Influence of Local Icosahedral Short-Range Order on the Magnetization Dynamics of Amorphous Cobalt-Iron Nanodisks

TL;DR

This study uses multiscale simulations to link local icosahedral order in amorphous Co-Fe nanodisks to their magnetic dynamics, revealing how structural heterogeneity influences magnetic properties and damping.

Contribution

It introduces a combined spin-lattice dynamics approach to connect local topological disorder with magnetic behavior in amorphous Co-Fe nanodisks, highlighting the role of icosahedral order.

Findings

Cobalt atoms form solid-like icosahedral structures stabilizing magnetization.

Iron-rich regions exhibit disordered environments leading to exchange fluctuations.

Structural heterogeneity influences magnetic damping and relaxation.

Abstract

The microscopic origin of soft magnetic properties in amorphous alloys is fundamentally linked to the interplay between local topological disorder and magnetic exchange interactions. In this work, we employ a multiscale Spin-Lattice Dynamics (SLD) approach to investigate the magnetostructural correlations in amorphous Co$_{x}$Fe$_{1-x}$ nanodisks ($x=35, 50, 65$). By integrating classical molecular dynamics with a generalized magnetic Hamiltonian, we capture the dynamic feedback loop between lattice vibrations and spin precession. Topological analysis via Voronoi tessellation reveals a persistent species-dependent structural heterogeneity: Cobalt atoms preferentially adopt "solid-like" icosahedral packing, forming a rigid structural backbone, whereas Iron atoms exhibit a higher propensity for "liquid-like" disordered environments. We demonstrate that this topological disparity dictates the macroscopic magnetic response. The Cobalt-driven structural stiffness preserves a robust exchange network that maximizes saturation magnetization, while the local disorder inherent to Iron-rich regions introduces exchange fluctuations that act as an intrinsic damping mechanism, delaying magnetic relaxation. These findings provide an atomistic explanation for the stability of ferromagnetic order in Co-Fe metallic glasses and offer a pathway for tuning damping parameters in amorphous spintronic devices through stoichiometric control.