Skyrmion-Bimeron Transformation in Bilayer Chiral Magnets with Competing Magnetic Anisotropy

Abstract

In this work, we investigate the emergence of topological spin textures in a ferromagnetically coupled bilayer chiral magnet by means of Monte Carlo simulations of a classical spin model including exchange interaction, Dzyaloshinskii-Moriya interaction, magnetic anisotropy, and an external magnetic field. To characterize the topology of the system, we construct a scalar chirality map in the $(K/J,h/J)$ parameter space. Our results reveal several magnetic configurations, including labyrinth structures, skyrmion lattices, ferromagnetic states, and meron-antimeron crystal phases. In particular, we show that the transition from easy-axis to easy-plane anisotropy drives a continuous transformation from skyrmion textures to bimeron-type configurations. The bilayer geometry introduces an additional stabilization mechanism, where interlayer exchange coupling correlates the topological cores in the two layers and increases the energetic cost of defect collapse. These findings provide a systematic topological texture map for bilayer chiral magnets and highlight coupled magnetic layers as a promising platform for stabilizing bimeron-type spin textures in nanoscale spintronic systems.

Figures (8)

• Figure 1: Bilayer system that consists of (a) the top and (b) bottom layer for selected parameters: $D/J = 1$, $h/J = 0.5$, and $K/J = -0.3$.
• Figure 2: The density plot of the total scalar chirality $\chi_{T}$ as a function of $(K/J-h/J)$ plane for one layer for $D/J=1$.
• Figure 3: The real-space spin configurations (top panel) and real-space local chirality (middle panel) corresponding to that configuration $D/J=1$ without magnetic field $h/J=0$ for selected values of anisotropy (a) $K/J=-0.85$, (b) $K/J=-1.15$, respectively. The perpendicular $S_\bot(\vec{q})$ and parallel $S_{||}(\vec{q})$ components of the static structure factor with the corresponding structure are shown in the two rows below panel.
• Figure 4: The real-space spin configurations (top panel) and real-space local chirality (middle panel) corresponding to that configuration $D/J=1$ without magnetic field $h/J=0$ for selected values of anisotropy (a) $K/J=-1.2$, (b) $K/J=-1.4$, respectively. The perpendicular $S_\bot(\vec{q})$ and parallel $S_{||}(\vec{q})$ components of the static structure factor with the corresponding structure are shown in the two rows below panel.
• Figure 5: Real-space spin configurations (top panel) and real-space local chirality (bottom panel) corresponding to that configuration. Snapshots for $K/J=0$ and $D/J=1$ for selected magnetic field values (a) $h/J=0.0$, (b) $h/J=0.21$, (c) $h/J=0.41$, (d) $h/J=0.71$, respectively.