Suppression of surface barriers for flux penetration in Bi2Sr2CaCu2O8+delta whiskers by electron and heavy ion irradiation - art. no. 134517

We have used micron-sized linear Hall probe arrays to investigate the effec ts of irradiation on surface barriers for flux penetration in individual su perconducting Bi2Sr2CaCu2O8+delta whiskers. Samples were irradiated with 2. 5-MeV electrons or 9-GeV heavy (Pb) ions. The magnetization was investigate d in the temperature range between 5 K to above the superconducting transit ion temperature, in magnetic fields up to 1 T. At all temperatures, irradia tion by high-energy electrons or swift heavy ions reduces the penetration f ield substantially. At low temperatures (T<50 K) we attribute this to the s uppression of a Bean-Livingston (BL) surface barrier for two-dimensional "p ancake" vortices, and our results are in reasonable agreement with recent t heoretical predictions. At high temperatures (T>50 K) we tentatively propos e that the reduction in H-p(T) is due to suppression of a BL surface barrie r for flux lines. While electron irradiation strongly reduces magnetic irre versibility at high temperatures, the moderate hysteresis measured after he avy ion radiation suggests that this creates additional bulk pinning for fl ux lines on columnar defects.