Modeling coupled spin and lattice dynamics

TL;DR

This paper introduces a comprehensive model for coupled spin and lattice dynamics that captures energy and angular momentum transfer without phenomenological damping, analyzing spectral properties and relaxation processes.

Contribution

It presents a unified, atomistic model for spin-lattice interactions that operates in both microcanonical and canonical ensembles, avoiding phenomenological damping.

Findings

Spectral analysis reveals magnon modes and noise in spin systems.

Effective damping increases with coupling strength and temperature.

The model enhances understanding of magnetic relaxation beyond Gilbert damping.

Abstract

A unified model of molecular and atomistic spin dynamics is presented enabling simulations both in microcanonical and canonical ensembles without the necessity of additional phenomenological spin damping. Transfer of energy and angular momentum between the lattice and the spin systems is achieved by a coupling term based upon the spin-orbit interaction. The characteristic spectra of the spin and phonon systems are analyzed for different coupling strength and temperatures. The spin spectral density shows magnon modes together with the uncorrelated noise induced by the coupling to the lattice. The effective damping parameter is investigated showing an increase with both coupling strength and temperature. The model paves the way to understanding magnetic relaxation processes beyond the phenomenological approach of the Gilbert damping and the dynamics of the energy transfer between lattice and spins.