Adiabatic Domain Wall Motion and Landau-Lifshitz Damping

TL;DR

This paper discusses the physical interpretation of damping mechanisms in magnetic nanowires, arguing that Landau-Lifshitz damping offers a more sensible description of magnetization dynamics than Gilbert damping, supported by theoretical and experimental considerations.

Contribution

It provides a compelling argument favoring Landau-Lifshitz damping over Gilbert damping as the more physically consistent model for magnetic dissipation.

Findings

Landau-Lifshitz damping aligns better with thermodynamic principles.

Adiabatic spin-transfer torque dominates domain wall dynamics.

Damping decreases magnetic free energy.

Abstract

Recent theory and measurements of the velocity of current-driven domain walls in magnetic nanowires have re-opened the unresolved question of whether Landau-Lifshitz damping or Gilbert damping provides the more natural description of dissipative magnetization dynamics. In this paper, we argue that (as in the past) experiment cannot distinguish the two, but that Landau-Lifshitz damping nevertheless provides the most physically sensible interpretation of the equation of motion. From this perspective, (i) adiabatic spin-transfer torque dominates the dynamics with small corrections from non-adiabatic effects; (ii) the damping always decreases the magnetic free energy, and (iii) microscopic calculations of damping become consistent with general statistical and thermodynamic considerations.