Dynamic self-organisation and pattern formation by magnon-polarons

TL;DR

This paper demonstrates that chaos in magnetisation dynamics can lead to the formation of ordered, periodic magnetic domain patterns through phase synchronization of magnon-polaron waves, revealing a new mechanism of magnetization reversal.

Contribution

It uncovers a novel pattern formation mechanism in magnetic materials driven by magnon-polaron phase synchronization at short time scales.

Findings

Chaotic magnetisation dynamics can produce ordered magnetic domain patterns.

Pattern formation results from phase-synchronization of magnon-polaron waves.

A new magnetization reversal mechanism driven by coherent quasiparticle packets.

Abstract

Nonlinear dynamics can give rise, via the processes of self-organisation and pattern formation, to the spontaneous manifestation of order in open and complex systems far from equilibrium. Self-organising systems, transforming the inflow of energy into information, are ubiquitously found in current topical areas of science ranging from brainwave entrainment and neuromorphic computing to energy-efficient data storage technologies. In the latter, magnetic materials play a pivotal role combining very fast switching with permanent retention of information. However, it has been shown that, at very short time scales, magnetisation dynamics become chaotic due to internal instabilities, resulting in incoherent spin-wave excitations that ultimately destroy magnetic ordering. Here, contrary to all expectations, we show that such chaos gives rise to a periodic pattern of reversed magnetic domains, with a feature size far smaller than the spatial extent of the excitation. We explain this pattern as a result of phase-synchronisation of magnon-polaron waves, driven by strong coupling of magnetic and elastic modes. Our results reveal not only the peculiar formation and evolution of magnon-polarons at short time-scales, but also present a novel mechanism of magnetization reversal driven by coherent packets of short-wavelength quasiparticles.