EFFECTS OF HEAVY-ION IRRADIATION ON THE MAGNETIC ANOMALY IN BI2SR2CACU2O8-TEMPERATURE(Y CRYSTAL NEAR THE TRANSITION)

We report the observation of an anomalous magnetization behavior in si ngle crystal of Bi2Sr2CaCu2O8+y near the transition temperature after 200 MeV Ag ion irradiation with a fluence of 2.5 X 10(11) ions/cm(2). We argue that the magnetization anomaly (the virgin curve lying above the return leg and the presence of a characteristic crossover temperat ure, T) is the manifestation of fluctuation phenomena as were observe d in as-grown crystal. The columnar defects produced by the heavy ions could not reduce the anisotropy and enhance the interlayer coupling t o such an extent that the fluctuation effects near the transition temp erature region were suppressed.