The remarkable functionality of complex oxides provides many opportunities for new physics and applications in oxide heterostructures. The manganite and cobaltite materials crystallizing in the perovskite structure provide excellent examples, being of interest in solid oxide fuel cells, catalysis, ferroelectric RAM, gas sensing, resistive switching memory, and oxide spintronics. However, the same delicate balance between phases that provides such diverse functionality also leads to a serious problem - the difficulty of maintaining desired properties close to the interface with other oxides. Although this problem appears universal, manifests itself in many ways, and presents a significant “roadblock” to the development of heterostructured devices for oxide electronics, there is no clear consensus as to its origin, or even whether it is driven by electronic or chemical effects. In this work, using SrTiO3/La1-xSrxCoO3 as a model system (i.e. a non-magnetic semiconductor / ferromagnetic metal interface), we have determined the fundamental origin of the deterioration in interfacial transport and magnetic properties. The effect is found to be chemically-driven, being due to a profound interaction between the strain-state and the formation of oxygen defects, which dominates the interface magnetism and transport. Most importantly, it is demonstrated that a full understanding of these effects enables design and synthesis of interfaces where the suppression in physical properties is dramatically reduced, or perhaps even eliminated.
Work supported by DOE and NSF.