Signatures of higher order skyrmionic textures revealed by magnetic force microscopy

TL;DR

This paper demonstrates that higher-order skyrmionic textures in Co/Ni multilayers can be visualized at room temperature using high-resolution magnetic force microscopy, supported by micromagnetic simulations.

Contribution

It introduces magnetic force microscopy as a new method to observe higher-order skyrmions and antiskyrmions, previously only seen with electron microscopy.

Findings

Higher-order skyrmions are visualized at room temperature.

Distinct MFM contrast corresponds to different spin textures.

Micromagnetic simulations confirm experimental observations.

Abstract

Higher-order skyrmions and antiskyrmions are topologically protected spin textures with an integer topological charge other than $\pm 1$ and nucleate from topological point defects in regular Bloch walls, known as vertical Bloch lines. So far, they have only been observed using Lorentz transmission electron microscopy. In this work, we show that higher-order spin textures coexisting in Co/Ni multilayers at room temperature can be visualized by high-resolution magnetic force microscopy (MFM). The experimental results are supported by micromagnetic simulations confirming that different spin objects give rise to distinct MFM contrast in full agreement to our observations.