  Electronic structures of very dilute Cr- or Ru-doped Nd_{1/2}A_{1/2}MnO_{3}
(NAMO; A=Ca, Sr) manganites have been investigated using the Mn and Cr 2p -> 3d
resonant photoemission spectroscopy (PES). All the Cr- and Ru-doped NAMO
systems exhibit the clear metallic Fermi edges in the Mn e_g spectra near E_F,
consistent with their metallic ground states. The Cr 3d states with t^3_{2g}
configuration are at ~ 1.3 eV below E_F, and the Cr e_{g} states do not
participate in the formation of the band near E_F. Cr- and Ru-induced
ferromagnetism and insulator-to-metal transitions can be understood with their
measured electronic structures.
