T. Yokobori, M. Okawa, K. Konishi, R. Takei, K. Katayama, S. Oozono, T. Shinmura, T. Okuda, H. Wadati, E. Sakai, K. Ono, H. Kumigashira, M. Oshima, T. Sugiyama, E. Ikenaga, N. Hamada, T. Saitoh
We report the detailed electronic structure of a hole-doped delafossite oxide CuCr_{1-x}Mg_{x}O_{2} (0 <= x <= 0.03) studied by photoemission spectroscopy (PES), soft x-ray absorption spectroscopy (XAS), and band structure calculations within the local-density approximation+U (LDA+U) scheme. Cr/Cu 3p-3d resonant PES reveals that the near-Fermi level leading structure has primarily the Cr 3d character with a finite contribution from the Cu 3d through Cu 3d-O 2p-Cr 3d hybridization, having good agreement with the band structure calculations. This indicates that a doped hole will have primarily the Cr 3d character. Cr 2p PES and L-edge XAS spectra exhibit typical Cr^{3+} features for all x whereas the Cu L-edge XAS spectra exhibited a systematic change with x, now indicating that the Cu valence is monovalent at x=0 and the holes will be doped into the Cu sites. Nevertheless, we have surprisingly observed two types of charge-transfer satellites that should be attributed to Cu^{+} (3d^{10}) and Cu^{2+} (3d^{9}) like initial states in Cu 2p-3d resonant PES spectrum of CuCrO_{2}, while Cu 2p PES spectra with no doubt shows the Cu^{+} character even for the lightly doped samples. We propose that these contradictory results can be understood by introducing not only the Cu 4s state but also finite Cu 3d, 4s-Cr 3d charge transfer via O 2p states in the ground-state electronic configuration.
View original:
http://arxiv.org/abs/1211.1829
No comments:
Post a Comment