Stimulated nucleation of skyrmions in a geometrically asymmetric structure

Understanding the dynamics of skyrmion nucleation and manipulation is important for applications in spintronic devices. Here, we have investigated the magnetic texture transformation using Lorentz transmission electron microscopy (LTEM) in a centrosymmetric magnet Fe₃Sn₂ with an engineered geometrical asymmetry in the form of a thickness gradient. Using sample tilting and tunable magnetic field strength in the LTEM we developed a new approach for skyrmion nucleation at magnetic domain boundaries. This approach enables nucleation of isolated skyrmions in Fe₃Sn₂ using in-plane fields (< 5 mT) that are two orders of magnitude lower than the previously reported critical magnetic field (~800 mT). Micromagnetic simulations combined with LTEM experiments reveal that the rotatable anisotropy and thickness dependence of the response to the external in-plane field are the critical factors for the skyrmion formation. These results suggest that magnetic materials with rotatable anisotropy are potential skyrmionic systems and provide a novel approach for the manipulation of skyrmions in spintronic devices.