Antiferromagnetic Spin Wave Amplification by Scattering in the Presence of Non-Uniform Dzyaloshinskii–Moriya Interaction

In this study, we suggest a method to amplify spin waves (SWs) in antiferromagnets (AFMs). By introducing a non-uniform Dzyaloshinskii-Moriya (DM) interaction, the potential barrier forms a resonant cavity. SWs with an opposite chirality undergo scattering and are resonantly amplified at a phase-matching condition. The calculation is performed in the insulating AFMs where the electric-field-induced DM interaction and pseudo-dipole anisotropy broaden the parabolic-like SW band for multiple resonant modes. Using a transfer matrix method, we also show numerically that scattering between SWs contributes significantly to the SW amplification. Since the electric field selectively amplifies the SWs with resonant frequencies, the proposed device works as an SW transistor and rectifier. This finding will contribute to insulating AFM-based magnon devices where Joule heating is, in principle, avoided.