Operando Control of Skyrmion Density in a Lorentz Transmission Electron Microscope with Current Pulses

TL;DR

This study demonstrates how current pulses can be used in a Lorentz TEM to control and study the stability of skyrmion densities in magnetic materials, revealing that higher densities enhance skyrmion stability.

Contribution

It introduces an operando method combining electrical pulsing and microscopy to control and analyze skyrmion density and stability in magnetic multilayers.

Findings

High-density skyrmion states are more stable against magnetic field variations.

Thermal effects significantly influence skyrmion creation and annihilation.

Controlled current pulsing enables manipulation of skyrmion populations.

Abstract

Magnetic skyrmions hold promise for spintronic devices. To explore the dynamical properties of skyrmions in devices, a nanoscale method to image spin textures in response to a stimulus is essential. Here, we apply a technique for operando electrical current pulsing of chiral magnetic devices in a Lorentz transmission electron microscope. In ferromagnetic multilayers with interfacial Dzyaloshinskii-Moriya interaction (DMI), we study the creation and annihilation of skyrmions localized by point-like pinning sites due to defects. Using a combination of experimental and micromagnetic techniques, we establish a thermal contribution for the creation and annihilation of skyrmions in our study. Our work reveals a mechanism for controlling skyrmion density, which enables an examination of skyrmion magnetic field stability as a function of density. We find that high-density skyrmion states are more stable than low-density states or isolated skyrmions resisting annihilation over a magnetic field range that increases monotonically with density.