Eur. Phys. J. B 57, 257-263 (2007)
https://doi.org/10.1140/epjb/e2007-00172-9

Response of La_0.8Sr_0.2CoO_3-δ to perturbations on the CoO₃ sublattice

¹ Department of Nuclear Chemistry, Eötvös Loránd University, P.O. Box 32, Budapest, 1518, Hungary
² Department of Mathematics and Physics, University of Kaposvár, Guba Sándor u. 40., Kaposvár, 7400, Hungary
³ Research Group of Chemical Research Center Hungarian Academy of Sciences at ELTE, P.O. Box 32, Budapest, 1518, Hungary
⁴ Institute of Nuclear Research of the Hungarian Academy of Sciences, P.O. Box 51, 4001 Debrecen, Hungary
⁵ Institut für Chemische Technologie Anorganischer Stoffe, Johannes Kepler Universität, 4040 Linz, Austria
⁶ Division of Materials Chemistry, Graduate School of Engineering, Hokkaido University, Sapporo, 060-8628, Japan
⁷ Laboratoire de Physique de l'État Condensé, UMR CNRS 6087 Université du Maine, 72085 Le Mans Cedex 9, France

Corresponding author: ^a hentes@chem.elte.hu

Received: 9 January 2007
Revised: 15 May 2007
Published online: 20 June 2007

Abstract

Emission and transmission Mössbauer studies of La_0.8Sr_0.2CoO_3-δ perovskites doped with ∼0.02 stoichiometric units of oxygen vacancy or 2.5% iron corroborate the occurrence of electronic phase separation in these systems. The effect of the small perturbation of the CoO₃ sublattice with either iron ions or oxygen vacancies on the bulk magnetization as well as on the Mössbauer spectra is in good agreement with the double exchange based cluster model. The magnetoresistance does not show any peak near the Curie temperature, but reaches -84% in a field of 7.5 T at T = 8 K. Below T_C ≈ 180 K the Mössbauer spectra distinctly include the contribution from paramagnetic and ferromagnetic regions, providing direct evidence for phase separation. No contribution to the spectra from Fe⁴⁺ ions can be observed, which is an unambiguous evidence that at low concentration iron (either directly doped or formed from ⁵⁷Co by nuclear decay) is accommodated in the cobaltate lattice as Fe³⁺ ion.