Domain wall motion of magnetic nanowires under a static field

TL;DR

This paper analyzes how magnetic domain walls move in nanowires under static magnetic fields, emphasizing the role of energy dissipation and damping in controlling the velocity and behavior of the walls.

Contribution

It introduces a theoretical relationship between domain wall velocity, structure, and energy dissipation, clarifying the necessity of damping for field-driven DW motion and explaining velocity dependencies.

Findings

DW velocity is proportional to energy dissipation rate.

Damping is essential for DW propagation along the wire.

Wire width influences DW velocity and oscillation beyond Walker breakdown.

Abstract

The propagation of a head-to-head magnetic domain-wall (DW) or a tail-to-tail DW in a magnetic nanowire under a static field along the wire axis is studied. Relationship between the DW velocity and DW structure is obtained from the energy consideration. The role of the energy dissipation in the field-driven DW motion is clarified. Namely, a field can only drive a domain-wall propagating along the field direction through the mediation of a damping. Without the damping, DW cannot propagate along the wire. Contrary to the common wisdom, DW velocity is, in general, proportional to the energy dissipation rate, and one needs to find a way to enhance the energy dissipation in order to increase the propagation speed. The theory provides also a nature explanation of the wire-width dependence of the DW velocity and velocity oscillation beyond Walker breakdown field.