Artificially induced reconfiguration of the vortex lattice by arrays of magnetic dots

Vortex pinning in Nb thin films with rectangular submicrometric magnetic do t arrays exhibits interesting effects. Magnetotransport reveals the existen ce of two pinning regimes that correspond to two types of resistivity minim a with different constant held intervals. The relation with the array latti ce parameters indicates that a reconfiguration in the vortex lattice from r ectangular to square is induced artificially by the interaction with the do t array. The transition occurs when the elastic energy of the vortex lattic e becomes larger than the pinning energy provided by the artificial pinning sites. Using this reconfiguration the pinning energy associated with the m agnetic dots can be estimated directly.