Gilbert Damping in Conducting Ferromagnets I: Kohn-Sham Theory and Atomic-Scale Inhomogeneity

TL;DR

This paper derives an approximate formula for the Gilbert damping coefficient in conducting ferromagnets using spin-density-functional theory, emphasizing atomic-scale inhomogeneity effects on magnetization dynamics.

Contribution

It introduces a new SDFT-based expression for Gilbert damping that accounts for atomic-scale variations in exchange-correlation effects.

Findings

Derived an approximate Gilbert damping formula within SDFT framework

Linked the damping to spin-dependent exchange-correlation potential variations

Related the result to existing spin-torque correlation-function models

Abstract

We derive an approximate expression for the Gilbert damping coefficient \alpha_G of itinerant electron ferromagnets which is based on their description in terms of spin-density-functional-theory (SDFT) and Kohn-Sham quasiparticle orbitals. We argue for an expression in which the coupling of magnetization fluctuations to particle-hole transitions is weighted by the spin-dependent part of the theory's exchange-correlation potential, a quantity which has large spatial variations on an atomic length scale. Our SDFT result for \alpha_G is closely related to the previously proposed spin-torque correlation-function expression.