Josephson effect in superconductor/ferromagnet-normal/superconductor structures

The critical current I-C of superconductor/ferromagnet-normal/superconductor (S/FN/S) Josephson junctions is calculated in the framework of linearized Usadel equations. The dependence of I-C on the distance L between superconductors and thicknesses d(F,N) of ferromagnetic and normal layers is analyzed. It is shown that I-C(L,d(F)) may exhibit damping oscillations as a function of both arguments. The conditions have been determined under which the decay length and period of oscillation of I-C(L) at fixed d(F) are on the order of decay length of superconducting correlations in the N metal, xi(N), that is much larger than in F film. We demonstrate also that the positions of the points L=L-n, at which I-C=0 exhibit damping oscillations as a function of d(F). The number of transitions from 0 to pi states in I-C(L,d(F)) increases under L -> L-n. Outside these narrow intervals of L around L-n sign and value of I-C are independent on d(F) for d(F)greater than or similar to xi(F). This fact is important for possible applications of S/FN/S Josephson junctions and S/FNF/S spin valve Josephson devices.