Performance of synthetic antiferromagnetic racetrack memory: domain wall vs skyrmion

A storage scheme based on racetrack memory, where the information can be coded in a domain or a skyrmion, seems to be an alternative to conventional hard disk drive for high density storage. Here, we perform a full micromagnetic study of the performance of synthetic antiferromagnetic (SAF) racetrack memory in terms of velocity and sensitivity to defects by using experimental parameters. We find that to stabilize a SAF skyrmion, the Dzyaloshinskii-Moriya Interaction in the top and the bottom ferromagnet should have an opposite sign. The velocity of SAF skyrmion and SAF Neel domain wall are of the same order and can reach values larger than 1200 m/s if a spin-orbit torque from the spin-Hall effect with opposite sign is applied to both ferromagnets.