Micromagnetic simulations of the dynamics in an antiferromagnetic spin-Hall oscillator

We have developed a micromagnetic code which performs numerical simulations of an antiferromagnetic (AFM) layer by solving the Landau-Lifshitz equations of motion for the magnetizations of the two AFM sublattices. Here, we propose an AFM spin-Hall oscillator, consisting of an AFM layer coupled to a heavy metallic layer. The AFM layer has in-plane dimensions 40x40 nm2, and it is modeled with in-plane anisotropy. The heavy metal is designed with 4 terminals that can be used to apply a charge current, and/or to read the device resistance. The direction of the spin-Hall polarization depends on the direction of the current, and it can be modified by applying the current differently at the terminals. Simulations show that, whatever the direction of the spin-Hall polarization, the magnetizations of the sublattices precess around that direction, with uniform magnetic configurations. Moreover, excitation shows a hysteretic behavior, since the current to switch off the dynamics is lower than the ignition current. Frequency of dynamics is in the range of THz, and increases with the applied current. Such properties, highlighted within a systematic study performed by varying the exchange constant, damping, and thickness of the AFM, agree with theoretical predictions. Micromagnetic simulations have also predicted that dynamics in presence of Dzyaloshinskii–Moriya interaction are characterized by a translation of non-uniform domain walls along the AFM layer