Formation and current-induced motion of synthetic antiferromagnetic skyrmion bubbles

TLDR

Skyrmions are topologically protected spin textures that can be driven by low current densities, yet ferromagnetic systems struggle to stabilize ultrasmall room‑temperature skyrmions, suffer from the skyrmion Hall effect, and have limited velocities. Synthetic antiferromagnetic multilayers produce room‑temperature skyrmion bubbles that are smaller, require lower threshold currents, move faster, and exhibit negligible Hall effect, providing a route toward nanoscale, energy‑efficient devices.

Abstract

Skyrmion, a topologically-protected soliton, is known to emerge via electron spin in various magnetic materials. The magnetic skyrmion can be driven by low current density and has a potential to be stabilized in nanoscale, offering new directions of spintronics. However, there remain some fundamental issues in widely-studied ferromagnetic systems, which include a difficulty to realize stable ultrasmall skyrmions at room temperature, presence of the skyrmion Hall effect, and limitation of velocity owing to the topological charge. Here we show skyrmion bubbles in a synthetic antiferromagnetic coupled multilayer that are free from the above issues. Additive Dzyaloshinskii-Moriya interaction and spin-orbit torque (SOT) of the tailored stack allow stable skyrmion bubbles at room temperature, significantly smaller threshold current density or higher speed for motion, and negligible skyrmion Hall effect, with a potential to be scaled down to nanometer dimensions. The results offer a promising pathway toward nanoscale and energy-efficient skyrmion-based devices.