Nanoscale physics

Antiferromagnetic spin-Hall oscillators for signal processing
O. Sulymenko1, O. Prokopenko1
1Faculty of Radio Physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska Street, Kiev-01601, Ukraine
E-mail: olgasulymenko@gmail.com

It has been shown [1, 2] that in spin-Hall oscillator (SHO) that uses canted antiferromagnet (AFM) / Pt layered structure driven by a sufficient bias direct current jdc larger than the threshold current jth the generation of sinusoidal THz-frequency signals is possible. If one applies to such an AFM SHO a combination of a sub-threshold dc current (jdc < jth) and a relatively low-frequency (fac ~ 10–30 GHz) ac current jac the AFM-based SHO will generate a series of short pulses with the duration ~10 ps and the repetition rate ~1/fac. We propose to use the mutual electrical coupling between such SHOs for the development of neuron logical circuits.
We show theoretically that arrays of such SHOs coupled by the signals propagating in a shared Pt bus can be used as elements for logical circuits and as active elements in neuromorphic computation systems. In such devices, every SHO produces a voltage in the shared Pt bus and these signals create a mutual coupling between the SHOs. The amplitude of the ac voltage created in the output Pt line could act as a control signal that determines what kind of a logical operation is performed by the SHOs array. For example, SHO can perform operations “OR” or “AND”, depending on the ac bias at the input gate. Thus, one can choose the mode of the array’s operation by tuning the ac voltage at the input gate. Our analysis shows that large arrays of AFM-based SHOs demonstrate a complex collective behavior, which can be controlled by the ac amplitude at the control (input) gates with high efficiency.
This work was supported in part by the grants 18BF052-01M and 19BF052-01 from Taras Shevchenko National University of Kyiv and grant 1F from the National Academy of Sciences of Ukraine.

1.	R. Cheng, et al., Phys. Rev. Lett. 116, 207603 (2016). 
2.	R. Khymyn et al., Sci. Rep. 7, 43705 (2017).