Anomalous Eu valence state and superconductivity in undoped Eu3Bi2S4F4

Hui Fei Zhai, Pan Zhang, Si Qi Wu, Chao Yang He, Zhang Tu Tang, Hao Jiang, Yun Lei Sun, Jin Ke Bao, Israel Nowik, Israel Felner, Yue Wu Zeng, Yu Ke Li, Xiao Feng Xu, Qian Tao, Zhu An Xu, Guang Han Cao*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

78 Scopus citations

Abstract

We have synthesized a novel europium bismuth sulfofluoride, Eu3Bi2S4F4, by solid-state reactions in sealed evacuated quartz ampules. The compound crystallizes in a tetragonal lattice (space group I4/mmm, a = 4.0771(1) Å, c = 32.4330(6) Å, and Z = 2), in which CaF2-type Eu3F4 layers and NaCl-like BiS2 bilayers stack alternately along the crystallographic c axis. There are two crystallographically distinct Eu sites, Eu(1) and Eu(2) at the Wyckoff positions 4e and 2a, respectively. Our bond valence sum calculation, based on the refined structural data, indicates that Eu(1) is essentially divalent, while Eu(2) has an average valence of ∼+2.64(5). This anomalous Eu valence state is further confirmed and supported, respectively, by Mössbauer and magnetization measurements. The Eu3+ components donate electrons into the conduction bands that are mainly composed of Bi 6px and 6py states. Consequently, the material itself shows metallic conduction and superconducts at 1.5 K without extrinsic chemical doping.

Original languageEnglish
Pages (from-to)15386-15393
Number of pages8
JournalJournal of the American Chemical Society
Volume136
Issue number43
DOIs
StatePublished - 29 Oct 2014

Bibliographical note

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© 2014 American Chemical Society.

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