Origin of hysteresis in resistive switching in magnetite is Joule heating

Abstract

In many transition metal oxides the electrical resistance is observed to undergo dramatic changes induced by large biases. In magnetite, Fe3O4, below the Verwey temperature, an electric field driven transition to a state of lower resistance was recently found, with hysteretic current-voltage response. We report the results of pulsed electrical conduction measurements in epitaxial magnetite thin films. We show that while the high-to low-resistance transition is driven by electric field, the hysteresis observed in I − V curves results from Joule heating in the low resistance state. The shape of the hysteresis loop depends on pulse parameters, and reduces to a hysteresis-free "jump" of the current provided thermal relaxation is rapid compared to the time between voltage pulses. A simple relaxation time thermal model is proposed that captures the essentials of the hysteresis mechanism.PACS numbers: 71.30.+h,72.20.Ht Dramatic changes in resistance induced by electric fields, so called resistive switching (RS), have recently attracted much attention due to this phenomenon's potential application in memory devices (resistive random access memory, ReRAM) [1,2]. RS from high-to lowresistance states is driven by application of high voltage, and corresponding up-and-down sweeps of currentvoltage (I-V ) characteristics often show hysteresis, i.e. in sweeps up and down in bias voltage, the current does not retrace itself. Systems exhibiting hysteretic RS include organic compounds [3] and transition-metal oxides such as widely-studied colossal resistance manganites [4], perovskites (e.g. SrTiO 3 [5]), 1D cuprates Sr 2 CuO 3 [6], NiO [7], TiO 2 [8] etc.For some RS systems, while sweeping out a hysteresis loop in I-V with a switch to a low resistance state at high bias, the low resistance state persists down to zero current as voltage approaches zero. This behavior is often the case for RS systems where the switching is based on metallic filament formation at a transition point [5]. However, for some RS systems the low-resistance state persists only in some voltage interval, and the system returns to the high-resistance state before voltage returns to zero. This is the case for some complex oxides [4,9,10] as well as for magnetite nanostructures, which were recently shown to exhibit RS at low temperatures [11,12].Magnetite, Fe 3 O 4 , is an example of strongly correlated material. In equilibrium, bulk magnetite undergoes a structural transition at the Verwey temperature, T V ∼120 K, accompanied by three-order-of-magnitude change in electrical conductivity, i.e. a metal-insulator transition (MIT) [13]. Recently we demonstrated that magnetite nanoparticles and thin films, once in the insulating state below T V , exhibit RS under a sufficiently large voltage bias [11]. By examining RS systematically in different device geometries, the switching was demon-strated to be driven by the applied in-plane electric field. This is in contrast to previously observed transitions in magnetite driven by Joule heating of the samples above T V...

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