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

Abstract

A spin-wave theory that includes the antisymmetric Dzyaloshinskii–Moriya exchange interactions and long-range dipole–dipole interactions, in addition to the Heisenberg bilinear exchange and the applied magnetic field, 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.