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Evidence of paracrystalline cation order in the ruddlesden–popper phase LaSr3NiRuO8 through neutron total scattering techniques

DOI: 10.1021/acs.inorgchem.9b03382 DOI Help

Authors: Margaret Lea Robinson (Bates College) , Ernestine Whitaker (Bates College) , Lun Jin (University of Oxford) , Michael A. Hayward (University of Oxford) , Geneva Laurita (Bates College)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry

State: Published (Approved)
Published: February 2020
Diamond Proposal Number(s): 13284

Abstract: Cation ordering in perovskite-derived phases can lead to a wealth of tunable physical properties. Ordering is typically driven by a large difference between the cation size and charge, but many Ruddlesden–Popper phases An+1BnO3n+1 appear to lack such B-site ordering, even when these differences are present. One such example is the “double” Ruddlesden–Popper n = 1 composition LaSr3NiRuO8. In this material, a lack of B-site ordering is observed through traditional crystallographic techniques, but antiferromagnetic ordering in the magnetism data suggests that B-site cation ordering is indeed present. Neutron total scattering, particularly analysis of the neutron pair distribution function, reveals that the structure is locally B-site-ordered below 6 Å but becomes slightly disordered in the midrange structure around 12 Å. This provides evidence for paracrystalline order in this material: cation ordering within a single perovskite sheet that lacks perfect registry within the three-dimensional stack of sheets. This work highlights the importance of employing a structural technique that can probe both the local and midrange order in addition to the crystallographic structure and provides a structural origin to the observed magnetic properties of LaSr3NiRuO8. Further, it is proposed that paracrystalline order is likely to be common among these layered-type oxides.

Journal Keywords: Chemical structure; Order; Layers; Cations; Perovskites

Subject Areas: Chemistry

Instruments: I11-High Resolution Powder Diffraction