Ab-initio calculation of the Gilbert damping parameter via linear response formalism

TL;DR

This paper introduces a first-principles linear response approach to calculate the Gilbert damping parameter, enabling accurate predictions for various alloys and accounting for thermal atomic displacements.

Contribution

It presents a novel ab-initio method using KKR and CPA to compute Gilbert damping, including thermal effects, applicable to complex alloy systems.

Findings

Accurate calculation of Gilbert damping in Fe-Co alloys.

Describes rapid damping change with Cu substitution in Ni.

Method applicable to a wide range of alloy compositions.

Abstract

A Kubo-Greenwood-like equation for the Gilbert damping parameter $\alpha$ is presented that is based on the linear response formalism. Its implementation using the fully relativistic Korringa-Kohn-Rostoker (KKR) band structure method in combination with Coherent Potential Approximation (CPA) alloy theory allows it to be applied to a wide range of situations. This is demonstrated with results obtained for the bcc alloy system Fe$_x$Co$_{1-x}$ as well as for a series of alloys of permalloy with 5d transition metals. To account for the thermal displacements of atoms as a scattering mechanism, an alloy-analogy model is introduced. The corresponding calculations for Ni correctly describe the rapid change of $\alpha$ when small amounts of substitutional Cu are introduced.