Crystallization dynamics of magnetic skyrmions in a frustrated itinerant magnet

TL;DR

This study explores the formation and evolution of skyrmion lattices in a metallic magnet, revealing a two-stage crystallization process influenced by topological defects and magnetic fields, with implications for magnetic material applications.

Contribution

It introduces a detailed dynamical model for skyrmion lattice formation, highlighting the role of dislocation dynamics and field-dependent annihilation processes.

Findings

Fast initial skyrmion crystallization observed

Dislocation annihilation follows a power-law with logarithmic correction

Late-stage phase ordering shows dynamical scaling symmetry

Abstract

We investigate the phase ordering kinetics of skyrmion lattice (SkL) in a metallic magnet. The SkL can be viewed as a superposition of magnetic stripes whose periods are determined by the quasi-nesting wave vectors of the underlying Fermi surface. An effective magnetic Hamiltonian that describes the electron-mediated spin-spin interaction is obtained for a two-dimensional s-d model with the Rashba spin-orbit coupling. Large-scale Landau-Lifshitz-Gilbert dynamics simulations based on the effective spin Hamiltonian reveal a two-stage phase ordering of the SkL phase after a thermal quench. The initial fast crystallization of skyrmions is followed by a slow relaxation dominated by the annihilation dynamics of dislocations, which are topological defects of the constituent magnetic stripe orders. The late-stage phase ordering also exhibits a dynamical scaling symmetry. We further show that the annihilation of dislocations follows a power-law time dependence with a logarithmic correction that depends on magnetic fields. Implications of our results for SkL phases in magnetic materials are also discussed.