O. R. Sulymenko, O. V. Prokopenko, V. S. Tiberkevich, A. N. Slavin, B. A. Ivanov, and R. S. Khymyn
We propose a design of a terahertz-frequency signal generator based on a layered structure consisting of a current-driven platinum (Pt) layer and a layer of an antiferromagnet (AFM) with easy-plane anisotropy, where the magnetization vectors of the AFM sublattices are canted inside the easy plane by the Dzyaloshinskii-Moriya interaction (DMI). The dc electric current flowing in the Pt layer creates due to the spin Hall effect, a perpendicular spin current that, being injected in the AFM layer, tilts the DMI-canted AFM sublattices out of the easy plane, thus exposing them to the action of a strong internal exchange magnetic field of the AFM. The sublattice magnetizations, along with the small net magnetization vector mDMI of the canted AFM, start to rotate about the hard anisotropy axis of the AFM with the terahertz frequency proportional to the injected spin current and the AFM exchange field. The rotation of the small net magnetization mDMI results in the terahertz-frequency dipolar radiation that can be directly received by an adjacent (e.g., dielectric) resonator. We demonstrate theoretically that the radiation frequencies in the range f=0.05–2 THz are possible at the experimentally reachable magnitudes of the driving current density, and we evaluate the power of the signal radiated into different types of resonators. This power increases with the increase of frequency f, and it can exceed 1 μW at f∼0.5 THz for a typical dielectric resonator of the electric permittivity ϵ∼10 and a quality factor Q∼750.
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