Partial filling of columnar defects by vortices as seen in measurements ofthe c-axis critical current of Bi2Sr2CaCu2O8+delta

The magnetic-field dependence of the c-axis critical current I-c of Bi2Sr2C aCu2O8+delta single crystals with columnar defects produced by heavy-ions i rradiation shows a pronounced maximum at approximately one third of the mat ching field B-phi. There is no additional feature at B = B-phi. The irrever sibility line determined from the c-axis resistivity data shifts to higher temperatures after the irradiation suggesting increased pinning of vortices . [S0163-1829(99)04433-1].