Irradiation effect of Co-60 gamma rays in YBCO thick films

Galvanomagnetic properties of YBa2Cu3O7-δ thick films under the action of 60Co γ-rays up to an exposure of 450 kGy are reported. The variation of physical parameters such as resistivity in the normal state, critical temperature and critical current density, as well as the increase of pinning energies with irradiation, suggests that these property changes are dominated by irradiated-induced randomly distributed oxygen defects. The three-dimensional collective pinning theory is used along with some approximations to estimate the pinning energies and critical current density. A comparison of the experimental data with the theoretical predictions demonstrates the importance of irradiation-induced oxygen defects as effective pinning centres. (author)