Zhang Xiaoqian, Lu Qiangsheng, Shen Zhen-Xiong, Niu Wei, Liu Xiangrui, Lu Jiahua, Lin Wenting, Han Lulu, Weng Yakui, Shao Tianhao, Yan Pengfei, Ren Quan, Li Huayao, Chang Tay-Rong, Singh David J, He Lixin, He Liang, Liu Chang, Bian Guang, Miao Lin, Xu Yongbing
Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University, Nanjing, 211189, China.
Material Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
Adv Mater. 2025 Jan;37(1):e2411137. doi: 10.1002/adma.202411137. Epub 2024 Nov 5.
2D van der Waals (vdW) magnets, which extend to the monolayer (ML) limit, are rapidly gaining prominence in logic applications for low-power electronics. To improve the performance of spintronic devices, such as vdW magnetic tunnel junctions, a large effective spin polarization of valence electrons is highly desired. Despite its considerable significance, direct probe of spin polarization in these 2D magnets has not been extensively explored. Here, using 2D vdW ferromagnet of CrTe as a prototype, the spin degrees of freedom in the thin films are directly probed using Mott polarimetry. The electronic band of 50 ML CrTe thin film, spanning the Brillouin zone, exhibits pronounced spin-splitting with polarization peaking at 7.9% along the out-of-plane direction. Surprisingly, atomic-layer-dependent spin-resolved measurements show a significantly enhanced spin polarization in a 3 ML CrTe film, achieving 23.4% polarization even in the absence of an external magnetic field. The demonstrated correlation between spin polarization and film thickness highlights the pivotal influence of perpendicular magnetic anisotropy, interlayer interactions, and itinerant behavior on these properties, as corroborated by theoretical analysis. This groundbreaking experimental verification of intrinsic effective spin polarization in CrTe ultrathin films marks a significant advance in establishing 2D ferromagnetic atomic layers as a promising platform for innovative vdW-based spintronic devices.
二维范德华（vdW）磁体可延伸至单层（ML）极限，在低功耗电子学的逻辑应用中迅速崭露头角。为了提高诸如vdW磁隧道结等自旋电子器件的性能，非常需要价电子具有较大的有效自旋极化。尽管其意义重大，但对这些二维磁体中自旋极化的直接探测尚未得到广泛研究。在此，以CrTe二维vdW铁磁体为原型，使用莫特极化法直接探测薄膜中的自旋自由度。跨越布里渊区的50 ML CrTe薄膜的电子能带表现出明显的自旋分裂，沿面外方向极化峰值为7.9%。令人惊讶的是，与原子层相关的自旋分辨测量表明，在3 ML CrTe薄膜中自旋极化显著增强，即使在没有外部磁场的情况下，极化也能达到23.4%。自旋极化与薄膜厚度之间的相关性证明了垂直磁各向异性以及层间相互作用和巡游行为对这些特性的关键影响，理论分析也证实了这一点。对CrTe超薄膜中本征有效自旋极化的这一开创性实验验证标志着在将二维铁磁原子层确立为基于vdW的创新自旋电子器件的有前景平台方面取得了重大进展。
