Qualitative Determination of Relationship Between Flux Pinning Effect and Irradiation Defects in Bi-2212 Single Crystal

Abstract

Bi-2212 single crystals irradiated with 18 MeV Fe8+ ions at 1×1012 ions/cm2 fluence were investigated by transmission electron microscope (TEM). Cascade defects generated by the irradiation were found in the crystal. The size and distribution of the cascade defects were quantitatively measured by using an image analysis method. The results were compared to that of theoretical calculations by using TRIM cord. Almost same results on the distribution of defects were found in the case of 18 MeV Fe8+ ion irradiation. Meanwhile, the differences of magnetization between before and after irradiation were detected by SQUID measurements. Optimum fluence for the enhancement of critical current density was found to be strongly dependent with size and distribution of the cascade defect. The relationship between irradiation condition and cascade defects can be used to build a model sample for controlling flux pinning centers with optimum size. Moreover, the cascade defects with wide distribution along the c-axis of B-i2212 induced by 18, 14 and 10 MeV Fe ion irradiation were also studied. The critical current density of this sample was enhanced, comparing with that of 18 MeV Fe8+ ion irradiation samples in same fluence.