Confinement of fluxons by surface columnar defects in Bi1.8Pb0.33Sr1.87Ca2Cu3Oy tapes

We study the effects of surface columnar defects created along about 5% of the sample thickness by means of 0.25 GeV Au ions at different doses on Bi1 .8Pb0.33Sr1.87Ca2Cu3Oy high-quality tapes on the vortex dynamics in the sam ple bulk. Strong phenomena of vortex localization inside the bulk are revea led by shifts of the irreversibility lines (IL's) as well as by their after -irradiation shape. The enhanced IL's exhibit specific characteristics, suc h as a Bose-glass-like behavior up to quite high fields, with a dose-depend ent onset point. Moreover, the irreversible regime expands with decreasing defect density. Such results are consistent with the setting up of confined vortices morphologies. Experimental data concerning the IL with the field orthogonal to the columnar defect direction as well as critical current den sity enhancements are also reported and discussed. [S0163-1829(99)01205-9].