A Multilevel Magnetic Synapse Based on Voltage‐Tuneable Magnetism by Nitrogen Ion Migration

Abstract

Advanced synaptic devices with simultaneous memory and processor capabilities are envisaged as core elements of neuromorphic computing (NC) for low‐power artificial intelligence. So far, most synaptic devices are based on resistive memories, where the device resistance is tuned with applied voltage or current. However, the use of electric current in such resistive devices causes significant power dissipation due to Joule heating. Higher energy efficiency has been reported in materials exhibiting voltage control of magnetism (VCM). In particular, voltage‐driven ion motion to modulate magnetism (magneto‐ionics) is an emerging VCM mechanism that can offer new prospects for low‐power implementation of NC. In the present work, voltage‐driven nitrogen ion motion is exploited in transition metal nitride (CoFeN) thin films (i.e., nitrogen magneto‐ionics) to emulate biological synapses. In the proposed device, distinct multilevel non‐volatile magnetic states for analog computing and multi‐state storage are realized. Moreover, essential synaptic functionalities of the human brain are successfully simulated. The device exhibits an excellent synapse with a remarkable retention time (≈6 months), high switching ratio and large endurance (≈103), for hardware implementation of NC. This research provides new insight into exploiting magneto‐ionic‐based synaptic devices for spin‐based neuromorphic systems.

Synaptic Characteristics of Fully Depleted Silicon‐on‐Insulator Metal‐Oxide‐Semiconductor Field‐Effect Transistors and Synapse‐Neuron Arrayed Neuromorphic Hardware System

“…The result of much research on the neuromorphic mimicking of memory and learning behaviors has rapidly developed through various nanoscale devices. [ 1 ] For example, devices emulating the function of biological synapses have been investigated through work in resistance random access memory (RRAM), [ 2 ] conductive bridge random access memory (CBRAM), [ 3 ] phase‐change memory (PCM), [ 4 ] spin‐torque transfer magnetic random access memory (STT‐MRAM), [ 5 ] flash memory, [ 6 ] and field‐effect transistors (FETs) to overcome limitations of conventional computing systems. [ 7 ] As the most crucial property for these devices, synapse plasticity is the ability to strengthen or weaken over time in response to the frequency and strength of stimulations.…”

Ionic control of magnetism in all-solid-state CoOx/yttria-stabilized zirconia heterostructures

“…These features suggest that this approach may find applications in solid-state magneto-ionic synaptic applications. [18][19][20] YSZ dielectric oxide films (60 nm in thickness) were grown by pulsed laser deposition (PLD) on n-doped (with resistivity in the range 0.01-0.015 X cm) Si(001) wafers. The Si(001) crystal acts as substrate and also as a bottom electrode during electrolyte gating.…”

Indirect magneto-ionic effect in FeSi2/Si nanocomposite induced by electrochemical lithiation and delithiation

“…[10][11][12][13][14]), nitrogen (see e.g. [15][16][17]) or hydrogen (see e.g. [18,19]) ion migration.…”