VORTEX DYNAMICS AND VORTEX PHASE-DIAGRAM IN ARTIFICIAL OXIDE SUPERLATTICES

DyBa2Cu3O7/(Y1-xPrx)Ba2Cu3O7 multilayers are model materials to study the nature of the vortex system in high-temperature superconductors an d its dynamics. Indeed, by changing in such structures the thickness o f the superconducting and the alloy layers, and the composition of the alloy, we can control at wish the critical temperature, the anisotrop y and the pinning strength. Additionally, finite thickness effects may be studied. We review here our results on the study of the flux motio n and phase diagram in coupled multilayers, displaying an intermediate anisotropy between those of YBa2Cu3 O-7 and Bi2Sr2CaCu2O8. Transport measurements with an applied field H/c allow to identify the solid and liquid phases in the mixed state, and reveal the presence of a field- induced crossover in the thermally activated dynamics of both phases, which lead us to draw a possible mixed state phase diagram for these a rtificial superconductors and correlate it to the existing results for other HTS.