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Title: Eu{sub 3}F{sub 4}S{sub 2}: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF{sub 2}.(EuFS){sub 2}

Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS (M=Y, La, Ce-Lu), in some cases we were able to obtain mixed-valent compounds such as Yb{sub 3}F{sub 4}S{sub 2} instead. With Eu{sub 3}F{sub 4}S{sub 2} another isotypic representative has now been synthesized. Eu{sub 3}F{sub 4}S{sub 2} (tetragonal, I4/mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 deg. C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF{sub 2}-type EuF{sub 2} is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu{sup 2+}) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu{sup 3+}) exhibits a monocapped square antiprismatic coordination sphere with four F{sup -} and five S{sup 2-} anions. Although the structural ordering of themore » different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu{sub 3}F{sub 4}S{sub 2} show Curie-Weiss behavior with an experimental magnetic moment of 8.19(5) mu{sub B} per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu{sup II})(Eu{sup III}){sub 2}F{sub 4}S{sub 2} only one third of the europium centers in Eu{sub 3}F{sub 4}S{sub 2} carry permanent magnetic moments. {sup 151}Eu-Moessbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of -12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu{sup 2+} and Eu{sup 3+}, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu{sup 2+}/Eu{sup 3+} fraction can be detected. - Graphical abstract: Crystal structure and {sup 151}Eu-Moessbauer spectra of mixed-valent Eu{sub 3}F{sub 4}S{sub 2}.« less
Authors:
;  [1] ;  [2] ;  [2] ; ;  [3] ;  [1]
  1. Institut fuer Anorganische Chemie, Universitaet Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany)
  2. Institut fuer Anorganische und Analytische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany)
  3. Institut fuer Physikalische Chemie, Westfaelische Wilhelms-Universitaet Muenster, Corrensstrasse 30, 48149 Muenster (Germany)
Publication Date:
OSTI Identifier:
21372388
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 182; Journal Issue: 11; Other Information: DOI: 10.1016/j.jssc.2009.08.023; PII: S0022-4596(09)00408-3; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANIONS; CATIONS; CURIE POINT; EUROPIUM FLUORIDES; EUROPIUM IONS; EUROPIUM SULFIDES; FLUORINE IONS; MAGNETIC MOMENTS; MAGNETIC SUSCEPTIBILITY; MOESSBAUER EFFECT; MONOCRYSTALS; PARAMAGNETISM; PLATINUM; SODIUM CHLORIDES; SULFUR IONS; TEMPERATURE RANGE 0000-0013 K; TEMPERATURE RANGE 0065-0273 K; TEMPERATURE RANGE 0273-0400 K; TETRAGONAL LATTICES ALKALI METAL COMPOUNDS; CHALCOGENIDES; CHARGED PARTICLES; CHLORIDES; CHLORINE COMPOUNDS; CRYSTAL LATTICES; CRYSTAL STRUCTURE; CRYSTALS; ELEMENTS; EUROPIUM COMPOUNDS; FLUORIDES; FLUORINE COMPOUNDS; HALIDES; HALOGEN COMPOUNDS; IONS; MAGNETIC PROPERTIES; MAGNETISM; METALS; PHYSICAL PROPERTIES; PLATINUM METALS; RARE EARTH COMPOUNDS; SODIUM COMPOUNDS; SULFIDES; SULFUR COMPOUNDS; TEMPERATURE RANGE; THERMODYNAMIC PROPERTIES; TRANSITION ELEMENTS; TRANSITION TEMPERATURE