Vortex pinning in Nb thin films with rectangular submicrometric magnetic dot arrays exhibits interesting effects. Magnetotransport reveals the existence of two pinning regimes that correspond to two types of resistivity minima with different constant field intervals. The relation with the array lattice parameters indicates that a reconfiguration in the vortex lattice from rectangular to square is induced artificially by the interaction with the dot array. The transition occurs when the elastic energy of the vortex lattice becomes larger than the pinning energy provided by the artificial pinning sites. Using this reconfiguration the pinning energy associated with the magnetic dots can be estimated directly.

• Received 20 January 1999

DOI:https://doi.org/10.1103/PhysRevLett.83.1022