Amplifying spin waves along N\'eel domain wall by spin-orbit torque

Traveling spin waves in magnonic waveguides undergo severe attenuation, which tends to result in a finite propagation length of spin waves, even in magnetic materials with the accessible lowest damping constant, heavily restricting the development of magnonic devices. Compared with the spin waves in traditional waveguides, propagating spin waves along strip domain wall are expected to exhibit enhanced transmission. Here, we demonstrate, theoretically and through micromagnetic simulations, that spin-orbit torque associated with a ferromagnet/heavy metal bilayer can efficiently control the attenuation of spin waves along a N\'eel-type strip domain wall, despite the complexity in the ground-state magnetization configuration. The direction of the electric current applied to the heavy-metal layer determines whether these spin waves are amplified or further attenuated otherwise. Remarkably, our simulations reveal that the effective current densities required to efficiently tune the decay of such spin waves are just ~10^10 Am-2, roughly an order smaller than those required in conventional spin waveguides. Our results will enrich the toolset for magnonic technologies.