Topological quasiparticle dynamics in constricted nanomagnets

The dynamic properties in nanostructured magnets are conventionally described by domain wall motion. However, when the geometrical size is constricted to the limiting domain wall length scale, the competing energetics between anisotropy, exchange and dipolar interactions can cause emergent new kinetic events that can be viewed as quasi-particles. Using neutron scattering and simulations, we study ferro- and antiferromagnetic dynamics on a nanoscale honeycomb structure. In both types of materials topological defects in the spin texture are found to behave as dynamical quasi-one-dimensional particles, freely moving along honeycomb joints at picosecond timescales. The dynamic phenomena, arising due to chiral vortex-type topological quasi-particle kinetics, take place in the absence of any external stimuli and persist to much lower temperature than the boundary crossing energy for magnetization reversal, and persist well above the Néel temperature of the antiferromagnetic ordering. This quasi-particle behavior appears to be universal in constricted nanomagnets, in contrast with the conventional understanding of domain wall transport as the only possible mode of dynamics at this scale.