Spin-state transition, magnetism and local crystal structure in Eu 1-xCaxCoO3-δ

Alexander N. Vasiliev*, Tatyana M. Vasilchikova, Olga S. Volkova, Anton A. Kamenev, Andrey R. Kaul, Tatyana G. Kuzmova, Dmitry M. Tsymbarenko, Kirill A. Lomachenko, Alexander V. Soldatov, Sergey V. Streltsov, Jiunn-Yuan Lin, Cheng Nan Kao, Jin Ming Chen, Mahmoud Abdel-Hafiez, Anja Wolter, Rüdiger Klingeler

*Corresponding author for this work

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Abstract

The doping series Eu1-xCaxCoO3-δ provides a rather peculiar way to study the spin-state transitions in cobalt-based complex oxides since partial substitution of Eu3+ ions by Ca2+ ions does not increase the mean valence of cobalt but is accompanied by appearance of oxygen vacancies in the ratio δ ~ x/2. In the parent compound EuCoO3, the low spin (LS)-intermediate spin (IS) or high spin (HS) transition takes place at temperatures so high that the chemical decomposition prevents its direct observation. The substitution of Eu 3+ by Ca2+ shifts the spin state transition to lower temperatures and the associated energy gap Δ in octahedrally-coordinated Co3+ ions changes from 1940K in EuCoO3 to 1540K in Eu 0.9Ca0.1CoO2.95 and 1050K in Eu 0.8Ca0.2CoO2.9. Besides, each O2- vacancy reduces the local coordination of two neighboring Co3+ ions from octahedral to pyramidal thereby locally creating magnetically active sites which couple to dimers. These dimers form another gapped magnetic system with a very different energy scale, Ddim ~ 3 K, on the background of the intrinsically non-magnetic lattice of octahedrally-coordinated low-spin Co 3+ ions.

Original languageEnglish
Article number044714
JournalJournal of the Physical Society of Japan
Volume82
Issue number4
DOIs
StatePublished - 1 Apr 2013

Keywords

  • Cobaltites
  • Local crystal structure
  • Magnetic susceptibility
  • Specific heat
  • Spin state transitions
  • XANES

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    Vasiliev, A. N., Vasilchikova, T. M., Volkova, O. S., Kamenev, A. A., Kaul, A. R., Kuzmova, T. G., Tsymbarenko, D. M., Lomachenko, K. A., Soldatov, A. V., Streltsov, S. V., Lin, J-Y., Kao, C. N., Chen, J. M., Abdel-Hafiez, M., Wolter, A., & Klingeler, R. (2013). Spin-state transition, magnetism and local crystal structure in Eu 1-xCaxCoO3-δ. Journal of the Physical Society of Japan, 82(4), [044714]. https://doi.org/10.7566/JPSJ.82.044714