Electronic structure of lanthanum transition-metal oxyarsenides LaMAsO (M = Fe, Co, Ni) and LaFe_1−xM′_xAsO (M′ = Co, Ni) by X-ray photoelectron and absorption spectroscopy

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• 作者：Peter E.R. Blanchard ; Brianna R. Slater ; Ronald G. Cavell ; Arthur Mar ; Andrew P. Grosvenor
• 关键词：Oxyarsenides ; XPS ; XANES ; Charge transfer
• 刊名：Solid State Sciences
• 出版年：2010
• 出版时间：January 2010
• 年：2010
• 卷：12
• 期：1
• 页码：50-58
• 全文大小：1138 K

文摘

The electronic structures of the quaternary oxyarsenides LaMAsO (M = Fe, Co, Ni) were examined with X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES). Interpretation of the metal 2p_3/2 and arsenic 3d_5/2 binding energies, as well as a satellite feature in the Co 2p XPS spectrum, suggests charges that are much less extreme than expected (i.e., not M²⁺ and As³⁻) because of the strong covalent character within the M–As bonds. As M is varied, the differing degrees of charge transfer from M to As atoms within these bonds are manifested by shifts in the As 3d_5/2 binding energies and changes in the As K-edge intensities. This charge transfer is isolated within the [MAs] layer and does not influence the O 1s and La 3d XPS spectra. Fitting the experimental valence band spectra of these oxyarsenides LaMAsO yielded electron populations of states that support the formal charge assignment [La³⁺O²⁻][M²⁺As³⁻]. The mixed-metal series LaFe_1−xM′_xAsO (M′ = Co, Ni) was examined by XANES; analysis of the metal K- and L-edges, as well as of the Co 2p XPS satellite feature, revealed that no metal–metal charge transfer takes place.