Micromagnetic modeling of terahertz oscillations in an antiferromagnetic material driven by the spin Hall effect

The realization of terahertz (THz) sources is a fundamental aspect for a wide range of applications. Over different approaches, compact THz oscillators can be realized, taking advantage of dynamics in antiferromagnetic thin films driven by the spin Hall effect. Here we perform a systematic study of these THz oscillators within a full micromagnetic solver based on the numerical solution of two coupled Landau-Lifshitz-Gilbert-Slonczewski equations, considering ultrathin films. We find two different dynamical modes depending on the strength of the Dzyaloshinskii-Moriya interaction (DMI). At low DMI, a large-amplitude precession is excited, where both the magnetizations of the sublattices are in a uniform state and rotate in the same direction. At large enough DMI, the ground state of the antiferromagnet becomes nonuniform and the antiferromagnetic dynamics is characterized by ultrafast domain-wall motion.