Reorientations, relaxations, metastabilities and multidomains of skyrmion lattices

TL;DR

This study investigates how the orientation and stability of skyrmion lattices in magnetic materials are influenced by magnetic field direction, history, and spin-orbit coupling, revealing metastable states and multidomain formations.

Contribution

It provides new insights into the coupling mechanisms between crystallographic and skyrmion lattices, including metastability and multidomain phenomena, through neutron scattering experiments.

Findings

Skyrmion lattice orientation is mainly determined by magnetic field direction.

Metastable skyrmion lattices can persist or relax over time.

Multidomain lattices form when multiple crystallographic directions are favored.

Abstract

Magnetic skyrmions are nano-sized topologically protected spin textures with particle-like properties. They can form lattices perpendicular to the magnetic field and the orientation of these skyrmion lattices with respect to the crystallographic lattice is governed by spin-orbit coupling. By performing small angle neutron scattering measurements, we investigate the coupling between the crystallographic and skyrmion lattices in both Cu$_2$OSeO$_3$ and the archetype chiral magnet MnSi. The results reveal that the orientation of the skyrmion lattice is primarily determined by the magnetic field direction with respect to the crystallographic lattice. In addition, it is also influenced by the magnetic history of the sample which can induce metastable lattices. Kinetic measurements show that these metastable skyrmion lattices may or may not relax to their equilibrium positions under macroscopic relaxation times. Furthermore, multidomain lattices may form when two or more equivalent crystallographic directions are favored by spin-orbit coupling and oriented perpendicular to the magnetic field.