Relative pinning strength of twin boundaries and outgrowths in YBa2Cu3O7 thin films and superlattices - art. no. 144506

YBa2Cu3O7 films and superlattices displaying various structural properties were synthesized. X-ray diffraction, scanning electron microscopy, and tran smission electron microscopy characterization reveal that the defect densit ies can be changed over a large range of magnitude. In particular, by contr olling the strain relaxation in the material, superlattices without twin bo undaries as well as highly twinned ones are deposited. ac susceptibility me asurements are performed on many samples. Using a recent procedure based on flux-creep models, the relaxation rate of the vortices as a function of te mperature is plotted in the region of large creep. The qualitative correlat ion between the defects densities (outgrowths, twins) and the pinning prope rties provides a description of the pinning landscape. Twin boundaries seem to play a preponderant role in vortex pinning. Intersections between the t win planes are believed to be the main pinning sites when present in our sa mples.