Micromagnetic understanding of current-driven domain wall motion in patterned nanowires

TLDR

Models supporting the modified spin‑transfer torque term are discussed. The study proposes a modification of the spin‑transfer torque term in the Landau‑Lifshitz‑Gilbert equation to explain recent experiments on current‑driven domain‑wall motion in nanowires. The authors modify the torque term and model coercivity by incorporating wire roughness. The modified model reproduces measured domain‑wall velocities and propagation fields, predicts finite propagation fields and threshold currents, and concludes that threshold currents are extrinsic.

Abstract

In order to explain recent experiments reporting a motion of magnetic domain walls (DW) in nanowires carrying a current, we propose a modification of the spin transfer torque term in the Landau-Lifchitz-Gilbert equation. We show that it explains, with reasonable parameters, the measured DW velocities as well as the variation of DW propagation field under current. We also introduce coercivity by considering rough wires. This leads to a finite DW propagation field and finite threshold current for DW propagation, hence we conclude that threshold currents are extrinsic. Some possible models that support this new term are discussed.