Nanocomposite Oxide Thin Films For Novel Ionotronic Magnetoelectrics

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Ionotronic devices rely on charge effects based on ions instead of/or in addition to electrons. The field has begun to gain very wide attention recently. It has been applied mainly to oxide thin film memristors (resistance depends on voltage and can be switched between an 'on' and an 'off' state of high and low resistance). These devices are interesting for creating electrically switchable memory, but there are challenges with these structures including the requirement of a setting process and variable properties from one film to another. In this proposal, we have the new idea to utilise ionotronic effects to create a new kind of electrically switchable memory. Here ionic defects at vertical interfaces in vertical nanocomposite thin films charge couple to magnetism in a magnetic transition metal oxide. Since the cation valences in the metal oxide depend on oxygen concentration or charge state, and since the magnetic properties depend on cation valences, it should be possible to switch magnetism on and off by applying an electric field. This device is an ionotronic magnetoelectric, and it represents a completely new form of magnetoelectric RAM. Magnetoelectric RAM is where electric field controls magnetism instead of electric current doing so as in other forms of RAM, and it is a long sought-after goal. It offers the possibility of low power, very high density, high-speed reading and writing times, and non-volatility. Low energy, high performance computing is promised with this technology. However, while a range of structures and materials have been studied to date, none has proved practical in terms of ease of structure formation, stability, temperature of operation, or size of magnetoelectric effect. Making the ionotronic magnetoelectric a practical reality is not trivial, and relies on advanced materials science - the growth of very thin films, the creation of highly ordered materials combinations on a very small scale (1/0000 the thickness of a human hair), the movement of charges along interface nanochannels near to room temperature, the knowledge of which materials combine together in a compatible way, the imaging of materials at the atomic scale, etc. To attain the 'practical magnetoelectric' dream we propose to create and measure new structures, we will use unique experimental capabilities and will also collaborate with world-leading researchers. Our starting point for the research is our ability to create, at the nanometre scale, ionic interface channels in perfect vertical nanocomposite films. We have also observed the first signs that ions can indeed charge couple to magnetic properties.