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Title: EuBaFe{sub 2}O{sub 5+w}: Valence mixing and charge ordering are two separate cooperative phenomena

Abstract

Mixed-valence EuBaFe{sub 2}O{sub 5+w} exhibits a robust Verwey-type transition. The trend in the volume change suggests a first-order transition up to the nonstoichiometry level of about w=0.25. {sup 57}Fe Mossbauer spectroscopy, differential scanning calorimetry and synchrotron X-ray powder diffraction are used to study the valence mixing and charge ordering in EuBaFe{sub 2}O{sub 5+w} as a function of the nonstoichiometry parameter w. {sup 151}Eu Mossbauer spectroscopy is used as a selective probe into the ferromagnetic valence-mixing coupling along c above the Verwey transition, and reveals that increasing w destroys this coupling in favor of a G-type magnetic order in parallel with the progressive removal of the valence-mixed iron states accounted for by {sup 57}Fe Mossbauer spectroscopy. This removal proceeds according to a probability scheme of mixing between ferromagnetically coupled divalent and trivalent neighbor iron atoms along c across the R layer. In contrast, the concentration decrease of the orbital- and charge-ordered states in EuBaFe{sub 2}O{sub 5+w} is found to be a linear function of w. Valence mixing and charge ordering are therefore two separate cooperative phenomena. The enthalpy of the Verwey-type transition between these two cooperative systems is a linear function of w, which suggests that it originates from the latentmore » heat of freezing into the long-range ordered orbital- and charge-ordered state. The enthalpy becomes zero at the nonstoichiometry level of about w=0.25.« less

Authors:
 [1];  [2];  [2]
  1. Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo (Norway), E-mail: pavel.karen@kjemi.uio.no
  2. Department of Physics, Abo Akademi, FI-20500 Turku (Finland)
Publication Date:
OSTI Identifier:
21015631
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Solid State Chemistry; Journal Volume: 180; Journal Issue: 1; Other Information: DOI: 10.1016/j.jssc.2006.09.031; PII: S0022-4596(06)00525-1; Copyright (c) 2006 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; BARIUM COMPOUNDS; CALORIMETRY; COUPLING; ENTHALPY; EUROPIUM COMPOUNDS; FREEZING; IRON OXIDES; LAYERS; MIXING; MOESSBAUER EFFECT; PEROVSKITE; PROBABILITY; SYNCHROTRON RADIATION; VALENCE; X-RAY DIFFRACTION

Citation Formats

Karen, P., Gustafsson, K., and Linden, J.. EuBaFe{sub 2}O{sub 5+w}: Valence mixing and charge ordering are two separate cooperative phenomena. United States: N. p., 2007. Web. doi:10.1016/j.jssc.2006.09.031.
Karen, P., Gustafsson, K., & Linden, J.. EuBaFe{sub 2}O{sub 5+w}: Valence mixing and charge ordering are two separate cooperative phenomena. United States. doi:10.1016/j.jssc.2006.09.031.
Karen, P., Gustafsson, K., and Linden, J.. Mon . "EuBaFe{sub 2}O{sub 5+w}: Valence mixing and charge ordering are two separate cooperative phenomena". United States. doi:10.1016/j.jssc.2006.09.031.
@article{osti_21015631,
title = {EuBaFe{sub 2}O{sub 5+w}: Valence mixing and charge ordering are two separate cooperative phenomena},
author = {Karen, P. and Gustafsson, K. and Linden, J.},
abstractNote = {Mixed-valence EuBaFe{sub 2}O{sub 5+w} exhibits a robust Verwey-type transition. The trend in the volume change suggests a first-order transition up to the nonstoichiometry level of about w=0.25. {sup 57}Fe Mossbauer spectroscopy, differential scanning calorimetry and synchrotron X-ray powder diffraction are used to study the valence mixing and charge ordering in EuBaFe{sub 2}O{sub 5+w} as a function of the nonstoichiometry parameter w. {sup 151}Eu Mossbauer spectroscopy is used as a selective probe into the ferromagnetic valence-mixing coupling along c above the Verwey transition, and reveals that increasing w destroys this coupling in favor of a G-type magnetic order in parallel with the progressive removal of the valence-mixed iron states accounted for by {sup 57}Fe Mossbauer spectroscopy. This removal proceeds according to a probability scheme of mixing between ferromagnetically coupled divalent and trivalent neighbor iron atoms along c across the R layer. In contrast, the concentration decrease of the orbital- and charge-ordered states in EuBaFe{sub 2}O{sub 5+w} is found to be a linear function of w. Valence mixing and charge ordering are therefore two separate cooperative phenomena. The enthalpy of the Verwey-type transition between these two cooperative systems is a linear function of w, which suggests that it originates from the latent heat of freezing into the long-range ordered orbital- and charge-ordered state. The enthalpy becomes zero at the nonstoichiometry level of about w=0.25.},
doi = {10.1016/j.jssc.2006.09.031},
journal = {Journal of Solid State Chemistry},
number = 1,
volume = 180,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}