Non-quasiparticle states in the core level spectra of ferromagnetic semiconductors and half-metallic ferromagnets

The Green's functions that determine x-ray spectra are calculated in the s-d exchange model of a saturated conducting ferromagnet in the presence of the core hole. A possibility to observe non-quasiparticle (NQP) states in the core level (x-ray absorption, emission and photoelectron) spectroscopy is demonstrated. It is shown that NQP contributions to resonant x-ray scattering spectra can be considerably enhanced by core hole effects in comparison with those to the density of states.Comment: 13 pages, 7 figures, final versio

Ground-state phase diagrams of the generalized Falicov-Kimball model with Hund coupling

Charge and spin orderings are studied on the simplest 1D and the 2D square lattice within the generalized Falicov-Kimball model with Hund coupling between localized and itinerant electrons. Using the restricted phase diagrams method (RPDM) a number of simple rules of formation of various sorts of ground state phases have been detected. In particular, relationships between density of current carriers (electrons or holes) and type of charge and magnetic arrangement has been determined. In 2D in the mixed valence regime only axial stripes (vertical or horizontal) have been found for intermediate values of the coupling constants. They are composed of ferromagnetic or antiferromagnetic chains interchanged with non-magnetic ones. For band fillings close to the half filling stripe phases oriented along one of the main diagonal direction are formed. The results suggest a possibility of tuning modulations of charge and magnetic superstructures with a change of doping.Comment: 10 pages, 6 figures; Fig. 2 slightly modified and the text adjusted accordingly, references adde

Examination of several density functionals in numerical Kohn-Sham calculations for atoms

Andrae D, Brodbeck R, Hinze J. Examination of several density functionals in numerical Kohn-Sham calculations for atoms. INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY. 2001;82(5):227-241.We studied several exchange-only and exchange-correlation energy density functionals in numerical, i.e., basis-set-free, nonrelativistic Kohn-Sham calculations for closed-shell IS states of atoms and atomic ions with N electrons, where 2 less than or equal to N less than or equal to 120. Accurate total energies are presented to serve as reference data for algebraic approaches, as do the numerical Hartree-Fock results, which are also provided. Gradient-corrected exchange-only functionals considerably improve the total energies obtained from the usual local density approximation, when compared to the Hartree-Fock results. Such an improvement due to gradient corrections is not seen in general for highest orbital energies, neither for exchange-only results (to be compared with Hartree-Fock results), nor for exchange-correlation results (to be compared with experimental ionization energies). (C) 2001 John Wiley & Sons, Inc