揭示DyFeO$_3$的电子结构和氧$K$边X射线吸收近边结构谱

中文摘要 AI 辅助

稀土正铁氧体如DyFeO$_3$表现出局域稀土与过渡金属矩之间丰富的相互作用，从而产生复杂的磁相和磁电现象。从第一性原理理解其电子和光谱性质，需要准确描述局域Fe-$3d$和Dy-$4f$态及其与O-$2p$态的杂化。在此，我们结合第一性原理计算和X射线吸收近边结构（XANES）测量，研究DyFeO$_3$的电子结构和O $K$边谱。我们采用密度泛函理论（DFT）加Hubbard $U$修正（DFT+$U$），其中$U$通过密度泛函微扰理论从第一性原理确定，还使用HSE06杂化泛函，以及轨道分辨的DFT+$U$，其Hubbard参数经过校准以重现HSE06计算的电子结构。我们发现，标准DFT+$U$尽管改善了带隙，但显著低估了未占据Fe-$3d$态的晶体场劈裂，因此未能准确重现O $K$边谱中两个最低能量特征的分离。HSE06提供了相关电子态（包括Fe-$3d$晶体场劈裂）更平衡的描述。将相应电子结构映射到轨道分辨的DFT+$U$上，所得谱显著重现了实验的两个最低能量特征，并捕捉了更高能量下谱的主要特征。这些结果确立了低能O $K$边特征作为Fe-$3d$晶体场劈裂的灵敏探针，同时表明局域Dy-$4f$态尽管对磁性重要，但未留下明显的谱指纹。

英文摘要

Rare-earth orthoferrites such as DyFeO$_3$ exhibit a rich interplay between localized rare-earth and transition-metal moments, giving rise to complex magnetic phases and magnetoelectric phenomena. Understanding their electronic and spectroscopic properties from first principles requires an accurate description of the localized Fe-$3d$ and Dy-$4f$ states and their hybridization with O-$2p$ states. Here, we combine first-principles calculations and x-ray absorption near-edge structure (XANES) measurements to investigate the electronic structure and the O $K$-edge spectrum of DyFeO$_3$. We employ density-functional theory (DFT) with Hubbard $U$ corrections (DFT+$U$) determined from first principles using density-functional perturbation theory, the HSE06 hybrid functional, and orbital-resolved DFT+$U$ with Hubbard parameters calibrated to reproduce the electronic structure computed using HSE06. We find that standard DFT+$U$, despite improving the band gap, substantially underestimates the crystal-field splitting of the unoccupied Fe-$3d$ states and consequently fails to accurately reproduce the separation of the two lowest-energy features in the O $K$-edge spectrum. HSE06 provides a more balanced description of the relevant electronic states, including the Fe-$3d$ crystal-field splitting. Mapping the corresponding electronic structure onto orbital-resolved DFT+$U$ yields a spectrum that remarkably reproduces the two lowest-energy experimental features and captures the main characteristics of the spectrum at higher energies. These results establish the low-energy O $K$-edge features as a sensitive probe of the Fe-$3d$ crystal-field splitting, while showing that the localized Dy-$4f$ states leave no distinct spectral fingerprints despite their importance for the magnetic properties.

发表机构

• University of Ghana（加纳大学）
• University of Bremen（不来梅大学）
• SISSA, Scuola Internazionale Superiore di Studi Avanzati（国际高等研究院）
• UCLouvain, Institute of Condensed Matter and Nanosciences (IMCN)（瓦隆天主教大学凝聚态与纳米科学研究所）
• Paul Scherrer Institute（保罗谢勒研究所）

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