Skyrmionium meta-matter: a topologically heterogeneous magnetic crystal with emergent hybrid dynamics

TL;DR

This paper introduces skyrmionium meta-matter, a new class of topological magnetic textures with hybrid dynamics, stabilized by mixed skyrmion and skyrmionium lattices, exhibiting unique excitations and tunable properties for spintronic applications.

Contribution

It systematically investigates the structure, stability, and dynamics of skyrmionium-skyrmion lattices, revealing new hybrid excitations and control mechanisms for topologically heterogeneous magnetic materials.

Findings

Stabilization of mixed Skm--Sk lattices by skyrmions acting as topological pins.

Identification of hybrid excitations including deformation-assisted rotations and orbital modes.

Resonant mode frequencies spanning sub-GHz to above 10 GHz, suitable for spintronic devices.

Abstract

We introduce and systematically investigate a new class of topological magnetic textures, skyrmionium meta-matter, composed of skyrmioniums (Skm, $Q=0$) and skyrmions (Sk, $Q=-1$) arranged in periodic lattices mimicking the richness of atomic materials. Pure skyrmionium lattices are unstable against elongation distortions and relax into the spiral phase, but even a small fraction of skyrmions acts as topological "pins" that stabilize diverse mixed Skm--Sk crystals. We classify these states by topological stoichiometry (Skm$_n$Sk$_m$) and show that each composition hosts multiple metastable polymorphs with distinct plane-group symmetries. Structural transformations between polymorphs are achieved by varying the lattice spacing, suggesting experimental control via pressure or strain. The collective spin dynamics is explored for both in-plane and out-of-plane AC magnetic fields. The resulting absorption spectra show resonant modes beyond the two rotational and one breathing mode of conventional skyrmion lattices. We identify hybrid excitations unique to Skm--Sk crystals, including (i) deformation-assisted rotations, where skyrmions acquire polygonal shapes and rotate, and (ii) orbital modes, where breathing skyrmioniums induce circular motion of confined skyrmions without changing their size. Mode frequencies span sub-GHz to above 10 GHz, consistent with exchange and DMI energy scales. Our results establish skyrmionium-based meta-matter as a versatile platform for tunable, topologically heterogeneous magnetic lattices with rich structural and dynamical properties, paving the way for reconfigurable magnonic and spintronic applications.