A theoretical study on the statics and dynamics of magnetic domain walls and skyrmions

Abstract

This thesis conducts a comprehensive theoretical study and numerical simulations on the statics and dynamics of magnetic domain walls (DWs) and skyrmions, two prominent examples of topological solitons in magnetic materials. For DWs, the focus is on their motion in ferrimagnetic nanowires, driven by external magnetic fields or spin-polarized currents. The research addresses challenges like the Walker breakdown, which limits DW speed. A significant finding is that high-speed DW motion occurs near the angular momentum compensation point (AMCP). The study uses energy conservation principles to explain DW dynamics, proving that static DWs cannot exist under uniform external fields and deriving a velocity formula consistent with experimental results. In the skyrmion section, the thesis investigates ferromagnetic skyrmion pinning by disk-shaped defects and the dynamics of current-driven antiferromagnetic skyrmions in disordered systems. It reveals how skyrmion type and disk size affect pinning and explores the impact of disorder on skyrmion trajectories. Overall, this work enhances the understanding of DWs and skyrmions, offering insights for future spintronic device development based on topological magnetic solitons.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Xiangrong WANG (Supervisor)