VORTEX SYSTEM IN COUPLED DYBA2CU3O7-DELTA(Y0.45PR0.55)BA2CU3O7-DELTA HETEROSTRUCTURES

Transport measurements have been used to determine the vortex phase di agram (H parallel to c) of coupled heterostructures made of supercondu cting ultra-thin DyBa2Cu3O7-delta layers separated by semiconducting ( Y0.45Pr0.55)Ba2Cu3O7-delta layers. These structures have an intermedia te anisotropy between those of YBa2Cu3O7-delta and Bi2Sr2CaCu2O8+d. Th e solid-to-liquid transition and the flux dynamics have been investiga ted as a function of the total sample thickness d. Analyses of the par ameters describing the thermally activated dissipation in the solid an d liquid phases reveal a field induced crossover characterized by two fields, H-on(T) and H>H-on. We discuss the meaning of these features and their relationship with results in bulk high temperature supercond uctors.