Strain Gradient Induced Skyrmion in a van der Waals Magnet by Wrinkling

Magnetic structures are profoundly influenced by mechanical deformation. In particular, strain has been employed to achieve the reconstruction of magnetic domains, paving a mechanical pathway to manipulate magnetic domains. However, experimentally applied strains typically exhibit non-uniform distributions. Therefore, how to distinguish the role of non-uniform strains (strain gradients) and uniform strains is crucial for understanding the mechanical manipulation of magnetic structures. Here, by directly comparing to strain tuning, it is revealed that strain gradient induced by mechanical wrinkles is critical for magnetic domain manipulation in van der Waals ferromagnet Fe₃GaTe₂. A ground-state labyrinthine domain transforms into a skyrmion state in the presence of an in-plane strain gradient. Additionally, an asymmetric evolutionary behavior of the magnetic domain occurs on both sides of wrinkle peaks. Theoretical simulations uncover that though opposite in-plane strain gradient hosts C₂ rotational symmetry, this asymmetric domain evolution can be achieved through the coupling of perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interaction. The finding highlights the vital role of strain gradient in manipulating magnetic properties, and also offers a new mechanism for generating field-free skyrmion.