Functionalizing electronic and magnetic properties in oxide thin films and heterointerfaces: electric polarization and polar discontinuity

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The integration of oxide materials with layered architectures often leads to intriguing, unexpected electronic and magnetic properties of layers and/or interfaces. Often the observed phenomena are of extrinsic nature and, e.g., caused by interdiffusion, defects, and impurities. Within this proposal we plan to investigate two type of intrinsic mechanisms – and their possible interplay –, which recently came into focus as generic means to control the electronic and magnetic properties of thin films and interfaces. The first is ‘electronic reconstruction’, i.e., the redistribution of charge to the interface in order to compensate the electrostatic potential due to the polar discontinuity when materials with different polar nature are combined in a layered architecture. The second is – concomitant with a structural rearrangement – electric polarization that either can be triggered to compensate a built-in potential as an alternative to or in competition with electronic reconstruction or forms spontaneously in a ferroelectric film material. For the materials selection to be studied these mechanisms are supposed to lead to thickness dependent magnetic transitions, spin-polarized interface electron systems and peculiar electronic layer and interface properties that make the hosting heterostructures photovoltaically active. The microscopic mechanisms at work in each case shall be elucidated by a combined approach of advanced electron spectroscopy and microscopy methods.