Relativistic and thermal effects on the magnon spectrum of a ferromagnetic monolayer

TL;DR

This paper investigates how relativistic effects, like Dzyaloshinsky-Moriya interactions, and thermal factors influence the magnon spectrum in a ferromagnetic monolayer, combining theoretical models with simulations.

Contribution

It introduces two methods to analyze finite-temperature magnon spectra and compares theoretical predictions with atomistic spin dynamics simulations.

Findings

Dzyaloshinsky-Moriya interactions cause spectrum asymmetry.

Anisotropy terms induce a gap in the magnon spectrum.

Lattice defects soften magnon energies.

Abstract

A spin model including magnetic anisotropy terms and Dzyaloshinsky-Moriya interactions is studied for the case of a ferromagnetic monolayer with C2v symmetry like Fe/W(110). Using the quasiclassical stochastic Landau-Lifshitz-Gilbert equations, the magnon spectrum of the system is derived using linear response theory. The Dzyaloshinsky-Moriya interaction leads to asymmetry in the spectrum, while the anisotropy terms induce a gap. It is shown that in the presence of lattice defects, both the Dzyaloshinsky-Moriya interactions and the two-site anisotropy lead to a softening of the magnon energies. Two methods are developed to investigate the magnon spectrum at finite temperatures. The theoretical results are compared to atomistic spin dynamics simulations and a good agreement is found between them.