Browsing by Author "Fitzsimmons, Michael R"

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    Data for Controlling Magnetism and Transport at Perovskite Cobaltite Interfaces via Strain-Tuned Oxygen Vacancy Ordering
    (2025-03-11) Leighton, Chris; Bose, Shameek; Sharma, Manish; Torija, Maria A; Walter, Jeff; Nandakumaran, Nileena; Dewey, John; Schmitt, Josh; Gazquez, Jaume; Varela, Maria; Zhernenkov, Mikhail; Fitzsimmons, Michael R; Ambaye, Haile; Lauter, Valeria; Hovoka, Ondrej; Berger, Andreas; leighton@umn.edu; Leighton, Chris; Leighton Electronic and Magnetic Materials Lab
    Complex oxides such as perovskite cobaltites exhibit rich phenomena at interfaces due to the complex interplay between their structural, defect, electronic, and magnetic degrees of freedom. We study this here in the ferromagnetic metallic cobaltite La1-xSrxCoO3-, using specific substrates to systematically vary both the heteroepitaxial strain (compressive vs. tensile) and growth orientation ((001) vs. (110)). Transmission electron microscopy, electron energy-loss spectroscopy, high-resolution X-ray diffraction, magnetometry, polarized neutron reflectometry, and electronic magnetotransport measurements are applied. Lattice mismatch and growth orientation are found to precisely control interfacial oxygen vacancy ordering in La1-xSrxCoO3-, thus dictating strain relaxation and chemical depth profiles, and in turn controlling thickness-dependent magnetic and electronic properties. In particular, compressive strain and (110) orientations are found to minimize deleterious magnetic/electronic dead layer effects, leading to optimization of interfacial magnetism and transport. Strain and orientation tuning of oxygen vacancy ordering are thus established as powerful means to control physical properties at cobaltite-based interfaces, of relevance to several fields.
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    Data for Room-Temperature Valence Transition in a Strain-Tuned Perovskite Oxide
    (2022-11-09) Chaturvedi, Vipul; Ghosh, Supriya; Gautreau, Dominique; Postiglione, William M; Dewey, John E; Quarterman, Patrick; Balakrishnan, Purnima P; Kirby, Brian J; Zhou, Hua; Cheng, Huikai; Huon, Amanda; Fitzsimmons, Michael R; Korostynski, Caroline; Jacobson, Andrew; Figari, Lucca; Barriocanal, Javier G; Birol, Turan; Mkhoyan, K Andre; Leighton, Chris; leighton@umn.edu; Leighton, Chris; Leighton Electronic and Magnetic Materials Lab
    Cobalt oxides have long been understood to display intriguing phenomena known as spin-state crossovers, where the cobalt ion spin changes vs. temperature, pressure, etc. A very different situation was recently uncovered in praseodymium-containing cobalt oxides, where a first-order coupled spin-state/structural/metal-insulator transition occurs, driven by a remarkable praseodymium valence transition. Such valence transitions, particularly when triggering spin-state and metal-insulator transitions, offer highly appealing functionality, but have thus far been confined to cryogenic temperatures in bulk materials (e.g., 90 K in Pr1-xCaxCoO3). Here, we show that in thin films of the complex perovskite (Pr1-yYy)1-xCaxCoO3-delta, heteroepitaxial strain tuning enables stabilization of valence-driven spin-state/structural/metal-insulator transitions to at least 291 K, i.e., around room temperature. This dataset contains all digital data published in the Nature Communications paper of the same name.