Local orbital occupation and energy levels of Co in NaxCoO 2: A soft x-ray absorption study
Journal
Physical Review B - Condensed Matter and Materials Physics
Journal Volume
81
Journal Issue
11
Date Issued
2010
Author(s)
Lin, H. J.
Chin, Y. Y.
Hu, Z.
Shu, G. J.
Ohta, H.
Yoshimura, K.
Hébert, S.
Maignan, A.
Tanaka, A.
Tjeng, L. H.
Chen, C. T.
Abstract
We present a combined experimental and theoretical investigation on the orbital occupation and local symmetry of Co in NaxCoO2. We have carried out polarization dependent Co- L2,3 soft x-ray absorption spectroscopy measurements. By comparing the spectra with the results of configuration-interaction cluster calculations which include the full-atomic multiplet theory, we have found that the local symmetry for the Co ions are well-described by the D3d point group with intermixing between the cubic t 2g ± and eg± orbitals. We have determined that the t2g holes in both the Na0.75CoO2 and Na0.5CoO2 compositions reside mainly in the a1g orbital. The spectroscopically deduced Co+4/Co+3 ratio agrees well with the nominal Na concentration. We discuss the surprising observation that the single-site cluster approach is still adequate to reproduce the spectra despite the mixed valent character of the Co ions in this compound. © 2010 The American Physical Society.
SDGs
Type
journal article