Critical currents, flux-creep activation energy, and potential barriers for the vortex motion from flux-creep experiments - art. no. 184516

We present an experimental study of thermally activated flux creep in a sup erconducting ring-shaped epitaxial YBa2Cu3O7-x film as well as a different way of analyzing the experimental data. The measurements were made in a wid e range of temperatures between 10 and 83 K. The upper temperature limit wa s dictated by our experimental technique and at low temperatures we were li mited by a crossover to quantum tunneling of vortices. It is shown that the experimental data can very well be described by assuming a simple thermall y activated hopping of vortices or vortex bundles over potential barriers, whereby the hopping Aux objects remain the same for all currents and temper atures. This procedure of data analysis also allows us to establish the cur rent and temperature dependencies of the flux-creep activation energy U. as well as the temperature dependence of the critical current I-c, from the f lux-creep rates measured at different temperatures. The variation of the ac tivation energy with current, U(I/I-c), is then used to reconstruct the pro file of the potential barriers in real space.