Thermal and structural disorder effects on spin-transfer-torque-driven domain wall mobility in CoFeB nanostrips

The development of spintronic memory and logic devices depends on an understanding of current-driven domain wall dynamics in realistic nanostructures. Using micromagnetic simulations, we investigate transverse head-to-head domain wall motion in CoFeB nanostrips under deterministic (0 K) and thermally activated (300 K) circumstances, considering both smooth and structurally disordered geometries. The domain wall velocity in smooth nanostrips increases almost linearly with current density at 0 K, indicating effective spin-transfer-torque-driven propagation. However, thermal fluctuations cause domain-wall deformation and a tendency toward velocity saturation at 300 K, especially in thicker nanostrips. To simulate realistic polycrystalline microstructures, structural disorder is introduced using Voronoi tessellation with 10% variations in saturation magnetization and exchange stiffness. Domain wall motion in rough nanostrips exhibits creep-like dynamics, characterized by intermittent propagation and thermally aided depinning from pinning sites induced by disorder. Additionally, as the nanostrip thickness increases, domain wall mobility decreases, accompanied by increased wall deformation and roughness. These findings show that current-driven domain wall dynamics are collectively governed by thermal fluctuations, structural disorder, and geometrical confinement, offering guidance for the design of thermally robust CoFeB-based spintronic devices.