Effects of rare-earth substitution in the oxyarsenides REFeAsO (RE=Ce, Pr, Nd, Sm, Gd) and CeNiAsO by X-ray photoelectron and absorption spectroscopy
✍ Scribed by Peter E.R. Blanchard; Ronald G. Cavell; Arthur Mar
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 892 KB
- Volume
- 183
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES) have been applied to examine the electronic structure of the rare-earth transition-metal oxyarsenides REFeAsO (RE ¼ Ce, Pr, Nd, Sm, Gd) and CeNiAsO. Within the metal-arsenic layer [MAs], the bonding character is predominantly covalent and the As atoms are anionic, as implied by the small energy shifts in the M 2p and As 3d XPS spectra. Within the rare-earth-oxygen layer [REO], the bonding character is predominantly ionic, as implied by the similarity of the O 1s binding energies to those in highly ionic oxides. Substitution with a smaller RE element increases the O 1s binding energy, a result of an enhanced Madelung potential. The Ce 3d XPS and Ce L 3 -edge XANES spectra have lineshapes and energies that confirm the presence of trivalent cerium in CeFeAsO and CeNiAsO. A population analysis of the valence band spectrum of CeNiAsO supports the formal charge assignment [Ce 3 + O 2 À ][Ni 2 + As 3 À ].