Terahertz-Frequency Signals Generated in a Dual-Antiferromagnetic-Layer Spin Hall Oscillator

Antiferromagnetic (AFM) spin Hall oscillators (SHOs) have been shown to enable the use of ultrafast terahertz-frequency dynamics in antiferromagnets. These spintronic structures exhibit tunability of their DC current-driven operational frequencies. However, this advantageous feature could become a critical bottleneck because the range of SHO working frequencies is limited due by the limit of the applied driving DC current. In this paper, we propose to overcome this difficulty by proposing a novel type of an SHO, the so-called dual-antiferromagnetic-layer (DAL) SHO, which is an analog of a dual-free-layer spin-torque nano-oscillator made of ferromagnets. The numerical solution of the Landau-Lifshitz-Gilbert-Slonczewski equations for the net magnetizations in the AFM layers shows that the proposed structure can operate at the sum of the frequencies of the bottom and top antiferromagnetic layers, providing the frequency of about 1.15 THz at the applied current density of $4 \cdot 10^{8} \mathrm{~A} / \mathrm{cm}^{2}$, which is higher than the typical values for traditional AFM SHO. The power generated by the DAL SHO is 10 nW (for the circular SHO with the radius of 100 nm). We believe that the proposed DAL SHOs could be used for the development and optimization of AFM spintronic devices operating at frequencies above 1 THz, such as signal sources, detectors, modulators, etc.