Enhanced Stability In Spin Transfer Nanopillars Due To A Fe/Gd/Fe Trilayer

A sharp antiferromagnetic boundary of Fe/Gd is found to affect notoriously the critical current for spin transfer torque (STT). Transport measurements performed on nano-patterned spin valves show that when a Fe/Gd/Fe is added as a top layer, the effect of spin transfer on the free layer is dramatically reduced. The critical current increases up to one order of magnitude at 10K and five times at room temperature. We show that this increase cannot be fully explained by the macrospin approximation and we argue that it is due to a torque at the Gd/Fe interface that opposes the STT in the free layer. (C) 2013 AIP Publishing LLC.