Flux pinning in Nb-Ti based nanoscale superconducting multilayers

Nanoscale Nb-Ti/Nb/Cu-Ni-Si-Zn multilayers have been fabricated by means of a plastic deformation technique where a precipitation - hardening copper a lloy was used. When the thickness dependence of the global pinning force wa s examined at constant magnetic fields, it increased monotonically with inc reasing Nb-Ti layer thickness at 5 T from 4.8 to 120 nm, but it showed a ma ximum at 24 nm at 1.5 T, The critical temperature (T-c) decreased with decr easing thickness when the layer thickness was smaller than 20 nm. The prese nt experimental results suggested that the major flux pinning is attributed to the superconducting/normal interface and the proximity effect resulted in the degradation of T-c.