Effects of successive proton irradiation on the peak effect in YBa2Cu3O7-delta single crystals

The effect of increasing the density of uncorrelated defects on the peak ef fect is studied in a detwinned YBa2Cu3O7-delta single crystal. The defects were introduced with 9 MeV proton irradiation where the total dose ranged f rom 0.25 x 10(15) to 2 x 10(15) p/cm(2). With each successive irradiation, the peak effect shifts down in field and is eventually suppressed in both t he electrical resistivity and the dc magnetization by a sufficiently high i rradiation dose. The peak effect reappears after a high temperature anneal, suggesting that it is primarily the point defects introduced by the irradi ation which interfere with the formation of the peak effect. (C) 2001 Ameri can Institute of Physics.