Short-Term Plasticity and Long-Term Potentiation in Magnetic Tunnel Junctions: Towards Volatile Synapses

TL;DR

This paper demonstrates that Magnetic Tunnel Junctions can emulate biological synaptic plasticity, with their magnetization dynamics showing short-term and long-term behaviors influenced by stimulus frequency, enabling efficient neuromorphic systems.

Contribution

It introduces a novel approach to mimic synaptic plasticity using MTJs, highlighting the importance of stimulus frequency in achieving long-term potentiation.

Findings

MTJs exhibit dynamics similar to biological synapses.

Frequency of input stimuli determines long-term potentiation.

MTJ-based synapses enable compact, fast, low-power neural systems.

Abstract

Synaptic memory is considered to be the main element responsible for learning and cognition in humans. Although traditionally non-volatile long-term plasticity changes have been implemented in nanoelectronic synapses for neuromorphic applications, recent studies in neuroscience have revealed that biological synapses undergo meta-stable volatile strengthening followed by a long-term strengthening provided that the frequency of the input stimulus is sufficiently high. Such "memory strengthening" and "memory decay" functionalities can potentially lead to adaptive neuromorphic architectures. In this paper, we demonstrate the close resemblance of the magnetization dynamics of a Magnetic Tunnel Junction (MTJ) to short-term plasticity and long-term potentiation observed in biological synapses. We illustrate that, in addition to the magnitude and duration of the input stimulus, frequency of the stimulus plays a critical role in determining long-term potentiation of the MTJ. Such MTJ synaptic memory arrays can be utilized to create compact, ultra-fast and low power intelligent neural systems.