Magnon Torques Mediated by Orbital Hybridization at the Light Metal-Antiferromagnetic Insulator Interface

Magnon torques, which can operate without involving moving electrons, could circumvent the Joule heating issue. In conventional magnon torque systems, the spin source layer with strong spin-orbit coupling is utilized to inject magnons, and the efficiency is limited by the inherent spin Hall conductivity of the spin source layer. In this Letter, we observe magnon torques in the Cr/NiO/ferromagnet heterostructure with the effective spin Hall conductivity of 2.45×10^{5}ℏ/2eΩ^{-1}  m^{-1}, twice that of the best conventional magnon torque system. We demonstrate the magnon-torque-driven switching of a perpendicularly magnetized CoFeB layer at room temperature, with a switching power consumption density of 0.136  mW μm^{-2}. We find that the magnon torque originates from the orbital hybridization and interfacial inversion symmetry breaking at the Cr/NiO interface. Our findings not only significantly enhance the efficiency of magnon torques but also provide key insights into the fundamental mechanisms of magnon injections.