thick films crossovers at high fields for T>50 K, where the 0.2-mum-thick film carries significantly lower J(c)(H) than the 3-mum-thick film at high fields, even though the zero- or low-field J(c) for the 0.2-mum-thick film is more than twice the value for the 3-mum-thick film. (C) 2004 American Institute of Physics.