Electronic state of Fe-57 used as Mossbauer probe in the perovskites LaMO3 (M = Ni and Cu)статья
Информация о цитировании статьи получена из
Web of Science,
Scopus
Статья опубликована в журнале из списка Web of Science и/или Scopus
Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:For the first time a comparative study of rhombohedral LaNiO3 and LaCuO3 oxides, using Fe-57 Mossbauer probe spectroscopy (1% atomic rate), has been carried out. In spite of the fact that both oxides are characterized by similar crystal structure and metallic properties, the behavior of Fe-57 probe atoms in such lattices appears essentially different. In the case of LaNi0.99Fe0.01O3, the observed isomer shift (delta) value corresponds to Fe3+ (3d(5)) cations in high-spin state located in an oxygen octahedral surrounding. In contrast, for the LaCu0.99Fe0.01O3, the obtained d value is comparable to that characterizing the formally tetravalent high-spin Fe4+(3d(4)) cations in octahedral coordination within Fe(IV) perovskite-like ferrates. To explain such a difference, an approach based on the qualitative energy diagrams analysis and the calculations within the cluster configuration interaction method have been developed. It was shown that in the case of LaNi0.99Fe0.01O3, electronic state of nickel is dominated by the d 7 configuration corresponding to the formal ionic "Ni3+ - O2-'' state. On the other hand, in the case of LaCu0.99Fe0.01O3 a large amount of charge is transferred via Cu-O bonds from the O:2p bands to the Cu:3d orbitals and the ground state is dominated by the d(9)(L) under bar configuration ("Cu2+-O'' state). The dominant d(9)(L) under bar ground state for the (CuO6) sublattice induces in the environment of the Fe-57 probe cations a charge transfer Fe3+ + O-(L) -> Fe4+ + O2-, which transforms "Fe3+'' into "Fe4+" state. The analysis of the isomer shift value for the formally "Fe4+'' ions in perovskite-like oxides clearly proved a drastic influence of the 4s iron orbitals population on the Fe - O bonds character. (C) 2007 Elsevier Inc. All rights reserved.