The role of intrinsic random pinning in superconducting Nb films with periodic magnetic and non magnetic pinning sites.

V. BEKERIS

Madrid

Simposio; Physics at the nanoscale,; 2011

Universidad Autonoma

The role of intrinsic random pinning in superconducting Nb films with periodic magnetic and non magnetic pinning sites.     C. Chiliotte, G. Pasquini, V. Bekeris, J. E. Villegas, C-P Li and Ivan K. Schuller         We study vortex lattice (VL) dynamics in patterned Nb films containing dense periodic arrays of sub 50 nm magnetic nanodots or holes, by means of ac susceptibility measurements. For temperatures near the critical temperature TC, reversible matching effects are observed that are related to the periodicity of the strong artificial pinning potentials. As the temperature is reduced below a characteristic cross over temperature T* ~ 0.75 TC in both samples, an anomalous hysteretical behavior is observed, with a history dependent apparent matching field value. We find that this behavior is consistent with the competition below T* between periodic pinning, independent of its origin, and intrinsic random pinning.