Interface Engineered Room-Temperature Ferromagnetic Insulating State in Ultrathin Manganite Films

Ultrathin epitaxial films of ferromagnetic insulators (FMIs) with Curie temperatures near room temperature are critically needed for use in dissipationless quantum computation and spintronic devices. However, such materials are extremely rare. Here, a room-temperature FMI is achieved in ultrathin La_0.9Ba_0.1MnO₃ films grown on SrTiO₃ substrates via an interface proximity effect. Detailed scanning transmission electron microscopy images clearly demonstrate that MnO₆ octahedral rotations in La_0.9Ba_0.1MnO₃ close to the interface are strongly suppressed. As determined from in situ X-ray photoemission spectroscopy, O K-edge X-ray absorption spectroscopy, and density functional theory, the realization of the FMI state arises from a reduction of Mn e_g bandwidth caused by the quenched MnO₆ octahedral rotations. The emerging FMI state in La_0.9Ba_0.1MnO₃ together with necessary coherent interface achieved with the perovskite substrate gives very high potential for future high performance electronic devices.