VORTEX PROPERTIES IN SUPERCONDUCTING NB PD MULTILAYERS/

We have investigated the upper critical magnetic field H-c2, the criti cal current density J(c), and the pinning force F-p in sputtered Nb/Pd multilayers, varying the temperatures T, the Pd thicknesses d(Pd) and the magnetic field H orientation (parallel and perpendicular to the p lane of the sample. In perpendicular fields, the vortex dynamics was s trongly influenced by grain-boundary pinning. In parallel fields, a pe ak was observed in the J(c)(H) curves for samples with Pd thicknesses d(Pd) > 100 Angstrom. After comparing the experimental results with th e existing theories, we have related the presence of this peak effect to the matching of vortex kinks with the layered artificial structure.