Journal Article electrolyte gating 1K09F3G675 Bismuth Fe3N Ferric Compounds Research Support, Non-U.S. Gov't U015TT5I8H artificial synapse artificial synapses cobaltites complex oxide superlattices complex oxides cylinder diameter engineering exchange bias ferric oxide ferromagnetism freestanding membranes grain boundaries lateral homostructures magnetic anisotropy metal-to-insulator transition oxide interfaces polarized neutron reflectometry spintronics strain engineering synaptic transistor synaptic transistors topotactic transformations transition metal nitrides