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Multiple Scattering Analysis of O KEdge NEXAFS in Iron Oxides

机译:O KEdge NEXAFS在氧化铁中的多重散射分析

摘要

We report a detailed analysis of O K-edges near edge x-ray absorption of maghemite, hematite and magnetite iron oxides. Measurements were performed on powder in Fluorescence Yield mode of detection. Iron forms several stable oxides and its phase diagram is more complicated than that of other transition metal as Ni or Co. The differences in the local symmetry of the three iron oxides are related with the distinguishable NEXAFS spectra. In particular the spectra are characterized by a sharp doublet ascribable to transitions to the empty metal d-bands involving the t2g and eg states whose energy splitting and intensities depend on the structure and state of ionicity. The NEXAFS spectra have been simulated and fitted by MXAN code. The aim of these simulations was the test of light Z element NEXAFS spectra calculation performed by phenomenological no-self-consistent potential in the near edge region, the most sensible to electronic properties details; a fit procedure of the potential parameters was performed in the extended NEXAFS photon energy range and subsequently used for near edge calculations. The MXAN simulations obtained in this way, reproduce the experimental data with good agreement and evidentiate the differences in the spectra of the three compounds. In particular maghemite, that has oxygen in two different sites, has been well simulated using potential details found for the other oxides hematite and magnetite.
机译:我们报告了对磁赤铁矿,赤铁矿和磁铁矿氧化铁的边缘X射线吸收附近的O K边缘的详细分析。以荧光产率检测模式对粉末进行测量。铁形成几种稳定的氧化物,并且其相图比其他过渡金属(如Ni或Co)的相图更为复杂。这三种铁氧化物的局部对称性差异与可分辨的NEXAFS光谱有关。特别地,光谱的特征在于归因于过渡到涉及t 2g的空金属d-带的尖锐双峰,例如,其能量分裂和强度取决于离子性的结构和状态的状态。 NEXAFS光谱已通过MXAN代码进行了模拟和拟合。这些模拟的目的是测试光Z元素NEXAFS光谱的计算,该计算是通过现象学的非自洽电位在近边缘区域进行的,这对电子特性的细节最敏感。在扩展的NEXAFS光子能量范围内执行势能参数的拟合过程,然后将其用于近边缘计算。以这种方式获得的MXAN模拟,以良好的一致性再现了实验数据,并证明了这三种化合物的光谱差异。特别是,使用发现的其他氧化物赤铁矿和磁铁矿的潜在细节,可以很好地模拟在两个不同位置具有氧的磁赤铁矿。

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