Longitudinal magnetic excitations in classical spin systems

TL;DR

This paper predicts a splitting of longitudinal spin wave peaks in antiferromagnets with anisotropy, suggesting experimental verification via neutron scattering, and clarifies the nature of longitudinal excitations in classical Heisenberg models.

Contribution

It introduces a prediction of peak splitting in longitudinal spin waves and clarifies the excitations as multiple spin-waves in classical models.

Findings

Predicted peak splitting in antiferromagnets with anisotropy.

Identified longitudinal excitations as multiple spin-waves.

Suggested experimental verification through neutron scattering.

Abstract

Using spin dynamics simulations we predict the splitting of the longitudinal spin wave peak in all antiferromagnets with single site anisotropy into two peaks separated by twice the energy gap at the Brillouin zone center. This phenomenon has yet to be observed experimentally but can be easily investigated through neutron scattering experiments on MnF$_2$ and FeF$_2$. We have also determined that for all classical Heisenberg models the longitudinal propagative excitations are entirely multiple spin-wave in nature.