Dimensional crossover and commensurability effect in V/Ag superconducting multilayers

Using V/Ag superconducting multilayers prepared by vacuum evaporation we have observed dimensional crossover from anisotropic three-dimensional to two-dimensional behavior in terms of the upper critical field versus temperature. At a higher temperature we have also observed an anomalous turning in the curve of the critical field, which implies the existence of a commensurability effect between the lattice of vortices and the periodic superstructure.