Anisotropic Fe K-edge and As K-edge X-ray absorption near edge spectrum (XANES) measurements on superconducting (T_c = 52 K) (Sm_{0.95}La_{0.05})FeAs(O_{0.85}F_{0.15}) field-aligned microcrystalline powder are presented. The angular dependence of Fe pre-edge peak (dipole transition of Fe-1s electrons to Fe-3d/As-4p hybrid bands) relative to the tetragonal ab-plane of aligned powder indicates larger density of state (DOS) along the c-axis, and is consistent with the LDA band structure calculation. The anisotropic Fe K-edge spectra exhibit a chemical shift to lower energy compared to FeO which are closely related to the itinerant character of Fe^{2+}-3d^6 orbitals. The anisotropic As K-edge spectra are more or less the mirror images of Fe K-edge due to the symmetrical Fe-As hybridiztion in the FeAs layer. Angular dependence of As main peak (dipole transition of As-1s electrons to higher energy hybrid bands) was observed suggesting character of As-4d e_g orbitals.
@article{arxiv.0909.3904,
title = {Angular Dependence of X-ray Absorption Spectrum for Field-aligned Fe-based Superconductors},
author = {B. C. Chang and Y. B. You and T. J. Shiu and M. F. Tai and H. C. Ku and Y. Y. Hsu and L. Y. Jang and J. F. Lee and Z. Wei and K. Q. Ruan and X. G. Li},
journal= {arXiv preprint arXiv:0909.3904},
year = {2009}
}
Comments
4 pages, 6 figures, accepted 9/11/2009 Physical Review B (B15)