Electronic and magnetic phenomena at the interface of LaAlO{sub 3} and Ru doped SrTiO{sub 3}

We have investigated the effect of Ru doping the SrTiO{sub 3} (STO) side of the LaAlO{sub 3}/STO (LAO/STO) interface. The metallic behavior at the interface is remarkably robust to defects and disorder. Despite spin moment contribution from Ru ions, we see no evidence of magnetic ordering at the Ti L{sub 3},{sub 2} edge in either doped or undoped interfaces using X-ray magnetic circular dichroism. Magnetotransport measurements also do not show any evidence of magnetic scattering beyond that observed in undoped LAO/STO interfaces. Insertion of more than 7 unit cells of Ru doped STO at the interface suppresses metallic conductivity with a surprisingly sharp metal insulator transition. A similar metal-insulator transition is observed when a homoepitaxial STO film is grown on the single crystal substrate before LAO deposition. Together, our results indicate that ferromagnetism is not intrinsic to the interface, magnetic Ru dopants are not significant sources of scattering, and that cation vacancy formation alone cannot explain the insulating behavior observed in thick homoepitaxial LAO/STO/STO bilayers.