  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 minor 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, while the Cu L-edge XAS spectra exhibited a systematic change with
x. This indicates now that the Cu valence is monovalent at x=0 and the doped
hole should have Cu 3d character. Nevertheless, we 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 for at x=0, 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 no 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.
