  LaFe3/4Ni1/4O3 was subjected to oxygen near edge x-ray absorption fine
structure (NEXAFS) spectroscopy for 300 K < T < 773 K. The spectra show in the
pre-edge a small hole doped peak originating from Ni substitution. The relative
spectral weight of this transition to the weight of the hybridized O(2p) -
Fe(3d) transitions scales with T and has a maximum at around 600 K. The
characteristic energies of the thermal activated spectral intensity and
conductivity suggest that the concentration of charge transferred electrons
from O(2p) to Ni(3d) increases and that the pre-edges account in part for the
polaron activated transport.
