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Voltage control of magnetism via electric-field-driven ion migration (magneto-ionics) has generated intense interest due to its potential to greatly reduce heat dissipation in a wide range of information technology devices, such as magnetic memories, spintronic systems or artificial neural networks. Oxygen ion migration in transition-metal-oxide thin films (Fig. 1) can lead to, among other effects, either the generation or full suppression of controlled amounts of ferromagnetism (‘ON-OFF’ magnetic transitions) in a non-volatile and fully reversible manner (Fig. 2). However, oxygen magneto-ionic rates at room temperature have generally been considered too slow for industrial applications.
Here, we demonstrate that sub-second ON-OFF transitions in electrolyte-gated paramagnetic cobalt oxide films can be achieved by drastically reducing the film thickness from > 200 nm down to 5 nm. Remarkably, cumulative effects at 100 Hz indicate that activation times are on the order of 10-2 s in the thinner films, among the fastest reported so far in magneto-ionic systems relying on O2- ion migration.
Neuromorphic-like dynamic effects occur at these frequencies, including potentiation (cumulative increase of magnetization), depression (i.e., partial recovery of magnetization with time), threshold activation, and spike time-dependent magnetic plasticity (learning and forgetting capabilities), mimicking many of the main biological synapse functions. The systems under investigation show features (including the operational dynamic range) that could be useful for the design of artificial neural networks whose magnetic properties would be governed with applied voltage (i.e., magneto-ionic neuromorphic-like computing applications).
Dynamic Electric-Field-Induced Magnetic Effects in Cobalt Oxide Thin Films: towards Magneto-Ionic Synapses.
