Precipitating Ordered Skyrmion Lattices from Helical Spaghetti

TL;DR

This paper demonstrates a method to transform disordered magnetic skyrmion states into ordered, oriented skyrmion lattices using a specific magnetic field sequence, applicable across different materials and aiding skyrmion research.

Contribution

It introduces a universal field treatment technique to induce ordered skyrmion lattices from disordered states in various materials.

Findings

Field sequence disentangles jammed states into ordered lattices.

Ordered skyrmion lattices achieved in both single crystals and powders.

Simulations confirm orientation promotion independent of initial configuration.

Abstract

Magnetic skyrmions have been the focus of intense research due to their potential applications in ultra-high density data and logic technologies, as well as for the unique physics arising from their antisymmetric exchange term and topological protections. In this work we prepare a chiral jammed state in chemically disordered (Fe, Co)Si consisting of a combination of randomly-oriented magnetic helices, labyrinth domains, rotationally disordered skyrmion lattices and/or isolated skyrmions. Using small angle neutron scattering, (SANS) we demonstrate a symmetry-breaking magnetic field sequence which disentangles the jammed state, resulting in an ordered, oriented skyrmion lattice. The same field sequence was performed on a sample of powdered Cu2OSeO3 and again yields an ordered, oriented skyrmion lattice, despite relatively non-interacting nature of the grains. Micromagnetic simulations confirm the promotion of a preferred skyrmion lattice orientation after field treatment, independent of the initial configuration, suggesting this effect may be universally applicable. Energetics extracted from the simulations suggest that approaching a magnetic hard axis causes the moments to diverge away from the magnetic field, increasing the Dzyaloshinskii-Moriya energy, followed subsequently by a lattice re-orientation. The ability to facilitate an emergent ordered magnetic lattice with long-range orientation in a variety of materials despite overwhelming internal disorder enables the study of skyrmions even in imperfect powdered or polycrystalline systems and greatly improves the ability to rapidly screen candidate skyrmion materials.