Handedness filter and Doppler shift of spin waves in ferrimagnetic domain walls

Excitation and propagation of spin waves inside magnetic domain walls (DWs) have received attention because of their potentials in spintronic and communication applications. In addition to wave amplitude and frequency, spin waves have a third character: handedness, whose manipulation is certainly of interest. We propose in this paper that the handedness of low-energy spin-wave excitations can be controlled by tuning the net angular momentum 8s in a ferrimagnetic (FiM) DW, attributing to the inequivalent magnetic sublattices. The results indicate that the spin-wave dispersion depends on both 8s and wave handedness. For a positive (negative) 8s, a gapless dispersion is observed for left-handed (right-handed) spin waves, while a frequency gap appears for right-handed (left-handed) spin waves. Thus, a FiM wall could serve as a filter of low-energy spin waves in which only spin waves with a specific handedness can propagate. Furthermore, the energy consumption loss for spin-wave excitation in the wall is much lower than that inside the domain, while the group velocity is much faster too, demonstrating the advantages of DWs serving as spin waveguides. Moreover, the current-induced spin-wave Doppler shift in the FiM wall is also revealed and can be controlled by 8s. In this paper, we unveil the interesting spin-wave dynamics in FiM DWs, benefiting future spin-wave applications.

Automated summary

This paper investigates the excitation and propagation of spin waves inside magnetic domain walls and proposes that the handedness of low-energy spin-wave excitations can be controlled by tuning the net angular momentum in a ferrimagnetic domain wall. The results suggest that ferrimagnetic walls can serve as filters for specific handedness of spin waves, with lower energy consumption and faster group velocities compared to spin waves inside the domain. The paper also reveals the current-induced spin-wave Doppler shift in the ferrimagnetic wall, which can be controlled by the net angular momentum.