EFFECTS OF Gd DOPING IN YBa₂Cu₃O_7-delta ON THE CRITICAL CURRENT DENSITY

Gd is successfully embedded into YBa₂Cu₃O_7-δ by the solid state reaction. Rietveld refinements show that Gd replaces Cu in the unit cell. By magnetization and resistivity measurements, the effects of Gd-doping in YBCO on the critical current density J_c and the critical temperature T_c in YBa₂Cu₃O_7-δ(YBCO) have been investigated. J_c varies with the applied field and the content of Gd and has a maximum at x = 0.03. The characteristic behavior of J_c with varying the Gd content can be explained in terms of the competition between two different effects caused by Gd-doping in YBCO: the inhomogeneity of grains distribution in nano-scale and the variation of superconductivity.