Vortex pinning and anisotropy in Ag/(Bi, Pb)2Sr2Ca2Cu3O10 tapes by means of surface columnar defects

Abstract

Abstract Surface columnar defects (SCDs) are produced in high-quality Ag/(Bi, Pb)2Sr2Ca2Cu3O10 tapes by irradiating them with 0.25 GeV gold ions only on a top layer up to about 10% of the fuli volume. The ion beam is orthogonal to the tape piane. Such defects seem to be able to confine the vortices inside ‘tubes’ having a diameter determined by the SCD average distance. This confinement shows itself in the shift of irreversibility lines (ILs) towards high temperatures and magnetic fields, in the enhancement of critical current densities and in the strong decrease in the dependence of ILs on freauency. In this paper we concentrate on the shutdown of the IL anisotropy (low-current regime) as well as on the decrease in the critical current density anisotropy (high-current regime). IL anisotropy is also studied as a function of the angle between the applied magnetic field and the ion tracks. The following results should be emphasized, because they are peculiar to the SCD topology. Firstly, the enhancement of ...