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The electronic structure of Cu-doped ZnO thin films, synthesized with a nominal composition of Zn1-xCuxO (x=0.03, 0.05, 0.07, and 0.10) by using spray pyrolysis method, has been investigated using near-edge x-ray absorption fine structure (NEXAFS) experiments at the O K- and the Cu L3,2-edges and resonant inelastic x-ray scattering (RIXS) measurements at Cu L3,2 edge. The Zn1-xCuxO thin films showed single phase wurtzite-hexagonal like crystal structure and ferromagnetic behavior at room temperature (RT). The intensity of the pre-edge spectral feature at the O K-edge increases with the Cu concentration, which clearly reveals that there is strong hybridization of O 2p–Cu 3d orbitals in the ZnO matrix. Spectral features of the Cu L3,2-edge NEXAFS exhibit multiple absorption peaks and appreciable x-ray magnetic circular dichroism signal that persists even at RT. These results demonstrate that Cu is in mixed valence state of Cu2+,3+/Cu1+, substituting at the Zn site and Cu2+/3+ ions are magnetically polarized. RIXS experiments at Cu L3 edge show strong d-d excitations due to localized nature of Cu ions in the ZnO matrix. [ABSTRACT FROM AUTHOR]

The magnetic screening of localized excitations in Ni and Fe ferromagnetic metal hosts has been investigated by magnetic circular dichroism of inelastic x-ray resonant scattering in perpendicular geometry at the Ni L2,3 absorption region. The method probes the spin-dependent screening by the electron population initially in thermodynamic equilibrium. A screening time constant of 1.5 fs in Ni metal has been reported in literature. Here an upper limit of 150 as is set for the screening time constant in Fe metal by measuring the scattering from Ni impurities in dilute Fe metal. The present time scale is among the shortest experimentally investigated in magnetic phenomena. [ABSTRACT FROM AUTHOR]

Bulk NdNiO3 and thin films grown along the pseudocubic (001)pc axis display a 1st order metal to insulator transition (MIT) together with a Néel transition at T = 200 K. Here, we show that for NdNiO3 films deposited on (111)pc NdGaO3, the MIT occurs at T = 335 K and the Néel transition at T = 230 K. By comparing transport and magnetic properties of layers grown on substrates with different symmetries and lattice parameters, we demonstrate a particularly large tuning when the epitaxy is realized on (111)pc surfaces. We attribute this effect to the specific lattice matching conditions imposed along this direction when using orthorhombic substrates. [ABSTRACT FROM AUTHOR]

Nickelates are known for their metal to insulator transition (MIT) and an unusual magnetic ordering, occurring at T = TNéel. Here, we investigate thin films of SmNiO3 subjected to different levels of epitaxial strain. We find that the original bulk behavior (TNéel < TMI) is strongly affected by applying compressive strain to the films. For small compressive strains, a regime where TNéel = TMI is achieved, the paramagnetic insulating phase characteristic of the bulk compound is suppressed and the MIT becomes 1st order. Further increasing the in-plane compression of the SmNiO3 lattice leads to the stabilization of a single metallic paramagnetic phase. [ABSTRACT FROM AUTHOR]

We present the optical design of the Centurion soft X-ray resonant inelastic X-ray scattering (RIXS) spectrometer to be located on the SIX beamline at NSLS-II. The spectrometer is designed to reach a resolving power of 100 000 at 1000 eV at its best resolution. It is also designed to have continuously variable 2θ motion over a range of 112° using a custom triple rotating flange. We have analyzed several possible spectrometer designs capable of reaching the target resolution. After careful analysis, we have adopted a Hettrick-Underwood spectrometer design, with an additional plane mirror to maintain a fixed direction for the outgoing beam. The spectrometer can cancel defocus and coma aberrations at all energies, has an erect focal plane, and minimizes mechanical motions of the detector. When the beamline resolution is accounted for, the net spectral resolution will be 14 meV at 1000 eV. This will open up many low energy excitations to study and will expand greatly the power of soft X-ray RIXS.