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

Abstract

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