Fast pulsed measurements of the electric-field-driven metal-insulator transition in magnetite

Magnetite, Fe3O4, is an example of a strongly correlated material in which strong electron-electron interactions lead to unusual magneto-electronic properties. ~In particular, it undergoes a first-order phase transition on cooling through TV$\sim $122K in bulk, in which a structural transition is accompanied by a significant drop in electrical conductivity. ~Recent electronic transport measurements have shown an electric-field driven breakdown of the insulating state in large aspect-ratio nanogaps fabricated on magnetite thin-films. ~The mechanism of this breakdown is of great interest in understanding the Verwey transition, and probing the intrinsic speed of the breakdown may further constrain possible mechanisms. ~We investigate the kinetics of this nonequilibrium transition by employing a high-speed pulse generator to apply voltages approaching the nanosecond time scale that exceed the critical switching value, and measuring the transmitted pulse via a high-speed oscilloscope. ~A significant change in transmission is observed for pulses that exceed the critical amplitude necessary to initiate the transition. ~Our initial results include an evaluation of the material response as a function of temperature and amplitude of the applied voltage.