Micromagnetic Simulations of field-driven antiferromagnetically coupled skyrmions pairs*

Antiferromagnetically (AF) coupled skyrmions, characterized by antiparallel spin alignment between skyrmion pairs, offer significant advantages for spintronic applications, including increased data storage density and suppression of the Skyrmion Hall Effect. Our previous micromagnetic simulations on [Co/Gd/Pt]₁₀ multilayers with the application of vertical periodic boundary conditions confirmed the AF coupling between the bubble skyrmions in adjacent Co and Gd layers, consistent with photoemission electron microscopy (PEEM) results. While the application of vertical periodic boundary conditions can increase computational efficiency, they cannot precisely account for the long-range dipolar interactions across all layers. Here, we perform micromagnetic simulations of AF-coupled skyrmions pairs in [Co/Gd/Pt]₁₀ multilayers using Mumax³ without vertical periodic boundary conditions to clarify the correlation of magnetic behavior across different layers and to investigate the effect of applied pulsed magnetic field on AF-coupled skyrmions pairs. Analysis of the simulation results with customized Python code confirmed that spin configurations of different layers are vertically coherent across the entire sample, except for the surface layer. The subtle differences in magnetic behavior among the layers provide insights into the mechanism of imaged evolution AF coupled skyrmion pairs excited by pulsed magnetic field.