Strong vortex pinning and anisotropy in Ag/BSCCO-2223 tapes caused by surface columnar defects

Abstract

This paper is aimed at investigating the vortex dynamics driven by 0.25 GeV Au ion implantation in Ag/BSCCO-2223 tapes. Columnar defects are produced perpendicularly to the tape plane and only affect a surface layer of about 10% of the whole sample volume. The paper shows that this defect topology does not deteriorate the critical temperature significantly. Moreover, the irreversibility line (IL) measured with the applied field perpendicular to the tracks is nearly unaffected. On the contrary, the IL with the applied field either parallel to the tracks or moderately tilted is shifted towards higher fields and temperatures. The amount of the shift is comparable with that obtained for tracks crossing the whole sample. In a large range of magnetic fields near the dose equivalent field the IL anisotropy falls to zero. However, the ILs after surface implantation exhibit very peculiar features.