发表机构
Thermo Fisher Scientific; University of Twente; Utrecht University（赛默飞世尔科技; 特文特大学; 乌得勒支大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
提出一种结合Dirac-Hartree-Fock截面与配体场多重态理论的方法，从近原子分辨EELS定量映射复杂氧化物中过渡金属和稀土元素的氧化态，并成功应用于多个异质结构。
AI 中文摘要
我们提出了一个理论框架，用于从复杂氧化物异质结构中的近原子分辨电子能量损失谱（EELS）定量映射过渡金属和稀土元素的氧化态。通过将松弛的Dirac-Hartree-Fock电离截面与配体场多重态理论结合用于离散跃迁，计算了过渡金属L$_{2,3}$和稀土M$_{4,5}$边的总非弹性微分截面。我们将该方法应用于两个关联氧化物异质结构：La$_{0.67}$Sr$_{0.33}$MnO$_3$/LaCr$_{0.2}$Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$O$_3$/SrTiO$_3$和NdNiO$_3$/La$_{0.67}$Sr$_{0.33}$MnO$_3$/NdGaO$_3$，这些结构包含多种具有重叠特征的过渡金属和稀土元素。该方法在近原子分辨下解析了Cr、Mn、Fe和Co的氧化态，并识别了LaCr$_{0.2}$Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$O$_3$层内的Ni贡献。我们发现主要为Co$^{2+}$，同时具有混合的Mn$^{2+}$/Mn$^{3+}$/Mn$^{4+}$特征，表明层内存在位点特异性价态再分布。我们还分离了重叠的光谱特征，如NdNiO$_3$/La$_{0.67}$Sr$_{0.33}$MnO$_3$/NdGaO$_3$异质结构中的La-M$_{4,5}$和Ni-L$_{2,3}$边，从而恢复了本征的Ni-L$_{2,3}$激发谱。我们发现NdNiO$_3$中有效Ni价态偏离简单离子图像。更广泛地，这项工作建立了一种从近原子分辨EELS进行定量价态映射的通用方法，适用于多种实验条件，用于研究复杂氧化物的局域电子结构。
英文摘要
We present a theoretical framework for quantitative oxidation state mapping of transition-metal and rare-earth elements from near-atomic-resolution electron energy-loss spectroscopy (EELS) in complex oxide heterostructures. The total inelastic differential cross section of transition-metal L$_{2,3}$ and rare-earth M$_{4,5}$ edges is calculated by combining the relaxed Dirac-Hartree-Fock ionization cross section with ligand-field multiplet theory for the discrete transitions. We apply the approach to two correlated-oxide heterostructures, La$_{0.67}$Sr$_{0.33}$MnO$_3$/LaCr$_{0.2}$Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$O$_3$/SrTiO$_3$ and NdNiO$_3$/La$_{0.67}$Sr$_{0.33}$MnO$_3$/NdGaO$_3$, which include a wide range of transition-metal and rare-earth elements with overlapping features. The method resolves the oxidation states of Cr, Mn, Fe and Co and identifies the Ni contribution within the LaCr$_{0.2}$Mn$_{0.2}$Fe$_{0.2}$Co$_{0.2}$Ni$_{0.2}$O$_3$ layer at near-atomic resolution. We find predominantly Co$^{2+}$ together with mixed Mn$^{2+}$/Mn$^{3+}$/Mn$^{4+}$ character, indicating site-specific valence redistribution within the layer. We also separate overlapping spectral features, such as La-M$_{4,5}$ and Ni-L$_{2,3}$ edges in the NdNiO$_3$/La$_{0.67}$Sr$_{0.33}$MnO$_3$/NdGaO$_3$ heterostructure, thereby recovering the intrinsic Ni-L$_{2,3}$ excitation spectrum. We find that the effective Ni valence in NdNiO$_3$ deviates from the simple ionic picture. More broadly, this work establishes a generic method for quantitative valence mapping from near-atomic-resolution EELS, applicable to a wide range of experimental conditions for the study of local electronic structure of complex oxides.
Comments14 pages, 15 figures
