Abstract
The spin Hall nano-oscillator (SHNO) is a promising spintronic device to produce high-frequency and low-linewidth microwave signals. We study a type of SHNO based on the $L{1}_{0}\text{\ensuremath{-}}\mathrm{Fe}\mathrm{Pt}/\mathrm{Ni}\mathrm{Fe}/\mathrm{Pt}$ exchange-spring system with an ultrahigh perpendicular magnetic anisotropy by micromagnetic simulation. The hard-soft magnetic exchange-spring system has a very high interlayer-exchange-interaction field, resulting in a more than 30-GHz emission frequency and 38.6-GHz/T field tunability. Apart from conventional localized and nonlocalized auto-oscillation modes, localized or nonlocalized modes with central antisymmetry also appear in this SHNO. Two oscillation centers possess nonequal amplitudes and opposite phases in these antisymmetrical modes. Different modes are determined by the competition between three factors: the exchange-interaction field, the perpendicular anisotropic field, and spin-orbit torque. The spin dynamics in the SHNO exhibit complex field and current dependence. Our results provide a possible direction for the design of SHNOs, which may be beneficial for the research and development of spintronic nano-oscillators.
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