Micromagnetic Simulations of Field-Driven Antiferromagnetically-Coupled Skyrmions

Magnetic skyrmions are chiral spin textures with potential applications in spintronic devices and quantum computing. The discovery of a topological spin memory effect in [Co/Gd/Pt]₁₀ films demonstrated the robust topological protection of the antiferromagnetically (AF) coupled skyrmion pairs[1]. Our recent photoemission electron microscopy (PEEM) imaging of [Co/Gd/Pt]₁₀ multilayers revealed changes in the size and shape of AF-coupled skyrmions driven by in-plane magnetic fields. However, the underlying mechanism remains to be fully understood. Here we report micromagnetic simulation studies on the evolution of spin configurations in AF-coupled skyrmions driven by pulsed magnetic fields. We have built a full 30‑layer model in MuMax³ to simulate the spin configurations in [Co/Gd/Pt]₁₀ multilayers. Simulated layer‑resolved magnetization maps reveal antiferromagnetic coupling of the adjacent Co and Gd layers. The shrinking of the simulated skyrmion bubbles (diameter<400 nm) at the remanent states after the application of pulsed fields (82 Oe and 162 Oe) aligns well with the PEEM observations of small skyrmion bubbles.