Emergent electronic landscapes in a novel valence-ordered nickelate with tri-component nickel coordination

Abstract

The metal-hydride-based topochemical reduction process has produced novel thermodynamically unstable phases across various transition metal oxide series with unusual crystal structures and non-trivial ground states. Here, by such an oxygen (de-) intercalation method we synthesis a novel samarium nickelate with ordered nickel valences associated with tri-component coordination configurations. This structure, with a formula of Sm${}_9$Ni${}_9$O${}_{22}$ as revealed by four-dimensional scanning transmission electron microscopy, emerges from the intricate planes of {303}${}_{\text{pc}}$ ordered apical oxygen vacancies. X-ray spectroscopy measurements and ab-initio calculations show the coexistence of square-planar, pyramidal and octahedral Ni sites with mono-, bi- and tri-valences. It leads to an intense orbital polarization, charge-ordering, and a ground state with a strong electron localization marked by the disappearance of ligand-hole configuration at low-temperature. This new nickelate compound provides another example of previously inaccessible materials enabled by topotactic transformations and presents a unique platform where mixed Ni valence can give rise to exotic phenomena.

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Cited by in corpus (4)

• $\text{In situ}$ preparation of superconducting infinite-layer nickelate thin films with atomically flat surface
• Unraveling p-type and n-type interfaces in Superconducting Infinite-Layer Nickelate thin films
• Emergent electronic landscapes in a novel valence-ordered nickelate with tri-component nickel coordination
• Signatures of canted antiferromagnetism in infinite-layer nickelates studied by x-ray magnetic dichroism