Spin polarization and π-phase state of the Josephson contact: Critical current of mesoscopic SFIFS and SFIS junctions

On the basis of a microscopic proximity effect model, the critical current of superconductor/ferromagnet/insulator/ferromagnet/superconductor (SFIFS) and superconductor/ferromagnet/insulator/superconductor Josephson junctions have been calculated. Both metals, a superconductor (S) and a ferromagnet $(F),$ are supposed to be in a ``dirty'' limit and the thickness of the F layer is assumed to be small compared to its coherence length. It is shown that critical current in the SFIFS contact can reverse its sign and a crossover to the ``{π}'' state of the junction takes place even at a mesoscopic thickness of the F layer. We discuss, how by changing the SF sandwich parameters (a ferromagnetic exchange field, boundary transparency, and strength of proximity effect) the conditions for crossover from ``0'' to ``{π}'' phase shift across the contact are changed.