Thickness‐Dependent Skyrmion Evolution in Fe ₃ GeTe ₂ During Magnetization Reversal

Abstract The van der Waals (vdW) ferromagnet Fe 3− x GeTe 2 (FGT) offers a versatile platform for studying 2D magnetism and for potential spintronic applications, owing to its relatively high Curie temperature (200 K to 230 K) and strong perpendicular magnetic anisotropy. Although some efforts at skyrmion control in FGT have been reported, the details of domain behavior during magnetization reversal remain largely unexplored. Here, in situ cryo‐Lorentz transmission electron microscopy (LTEM) is used to image the magnetic domain behavior during the field‐driven reversal in a single exfoliated FGT flake with stepped thicknesses. The field‐cooling conditions are varied to establish the initial domain state, and the evolution of stripe domains, skyrmions, and a faceted, patch‐like domain phase formed by 360° domain walls is directly observed. These transitions show a strong dependence on thickness, and naturally occurring step edges between thickness regions act as strong pinning sites. Micromagnetic simulations reproduce the experimental behavior and reveal the role of sample thickness, magnetic anisotropy, and applied field on the resulting domain behavior. This systematic study demonstrates efficient control of skyrmion size, density, and transitions to novel domain structures, offering more precise mechanisms for tailoring topological spin textures.