Thermally activated flux creep in YBa2Cu3O7-x film

We report on a study of thermally activated flux creep in a ring-shaped epi taxial YBa2Cu3O7-x film over a wide range of temperatures, using an experim ental technique that allows us to obtain voltage-current (V-I) characterist ics of the sample at low voltages without electric contacts to the film. It is shown that in the temperature range between 10 and 60 K, the flux creep can be described in terms of a thermally activated hopping of vortices ove r potential barriers. Taking into account the temperature dependence of the critical current, all V-I characteristics in the above temperature range m ay be merged onto a single continuous curve, from which the current depende nce of the activation energy for 0.4 <I/I-c < 0.9 may be established. Subse quently, this information allows us to reconstruct the profile of potential barriers in real space. (C) 2000 Elsevier Science B.V. All rights reserved .