Critical current in SFIFS junctions

A quantitative theory of the Josephson effect in SFIFS junctions (S denotes bulk superconductor, F is metallic ferromagnet, and I is insulating barrier) is presented in the dirty limit. A fully self-consistent numerical procedure is employed to solve the Usadel equations for arbitrary values of the F-layer thicknesses, magnetizations, and interface parameters. In the case of antiparallel ferromagnet magnetizations, the effect of critical current I-c enhancement by the exchange energy H is observed, while in the case of parallel magnetizations the junction exhibits a transition to the pi state. In the limit of thin F layers, we study these peculiarities of the critical current analytically and explain them qualitatively; the scenario of the 0-pi transition in our case differs from those studied before. The effect of switching between 0 and pi states by changing the mutual orientation of F layers is demonstrated. (C) 2002 MAIK "Nauka / Interperiodica".