Haque, Zeba and Thakur, Gohil Singh and Parthasarathy, Rangasamy and Gerke, Birgit and Block, Theresa and Heletta, Lukas and Pottgen, Rainer and Joshi, Amish G. and Selvan, Ganesan Kalai and Arumugam, Sonachalam and Gupta, Laxmi Chand and Ganguli, Ashok Kumar (2017) Unusual Mixed Valence of Eu in Two Materials-EuSr2Bi2S4F4 and Eu2SrBi2S4F4: Mossbauer and X-ray Photoemission Spectroscopy Investigations. Inorganic Chemistry, 56 (6). pp. 3182-3189. ISSN 0020-1669

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Abstract

We have synthesized two new Eu-based compounds, EuSr2Bi2S4F4 and Eu2SrBi2S4F4, which are derivatives of Eu3Bi2S4F4, an intrinsic superconductor with I-c = 1.5 K. They belong to a tetragonal structure (SG: I4/mmm, Z = 2), similar to the parent compound Eu3Bi2S4F4. Our structural and Eu-151 Mossbauer spectroscopy studies show that, in EuSr2Bi2S4F4, Eu-atoms exclusively occupy the crystallographic 2a -sites. In Eu2SrBi2S4F4, 2a -sites are fully occupied by Eu-atoms and the other half of Eu-atoms and Sr -atoms together fully occupy 4e -sites in a statistical distribution. In both compounds Eu atoms occupying the crystallographic 2a -sites are in a homogeneous mixed valent state similar to 2.6-2.7. From our magnetization studies in an applied H <= 9 T, we infer that the valence of Eu-atoms in Eu2SrBi2S4F4 at the 2a -sites exhibits a shift toward 2+. Our XPS studies corroborate the occurrence of valence fluctuations of Eu and after Ar-ion sputtering show evidence of enhanced population of Eu2+-states. Resistivity measurements, down to 2 K, suggest a semimetallic nature for both compounds.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s American Chemical Society.
Subjects:	Chemistry > Inorganic Chemistry
Divisions:	UNSPECIFIED
Depositing User:	Users 27 not found.
Date Deposited:	31 May 2019 10:38
Last Modified:	31 May 2019 10:38
URI:	http://npl.csircentral.net/id/eprint/2928

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