The electronic properties of Co in bulk Na0.7 Co O2 and the superconducting hydrated compound Na0.35 Co O2 y H2 O have been investigated by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS) using hard x rays. The XAS spectra at the Co K -edge were measured in both compounds with two different polarization directions. The changes in the XAS spectra upon hydration and their polarization dependence are well accounted for by linear muffin-tin orbital calculations in the local density approximation. The underlying electronic structure indicates the strong hybridization between the Co 3d and O 2p states in both compounds, while the electron localization is enhanced in the hydrated compound due to the increase of the Co-Co interplanar distance. The Co K preedge further highlights the splitting of the d band as a result of the crystal field effect and demonstrates the Co valency increase when Na0.7 Co O2 is hydrated. The RIXS spectra measured at the Co K edge show an energy loss feature around 10 eV in both compounds, in fair agreement with the calculated dynamical structure factor. The RIXS feature is associated to a damped plasmon excitation.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2006|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics