Probing of current-tailoring mechanisms in YBa2Cu3O7−δ films by means of heavy ion irradiation

This paper deals with the origin of the plateau-like feature of the critical current density vs. logarithm of the field in YBCO films. By means of a suitable model, we check the hypothesis that this trend depends on a particular grain boundary (GB) network modulated by intrinsic correlated defects, coherently trapping the vortices. Such network consists of a 1D row of high-Jc intergrain Josephson junctions (JJ). Irradiation with gold ions provides extrinsic columnar defects. The fit of the data with the model indicates that the columnar defects change the length and distribution of the JJ. In interpreting our data, it results that at least in a range of temperature up to 0.5 T/Tc, Jc depends on the defect-induced modulation (either intrinsic or extrinsic) of the JJ network.