Nano-scale spin-torque switches as “neurons” can make energy-efficient neuromorphic computers. Using simple device-circuit analysis researchers showed that spin neurons provide essential terminal characteristics like low input impedance and transfer characteristics like high-transimpedance-gain and fast state-switching. These properties combined with ultra-low voltage operation of compact spin-neurons can facilitate the design of ultra low-energy and high-performance bio-inspired computing systems.
Recent years have witnessed growing interest in the field of brain-inspired computing based on neural-network architectures. In order to translate the related algorithmic models into powerful, yet energy-efficient cognitive-computing hardware, computing-devices beyond CMOS may need to be explored. The suitability of such devices to this field of computing would strongly depend upon how closely their physical characteristics match with the essential computing primitives employed in such models. In this work we discuss the rationale of applying emerging spin-torque devices for bio-inspired computing. Recent spin-torque experiments have shown the path to low-current, low-voltage and high-speed magnetization switching in nano-scale magnetic devices. Such magneto-metallic, current-mode spin-torque switches can mimic the analog summing and thresholding operation of an artificial neuron with high energy-efficiency. Comparison with CMOS-based analog circuit-model of neuron shows that spin neurons can achieve more than two orders of magnitude lower energy and beyond three orders of magnitude reduction in energy-delay product. The application of spin neurons can therefore be an attractive option for neuromorphic computers of future.