Evolution of antiferromagnetically coupled skyrmion pair excited by magnetic field

Antiferromagnetically (AF) coupled skyrmions offer potential advantages for spintronic devices, including reduced dipolar fields that may enable smaller skyrmion sizes and a reduction of the skyrmion Hall effect. Here, we combined photoemission electron microscopy (PEEM) imaging and micromagnetic simulations using MuMax³ to investigate the evolution of AF-coupled skyrmion pairs in [Co(0.5 nm)/Gd (1 nm)/Pt (1 nm)]₁₀ multilayered thin films excited by pulsed magnetic fields ranging from 3 to 162 Oe. PEEM images of the top Co and Gd layers obtained at remanence confirm AF coupling between these two layers and further show that skyrmions with radii smaller than ~1.5 μm contracted while larger ones expanded when excited by in-plane fields. Simulations with a cell size of 2 nm × 2 nm × 0.5 nm and material parameters extracted from magnetometry results show skyrmions with a radius of 0.25 μm shrinking, consistent with the experimental results, and reveal that spin configurations are vertically coherent across the sample, except for the surface layer. Our results on magnetic field-driven skyrmion evolution shed light on the competition among the exchange, dipolar, Zeeman, and Dzyaloshinskii-Moriya interactions, which may lead to future field-driven spintronic devices.