Complex transition metal oxides for resistive switching applications

Oxide materials embedded in complex multilayer material stacks can show the phenomena of resistive switching in which the electrical resistivity can be modified by applied electric voltages. This facilitates novel data-storage and processing devices with possible applications in concepts like neuromorphic computing or energy efficient computing. Our simulations are closely linked to experimental and theoretical work within the DFG SFB run at RWTH-Aachen University and Forschungszentrum Juelich. For example, we recently investigated the Ferroelectric switching in -Fe2O3. Isostructural Ga0.6Fe1.4O3 (GFO) and -Fe2O3 (eFO) are known as rare representatives of room-temperature multiferroics, simultaneously combining ferroelectric and ferromagnetic ordering. This makes them prospective materials for electronic devices with functionality based on multiple ferroic orders, such as the multistate non-volatile memory cells.

In contrast to GFO, where disorder in the occupancy of Ga and Fe sites is presented, the eFO is a fully ordered compound. In order to understand the microscopic mechanism of ferroelectric switching in these materials, we employ an evolutionary algorithm to explore possible structures as a function of the relative ordering of Ga and Fe cations in GFO, as well as the evolutionary metadynamics to model ferroelectric domain switching in eFO. This allows us to understand the role of disorder in possible ferroelectric properties and to develop the criteria to maximize the effect. We investigated the condition, at which the proper ferroelectricity arises in eFO multiferroics and characterized the parameters of the ferroelectric phase transition. (K.Z. Rushchanskii and M. Ležaić)