Tailoring Optical Excitation to Control Magnetic Skyrmion Nucleation

TL;DR

This paper demonstrates a method to control the spatial nucleation of magnetic skyrmions using patterned reflective masks and optical excitation, enabling precise localization on the nanometer scale for potential data technology applications.

Contribution

It introduces a novel approach employing nanopatterned masks and optical near-field effects to achieve localized control of skyrmion nucleation in magnetic multilayers.

Findings

Patterned masks can locally tailor optical excitation for skyrmion nucleation.

The effect of masks depends on the layer sequence of the sample.

Optical near-field enhancements influence skyrmion spatial arrangement.

Abstract

In ferromagnetic multilayers, a single laser pulse with a fluence above an optical nucleation threshold can create magnetic skyrmions, which are randomly distributed over the area of the laser spot. However, in order to study the dynamics of skyrmions and for their application in future data technology, a controllable localization of the skyrmion nucleation sites is crucial. Here, it is demonstrated that patterned reflective masks behind a thin magnetic film can be designed to locally tailor the optical excitation amplitudes reached, leading to spatially controlled skyrmion nucleation on the nanometer scale. Using x-ray microscopy, the influence of nanopatterned back-side aluminum masks on the optical excitation is studied in two sample geometries with varying layer sequence of substrate and magnetic Co/Pt multilayer. Surprisingly, the masks' effect on suppressing or enhancing skymion nucleation reverses when changing this sequence. Moreover, optical near-field enhancements additionally affect the spatial arrangement of the nucleated skyrmions. Simulations of the spatial modulation of the laser excitation, and the following heat transfer across the interfaces in the two sample geometries are employed to explain these observations. The results demonstrate a reliable approach to add nanometer-scale spatial control to optically induced magnetization processes on ultrafast timescales.