发表机构
Yale University; University of California, Berkeley; Lawrence Berkeley National Lab; Cornell University; University of Southern California; Boston College（耶鲁大学; 加州大学伯克利分校; 劳伦斯伯克利国家实验室; 康奈尔大学; 南加州大学; 波士顿学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过结构表征与第一性原理计算，揭示镍取代诱导的高温铁磁性源于应变稳定的Fe6GeTe2纳米析出物，为原子工程提供机理基础。
AI 中文摘要
金属性范德华（vdW）体系 Fe$_N$GeTe$_2$ 中高温铁磁性的发现，将二维（2D）磁体带入了技术相关的温度尺度。具体而言，当 N = 5 时，通过镍取代稀释磁矩，反直觉地实现了创纪录的 478 K 居里温度。由于该化合物的结构复杂性、共存巡游与局域磁贡献以及介观成分畴，揭示镍取代诱导增强的起源变得复杂。通过协调的结构与电子表征，我们确定高 T$_C$ 磁性相源于应变稳定的 Fe$_6$GeTe$_2$ 纳米析出物。结合第一性原理计算与自旋和角度分辨光电子能谱（ARPES），我们揭示了一种位点特异性电子景观，其中内部铁原子主要承载局域磁矩，而邻近碲层的外部铁原子产生自旋极化的巡游载流子，这些载流子跨越 vdW 间隙。研究发现，均匀镍取代所需的大能量成本有利于结晶学和电子学上“纯净”的高 T$_C$ 相的自发析出。最后，我们将富金属 vdW 磁体与二元磁性合金进行比较，并讨论纳米析出物在稳定原本无法获得的体相中的统一作用。我们的工作为 (Fe,Ni)$_{5+δ}$GeTe$_2$ 中创纪录的高 T$_C$ 铁磁性提供了机理见解，为基于直接电子特征的 vdW 磁性金属原子工程奠定了坚实基础。
英文摘要
The discovery of high-temperature ferromagnetism in the metallic van der Waals (vdW) system Fe$_N$GeTe$_2$ has brought two-dimensional (2D) magnets into technologically relevant temperature scales. Specifically at N = 5, dilution of magnetic moments by nickel substitution counterintuitively achieves a record high Curie temperature of 478~K. Unraveling the origin of this nickel-substitution-induced enhancement is complicated by the compound's structural complexity, coexistent itinerant and local magnetic contributions, and mesoscopic compositional domains. Through coordinated structural and electronic characterization, we identify that the high-T$_C$ magnetic phase arises from a strain-stabilized Fe$_6$GeTe$_2$ nano-precipitate. Combining first-principles calculations and spin- and angle-resolved photoemission spectroscopy (ARPES), we uncover a site-specific electronic landscape in which interior iron atoms primarily host localized moments while the outer iron atoms neighboring the tellurium layers produce spin-polarized itinerant carriers that cross the vdW gap. The large energy cost associated with homogeneous nickel substitution is found to favor the spontaneous precipitation of the crystallographically and electronically ``clean'' high-T$_C$ phase. Finally, we compare metal-rich vdW magnets with binary magnetic alloys, and discuss the unifying roles of nano-precipitates in stabilizing otherwise unattainable bulk phases. Our work provides mechanistic insights into the record-high T$_C$ ferromagnetism in (Fe,Ni)$_{5+δ}$GeTe$_2$, establishing a rigorous foundation for the atomic engineering of vdW magnetic metals informed by direct electronic signatures.
Comments16 pages, 8 figures
