  Josephson junctions containing ferromagnetic (F) materials have been the
subject of intense study over the past two decades. The ground state of such
junctions oscillates between 0 and pi as the thickness of the ferromagnetic
layer increases. For some applications, it might be beneficial to replace a
very thin F layer with an unbalanced synthetic antiferromagnet (SAF) consisting
of two F layers of different thicknesses whose magnetizations are coupled
antiparallel to each other. According to theory, such a system should behave
similarly to a single F layer whose thickness is equal to the difference of the
two F-layer thicknesses in the SAF. We test that theoretical prediction with
Josephson junctions containing unbalanced Ni/Ru/Ni SAFs, keeping the thickness
of one layer fixed at 2.0 nm and varying the thickness of the other layer
between 2.0 and 5.0 nm. We observe the first 0-pi transition at a thickness
difference of 0.86 nm, which closely matches the position of the transition
observed previously using single Ni layers.
