The ability to manipulate magnetic properties through ionic motion in ferromagnet/oxide opens exciting opportunities for the development of advanced spintronic functionalities, including reconfigurable multistate memories and cumulative gate effects. Inspired by memristor technologies, magneto-ionics has emerged as one of the most advanced approaches for controlling magnetic properties through ionic motion. Integrating ionic and spintronic technologies provides new degrees of freedom for designing neuromorphic hardware that combines novel magnetic functionalities with the well-established analogue behavior of ionic devices.

In this talk, I will present different strategies for implementing synaptic functionalities by exploiting the magneto-ionic control of magnetic anisotropy in CoFeB-based ionic/spintronic devices. I will demonstrate that magneto-ionic nanodevices not only operate as synaptic elements, by encoding multiple non-volatile electrically readable states through voltage-control of magnetic anisotropy, but also provide a versatile platform for realising more advanced bioinspired functionalities. In particular, we show that synaptic depression/potentiation in magneto-ionic synaptic elements can be tuned by an applied magnetic field, enabling dynamic control of the linearity of synaptic weight updates. This behavior is reminiscent of neuromodulation in biological systems. Neural network simulations further reveal that the magnetically induced improvement in weight-update linearity enhances learning accuracy over a broad range of learning rates.

Beyond non-volatile magneto-ionic effects, other material systems enable the exploration of volatile ionic effects in spintronic devices. In this case, we exploit the gate-induced transient reduction of magnetic anisotropy to engineer a time-dependent switching probability in a spintronic memory element driven by spin-orbit-torque-induced domain wall motion. While the magnetic state remains binary and non-volatile, the gate-induced magneto-ionic state is volatile. The device therefore separates two distinct functions: long-term information storage in the magnetic state and short-term update eligibility in the volatile magneto-ionic state, a feature that could be particularly attractive for reward-based learning schemes.

These findings highlight the versatility and promise of magneto-ionic devices as multifunctional synaptic elements for next-generation neuromorphic hardware.