Journal ArticleDOI
Electronic and atomic structure of Mn-doped CaF2: An x-ray-absorption near-edge structure and extended x-ray-absorption fine-structure study.
J. H. Barkyoumb,Azzam N. Mansour +1 more
TLDR
In this article, an extended X-ray-absorption near-edge structure (XANES) and extended-x-ray absorption fine-structure (EXAFS) measurements have been performed on the calcium K edge and manganese K edge of a sample doped with manganous at molecular concentrations of 0.1--2.5 %.Abstract:
X-ray-absorption near-edge structure (XANES) and extended-x-ray-absorption fine-structure (EXAFS) measurements have been performed on the calcium K edge and manganese K edge of ${\mathrm{CaF}}_{2}$ doped with manganese at molecular concentrations of 0.1--2.5 %. The results are compared to other measurements of the calcium K edge in ${\mathrm{CaF}}_{2}$ and the Mn K edge in various manganese compounds. Major features in the XANES spectra are tentatively identified with transitions to high-symmetry points of the ${\mathrm{CaF}}_{2}$ energy bands in a one-electron picture. Expected deviations from the structure predicted by the one-electron formalism are discussed. The EXAFS analysis shows a reduction in the manganese-fluorine distance of (3.9\ifmmode\pm\else\textpm\fi{}0.4)% as compared to the calcium-fluorine separation in the doped or undoped samples. This compares well with previous results obtained by EPR. A significant increase in disorder of the first shell around the Mn dopant ion is observed as compared to the Ca ion. The significance of this shell contraction and disorder is discussed in terms of possible defect structures in the material.read more
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Journal ArticleDOI
X-ray absorption and dichroism of transition metals and their compounds
TL;DR: In this article, an overview of the X-ray absorption spectra of 3D transition metals and their compounds is presented, focusing on the description of the absorption process and the various routes to interpret the results within the framework of their electronic structure.
Journal ArticleDOI
Systematic empirical analysis of calcium?oxygen coordination environment by calcium K-edge XANES
Frank E. Sowrey,Laura J. Skipper,David M. Pickup,Kieran O. Drake,Zhongjie Lin,Mark E. Smith,Robert J. Newport +6 more
TL;DR: The X-ray absorption near edge structure (XANES) at the calcium K-edge is rich in information, but complex and difficult to interpret fully as discussed by the authors, and can be used to obtain qualitative information on the calcium coordination environment.
Journal ArticleDOI
Microscopic insight into properties and electronic instabilities of impurities in cubic and lower symmetry insulators: the influence of pressure
TL;DR: The phenomena associated with the Jahn-Teller effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu(2+) are discussed.
Journal ArticleDOI
Energy Migration Upconversion in Manganese(II)-Doped Nanoparticles
Xiyan Li,Xiaowang Liu,Daniel M. Chevrier,Xian Qin,Xiaoji Xie,Shuyan Song,Hongjie Zhang,Peng Zhang,Xiaogang Liu,Xiaogang Liu +9 more
TL;DR: Both experimental and theoretical studies provide evidence for Mn(2+) doping in the lanthanide-based host lattice arising from the formation of F(-) vacancies around Mn( 2+) ions to maintain charge neutrality in the shell layer.
Journal ArticleDOI
Ab initio model potential embedded cluster calculations including lattice relaxation and polarization: Local distortions on Mn2+‐doped CaF2
José Luis Pascual,Luis Seijo +1 more
TL;DR: In this article, the ab initio model potential embedding method is extended to include the effects of dipole polarization and site relaxation of lattice ions external to the cluster, which are represented by an empirical shell model.
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