Both band structure calculations and experiments show that the giant-magnet
oresistance (GMR) of a spin-valve with a synthetic-antiferromagnetic pinned
layer is smaller than that with a single pinned layer. This smaller GMR is
shown to come from the s-d scattering in the Ru layer and part of the pinn
ed layer that has the opposite moment direction. Half of the synthetic-anti
ferromagnet does not contribute to the GMR and only shunts the current.