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The layered structure of the iron based superconductors gives rise to a more or less pronounced two-dimensionality of their electronic structure, most pronounced in LaOFeAs. A consequence are distinct surface states to be expected to influence any surface sensitive experimental probe. In this work a detailed density functional analysis of the cleavage behavior and the surface electronic structure of LaOFeAs is presented. The surface states are obtained to form two-dimensional bands with their own Fermi surfaces markedly different from the bulk electronic structure.
Comment: 4 pages + supplementary information
Comment: 14 pages, 4 figures. Corrected some typos in references. Added reference to PAW+U. Increased size of Fig. 3
The electronic structure and magnetic properties of disordered Fe$_{x}$Pd$_{100-x}$ alloys $(50 < x < 85)$ are investigated in the framework of density functional theory using the full potential local orbital method (FPLO). Disorder is treated in the coherent potential approximation (CPA). Our calculations explain the experimental magnetization data. The origin of the tetragonal distortion in the Fe-Pd magnetic shape memory alloys is found to be a Jahn-Teller like effect which allows the system to reduce its band energy in a narrow composition range. Prospects for an optimization of the alloys' properties by adding third elements are discussed.
We report a density-functional study of the heteronuclear CoIr dimer adsorbed on benzene or graphene. In either case CoIr prefers an upright position above the center of a carbon hexagon with the Co atom next to it. The Ir atom stays away from the carbon ring and thus preserves its free-atom-like properties. This results in a very large magnetic anisotropy of more than 0.2 eV per dimer. So high a value should suffice for long-term data storage at the temperature of liquid nitrogen.
Comment: - 7 pages, 7 figures - the paper is intended for a special issue on the occasion of M. Faehnles 60th birthday
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