Imaging Skyrmion Magnetization Dynamics in Time-Resolved Lorentz Electron Microscopy

The creation, annihilation, movement, and control of magnetic skyrmions with different tools has been the subject of intensive research in recent years. So far, little attention has been given to the use of light as (yet another) external knob to trigger magnetic changes in skyrmion-hosting materials.
With a combination of camera-rate and ultrafast pump-probe Lorentz Transmission Electron Microscopy we directly resolve the spatio-temporal evolution of the skyrmion magnetization ensuing (fs and ns) optical excitation. The laser-induced creation and annihilation of skyrmions in bulk (Bloch) and interfacial (Néel) systems is reported, and the ultimate speed of such writing and erasing is discussed. In a 60-nm thick slab of the prototypical chiral magnet FeGe, we study how the extreme cooling rates of the crystal ( > 10⁷ K/s) following the photoexcitation can quench the magnetization into a disordered metastable skyrmion lattice.