We study the Josephson effect in a superconductor--ferromagnet--superconductor (SFS) junction with ferromagnetic domains of non-collinear magnetization. As a model for our study we consider a diffusive junction with two ferromagnetic domains along the junction. The superconductor is assumed to be close to the critical temperature , and the linearized Usadel equations predict a sinusoidal current-phase relation. We find analytically the critical current as a function of domain lengths and of the angle between the orientations of their magnetizations. As a function of those parameters, the junction may undergo transitions between 0 and phases. We find that the presence of domains reduces the range of junction lengths at which the phase is observed. For the junction with two domains of the same length, the phase totally disappears as soon as the misorientation angle exceeds . We further comment on possible implication of our results for experimentally observable 0-- transitions in SFS junctions.
Henrik Moodysson Rønnow, Ivica Zivkovic, Jian Rui Soh