First-principles study of spin-wave in non-collinear chiral magnet

Chiral magnets with novel non-collinear spin structures have gathered significant attention due to their potential applications in spintronics. In these systems, spin-wave (magnon) excitations are proposed as an energy-efficient tool of controlling non-trivial spin textures, such as skyrmions and spin spirals, for information processing. Traditional spin-wave descriptions rely on the Heisenberg model, which assumes localized spins and is suitable primarily for rare-earth and insulating systems. However, for materials dominated by itinerant 3d electrons, such as Mn-based compounds, this local spin approximation is insufficient, and a full electronic dispersion must be considered.

To overcome these limitations, in this talk, we present an ab initio framework for simulating spin-waves in chiral magnets. Using the density functional perturbation theory [1] with electron wave functions obtained from DFT calculations [2], we compute the spin susceptibility of non-collinear spin structures, which can be further interpreted as the magnon spectrum. This method is applied to MnSi, where we systematically compare the spin-wave spectra among different magnetic phases, including ferromagnetic, helical, conical, and skyrmion states. The calculated magnon dispersions are also compared with neutron scattering experiments.

Overall, our work bridges the gap between theoretical models and experimental data, offering a deeper understanding of spin-wave dynamics in chiral magnets with non-collinear spin textures.

[1] S. Ersoy, et al. "Wannier-function approach to spin excitations in solids." PRB 81 5 054434 (2010).

[2] H.-Y. Chen, et al. “Topological Hall effect of Skyrmions from First Principles” arXiv preprint:2407.05731