Magnetic skyrmion bundles and their current-driven dynamics

Topological charge Q classifies non-trivial spin textures and determines many of their characteristics. Most abundant are topological textures with |Q| <= 1, such as (anti)skyrmions, (anti)merons or (anti)vortices. In this study we created and imaged in real space magnetic skyrmion bundles, that is, multi-Q three-dimensional skyrmionic textures. These textures consist of a circular spin spiral that ties together a discrete number of skyrmion tubes. We observed skyrmion bundles with integer Q values up to 55. We show here that electric currents drive the collective motion of these particle-like textures similar to skyrmions. Bundles with Q not equal 0 exhibit a skyrmion Hall effect with a Hall angle of similar to 62 degrees, whereas Q = 0 bundles, the so-called skyrmioniums, propagate collinearly with respect to the current flow, that is, with a skyrmion Hall angle of similar to 0 degrees. The experimental observation of multi-Q spin textures adds another member to the family of magnetic topological textures, which may serve in future spintronic devices. Non-trivial topological magnetic textures, such as skyrmions, merons or vortices, possess topological charges Q with absolute values smaller or equal to one. Now, skyrmion bundles, multi-Q three-dimensional skyrmionic textures, are observed and their current-driven dynamics are studied.

Automated summary

Topological charge Q classifies non-trivial spin textures like skyrmions, merons, or vortices with absolute values smaller or equal to 1. Recently, multi-Q three-dimensional skyrmionic textures, known as skyrmion bundles, have been observed and studied for their current-driven dynamics.