Unattenuated conical spin wave in spiral magnet: The role of Dzyaloshinskii-Moriya interaction

A direct inter-conversion between conduction electron spin-current and spin wave spin-current has been experimentally realized in Pt/Y3Fe5O12 and Pt/Y3Fe5O12/Pt heterostructures [Y. Kajiwara et al., Nature 464, 262 (2010)]. We investigate the dynamics of this inter-conversion in an in-plane spiral magnet with the nearest-neighboring interaction and Dzyaloshinskii-Moriya interaction, using the modified Landau-Lifshitz-Gilbert equation. The calculations indicate that an unattenuated conical spin wave in the spiral magnet can be excited by a spin-torque representing a conduction-electron spin-current. The substantial role of the Dzyaloshinskii-Moriya interaction in stabilizing such unattentuated spin wave transmission is revealed. In addition, the influences of the spin-torque term and damping coefficient on the stability of the spin wave transmission are discussed.