Low-energy orbital excitations in strained LaCoO3 films

Ru-Pan Wang, Jaap Geessinck, Hebatalla Elnaggar, Yorick A. Birkholzer, Keisuke Tomiyasu, Jun Okamoto, Boyang Liu, Chao-Hung Du, Di-Jing Huang, Gertjan Koster, Frank M. F. de Groot

    Research output: Contribution to journalArticleAcademicpeer-review

    Abstract

    We present 90 meV resolved Co
    2
    p
    3
    d
    resonant inelastic x-ray scattering linear dichroism spectra of strained
    LaCoO
    3
    films and a
    LaCoO
    3
    single crystal. A polarization-dependent low-energy excitation is observed at

    0.2
    eV
    on the tensile-strained
    LaCoO
    3
    /
    SrTiO
    3
    film, while it is not observed in either bulk
    LaCoO
    3
    or the compressive-strained
    LaCoO
    3
    /
    LaAlO
    3
    film. Guided by cluster calculations, we are able to distinguish the spin-state manifolds close to their transition point of
    Co
    3
    +
    ions in
    LaCoO
    3
    systems. Through a polarization analysis, we show that the spin state can easily flip from a low-spin
    1
    A
    1
    g
    state in an octahedral symmetry to the high-spin
    5
    B
    2
    g
    or
    5
    E
    g
    states with a small tetragonal distortion. A mixture of spin states suggests that the high-spin
    Co
    3
    +
    plays an important role in long-range ferromagnetic order on both tensile- and compressive-strained
    LaCoO
    3
    films.
    Original languageEnglish
    Article number165148
    JournalPhysical Review B
    Volume100
    Issue number16
    DOIs
    Publication statusPublished - 31 Oct 2019

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