LDA++ approach to the electronic structure of magnets: correlation effects in iron

A novel approach to the investigation of correlation effects in the electronic structure of magnetic crystals which takes into account a frequency dependence of the self-energy (the so-called 'LDA++ approach') is developed. The fluctuation-exchange approximation is generalized to the spin-polarized multi-band case and a local version of it is proposed. As an example, we calculate the electronic quasiparticle spectrum of ferromagnetic iron. It is shown that the Fermi-liquid description of the bands near the Fermi level is reasonable, while the quasiparticle states beyond approximately the 1 eV range are strongly damped, in agreement with photoemission data. The result of the spin-polarized thermoemission experiment is explained satisfactorily. The problem of satellite structure is discussed.