Enhancement of perpendicular magnetic anisotropy thanks to Pt insertions in synthetic antiferromagnets

Synthetic antiferromagnets are of great interest as reference layers in magnetic tunnel junctions since they allow decreasing the dipolar coupling between the two magnetic electrodes and exhibit larger pinning fields than single reference layers. In this letter, we investigate the effect of the insertion of an ultrathin Pt layer in contact with the Ru spacer in synthetic antiferromagnets with perpendicular magnetic anisotropy. Surprisingly, for Ru thickness below 0.75 nm, the antiferromagnetic coupling amplitude through Ru first increases upon Pt insertion up to a critical Pt thickness (∼0.25 nm) above which coupling decreases. In addition, the corresponding increase of perpendicular magnetic anisotropy enhances the thermal stability of the structure.