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2 results on '"XLD"'

1. Observation of the Onset of Magnetic Clustering in Superparamagnetic Zn1− xCo xO Films.

Author

Ye, S., Ney, V., Kammermeier, T., Ollefs, K., Ney, A., Wilhelm, F., and Rogalev, A.

Subjects
*MAGNETIC properties of thin films, *MAGNETRON sputtering, *X-ray diffraction, *HYSTERESIS loop, *PARAMAGNETISM
Abstract

A series of high quality Zn1− xCo xO thin films were obtained by UHV-magnetron reactive sputtering. Detailed X-ray diffraction, X-ray absorption near edge spectra, and X-ray linear dichroism measurements were used for analyzing the long- and short-range crystalline structure, respectively. These techniques reveal excellent crystalline ordering on both scales for films with oxygen-rich conditions and indicate that Co2+ ions are located on substitutional Zn sites without detectable phase separation. Interestingly, decreasing the structural quality of such Zn1− xCo xO films leads to altered magnetic properties as measured by SQUID magnetometry, ranging from paramagnetism to the emergence of magnetic clustering exhibited by superparamagnetism. In some cases, a small shift of the hysteresis loop is visible after field cooling indicating weak exchange bias typical for the AFM/FM (CoO/Co) system. In the light of detailed structural investigations, the transition regime from paramagnetic to superparamagnetic behavior is discussed. [ABSTRACT FROM AUTHOR]

Published
2010
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2. Localized and Dispersive Electronic States at Ordered FePc and CoPc Chains on Au(110)

Author

Riccardo Frisenda, Roberto Biagi, Maria Grazia Betti, Luca Floreano, Pierluigi Gargiani, Alberto Verdini, Albano Cossaro, and Carlo Mariani

Subjects
phthalocyanine, iron, cobalt, gold, Fe, Co, Au(110), NEXAFS, XLD, Fermi level, chemistry.chemical_element, XANES, Surfaces, Coatings and Films, Electronic, Optical and Magnetic Materials, Metal, symbols.namesake, Crystallography, General Energy, chemistry, Atomic orbital, visual_art, symbols, visual_art.visual_art_medium, Molecule, Physical and Theoretical Chemistry, Absorption (chemistry), Spin (physics), Cobalt
Abstract

Iron and cobalt phthalocyanines assemble on the Au(110) surface lying parallel to the surface, as deduced by near-edge X-ray absorption fine structure (NEXAFS) taken with linearly polarized radiation at the C and N K edges. The molecular chains, firmly anchored to the underlying metal surface, arrange into long-range ordered rows with a (5 × 3) symmetry along the [001] azimuthal direction at completion of the first single layer. The interaction process is mainly determined by the d orbitals associated with the central Fe and Co atoms, as observed by valence band photoemission and NEXAFS at the Fe and Co L2,3 edges. The spin and orbital configuration of the FePc and CoPc molecules is strongly influenced by the interface with a charge transfer from the underlying metal to the out-of-plane empty states located at the Fe and Co centers of the molecules. This interaction process induces electronic states located at the interface, localized on the central metal atoms and close to the Fermi level (0.2 eV binding energy for FePc and 0.7 eV for CoPc) without energy dispersion, as deduced by angular-resolved photoemission. On the contrary, a delocalized state has been observed with dispersion along the molecular chains, mainly due to the overlapping of the ? charge of the macrocycles ligands mediated by the Au substrate.

Published
2010
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