Enhanced stability in spin transfer nanopillars due to a Fe/Gd/Fe trilayer

Abstract

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 10 K 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.