Resonate and Fire Neuron with Fixed Magnetic Skyrmions

TL;DR

This paper proposes a theoretical implementation of resonate-and-fire neurons using fixed magnetic skyrmions in magnetic tunnel junctions, demonstrating their potential for neuromorphic computing through resonant magnetization dynamics.

Contribution

It introduces a novel nanomagnetic neuron model utilizing skyrmion breathing modes controlled by voltage, with detailed micromagnetic simulations showing its resonant firing behavior.

Findings

Resonant firing occurs when input frequency matches skyrmion breathing mode.

The skyrmion-based neuron can produce spike outputs driven by electrical resistance changes.

Potential application in nanomagnetic associative memory arrays.

Abstract

In the brain, the membrane potential of many neurons oscillates in a subthreshold damped fashion and fire when excited by an input frequency that nearly equals their eigen frequency. In this work, we investigate theoretically the artificial implementation of such "resonate-and-fire" neurons by utilizing the magnetization dynamics of a fixed magnetic skyrmion in the free layer of a magnetic tunnel junction (MTJ). To realize firing of this nanomagnetic implementation of an artificial neuron, we propose to employ voltage control of magnetic anisotropy or voltage generated strain as an input (spike or sinusoidal) signal, which modulates the perpendicular magnetic anisotropy (PMA). This results in continual expansion and shrinking (i.e. breathing) of a skyrmion core that mimics the subthreshold oscillation. Any subsequent input pulse having an interval close to the breathing period or a sinusoidal input close to the eigen frequency drives the magnetization dynamics of the fixed skyrmion in a resonant manner. The time varying electrical resistance of the MTJ layer due to this resonant oscillation of the skyrmion core is used to drive a Complementary Metal Oxide Semiconductor (CMOS) buffer circuit, which produces spike outputs. By rigorous micromagnetic simulation, we investigate the interspike timing dependence and response to different excitatory and inhibitory incoming input pulses. Finally, we show that such resonate and fire neurons have potential application in coupled nanomagnetic oscillator based associative memory arrays.