Josephson effect in SFXSF junctions

We investigate the Josephson effect in SFXSF junctions, where S-F is a superconducting material with a ferromagnetic exchange field, and X is a weak link. The critical current I-c increases with the (antiparallel) exchange fields, if the distribution of transmission eigenvalues of the X layer has its maximum weight at small values. This exchange-field enhancement of the supercurrent does not exist if X is a diffusive normal metal. At low temperatures, there is a correspondence between the critical current in an SFISF junction with collinear orientations of the two exchange fields, and the AC supercurrent amplitude in an SIS tunnel junction. The difference in the exchange fields h(1) - h(2) in an SFISF junction corresponds to the potential difference V-1 - V-2 in an SIS junction; i.e., the singularity in I-c [in an SFISF junction] at parallel to h(1) - h(2) parallel to = Delta(1) + Delta(2) is the analogue of the Riedel peak. We also discuss the AC Josephson effect in SFISF junctions. (C) 2002 MAIK Nauka / Interperiodica.