Decoupling Magnetic and Electric Field Control in Magneto-Ionic Materials for Energy-Efficient Brain-Inspired Memory Devices.

Magneto-ionic materials, which enable nonvolatile control of magnetism through voltage-driven ion migration, are emerging as promising candidates for neuromorphic computing. Unlike conventional memristors, these systems allow dual actuation by both electric and magnetic fields, providing a broader range of functional capabilities. The reliance on voltage rather than current significantly reduces Joule heating and enhances the energy efficiency. However, the general need for external magnetic fields to modulate the voltage-induced magnetic response remains a key limitation, undermining the full energy-saving potential of these systems. In this work, we present a magneto-ionic strategy in CoFeN that fully decouples the electric and magnetic field requirements. By taking advantage of a planar N3- ion migration and the ferromagnetic exchange interactions between preexisting and newly generated CoFe magnetic regions, we achieve remanent-state magnetization control solely through applied voltage. The system exhibits behaviors reminiscent of neuromorphic-inspired functionalities, such as synaptic potentiation and depression, while also exhibiting a cumulative voltage-driven increase in magnetization in the absence of a magnetic field. Once the magnetic field is switched off, synaptic weight remains influenced by both the sample's magnetic and electric history. By eliminating the need for magnetic fields, our approach contributes to reduce energy consumption, offering a more efficient pathway for brain-inspired magneto-ionic devices.