Current-dependent crossover in the flux dynamics of thin filmsS. L. Prischepa, M. Salvato and L. Maritato
Dipartimento di Fisica "E. R. Caianiello", Università di Salerno and INFM/Coherentia - Via S. Allende, I-84081 Baronissi (SA), Italy
(Received 19 June 2003; accepted in final form 10 December 2003)
We have investigated the dissipative behaviour of textured thin films at different perpendicular magnetic fields H and bias currents J, to study activation energy dependencies U(J) and U(H). For J<J*, where J* is a magnetic-field-dependent crossover current, activation energies are weakly current dependent, const, while, for J>J*, . At J<J*, the magnetic-energy dependencies are logarithmic, , while for J>J*, , up to . The J*(H) curve separates two zones with different vortex dynamics. We discuss the J*(H) curve in terms of a current-driven transition from a thermally activated flux flow to a flux creep regime. For pronounced disorder, the data suggest the influence of the activation energy distribution on the U(J) and U(H) dependencies.
74.78.-w - Superconducting films and low-dimensional structures.
© EDP Sciences 2004