CASCADE DEFECTS AS FLUX-PINNING CENTERS IN BI2SR2CACU2OX SINGLE-CRYSTAL GENERATED BY ION IRRADIATION

Cascade defects generated by ion irradiation in Bi2212 single crystal were investigated by transmission electron microscopy (TEM). The irrad iation was performed by 18 MeV Fe8+ ions at 1x10(12)ions/ cm(2). The s ize and distribution of cascade defects were quantitatively measured b y using an image analysis method. TRIM cord was applied to theoretical calculation compared with the results obtained from quantitative meas urement results. The calculation results were consistent with experime ntal. Meanwhile, the differences of magnetization before and after irr adiation were detected by SQUID measurements. The size and distributio n of the cascade defects were found to be much influential for enhance ment of critical current density. The relationship between irradiation condition and cascade defect can be used to form a model sample for c ontrolling flux pinning centers with optimum size. In addition, the cr itical current density and cascade defects induced by 18, 14, and 10 M eV Fe ion irradiation along c-axis were also studied. The critical cur rent density of this sample was compared with that of 18 MeV Fe8+ ion irradiation sample in same fluence.