Engineering nonreciprocal damping and polarization of spin waves in ferromagnetic domain wall via Dzyaloshinskii–Moriya interaction and spin-transfer torque

Manipulation of spin-wave polarization is fundamental for designing novel magnonic devices based on the polarization coding technique. Here, we demonstrate the generation of left-handed polarized spin waves (LPSWs) in a ferromagnetic domain wall and their polarization modulation through the combined effect of the Dzyaloshinskii–Moriya interaction (DMI) and spin-polarized electric current. A phase diagram delineating the stability regions of left- and right-handed polarized spin waves (RPSWs) is constructed as a function of DMI strength and current density. Our results reveal a pronounced DMI-induced nonreciprocal damping effect, predominantly manifested in RPSWs while leaving LPSWs largely unaffected. This phenomenon enables effective filtering of RPSWs in one direction, allowing the realization of pure LPSW propagation as well as elliptically polarized spin waves with tunable eccentricity. Our work provides a viable method for controlling spin-wave polarization and nonreciprocal propagation in ferromagnetic systems.