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Spin Hall nano oscillators have been of great interest due to their simple realization and potential applications. The requirement of the external field is a major obstacle for the on-chip applications of spin Hall nano oscillators. In this work, we propose a field-free spin Hall nano oscillator based upon the exchange bias in ferro/anti-ferromagnetic (FM/AFM) structures. Owing to the spin-orbit coupling and the exchange interactions, the AFM can provide the exchange bias field as well as the spin currents required for driving the FM magnetization into spontaneous oscillations. We have performed macrospin as well as micromagnetic simulations in great detail to study the effects of the applied current, exchange bias, and spin Hall angle on the frequency and power spectral density (PSD) of these oscillations. For further improvement in PSD and linewidth of these oscillations, we employ the technique of injection locking. With this technique, the output power has increased by almost 13 dB, the linewidth has decreased by ~4 times and the quality factor has improved by ~4 times. These results can be beneficial for communication systems or neuromorphic computing kind of applications.
Sravani et al. (Mon,) studied this question.