Magnetic domain wall Skyrmions

TL;DR

This paper introduces a new topological excitation called a DW Skyrmion, formed within Dzyaloshinskii domain walls, and proposes experimental identification methods using Lorentz TEM.

Contribution

It presents the theoretical and micromagnetic description of DW Skyrmions and suggests an experimental imaging technique to detect them.

Findings

Identification of DW Skyrmions as a new topological magnetic structure.

Analytical and micromagnetic models describing DW Skyrmions.

Simulation of Lorentz TEM images for experimental detection.

Abstract

It is well established that the spin-orbit interaction in heavy metal/ferromagnet heterostructures leads to a significant interfacial Dzyaloshinskii-Moriya Interaction (DMI) that modifies the internal structure of magnetic domain walls (DWs) to favor N\'{e}el over Bloch type configurations. However, the impact of such a transition on the structure and stability of internal DW defects (e.g., vertical Bloch lines) has not yet been explored. We present a combination of analytical and micromagnetic calculations to describe a new type of topological excitation called a DW Skyrmion characterized by a $360^\circ$ rotation of the internal magnetization in a Dzyaloshinskii DW. We further propose a method to identify DW Skyrmions experimentally using Fresnel mode Lorentz TEM; simulated images of DW Skyrmions using this technique are presented based on the micromagnetic results.