Probing Random-Bond Disorder Effects on Ferromagnetic Skyrmion Arrays

TL;DR

This study investigates how random-bond disorder affects ferromagnetic skyrmion arrays, revealing disorder-induced phase transitions, topological robustness, and model-dependent behaviors through extensive Monte Carlo simulations.

Contribution

It introduces two models of bond disorder in skyrmion lattices and systematically analyzes their effects on phase stability and topological properties.

Findings

Moderate disorder induces bimeron phases at low magnetic fields.

Skyrmion lattice phases retain topological features despite losing periodicity.

Disorder suppresses or enhances skyrmion phases depending on the model.

Abstract

In this work, we examined the impact of disorder in a ferromagnetic skyrmion lattice by introducing random-bond disorder based on two different models for both exchange and Dzyaloshinskii-Moriya interactions: Model I, where both interactions present the same disorder distribution and thus the same local distortion, and Model II, where both interactions have different disorder distributions. Through extensive Monte Carlo simulations, we explored the effect of bond disorder on the emergent phases induced by an external magnetic field at different temperatures, varying the disorder amplitude across a range from weak (10%) to strong (200%) regimes. Our study shows that for both models, moderate disorder at low magnetic fields breaks the helical order and induces a topologically non-trivial bimeron phase. We also found that the skyrmion lattice phase loses its periodicity, but surprisingly, the resulting phases retain topological characteristics up to high disorder amplitudes. Moreover, a significant difference between both disorder models is found at large magnetic fields: while in the first model, the high-field skyrmion phase is suppressed by disorder, in the second model, this phase is enhanced and expanded in temperature and magnetic field. Furthermore, for the second model, intermediate values of disorder induce a diluted skyrmion phase and chiral textures emerging from the ferromagnetic phase at low temperatures. Our results are relevant for layered magnets and provide valuable insights into the intricate behavior of skyrmion systems under varying disorder conditions.