Dynamic matching of vortex lattice in superconducting multilayers

We observed oscillations of a nonlinear flux flow resistivity R(j,H) as a function of a parallel magnetic field 6 < H < 9 T in Nb-Ti/Cu multilayers. We show that the oscillations in R(H), which have the field period Delta H approximate to 0.1 T independent of temperature and current, indicate a long-range order in the rapidly moving vortex structure. The critical current I-c(H) exhibits no oscillations characteristic of R(H). We propose an explanation of the effect in terms of dynamic matching of the moving vortex lattice with periodic microstructure and show that both Delta H and the amplitude of the oscillations of R(H) are inversely proportional to the sample thickness.