Mixed valence states of Cr and Fe in La_1−xSr_xFe_0.8Cr_0.2O_3−y

M. D. Carvalho (1) , T. Ramos (1) , L. P. Ferreira (2, 3) , Alain Wattiaux (4)

1 Departemento de Quimica e Bioquimica
2 CFMC
3 Departm. Física
4 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

The La_1−xSr_xFe_0.8Cr_0.2O_3−y (x = 0.2, 0.4, 0.6 and 0.8) phases were studied by X-ray photoelectron spectroscopy at room temperature and ⁵⁷Fe Mössbauer spectroscopy at different temperatures. Mixed valence states were observed both for chromium and iron ions, justifying the complex magnetic behaviour exhibited by these compounds. The Mössbauer results indicate the simultaneous presence of Fe³⁺, Fe⁴⁺ and Fe⁵⁺ at 4.2 K and the co-existence of Fe³⁺ and Fe⁽³⁺ⁿ⁾⁺ at T = 293 K, with the latter fraction increasing with increasing strontium content. The presence of Cr^3+/4+ is interpreted as being mainly responsible for the incomplete charge disproportionation reaction of iron at low temperature, as deduced from the Mössbauer results.

Mots clés: Mössbauer spectroscopy; X-ray photoelectron spectroscopy; Disproportionation reaction; Perovskite oxides

Domaines: Matériaux

M. D. Carvalho, T. Ramos, L. P. Ferreira, Alain Wattiaux. Mixed valence states of Cr and Fe in La_1−xSr_xFe_0.8Cr_0.2O_3−y. Solid State Sciences, 2010, 12 (4), pp.476-481. ⟨10.1016/j.solidstatesciences.2009.12.011⟩. ⟨hal-00470661⟩