Controlling the configuration and creation of magnetic skyrmions by various manipulation techniques studied based on full-field soft X-ray microscopy

Abstract

Magnetic skyrmion is a topologically protected spin structure stabilized by Dzyaloshinskii- Moriya interactions and/or dipolar interactions. Magnetic skyrmions have attracted enormous interests not only because of their fascinating topological characters to understand fundamental physics of nanospin behavior but also due to their potentials in a wealth of technological applications such as high efficient storage and memory devices. Recently, Magnetic skyrmions have also been considering as a promising candidate for neuromorphic computing with their particle-like behaviors and effective motions at low energy consumption. From the perspective for skyrmions to be practically used, one of the critical issues is whether the configuration of skyrmions including their sizes and densities and creating/deleting of skyrmions is manageable or not. In our work, we experimentally addressed the issue by direct observation of skyrmions and skyrmion configurations in Pt/Co/Fe/Ir, Pt/Co/Pt, Fe/Gd, Pt/Co/Ta multilayered heterostructures utilizing a soft X-ray transmission microscope at Advanced Light Source (XM-1, BL6.1.2), enabling the direct observation of in-plane and out-of-plane magnetic components with a high spatial resolution down to 25 nm. We demonstrated that the properties of skyrmions such as size and density of skyrmions could be controlled by varying thickness of ferromagnetic layers and by changing the strength of magnetic field [1-3]. Additionally, it was found that skyrmions could be either created or annihilated by the injected current pulses depending on the strength of applied magnetic fields [4] where the Joule heating than spin-orbit torque effect plays a critical role in the formation and/or elimination of skyrmions. We also proposed a way to create and delete skyrmions in a certain selective area of systems based on using Oersted fields and Joule heating by optimizing design of sample geometries including electrodes [5].