Valence changes associated with the metal-insulator transition in Bi1-xLaxNiO3

H. Wadati, M. Takizawa, T. T. Tran, K. Tanaka, T. Mizokawa, A. Fujimori, A. Chikamatsu, H. Kumigashira, M. Oshima, S. Ishiwata, M. Azuma, M. Takano

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26 Citations (Scopus)


Perovskite-type BiNiO3 is an insulating antiferromagnet in which a charge disproportionation occurs at the Bi site. La substitution for Bi suppresses the charge disproportionation and makes the system metallic. We have measured the photoemission and x-ray-absorption (XAS) spectra of Bi1-xLaxNiO3 to investigate how the electronic structure changes with La doping. From Ni 2p XAS, we observed an increase of the valence of Ni from 2+ toward 3+. Combined with the core-level photoemission study, it was found that the average valence of Bi remains ∼4+ and that the Ni valence behaves as ∼(2+x)+, that is, La substitution results in a hole doping at the Ni sites. In the valence-band photoemission spectra, we observed a Fermi cutoff for x>0, consistent with the metallic behavior of the La-doped compounds. The Ni 2p XAS, Ni 2p core-level photoemission, and valence-band photoemission spectra were analyzed by configuration-interaction cluster-model calculation, and the spectral line shapes were found to be consistent with the gradual Ni2+→Ni3+ valence change.

Original languageEnglish
Article number155103
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number15
Publication statusPublished - 2005 Oct 15


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