Dzyaloshinskii-Moriya Interaction and Dipole-Exchange Curvature Effects on the Spin-Wave Spectra of Magnetic Nanotubes

Abstract: This work explores spin-wave dynamics in magnetic nanotubes, focusing on the influence of the Dzyaloshinskii-Moriya interaction and curvature. The study uses analytical methods to examine how these factors influence the emergence of nonreciprocity and azimuthal standing waves in nanotubes with longitudinal magnetization along the axis or with a vortex-like magnetization. The interplay between exchange, Dzyaloshinskii-Moriya, and dipolar couplings in determining the chirality of spin waves is discussed. When the magnetization is saturated along an axis, the spin waves propagating along it are symmetric under the inversion of the wave vector. However, magnetochirality, mainly driven by exchange and Dzyaloshinskii-Moriya couplings, is observed in the azimuthal standing modes. In the vortex state, frequency nonreciprocity occurs for waves propagating along the tube, while the azimuthal modes remain reciprocal. For positive Dzyaloshinskii-Moriya interaction, and depending on the helicity of the vortex, the asymmetry induced by the dipolar interaction is reinforced, whereas a negative coupling opposes this asymmetry. The influence of radial anisotropy is also examined. It is found that radial anisotropy reduces the frequency of the modes and shifts the dispersion minimum to a finite wave vector in the vortex state. The properties of modes near zero frequency offer insight into the emergence of chiral magnetic textures.