The effect of swift heavy ion irradiation on critical current density in YB₂Cu₃O_7−δ thick film with Y₂O₃ addition

Abstract

The effect of 200 MeV Ag ion irradiation on thick films of YBCO grown by the diffusion reaction technique has been studied. Magnetization at 40 K marks a substantial change in the critical current density (J _c) of the irradiated sample when compared with unirradiated ones. The critical current density was estimated from the widths of magnetization loops using Bean's critical state model. The enhancement of J _c from 1.06×10⁵ to 2.5×10⁵ A/cm² with irradiation up to a fluence of 5×10¹¹ ions/cm² in YBCO samples is associated with an increase in the flux pinning created by the irradiation-induced columnar defects. In excess Y₂O₃ (10 wt%) to YBCO, the J _c increases in the pristine sample to 1.33×10⁵ A/cm² but decreases with increasing fluence. This may be due to an excess of defects, overlapping of defected zones and weakening of the pinning barriers. Further studies using X-ray diffraction and a scanning electron microscope reveal microstructural changes in the irradiated samples.

Keywords:

• columnar defects
• critical current density
• SHI irradiation

Acknowledgements

The authors are thankful to the Pelletron group of the IUAC, New Delhi, for providing the facility for ion irradiation. We also acknowledge the Centre for UGC-DAE-CSR, Indore, for providing the facility for magnetic study.