Multiscale modeling of ultrafast element-specific magnetization dynamics of ferromagnetic alloys

TL;DR

This paper presents a hierarchical multiscale modeling approach combining first-principles calculations and spin dynamics models to study ultrafast, element-specific magnetization dynamics in ferromagnetic alloys, revealing sublattice-specific demagnetization behaviors.

Contribution

The paper introduces a novel multiscale framework linking first-principles calculations with atomistic and continuum spin models for ultrafast magnetization dynamics in alloys.

Findings

Ni demagnetizes faster than Fe after heat pulse

The method accurately predicts temperature-dependent demagnetization times

Application to FeNi and Cu-doped FeNi alloys demonstrates versatility

Abstract

A hierarchical multiscale approach to model the magnetization dynamics of ferromagnetic ran- dom alloys is presented. First-principles calculations of the Heisenberg exchange integrals are linked to atomistic spin models based upon the stochastic Landau-Lifshitz-Gilbert (LLG) equation to calculate temperature-dependent parameters (e.g., effective exchange interactions, damping param- eters). These parameters are subsequently used in the Landau-Lifshitz-Bloch (LLB) model for multi-sublattice magnets to calculate numerically and analytically the ultrafast demagnetization times. The developed multiscale method is applied here to FeNi (permalloy) as well as to copper- doped FeNi alloys. We find that after an ultrafast heat pulse the Ni sublattice demagnetizes faster than the Fe sublattice for the here-studied FeNi-based alloys.