Chemical disorder effects on the Gilbert damping of FeCo alloys

TL;DR

This study investigates how local chemical environments in FeCo alloys influence Gilbert damping, revealing that atomic-scale disorder significantly affects magnetic relaxation properties relevant for spintronics.

Contribution

It demonstrates the sensitivity of Gilbert damping to local chemical configurations and provides insights into how atomic-scale disorder impacts magnetic relaxation in FeCo alloys.

Findings

Damping varies significantly with local Co concentration and atomic arrangements.

Short-range disorder can alter the overall magnetic relaxation rate.

Local chemical engineering can potentially tune Gilbert damping for spintronics.

Abstract

The impact of the local chemical environment on the Gilbert damping in the binary alloy Fe$_{100-x}$Co$_{x}$ is investigated, using computations based on density functional theory. By varying the alloy composition x as well as Fe/Co atom positions we reveal that the effective damping of the alloy is highly sensitive to the nearest neighbor environment, especially to the amount of Co and the average distance between Co-Co atoms at nearest neighbor sites. Both lead to a significant local increase (up to an order of magnitude) of the effective Gilbert damping, originating mainly from variations of the density of states at the Fermi energy. In a global perspective (i.e., making a configuration average for a real material), those differences in damping are masked by statistical averages. When low-temperature explicit atomistic dynamics simulations are performed, the impact of short-range disorder on local dynamics is observed to also alter the overall relaxation rate. Our results illustrate the possibility of local chemical engineering of the Gilbert damping, which may stimulate the study of new ways to tune and control materials aiming for spintronics applications.