  The electronic band structures of the LaOFeP superconductor have been
calculated theoretically by the first principles method and measured
experimentally by electron energy loss spectroscopy. The calculations indicate
that the Fe atom in LaOFeP crystal shows a weak magnetic moment and does not
form a long-range magnetic ordering. Band structure, Fermi surfaces and
fluorine-doping effects are also analyzed based on the data of the density
functional theory. The fine structures of the EELS data have been carefully
examined in both the low loss energy region and the core losses region (O K, Fe
L2,3, and La M4,5). A slight bump edge at 44 eV shows notable
orientation-dependence: it can be observed in the low loss EELS spectra with q
parallel to c, but becomes almost invisible in the q vertical to c spectra.
Annealing experiments indicate that low oxygen pressure favors the appearance
of superconductivity in LaOFeP, this fact is also confirmed by the changes of
Fe L2,3 and O K excitation edges in the experimental EELS data.
