CNR ExploRA

Articolo in rivista, 2010, ENG, 10.1016/j.physc.2010.02.053

Pinning effects on the vortex critical velocity in type-II superconducting thin films

Leo, A; Grimaldi, G; Nigro, A; Pace, S; Verellen, N; Silhanek, AV; Gillijns, W; Moshchalkov, VV; Metlushko, V; Ilic, B

A. Leo, G. Grimaldi, A. Nigro, S. Pace, CNR-SPIN-Salerno and Dipartimento di Fisica ''E R Caianiello", Universitá di Salerno, via Ponte Don Melillo, 84084 Fisciano (SA), Italy N. Verellen, A.V. Silhanek, W. Gillijns, V.V. Moshchalkov,INPAC-Institute for Nanoscale Physics and Chemistry, KU Leuven, Celestijnenlaan 200D, Leuven B-3001, Belgium V. Metlushko, Department of Electrical and Computer Engineering, University of Illinois at Chicago, Chicago, IL 60607, USA B. Ilic Cornell Nanofabrication Facility, Cornell University, Ithaca, NY 14853, USA

We study the influence of artificial pinning centers on the vortex critical velocity in Al thin films deposited on top of a periodic array of Permalloy (FeNi) square rings. We demonstrate that the field dependence of the flux flow velocity strongly depends on the particular magnetic state of the rings. In particular, we find that, even when the rings are in a flux closure state, i.e. with little stray field, the vortex critical velocity shows a non-monotonic magnetic field dependence. This behaviour is in sharp contrast with the results obtained in a reference plain film, with no rings underneath. A comparison with the intrinsic strong pinning Nb films previously studied, suggests an interpretation in terms of a channel-like motion of vortices, here induced by the artificial pinning structure.

Physica. C, Superconductivity (Print) 470 (19), pp. 904–906