Vortex-creep activation energy in YBa2Cu3O7/PrBa2Cu3O7 superlattices

YBa2Cu3O7/PrBa2Cu3O7 (YBCO/PBCO) superlattices with a different ratio of the superconducting and insulating layer thicknesses were prepared by high pressure dc sputtering. The vortex-creep activation energy U-o was determined by analyzing the in-plane resistive transition of 200 mu m, wide bridges with the external magnetic field B oriented along the c axis. It was found that U-o is proportional to the thickness of the YBCO layers, and does only weakly depend on the PBCO layer thickness, when the latter exceeds two unit cells. We observed a change in the variation of U-o with the current I in the specimen: U-o exhibits a plateau in the low-I region, then decreases significantly with increasing I. This behaviour is explained in terms of a crossover plastic vortex creep - elastic (collective) creep induced by the transport current. (C) 2009 Elsevier B.V. All rights reserved.