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Exploring the Verwey-Type Transition in GdBaFe2O5+w Using 57Fe Mössbauer Spectroscopy

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Abstract

57Fe Mössbauer spectroscopy was used to study the double perovskite GdBaFe2O5+w , which exhibits mixing of the integer valence states of iron. The valence mixing/separation process Fe2++Fe3+↔2Fe2.5+ was investigated as a function of temperature. For nearly stoichiometric compositions of w≈0, a two-step Verwey-type transition is registered that separates Fe2.5+ into intermediate valence- and spin states Fe2.5−∈ and Fe2.5+∈ and then into the integer valences Fe2+ and Fe3+. Both steps are accompanied by a decrease in electrical conductivity, altogether by two orders of magnitude. Seebeck measurements identify holes as dominating charge carriers, with activation energy for hopping of ∼0.10 eV in the valence-mixed state. It is inferred that the mixing electrons are not simply delocalized over the lattice, but rather form bridges connecting pairs of adjacent Fe atoms along the c axis.

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Authors and Affiliations

  1. Physics Department, Åbo Akademi, FIN-20500, Turku, Finland

    J. Lindén

  2. Department of Chemistry, University of Oslo, N-0315, Oslo, Norway

    P. Karen

  3. Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, 226-8503, Japan

    H. Yamauchi & M. Karppinen

Authors
  1. J. Lindén
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  2. P. Karen
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  3. H. Yamauchi
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  4. M. Karppinen
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Lindén, J., Karen, P., Yamauchi, H. et al. Exploring the Verwey-Type Transition in GdBaFe2O5+w Using 57Fe Mössbauer Spectroscopy. Hyperfine Interactions 156, 321–325 (2004). https://doi.org/10.1023/B:HYPE.0000043248.99004.65

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  • DOI: https://doi.org/10.1023/B:HYPE.0000043248.99004.65

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