Surface columnar defects on melt textured Y-Ba-Cu-O

In this paper we report on the effect of columnar defects created only in a surface sheet of high quality melt textured YBCO by means of 2 GeV gold ions. The ion tracks implant in a few percent fraction of the full sample thickness. Maps of the trapped field at 77 K in a large size pellet, before and after irradiation, are shown. A full magnetic characterization of small size samples in the high temperature regime is also presented. The data point coherently to the conclusion that in this region some correlated disorder, artificially created only in a small fraction of the sample, can extend its benefits to the whole sample.