15:15 〜 15:30
▲ [21p-235-7] Valence Sensitive X-ray Fluorescence Holography of Magnetite
キーワード：X-ray fluorescence Holography, Valence sensitive
X-ray fluorescence holography (XFH) is an atomic resolution, element sensitive experiment that can directly provide a 3-dimensional picture of the atoms surrounding a selected element in a material. Fluorescent X-rays from the target element is scattered by the surrounding atoms, and the interference is recorded as holograms. A 3D atomic image can be reconstructed from the holograms by numerical processing.
In this presentation, we report a XFH experiment that is not only element sensitive, but also sensitive to the electronic state of the target element. Careful tuning of the incident X-ray energies with respect to the shifts of the absorption edges of the different valence states the element allows us to record valence sensitive holograms. This allows the direct imaging of the local structure around the different valence states of the target element.
Magnetite (Fe3O4), is a classic mixed valence compound, where both Fe2+ and Fe3+ occupy octahedral B-sites, and Fe3+ occupies tetrahedral A-sites. It has a MI transition upon cooling below 120 K, and is one of the most studied material in strongly correlated electron systems. We demonstrate valence sensitive XFH on a magnetite reference sample, and show that Fe Kα holograms, and their corresponding atomic reconstruction can be obtained from all Fe cation as emitters, or separately for Fe2+ cations only, or Fe3+ cations only. The results of the experiment show that Fe2+ emitters are in the octahedral sites, while Fe3+ are on the tetrahedral sites.
Our results show that valence sensitive XFH is a promising new technique that can be used to address unresolved questions about the structure of mixed valence compounds by clarifying the difference in local atomic structure around the different ions in a crystal.
In this presentation, we report a XFH experiment that is not only element sensitive, but also sensitive to the electronic state of the target element. Careful tuning of the incident X-ray energies with respect to the shifts of the absorption edges of the different valence states the element allows us to record valence sensitive holograms. This allows the direct imaging of the local structure around the different valence states of the target element.
Magnetite (Fe3O4), is a classic mixed valence compound, where both Fe2+ and Fe3+ occupy octahedral B-sites, and Fe3+ occupies tetrahedral A-sites. It has a MI transition upon cooling below 120 K, and is one of the most studied material in strongly correlated electron systems. We demonstrate valence sensitive XFH on a magnetite reference sample, and show that Fe Kα holograms, and their corresponding atomic reconstruction can be obtained from all Fe cation as emitters, or separately for Fe2+ cations only, or Fe3+ cations only. The results of the experiment show that Fe2+ emitters are in the octahedral sites, while Fe3+ are on the tetrahedral sites.
Our results show that valence sensitive XFH is a promising new technique that can be used to address unresolved questions about the structure of mixed valence compounds by clarifying the difference in local atomic structure around the different ions in a crystal.