CALCULATION OF OPTICAL-PROPERTIES AND SELF-ENERGY SHIFTS FOR FERROMAGNETIC NI, CO AND FE

The diagonal and off-diagonal elements of the optical conductivity ten sors of ferromagnetic Ni, Co and Fe have been calculated using the dir ect interband transition model from the self-consistent spin-polarized band structures. At low photon energies (< 3 eV), most of the interba nd transitions making peaks in both the diagonal and off-diagonal elem ents involve the localized 3d character in the minority-spin bands wit h the majority-spin bands only contributing structureless backgrounds. At higher photon energies, both the majority- and minority-spin bands construct separate peaks with the minority-spin peak being located at higher energies. The energy differences between the two peaks for Ni, Co and Fe are 0.3 eV, 0.8 eV and 1.5 eV respectively, which agree wel l with the spin-exchange splittings determined from angle-resolved pho toemission measurements. For Ni and Co significant differences have be en found in energy positions of the interband peaks between the calcul ated and experimental spectra. An empirical self-energy correction mod el has been applied, in which the sizes of the energy shifts of the ex cited-state quasiparticle states from those of the ground state are pr oportional-to die density of d character in each state and the energy difference between each state and the Fermi level. The self-energy-cor rected spectra for Ni and Co have been brought into good agreement wit h the experimental spectra.