https://doi.org/10.1140/epjb/e2007-00172-9
Response of La0.8Sr0.2CoO3-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
Emission and transmission Mössbauer studies of La0.8Sr0.2CoO3-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 TC ≈ 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.
PACS: 75.47.Gk – Colossal magnetoresistance / 75.30.Kz – Magnetic phase boundaries / 75.10.Nr – Spin-glass and other random models / 71.30.+h – Metal-insulator transitions and other electronic transitions / 76.80.+y – Mossbauer effect; other gamma-ray spectroscopy
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2007