Signatures of a Two-Dimensional Ferromagnetic Electron Gas at the La0.7Sr0.3 MnO3 /SrTiO3 Interface Arising From Orbital Reconstruction

Abstract

Electronic reconstruction at interfaces between different oxides is giving rise to a plethora of new functionalities and novel phenomena. Complex oxides are characterized by a strong interplay of the different degrees of freedom (orbital, spin and lattice)which can be engineered and modified at interfaces and surfaces. For instance, the interface between two insulating non-magnetic oxides (for instance, LaAlO3 and SrTiO3) can be metallic and ferromagnetic. Another example is that of heterostructures involving manganites, in which interfacial orbital and magnetic reconstructions can affect transport properties. This work constitutes a joint theoretical-experimental effort to understand the properties of a multilayer formed by a metallic ferromagnetic manganite oxide (La0.7Sr0.3MnO3) and the insulating SrTiO3. Magnetoresistance has been measured under a magnetic field which rotates with respect to the interface plane. In such a geometry, a peak in the magnetoresistance for a perpendicular magnetic field is expected and has been measured in other systems. However, our heterostructures also show an unexpected peak when the magnetic field is in plane. We have performed calculations of the resistivity in a model system which includes spin-orbit coupling. The results reveal that the unexpected in-plane maximum is due to transport through a two-dimensional ferromagnetic electron gas formed by orbital reconstruction at the manganite interface. These orbital and magnetic reconstructions are supported by X-ray linear dichroism and ab-initio calculations.