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Orbital correlations in the pseudo-cubic \emph{O} and rhombohedral ${R}$-phases of LaMnO$_3$

Xiangyun Qiu·Th. Proffen·J. F. Mitchell·S. J. L. Billinge
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Abstract

The local and intermediate structure of stoichiometric LaMnO$_3$ has been studied in the pseudocubic and rhombohedral phases at high temperatures (300 to 1150 K). Neutron powder diffraction data were collected and a combined Rietveld and high real space resolution atomic pair distribution function analysis carried out. The nature of the Jahn-Teller (JT) transition around 750 K is confirmed to be orbital order to disorder. In the high temperature orthorhombic ($O$) and rhombohedral ($R$) phases the MnO$_6$ octahedra are still fully distorted locally. The data suggest the presence of local orbitally ordered clusters of diameter $\sim 16$ Å($\sim$four MnO$_6$ octahedra) implying strong nearest neighbor JT anti-ferrodistortive coupling.

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Xiangyun Qiu, Th. Proffen, J. F. Mitchell, S. J. L. Billinge. 2004-08-13. Orbital correlations in the pseudo-cubic \emph{O} and rhombohedral ${R}$-phases of LaMnO$_3$. https://doi.org/10.1103/physrevlett.94.177203

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