Chen Qian, Sun Junwen, Liang Jian, Jiang Wei, Yu Zhipeng, Huang Zhaocong, Zeng Zhongming, Zhai Ya, Xia Ke, Wang Xiangrong
Key Laboratory of Quantum Materials and Devices of Ministry of Education, School of Physics, Southeast University, Nanjing, 211189, China.
School of Science and Engineering, Chinese University of Hong Kong, Shenzhen, Shenzhen, 518172, China.
Adv Sci (Weinh). 2025 Sep 12:e08244. doi: 10.1002/advs.202508244.
Interfaces can significantly influence the physical properties of systems, especially in 2D van der Waals (vdW) magnets, where atomically sharp interfaces (ASI) are intrinsic. However, the role of the ASI fields on magnetoresistance (MR) in vdW magnetic layers has largely been overlooked. Here, we investigate the angular dependence of MR in stacked ferromagnetic FeGeTe (FGT). Remarkably, the MR exhibits similar universal behaviors associated with unusual anisotropic magnetoresistance (UAMR), which has been widely observed in almost all magnet/non-magnet bilayers at the nanometer scale, featuring distinct characteristics. Unlike the exponential decay of UAMR with thickness in nanometer-thick bilayers, the UAMR of stacked FGT layers remains insensitive to thickness. The MR in the film plane displays dominant two-fold oscillation, while high-order oscillations of MR exceeding 1.4% are observed in the planes perpendicular to the film, nearly an order of magnitude larger than in-plane anisotropic MR. The UAMR of the FGT films cannot be explained by the well-known spin Hall MR theory based on spin/orbital current and charge current interconversion. Instead, it aligns with the predictions of the two-vector MR theory, particularly its sum-rule constraints. The results provide direct experimental evidence that the ASI field, rather than spin/charge current interconversion, governs the UAMR in vdW ferromagnets.
界面能够显著影响系统的物理性质，尤其是在二维范德华（vdW）磁体中，原子级尖锐界面（ASI）是其固有特性。然而，ASI场在vdW磁性层中对磁电阻（MR）的作用在很大程度上被忽视了。在此，我们研究了堆叠铁磁体FeGeTe（FGT）中MR的角度依赖性。值得注意的是，MR表现出与异常各向异性磁电阻（UAMR）相关的类似普遍行为，这种行为在几乎所有纳米尺度的磁体/非磁体双层中都广泛观察到，具有明显的特征。与纳米厚双层中UAMR随厚度呈指数衰减不同，堆叠FGT层的UAMR对厚度不敏感。薄膜平面内的MR呈现出占主导的两倍振荡，而在垂直于薄膜的平面中观察到超过1.4%的MR高阶振荡，几乎比面内各向异性MR大一个数量级。FGT薄膜的UAMR不能用基于自旋/轨道电流和电荷电流相互转换的著名自旋霍尔MR理论来解释。相反，它与双矢量MR理论的预测一致，特别是其求和规则约束。这些结果提供了直接的实验证据，表明ASI场而非自旋/电荷电流相互转换决定了vdW铁磁体中的UAMR。
