# Collective dynamics in atomistic models with coupled translational and spin degrees of freedom

## TL;DR

This study uses combined molecular and spin dynamics simulations to explore how phonons and magnons interact in ferromagnetic iron, revealing shifts in frequencies, reduced lifetimes, and new magnetic excitations due to their coupling.

## Contribution

It introduces a coupled atomistic model for simultaneous simulation of translational and spin dynamics, providing new insights into their mutual influence in ferromagnetic materials.

## Key findings

- Phonons and magnons influence each other's frequency spectra.
- Coupling reduces the lifetimes of vibrational and magnetic modes.
- Additional longitudinal magnetic excitations are observed with phonon frequencies.

## Abstract

Using an atomistic model that simultaneously treats the dynamics of translational and spin degrees of freedom, we perform combined molecular and spin dynamics simulations to investigate the mutual influence of the phonons and magnons on their respective frequency spectra and lifetimes in ferromagnetic bcc iron. By calculating the Fourier transforms of the space- and time-displaced correlation functions, the characteristic frequencies and the linewidths of the vibrational and magnetic excitation modes were determined. Comparison of the results with that of the stand-alone molecular dynamics and spin dynamics simulations reveals that the dynamic interplay between the phonons and magnons leads to a shift in the respective frequency spectra and a decrease in the lifetimes. Moreover, in the presence of lattice vibrations, additional longitudinal magnetic excitations were observed with the same frequencies as the longitudinal phonons.