Selective damping modulation in a synthetic antiferromagnet induced by spin-orbit torque

Magnetization dynamics in a synthetic antiferromagnet with an adjacent Pt layer are investigated. Using dc bias, magnetic damping can be effectively controlled by the spin-orbit torque from the Pt layer. In the spin-flop state, the acoustic mode is modulated by the dc bias, but the optical mode is not sufficiently modulated. In the saturation state, the optical mode is effectively modulated. By appropriately selecting acoustic and optical modes and magnetization states such as the spin-flop and saturation states, modulation of the mutual phases of the ac spin currents driven by the ac damping torques can be realized.