Controlling bubble and skyrmion lattice order and dynamics via stripe domain engineering in ferrimagnetic Fe/Gd multilayers

Abstract

Ferrimagnetic Fe/Gd multilayers host maze-like stripe domains that transform into a disordered bubble/skyrmion lattice under out-of-plane magnetic fields at ambient temperature. Femtosecond magneto-optics distinguishes these textures via their distinct coherent breathing dynamics. Crucially, applying a brief in-plane ``set'' magnetic field to the stripe state enhances both frequency and amplitude of the bubble/skyrmion lattice breathing mode. Lorentz transmission electron microscopy, magnetic force microscopy, and micromagnetic simulations reveal that this enhancement arises from field-aligned stripes nucleating a dense, near-hexagonal bubble/skyrmion lattice upon out-of-plane field application, with strong indications for a pure skyrmion lattice. Thus, modifying the initial domain configuration by in-plane fields enables precise control of coherent magnetization dynamics on picosecond to nanosecond timescales and potentially even of topology.