Ferromagnetic Josephson junctions incorporating both in and out-of-plane magnetic anisotropy.

Josephson junctions containing multiple ferromagnetic layers are a topic of intense research. In a junction where the magnetizations of all the layers are either aligned parallel or antiparallel, only the spin-singlet electron pairs carry supercurrent. Engineering adjacent F layers to have perpendicular magnetizations allows singlet pairs to convert to spin-aligned triplet pairs. Recent work in our group has shown the conversion to the spin-aligned triplet by the addition of a synthetic antiferromagnet (SAF) with perpendicular magnetic anisotropy (PMA) [1]. In this work, we show that by changing the order in which these layers are stacked inside the junction, one can either optimize or suppress generation of spin-triplet pairs. Such an approach should provide an unambiguous estimate of the fraction of the supercurrent carried by spin-singlet pairs in an otherwise dominant spin-triplet junction.
[1] Glick, J.A. et. al, arXiv:1710.07247