Stabilization of Ultrafast Domain Wall Motion by Edge-Anisotropy Engineering in Ferrimagnetic Nanowires

Abstract

Achieving stable, ultrafast current-induced domain wall motion (CIDWM) is essential for practical racetrack memory devices. Here, anisotropy-engineering at the edges of Pt/GdFe ferrimagnetic nanowires with composition near magnetic compensation is investigated through experimental laser-annealing (LA) treatments and Landau–Lifshitz–Gilbert (LLG)-based micromagnetic simulations. CIDWM measurements show that LA enhances DW velocity and stabilizes propagation over a wide current-density range. The velocity reaches approximately 3200 m s⁻¹ and remains relatively stable at high current densities, indicating a stable high-speed propagation regime. Kerr microscopy further reveals that LA transforms curved and distorted DW profiles into straighter, more uniform configurations. Simulations varying the local perpendicular magnetic anisotropy (K_u) and annealed-edge width clarify the underlying mechanism. Moderate edge-anisotropy reduction suppresses pinning, stabilizes the DW configuration, and enables coherent spin–orbit-torque-driven propagation. In contrast, excessive anisotropy reduction or excessively wide annealed regions induce multidomain instability and deteriorate DW motion. The simulated dynamics reproduce the experimentally observed velocity saturation and stable propagation behavior. LA-defined channels further suggest a scalable multi-lane architecture in which N laser traces can define up to N+1 DW transport paths within a single wire. These findings establish LA as an effective anisotropy-engineering technique and provide a quantitative design framework for racetrack memory and reconfigurable spintronic devices.