Towards terahertz spin Hall nano-oscillator with synthesized anti-ferromagnets

Abstract

Abstract We calculated the spectrum of synthetic antiferromagnets (SAF) based spin Hall nano-oscillators (SHNO) with micromagnetic simulations. It was found that, even without an applied field, the frequency of generated spin waves can reach up to THz range once both Ruderman–Kittel–Kasuya–Yosida (RKKY) interactions and DC current density being reasonably high enough. We have further investigated the origin of THz spectrum. Although the magnetization dynamics of SAF is driven by spin transfer torque (STT) via spin Hall effect (SHE) in heavy metal (HM). The RKKY interactions can obviously boost it by accelerating the wiggle of magnetization in SAF. We also found that the bottom ferromagnetic layer thickness in SAF should be thin and the total thickness of SAF should not exceed the spin diffusion length in order to maximize STT effect and achieve THz spectrum. Finally, we clearly demonstrated the nonreciprocity of generated THz spin wave by introducing interfacial Dzyaloshinskii-Moriya interaction (DMI) at normal metal/ferromagnet (NM/FM) interface. Our results will technically extend the application of spintronic devices into THz field.