Dynamics of Ordering of Isotropic Magnets

TL;DR

This paper investigates the dynamic ordering processes in isotropic Heisenberg magnets, revealing how reversible precession affects conserved versus nonconserved dynamics and identifying a new fixed point for conserved cases.

Contribution

It introduces a detailed analysis of the effects of torque in the dynamics of isotropic magnets, highlighting a new fixed point in conserved systems.

Findings

Torque is irrelevant in nonconserved dynamics at both T=0 and T=T_c.

Torque is relevant in conserved dynamics, leading to a new fixed point.

Different behaviors are observed for quenches to T=0 and T=T_c.

Abstract

We study the dynamics of ordering of the nonconserved and conserved Heisenberg magnet. The dynamics consists of two parts - an irreversible dissipation into a heat bath and a reversible precession induced by a torque due to the local molecular field. For quenches both to T=0 and T=T_c, we show that the torque is irrelevant when the dynamics is nonconserved but relevant when the dynamics is conserved and is governed by a new nontrivial fixed point.