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In this paper, using first-principles calculations based on density-functional theory, the electronic structures, magnetic properties, and half-metallicity in the bulk and (001) surface of quaternary Heusler alloy CoNbMnSi are studied. For the bulk, the CoNbMnSi compound shows half-metallicity with a band gap of 0.5 eV in the down-spin direction at a equilibrium lattice constant of 5.88 Ǻ. At a similar equilibrium lattice constant, the half-metallicity confirmed in the bulk CoNbMnSi, is ruined at both NbSi- and MnCo-terminated (001) surfaces and subsurfaces. Based on the magnetic property calculations, the magnetic moments of Mn and Nb atoms at the (001) surfaces increase with respect to the corresponding bulk values, while the magnetic moment of Co and Si atoms decreases. The spin-polarization ratio clearly decreases below 75% for (001) surfaces and subsurfaces of the CoNbMnSi alloy. [ABSTRACT FROM AUTHOR]

A novel design of high-voltage compatible polarimeter for spin-resolved hard X-ray photoelectron spectroscopy (Spin-HAXPES) went into operation at beamline BL09XU of SPring-8 in Hyogo, Japan. The detector is based on the well-established principle of electron diffraction from a W(001) single-crystal at a scattering energy of 103.5 eV. It's special feature is that it can be operated at a high negative bias potential up to 10 kV, necessary to access the HAXPES range. The polarimeter is operated behind a large hemispherical analyzer (Scienta R-4000). It was optimized for high transmission of the transfer optics. A delay-line detector (20 mm dia.) is positioned at the exit plane of the analyzer enabling conventional multichannel intensity spectroscopy simultaneously with single-channel spin analysis. The performance of the combined setup is demonstrated by the spin-resolved data for the valence-region of a FeCo functional layer of a tunneling device, buried beneath 3 nm of oxidic material. The well-structured spin polarization spectrum validates Spin-HAXPES in the valence energy range as powerful method for bulk electronic structure analysis. The spin polarization spectrum exhibits a rich structure, originating from clearly discernible transitions in the majority and minority partial spin spectra. [ABSTRACT FROM AUTHOR]

Abstract: The spin- and angle-resolved photoelectron spectroscopy from ultrathin Cr films on Fe(110) is investigated by means of first-principles electronic structure and photoemission calculations. The antiferromagnetic ordering in the Cr films leads in dependence on film thickness to a rapidly decreasing and oscillating photoelectron spin polarization, in reasonable agreement with recent experiments (Dedkov (2007) ). The oscillation period is explained by quantum-well states in the Cr film and by a Fermi surface nesting vector. The importance of transition matrix elements is highlighted. The findings point to a noncollinear magnetic structure at the Fe/Cr interface. [ABSTRACT FROM AUTHOR]

Abstract: We synthesize Cr x Ti1−x Se2 (x =0–0.83) and Cr x Ti1−x S2 (x =0.3–0.4) systems and study the structure of these materials on mono- and polycrystalline samples. It appeared that an increase in chromium content leads to inversion of titanium diselenide intercalated with chromium to chromium diselenide intercalated with titanium. The XPS of core levels and valence bands of 1T-Cr x Ti1−x Se2 and Cr x Ti1−x S2 was also investigated and it was shown that in in-layer and inter-layer positions the atoms of chromium and titanium are characterized by a slightly differing oxidation state. Chromium LDOS model calculations were carried out and the results being in agreement with the experimental data show that the Cr 3d density of electronic states of chromium in Ti-positions in the host lattice displays half-metallic properties, while the Cr 3d density of electronic states of intercalated chromium is far from being half-metallic. [ABSTRACT FROM AUTHOR]

Abstract: Soft X-ray spectroscopy plays an important role for understanding the electronic structure of correlated electron materials. We review two examples of soft X-ray spectroscopic investigation on electron correlations and orbital symmetry in transition-metal oxides. The measurements show the existence of Coulomb correlations in CrO2 and the Mott–Hubbard character of 3d electrons. We conclude that CrO2 has a dualistic electronic nature, in which the states at the Fermi level are bandlike and while those at higher energies are strongly localized of completely different origin and symmetry. In addition, we demonstrate that linear dichroism in Mn 2p X-ray absorption is a powerful method to test the validity of models for orbital ordering in transition-metal oxides. Our linear dichroism measurements indicate that orbital ordering of the Mn electrons in La0.5Sr1.5MnO4 is dominated by type of ordering. [Copyright &y& Elsevier]

• We report on the growth and characterization of Fe/Co bilayers on bcc W(110). • The bottom Co layer relaxes to its bulk hcp structure showing an hexagonal surface. • Even with the Co layer, we detect Fe relaxation with the formation of bcc nuclei. • We measure a not nil in-plane spectral spin polarization at magnetic remanence. We report on the growth of a Fe/Co bilayer on W(110) and its electronic and magnetic structure characterization by means of low energy electron diffraction and spin-resolved photoemission spectroscopies. The Co bottom layer, investigated in the thickness range from 2 to 10 monolayers (ML), relaxes immediately to its bulk hcp structure and is therefore used to provide an hexagonal top surface for the growth of metastable Fe films. Notwithstanding the presence of the Co layer, and similar to our previous findings concerning the growth of Fe on a Ni layer [Phys Rev B 94 195155], we report the formation of bcc nuclei, indicative of lattice relaxation, even for a Fe thicknesses as low as 2 ML. For all the Fe/Co thickness combinations and at magnetic remanence, we were able to measure a not nil in-plane spectral spin polarization. [ABSTRACT FROM AUTHOR]