Transport characteristics near the glass-liquid transition temperature before and after heavy-ion irradiation in a YBa2Cu3O7-δ thin film

We investigated the influence of flux pinning on the behavior of flux Lines in a c-axis oriented YBa2Cu3O7-delta thin film, by analyzing the critical scaling of current-voltage characteristics at various temperatures under the magnetic field parallel to the c-axis before and after irradiation. In the irradiation process, splayed columnar defects were produced in the Nm by tilting 200 MeV Au-ion beams off the c-axis by +/- 15 degrees. The enhancement of the glass-liquid transition temperature and the increment of the dynamic critical exponent z were observed after the irradiation. The depinning model taking into account a distribution of pinning strength can reasonably describe the origin of the changes of both the glass-liquid transition temperature and z owing to the introduction of defects. This fact indicates that the flux line dynamics is governed by the pinning interaction rather than the intrinsic property of the flux line system. (C) 1998 Elsevier Science B.V. All rights reserved.