POSSIBILITY OF PERIODICALLY REENTRANT SUPERCONDUCTIVITY IN FERROMAGNET SUPERCONDUCTOR LAYERED STRUCTURES/

We develop the theory of the proximity effect in layered ferromagnetic metal/superconductor (F/S) structures taking into account finite tran sparency Of the F/S interface as well as depression of the Cooper pair ing and diffusionlike motion of conduction electrons by a strong excha nge field of the ferromagnet. It is shown that the oscillatory depende nce of the critical temperature on the F-layer thickness is due to ape riodic modulation of the F/S boundary transparency by the oscillations of pair amplitude within the F layer. It is possible not only in the F/S multilayers, but in the F/S bilayers as well. The phenomena of ree ntrant and periodically reentrant superconductivity in the F/S contact s and superlattices are predicted. The competition between the ''0'' p hase and ''pi'' phase types of superconductivity in the F/S multilayer s is also discussed.