Magnetism and electronic phase transitions in isovalent manganite and ferrate superlattices*

The manganites and ferrates exhibit a host of collectively ordered states making them exciting candidates in which to identify new strategies for controlling local magnetism, orbital physics and metal-insulator transitions in oxide heterostructures. In this talk, I will demonstrate how magnetism can be enhanced at the sub-nm length scale through structural “delta doping” of octahedral rotations. By inserting two unit cells of La_0.7Sr_0.3MnO₃ within isovalent 20 unit cell La_0.7Ca_0.3MnO₃ layers, the magnetic exchange interactions are enhanced within spatially confined regions of suppressed octahedral rotations.[1] I will also discuss recent work on strained CaFeO₃ films and isovalent CaFeO₃/SrFeO₃ superlattices. Through a combination of X-ray spectroscopy and density functional theory, element-specific changes to the electronic structure induced by the metal-insulator transition in CaFeO₃ films are elucidated, revealing the central role of ligand holes in stabilizing the insulating state and a subtle electronic transfer from oxygen to iron states on cooling through the phase transition.[2] Efforts to understand how helical magnetism, electronic transport, and orbital polarization are altered through interfacial formation in CaFeO₃/SrFeO₃ superlattices will be presented.
[1] E. J. Moon, Q. He, S. Ghosh, B. J. Kirby, S. T. Pantelides, A. Y. Borisevich, and S. J. May. Physical Review Letters (2017).
[2] P. C. Rogge, R. U. Chandrasena, A. Cammarata, et al., in preparation (2017).