EFFECTS OF 300 MEV AU+24 ION IRRADIATION ON SUPERCONDUCTIVITY IN YBA2CU3O7 EPITAXIAL-FILMS

We report the effects of 300 MeV gold ion irradiation on the transition temperature (T(c)) and critical current density (J(c)) of YBa2Cu3O7 epitaxial films. The radiation at a dose as low as 5.6 X 10(10) ions/cm2 decreases the zero field T(c) and J(c). However, the response of the mixed state in 1-8 T field remains relatively unchanged up to a dose of approximately 9 X 10(10) ions/cm2. We argue that the stiffness of the flux lines in a film geometry and the pinning sites distributed at a length scale much smaller than that of the ion-induced defects are responsible for this null result.