Current-induced dynamics and instability pathways of skyrmioniums in chiral magnets

Abstract

We present a comprehensive study of current-driven dynamics, transformations, and instabilities of skyrmioniums in chiral magnetic films, considering both isolated objects and collective states forming skyrmionium-based meta-matter. Using micromagnetic simulations combined with an analytical description based on the generalized Thiele equation, we elucidate how the internal structure of skyrmioniums governs their nonequilibrium response to electric currents. Despite carrying zero total topological charge, skyrmioniums are shown to exhibit a finite transverse velocity under applied currents. We demonstrate that this skyrmionium Hall effect originates from an imbalance between the positive and negative topological contributions of the inner skyrmion and the surrounding ring, which generally occupy different surface areas. Current-induced deformations further enhance this imbalance, leading to Hall angles that can become comparable to those of isolated skyrmions. At higher current densities, skyrmioniums undergo distinct instability processes depending on magnetic field and uniaxial anisotropy, including elongation, collapse into an isolated skyrmion, transformation into a topologically trivial droplet, and expansion into stripe-like textures. We organize these regimes in current–field and current–anisotropy phase diagrams and resolve their microscopic pathways by monitoring the evolution of the topological charge and local rotational measures. Beyond isolated textures, mixed skyrmion–skyrmionium lattices exhibit rich collective dynamics, including elastic transport, current-induced polymorphic transitions, soliton exchange, and stripe formation. Pulsed-current driving provides additional control, enabling access to dynamic regimes beyond continuous driving. Overall, our results establish skyrmioniums and their meta-matter assemblies as highly tunable nonequilibrium systems and reveal how current-induced transformations probe the topological energy landscape far from equilibrium.