Iron mixed-valence compounds, BaSm(Cu0.5+xFe0.5-x)2O5+δ. II: the Fe2.5+ state and magnetic properties

J. Lindén*, J. Nakamura, T. Pietari, T. Taniyama, M. Karppinen, H. Yamauchi

*Corresponding author for this work

Research output: Contribution to journalConference articleScientificpeer-review

Abstract

Recently, a fluctuating mixed-valence state formally denoted as Fe2.5+ was observed in BaSmFe2O5+δ double-perovskite samples, having δ < 0.5 [J. Linden, P. Karen, A. Kjekshus, J. Miettinen, T. Pietari, M. Karppinen, Phys. Rev. B 60 (1999) 15251.]. Upon cooling such samples to the Verwey-type transition temperature (TV ≈ 200 K), a mixing-separation transition of the valence state occurs. In order to study in detail the formation of the mixed-valence state BaSm(Cu0.5+xFe0.5-x)2O5+δ, samples with a certain amount of Fe (0-10% and 40-50%) replaced by Cu have been characterized by 57Fe Mossbauer spectroscopy and magnetization measurements. All samples were found to be magnetically ordered at room temperature. The amount of Fe entering the Fe2.5+ state decreased rapidly as the Cu doping level was increased, as judged by the Mossbauer spectra. Increasing the Cu concentration also led to an increase of TV.

Original languageEnglish
Pages (from-to)126-131
Number of pages6
JournalPhysica C: Superconductivity and its Applications
Volume338
Issue number1
DOIs
Publication statusPublished - 1 Aug 2000
MoE publication typeA4 Article in a conference publication
EventInternational Discussion Meeting on Chemistry Approaches to High-Tc Superconductive Materials / 5th International Workshop on Chemical Designing and Processing of High-Tc Superconductors (Chem-HTSC-V) - Yokohama, Jpn
Duration: 15 Oct 199916 Oct 1999

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