Effects of Dzyaloshinskii-Moriya interactions and dipole-dipole interactions on spin waves in finite-length ferromagnetic chains

TL;DR

This paper develops a spin-wave theory for finite ferromagnetic chains incorporating Dzyaloshinskii-Moriya and dipole-dipole interactions, revealing how these interactions influence spin wave spectra and localization effects.

Contribution

It introduces a comprehensive model including antisymmetric Dzyaloshinskii-Moriya and dipole interactions for finite chains, analyzing their effects on spin wave behavior.

Findings

Different physical regimes depending on Dzyaloshinskii-Moriya vector orientation

Interfacial effects cause tilting of equilibrium orientations

Localized spin waves can occur at chain ends

Abstract

A spin-wave theory that includes the antisymmetric Dzyaloshinskii-Moriya exchange interactions and long-range dipole-dipole interactions is presented for finite-length ferromagnetic spin chains. It is found that three different physical situations arise, depending on the direction chosen in this geometry for the axial vector of the Dzyaloshinskii-Moriya interactions. In some cases this leads to a tilting of the equilibrium orientations near the ends of the chain due to interfacial effects and with consequential effects on the spectrum of discrete dipole-exchange spin waves. When variations are introduced for the dominant bilinear exchange interactions at the ends of the spin chain, it is shown that localized spin waves with spatial decay characteristics may occur.