Micromagnetic Simulations of Antiferromagnetically Coupled Bubble Skyrmions

Antiferromagnetically (AFM) 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 [1]. Our recent photoelectron emission microscopy (PEEM) imaging [2] results showed a sizeable field-driven response of AFM-coupled skyrmions in [Co/Gd/Pt]₁₀ multilayers, but the underlying mechanism of the observed changes in the skyrmion shapes and sizes remains to be clarified. Here we report on micromagnetic simulation [3] studies of the response of AFM-coupled skyrmions to pulsed magnetic fields. Simulations were performed using MuMax³ with material parameters extracted from magnetometry measurements of the [Co/Gd/Pt]₁₀ multilayers. Skyrmions were stabilized in [Co/Gd/Pt]₂ structures with no applied magnetic field with a mesh size of 2.0 nm x 2.0 nm x 0.5 nm, and periodic boundary conditions were used to approximate the effect of the additional 8 repeats. Pulsed magnetic fields ranging from 3 to 162 Oe were then applied at tilt angles of -3°, 0°, and 3° with respect to the plane of the sample. The simulation results show that changes in the shape and size of AFM-coupled skyrmions are driven primarily by the response of the chiral domain walls of the skyrmions to the in-plane component of the applied magnetic field.