Spin valve Josephson junctions

We are currently researching Nb-based Josephson junctions with magnetic barriers in which the magnetic character can be actively changed, with the final aim of producing a magnetically controllable π-junction. Pseudo-spin-valve Nb/Fe₂₀Ni₈₀/Cu/Co/Nb Josephson junctions have been grown by d.c. magnetron sputtering. As we have previously reported, the spin-valve magnetoresistance could be measured at high bias at 4.2 K. The zero field critical current of the junction could also be varied by preparing the spin valve in different remanent states. Jumps and smooth changes in the critical current were observed, in line with the changes in magnetoresistance. In this work we discuss the effect of varying the total barrier thicknesses on the change in the critical current, as well as varying the Co:Fe₂₀Ni₈₀ ratio.