Spin–Orbit-Torque-Driven Terahertz Oscillations in Pt/KFe ₃ (OH) ₆ (SO ₄ ) ₂ /W Trilayer Structure

We propose a nanoscale terahertz (THz) signal generator based on a Pt/KFe₃(OH)₆(SO₄)₂/W trilayer structure that produces stable THz output under direct-current driving. Spin currents injected from the Pt layer generate spin-orbit torque (SOT), exciting the magnetic moments of the noncollinear antiferromagnet (AFM) KFe₃(OH)₆(SO₄)₂ and inducing steady magnetization oscillations. These oscillations generate THz alternating-current (AC) signals, which are electrically detected via the inverse spin Hall effect (ISHE) in the W layer. The asymmetric heavy-metal/AFM/heavy-metal configuration, featuring opposite spin Hall angles, enables efficient spin-current injection and signal readout. Micromagnetic simulations and theoretical analysis reveal that the THz signal originates from the asymmetric distribution of Dzyaloshinskii-Moriya interaction (DMI) energy. A quantitative relationship between excitation current and signal output is established, and tunable frequency control with reduced threshold current is achieved by optimizing material and structural parameters.