Modulation of the dc Josephson current in pseudo-spin-valve Josephson multilayers

The dependence of the critical Josephson current (I-C) and magnetoresistance (MR) on the relative orientation of the ferromagnetic layers is investigated in current perpendicular to plane (CPP) measurements of superconductor/ferromagnetic (S/F) multilayers. Two different CuxNi1-x alloys were chosen so that alternate F-layers reversed at different applied magnetic fields and that the ferromagnetic coherence length was of the order of several nanometres. These structures show a significant CPP high-bias MR, which enables the magnetic state of the devices to be determined directly. We found that I-C is substantially larger when the adjacent F-layers are aligned antiparallel compared to the case of parallel orientation. Since in a pseudo-spin-valve structure the relative F-layer orientation is approximately parallel for zero applied magnetic field, I-C can experience an enhancement when a magnetic field is applied in the plane of the junction. The maximum change of I-C corresponds to the maximum change of MR.