AI 中文总结
研究以Cr2AlC MAX相为光响应磁性候选平台，结合超导量子干涉装置磁力测量、电子自旋共振及第一性原理计算等方法，确定其磁贡献层次结构，找出局部光学敏感性微观起源，为设计MAX相及相关MXene提供参考。
AI 中文摘要
通过高压固态退火合成了Cr2AlC MAX相，并将其作为光响应磁性的候选平台进行研究。结构表征证实了Cr2AlC相的形成，通过超导量子干涉装置（SQUID）磁力测量、电子自旋共振（ESR）和第一性原理计算研究了其磁性和光磁性质。SQUID磁力测量确定Cr2AlC为弱场线性金属顺磁体，其非单调温度依赖性由反铁磁耦合的Cr-Cr二聚体的额外贡献描述，低温居里样上升源于仅微量的局域Cr中心。红光照射下，SQUID磁力测量未揭示内在宏观光磁响应，而4K下的ESR显示局部磁信号的可逆光诱导降低，光学修饰的自旋种群仅对应Cr亚晶格的几十ppm。从头算Bethe-Salpeter方程（ai-BSE）计算与最大局域化Wannier函数分析表明，光激发可在具有相反局部磁矩的相邻Cr位点之间重新分配自旋极化。实验与理论相结合的方法确定了Cr2AlC中磁贡献的层次结构，并确定了其局部光学敏感性的微观起源。这为设计MAX相和相关MXene提供了参考，其中缺陷、表面终止或降低的维度可能增强光学活性磁态。
英文摘要
Cr2AlC MAX phase is synthesized by high-pressure solid-state annealing and investigated as a candidate platform for optically responsive magnetism. Structural characterization confirms the formation of the Cr2AlC phase, while magnetic and optical-magnetic properties are examined by superconducting quantum interference device (SQUID) magnetometry, electron spin resonance (ESR), and first principles calculations. SQUID magnetometry identifies Cr 2AlC as a weak, field-linear metallic paramagnet dominated by Pauli-like susceptibility of itinerant Cr-derived states. Its non-monotonic temperature dependence is described by an additional contribution from antiferromagnetically coupled Cr-Cr dimers, whereas the low-temperature Curie-like upturn originates from only a trace population of localized Cr centers. Under red-light illumination, SQUID magnetometry does not reveal an intrinsic macroscopic optomagnetic response. In contrast, ESR at 4 K shows a reversible light-induced reduction of a local magnetic signal, but the optically modified spin population corresponds only to several tens of ppm of the Cr sublattice. Ab initio Bethe-Salpeter equation (ai-BSE) calculations combined with the maximally localized Wannier function analysis suggest that optical excitation can redistribute spin polarization between neighboring Cr sites with the opposite local moments. The combined experiment-theory approach therefore establishes the hierarchy of magnetic contributions in Cr 2AlC and identifies the microscopic origin of its local optical sensitivity. This provides a reference for designing MAX phases and related MXenes in which defects, surface terminations or reduced dimensionality may enhance optically active magnetic states.
Comments19 pages, 7 figures and supplementary information
