Phase separation in the iron chalcogenide superconductor Fe 1+yTexSe1-x

Hefei Hu; Jian Min Zuo; Jinsheng Wen; Zhijun Xu; Zhiwei Lin; Qiang Li; Genda Gu; Wan Kyu Park; Laura H. Greene

doi:10.1088/1367-2630/13/5/053031

Phase separation in the iron chalcogenide superconductor Fe _1+yTe_xSe_1-x

Hefei Hu, Jian Min Zuo, Jinsheng Wen, Zhijun Xu, Zhiwei Lin, Qiang Li, Genda Gu, Wan Kyu Park, Laura H. Greene

Research output: Contribution to journal › Article › peer-review

Abstract

We present direct evidence for phase separation and chemical inhomogeneity in Fe_1+yTe_xSe_1-x single crystals from scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) data. In STEM, images recorded using a high-angle annular dark field (HAADF) detector show characteristic nanometer-scale patterns of phase separation from the Z-dependent image contrast. The separation was observed both in nonsuperconducting samples with excess iron and in superconducting samples. Using EELS, we determined ̃20% (or lower) fluctuation in Te concentration from the average local compositions by integrating the intensity of the Te-M_4,5 edge. The energy-loss near-edge structure (ELNES) of the Fe-L_2,3 edge changes with varying composition, especially the L ₃/L₂ white-line intensity ratio, which is sensitive to the d-state occupancy of the Fe. The results suggest a miscibility gap in the Fe_1+yTe_xSe_1-x system and changes in the d-electron states at the nanometer scale from the separated phases.

Original language	English (US)
Article number	053031
Journal	New Journal of Physics
Volume	13
DOIs	https://doi.org/10.1088/1367-2630/13/5/053031
State	Published - May 2011

ASJC Scopus subject areas

General Physics and Astronomy

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10.1088/1367-2630/13/5/053031

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@article{1d24626891984beebf9b13d1cda5bb0f,

title = "Phase separation in the iron chalcogenide superconductor Fe 1+yTexSe1-x",

abstract = "We present direct evidence for phase separation and chemical inhomogeneity in Fe1+yTexSe1-x single crystals from scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) data. In STEM, images recorded using a high-angle annular dark field (HAADF) detector show characteristic nanometer-scale patterns of phase separation from the Z-dependent image contrast. The separation was observed both in nonsuperconducting samples with excess iron and in superconducting samples. Using EELS, we determined{\~ }20% (or lower) fluctuation in Te concentration from the average local compositions by integrating the intensity of the Te-M4,5 edge. The energy-loss near-edge structure (ELNES) of the Fe-L2,3 edge changes with varying composition, especially the L 3/L2 white-line intensity ratio, which is sensitive to the d-state occupancy of the Fe. The results suggest a miscibility gap in the Fe1+yTexSe1-x system and changes in the d-electron states at the nanometer scale from the separated phases.",

author = "Hefei Hu and Zuo, {Jian Min} and Jinsheng Wen and Zhijun Xu and Zhiwei Lin and Qiang Li and Genda Gu and Park, {Wan Kyu} and Greene, {Laura H.}",

year = "2011",

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AU - Hu, Hefei

AU - Zuo, Jian Min

AU - Wen, Jinsheng

AU - Xu, Zhijun

AU - Lin, Zhiwei

AU - Li, Qiang

AU - Gu, Genda

AU - Park, Wan Kyu

AU - Greene, Laura H.

PY - 2011/5

Y1 - 2011/5

N2 - We present direct evidence for phase separation and chemical inhomogeneity in Fe1+yTexSe1-x single crystals from scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) data. In STEM, images recorded using a high-angle annular dark field (HAADF) detector show characteristic nanometer-scale patterns of phase separation from the Z-dependent image contrast. The separation was observed both in nonsuperconducting samples with excess iron and in superconducting samples. Using EELS, we determined ̃20% (or lower) fluctuation in Te concentration from the average local compositions by integrating the intensity of the Te-M4,5 edge. The energy-loss near-edge structure (ELNES) of the Fe-L2,3 edge changes with varying composition, especially the L 3/L2 white-line intensity ratio, which is sensitive to the d-state occupancy of the Fe. The results suggest a miscibility gap in the Fe1+yTexSe1-x system and changes in the d-electron states at the nanometer scale from the separated phases.

AB - We present direct evidence for phase separation and chemical inhomogeneity in Fe1+yTexSe1-x single crystals from scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) data. In STEM, images recorded using a high-angle annular dark field (HAADF) detector show characteristic nanometer-scale patterns of phase separation from the Z-dependent image contrast. The separation was observed both in nonsuperconducting samples with excess iron and in superconducting samples. Using EELS, we determined ̃20% (or lower) fluctuation in Te concentration from the average local compositions by integrating the intensity of the Te-M4,5 edge. The energy-loss near-edge structure (ELNES) of the Fe-L2,3 edge changes with varying composition, especially the L 3/L2 white-line intensity ratio, which is sensitive to the d-state occupancy of the Fe. The results suggest a miscibility gap in the Fe1+yTexSe1-x system and changes in the d-electron states at the nanometer scale from the separated phases.

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