Effect of local atomic phase separation in the x-ray absorption near edge structure spectroscopy of FeSexTe1−x. (September 2015)

• Record Type: Journal Article
• Authors: Vega-Flick, A.; Mustre de León, J.; Saini, N.L.
• Is Part Of: Journal of physics and chemistry of solids. Volume 84(2015:Sep.)
• Page Start: 80
• Page End: 84
• Publication Date: 2015-09
• Subjects: A. Chalcogenides -- A. Superconductors -- C. Abinitio calculations -- D. Electronic structure -- C. XAFS (EXAFS and XANES); Solids -- Periodicals; Solides -- Périodiques; Solids; Periodicals; 530.41
• DOI: 10.1016/j.jpcs.2014.09.009
• Languages: English
• ISSNs: 0022-3697

Abstract

Abstract: Ab initio X-ray absorption near edge structure (XANES) calculations for FeSe x Te1− x, using a structural model that combines FeSe and FeTe phases at the nanoscale, are compared with Fe K -edge XANES measurements in the "pre-edge" region. The important aspects of this model are (i) magnetic order in the FeTe phase; (ii) Se and Te atoms placed randomly in both FeSe and FeTe crystallographic positions and; (iii) the two distinct distances for Fe–Se and Fe–Te of the bulk phases. The calculated spectra reproduce the observed increase of spectral weight in the experiments on FeSe x Te1− x with Se concentration. This is consistent with an inhomogeneous local electronic structure of FeSe x Te1− x . Additionally, we have calculated projected electronic density of d -states for the Fe atom, revealing increased spectral weight in the "pre-edge" region of the XANES spectra, which correlates with the increase in Se concentration. The decrease of calculated Fe d -density of states for the Fermi level, N ( ε F ), for high Te content is consistent with the suppression of superconductivity in the title system. Highlights: We model Fe K -edge XANES for FeSe x Te1− x using a model of local phase separation. Our model includes magnetic order, compositional disorder and two FeSe(Te) lenghts. We reproduce the increase of spectral weight in the pre-edge with Se concentration. Calculated density of states correlates with the drop on Tc at high Te content.