Laser-Induced Real-Space Topology Control of Spin Wave Resonances

Femtosecond laser excitation of materials exhibiting magnetic spin textures promises advanced magnetic control via the generation of non-equilibrium spin dynamics. Ferrimagnetic [Fe(0.35 nm)/Gd(0.40 nm)]160 multilayers are used to explore this approach, as they host a rich diversity of magnetic textures from stripe domains at low magnetic fields, a dense bubble/skyrmion lattice at intermediate fields, and a single domain state for high magnetic fields. Using femtosecond magneto-optics, distinct coherent spin wave dynamics are observed in this material in response to a weak laser excitation, enabling an unambiguous identification of the different magnetic spin textures. Moreover, employing strong laser excitation, versatile control of the coherent spin dynamics via non-equilibrium transformation of magnetic spin textures becomes possible by both creating and annihilating bubbles/skyrmions. Micromagnetic simulations and Lorentz transmission electron microscopy with in situ optical excitation corroborate these findings. The coherent magneto-optical response of [Fe(0.35 nm)/Gd(0.40 nm)]160 multilayers to weak femtosecond laser excitation is shown to depend on the underlying magnetic spin texture (stripe domains, bubbles, and skyrmions, single domain state). Strong laser excitation can transform these spin textures and, in this way, the coherent response of the spin system can be controlled. image