Exploring the Verwey-type transition in GdBaFe2O5+w using 57Fe Mössbauer spectroscopy

J. Lindén*, P. Karen, H. Yamauchi, M. Karppinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)

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-ε and Fe2.5+ε 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.

Original languageEnglish
Pages (from-to)321-325
Number of pages5
JournalHyperfine Interactions
Volume156
DOIs
Publication statusPublished - Dec 2004
MoE publication typeA1 Journal article-refereed

Keywords

  • Fe Mössbauer spectroscopy
  • Charge ordering
  • Double perovskite
  • Valence mixing
  • Verwey-type transition

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