Multistep skyrmion phase transition driven by light-induced uniaxial strain.

Strain engineering in skyrmion-hosting multilayers holds promising potential for spintronic devices. However, conventional strain is below 0.5%, limiting exploration of unique properties under substantial strain. In addition, while uniaxial strain modifies magnetic interactions anisotropically, its influence on skyrmions is underexplored. Here, we integrate skyrmion-hosting multilayers with a flexible liquid crystal film, enabling multistep skyrmion phase transitions through light-induced uniaxial strain up to 1%. Our results demonstrate that skyrmion transitions are sensitive to strain magnitude and orientation. Strain below 0.6% parallel to stripes transforms them into skyrmions. Above 0.6%, skyrmions elongate perpendicularly to the strain direction, exhibiting a negative Poisson effect, with deformation up to 40% at 0.8% strain. Further strain reverts skyrmions back into stripes. Micromagnetic simulations reveal that these phenomena stem from strain-induced anisotropic modulation of Dzyaloshinskii-Moriya interaction. This approach, which combines flexibility, light activation, and substantial uniaxial strain, offers a promising strategy for low-power, multistate spintronic devices.