We have investigated the electrical transport properties of nanodevices fabricated from exfoliated flakes of two-dimensional metallic ferromagnets Fe3GeTe2 (FGT) and Fe5Ge2Te2 (FG2T) down to below three layers in thickness. The per-layer anomalous Hall conductivity even in thick FGT and FG2T devices is found to be much smaller than ∼e2h, the approximate value calculated for thick undoped crystals. Moreover, we obtain a power-law scaling relation between the per-layer anomalous Hall and per-layer longitudinal conductivities with an exponent close to 1.6, which agrees with the universal value for poor ferromagnetic conductors. Both FGT and FG2T devices show clear layer-dependent Curie temperatures and layer-dependent perpendicular magnetic anisotropy, with FG2T dominating the former and FGT dominating the latter for all thicknesses. Despite their declining trend as the device thickness decreases, both Curie temperature and magnetic anisotropy retain a significant fraction of their bulk values (>60% and >80% of the bulk values, respectively, even in the thinnest FG2T device), indicating attractive potential for practical applications.

中文翻译：

---

二维铁磁体的层依赖性研究：Fe3GeTe2 和 Fe5Ge2Te2

我们研究了由二维金属铁磁体 Fe3GeTe2 (FGT) 和 Fe5Ge2Te2 (FG2T) 的剥离薄片制成的纳米器件的电传输特性，其厚度低于三层。即使在厚 FGT 和 FG2T 器件中，每层反常霍尔电导率也远小于 ∼e2h（针对厚未掺杂晶体计算的近似值）。此外，我们获得了每层反常霍尔和每层纵向电导率之间的幂律标度关系，其指数接近1.6，这与不良铁磁导体的普遍值一致。 FGT 和 FG2T 器件都表现出明显的层相关居里温度和层相关垂直磁各向异性，在所有厚度上，FG2T 主导前者，FGT 主导后者。尽管随着器件厚度的减小，居里温度和磁各向异性呈下降趋势，但居里温度和磁各向异性仍保留其体积值的很大一部分（即使在最薄的 FG2T 器件中，也分别占体积值的 >60% 和 >80%），这表明实际应用具有诱人的潜力。