Replacing ruthenium with rhodium as the AFM coupling layer in a
synthetically pinned CPP GMR structure enables the AP1/AP2 thicknesses to
be increased. This results in improved stability and allows the free
layer and AFM layer thicknesses to be decreased, leading to an overall
improvement in the device performance. Another key advantage of this
structure is that the magnetic annealing requirements (to establish
antiparallelism between AP1 and AP2) can be significantly relaxed.