ICAME 2003 pp 321-325 | Cite as

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

Conference paper

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.

Key words

57Fe Mössbauer spectroscopy Verwey-type transition charge ordering valence mixing double perovskite 

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Copyright information

© Springer Science+Business Media Dordrecht 2004

Authors and Affiliations

  • J. Lindén
    • 1
  • P. Karen
    • 2
  • H. Yamauchi
    • 3
  • M. Karppinen
    • 3
  1. 1.Åbo AkademiPhysics DepartmentTurkuFinland
  2. 2.Department of ChemistryUniversity of OsloOsloNorway
  3. 3.Materials and Structures LaboratoryTokyo Institute of TechnologyYokohamaJapan

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