FLUX-PINNING IN A SUPERCONDUCTOR BY AN ARRAY OF SUBMICROMETER MAGNETIC DOTS

Triangular arrays of submicrometer magnetic dots, with typical spacing of 400-600 nm and diameters close to 200 nm, have been fabricated by electron beam lithography to study pinning effects on Nb thin films. T he resistivity versus magnetic field curves exhibit regular structure. Minima appear at constant field intervals, given by the lattice param eter of the dot array. The angular, current, and temperature dependenc ies of the resistivity imply synchronized pinning by the magnetic arra y which is relevant at high vortex velocities, when the order in the v ortex lattice increases.