Influence of a driving force on the pinning of a field-cooled vortex lattice

With the vibrating reed technique, we have measured an increase in the elas tic coupling between the flux line lattice (FLL) and pinning centers in fie ld-cooled YBa2Cu3O7 superconducting films by loading them with a de driving current. This result, obtained at different magnetic field orientations, i mplies a plastic rearrangement of the FLL to a more disordered and stronger pinned configuration at temperatures and fields fap below the thermally ac tivated depinning transition and at driving currents orders of magnitude lo wer than the critical one.