Electric-field control of magnetism in arrays of nanoporous iron oxide microdisks

Electric-field control of magnetism is a fundamentally different approach towards the implementation of ultralow heat-dissipation memories operated on nanoscale as it does not involve the use of electric currents and thus minimizes Joule heating effect (resistive heating). Here, highly porous iron oxide films with virtually no magnetic response, i.e., OFF state, are grown by sol-gel chemistry. Subsequently, arrays of microdisks (8 µm in diameter) are obtained combining lithography with wet chemical etching processes. Electrolyte-gating is then employed to induce a tunable ferromagnetic response in these disks at room temperature, thus accomplishing an OFF-ON switching of magnetism. The changes in magnetic properties are attributed to magnetoelectrically-driven oxygen ion exchange with liquid anhydrous electrolyte, which is enhanced due to nanoporosity. This causes partial reduction of various iron oxide phases present in pristine samples to metallic Fe. The effect can be considerably reversed by applying voltage of opposite polarity. These results are appealing for diverse technological applications that require the use of patterned structures with easily tunable magnetic properties, such as magnetic micro-electro-mechanical systems, microfluidic and lab-on-a-chip platforms for biomedical therapies and, ultimately, energy-efficient magnetic memories or neuromorphic computing.