Probing magneto-elastic phenomena through an effective spin-bath coupling model

TL;DR

This paper develops a phenomenological model to study magneto-elastic phenomena by coupling magnetic moments with an unresolved spin bath, analyzing dissipation and damping effects through stochastic differential equations.

Contribution

It introduces a novel effective spin-bath coupling model that captures magneto-elastic interactions and dissipation in magnetic systems, with numerical solutions and hierarchy analysis of moments.

Findings

Identification of dissipation effects from spin bath interactions

Numerical solutions of stochastic differential equations

Hierarchy of moment equations and their closure

Abstract

A phenomenological model is constructed, that captures the effects of coupling magnetic and elastic degrees of freedom, in the presence of external, stochastic perturbations, in terms of the interaction of magnetic moments with a bath, whose individual degrees of freedom cannot be resolved and only their mesoscopic properties are relevant. In the present work, the consequences of identifying the effects of dissipation as resulting from interactions with a bath of spins are explored, in addition to elastic, degrees of freedom. The corresponding stochastic differential equations are solved numerically and the moments of the magnetization are computed. The stochastic equations implicitly define a measure on the space of spin configurations, whose moments at equal times satisfy a hierarchy of deterministic, ordinary differential equations. Closure assumptions are used to truncate the hierarchy and the same moments are computed. We focus on the advantages and problems that each approach presents, for the approach to equilibrium and, in particular, the emergence of longitudinal damping.