Phase transitions and iron-ordered moment form factor in LaFeAsO

H. F. Li, W. Tian, J. Q. Yan, J. L. Zarestky, R. W. McCallum, T. A. Lograsso, D. Vaknin

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33 Scopus citations

Abstract

Elastic neutron-scattering studies of single-crystal LaFeAsO reveal that upon cooling, an onset of the tetragonal (T)-to-orthorhombic (O) structural transition occurs at TS ≈156 K, and it exhibits a sharp transition at TP ≈148 K. We argue that in the temperature range T S to TP, T and O structures may dynamically coexist possibly due to nematic spin correlations recently proposed for the iron pnictides, and we attribute TP to the formation of long-range O domains from the finite local precursors. The antiferromagnetic structure emerges at TN ≈140 K, with the iron moment direction along the O a axis. We extract the iron magnetic form factor and use the tabulated 〈 j0 〉 of Fe, Fe2+, and Fe3+ to obtain a magnetic moment size of ∼0.8 μB at 9.5 K.

Original languageEnglish
Article number064409
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume82
Issue number6
DOIs
StatePublished - Aug 9 2010
Externally publishedYes

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