Spin-polarized current versus stray field in a perpendicularly magnetized superconducting spin switch

In superconducting Co/Pt-Nb-Co/Pt multilayers with perpendicular magnetic anisotropy, the superconducting transition temperature T-c is considerably higher in the parallel (P) orientation of the two Co/Pt magnetizations compared to the antiparallel (AP) orientation. Low temperature magnetic-force microscopy reveals that the individual ferromagnetic layers are uniformly magnetized in both configurations and do not exhibit a magnetic stray field arising from a multidomain state. We also demonstrate that the difference Delta T-c=T-c(P)-T-c(AP) between both T-c values is enhanced at higher transport currents due to the increasing imbalance of spin-polarized charge carriers in the superconducting Nb layer. Hence, the spin switch can be controlled by the transport current in future superconducting devices. (C) 2007 American Institute of Physics.