Multiple peaks in the angular and field dependence of the critical currents in Nb-47wt%Ti/Cu multilayers

Abstract

The effect of Nb-Ti layer thickness d, on the angular and field dependencies of J, in Nb-47wt.% TVCu multilayers was investigated. J, exhibits several peaks in the field and angular dependencies for superconductor and pin layer thickness comparable to the coherence and proximity lengths. The shape of the J,(B) curve strongly depends on the thickness of Nb-Ti layer. A single peak is present for d, > 10 nm and multiple peaks (two and three) are observed in a sample with ds :=lo nm. The low field peak is temperature independent, while the high-field peaks have a pronounced temperature dependence. We suggest that a crossover between dominant pinning mechanisms and orientational transitions in the vortex lattice is responsible for the observed behavior of J,(B).

Comment on “Dimpling in critical current density vs. magnetic field angle in YBa2Cu3O7 films irradiated with 3-MeV gold ions” [J. Appl. Phys. 114, 233911 (2013)]

“…This is an astute observation and it stands to reason it must originate from some real property of the flux pinning landscape. However, we note that these shoulders which appear at a particular intermediate h range are also observed in low temperature superconductors, 2,3 which have no electron mass anisotropy to act as the source of this behaviour. Their conclusion would thus require that identically shaped features at the same angles have different origins in electronically anisotropic and isotropic superconductor samples.…”