Poster: Matching effects and hysteretic response in superconducting films with arrays of magnetic nanodots

C. CHILIOTTE; V. BEKERIS; G. PASQUINI; C. P. LI; F. CASANOVA; J. E. VILLEGAS; I. K. SCHULLER

Conferencia; International Conference of Superconductivity and Magnetism 2010; 2010

We explore commensurate vortex pinning effects in superconducting Nb thin films, deposited on triangular arrays of magnetic Fe nanodots. Artificial pinning is dominated by magnetic interactions, since the superconducting film was electrically isolated from the dots avoiding proximity effects. Matching and hysteresis in the field dependence of  ac susceptibility, cac(H),   is  examined for different initial magnetic state of dots. Robust matching effects are observed in a wide temperature range, and we find a cross over temperature T* above which vortex mobility becomes reversible, indicating that hysteretical response is not related to the magnetic hysteresis of dots but to pinning by random defects in the film.  This result is confirmed by similar observations in a porous Nb sample.  However, the absence of hysteresis in cac(H) in the Nb control film,  shows that random pinning of interstitial vortices and the periodic artificial pinning potential are both relevant in the observed hysteretical low temperature behavior.