Spin-orbit torque tunes the damping of ferrimagnetic insular films

Magnonics offers a promising route for low-loss information transport and processing. Developing strategies to compensate for magnon damping is critical for applications such as magnon transistors and amplifiers. Here, we investigate the spin–orbit torque effect in ferrimagnetic insulating films of Li0.5Al1.0Fe1.5O4 (LAFO). A Pt bar is used to inject spins into the LAFO layer via the spin Hall effect. Subsequently, magnons are probed by Brillouin light scattering (BLS). We find that the magnon damping in LAFO can be completely compensated by anti-damping torque, as evidenced by a sudden enhancement of the BLS intensity with increasing current. Moreover, in addition to the ferromagnetic resonance mode, an auto-oscillation mode emerges when the current exceeds a critical value, whose frequency decreases with an increase in current.