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

Research output: Contribution to journalArticlepeer-review


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.

Original languageEnglish (US)
Article number053031
JournalNew Journal of Physics
StatePublished - May 2011

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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