Alghamdi Mohammed, Lohmann Mark, Li Junxue, Jothi Palani R, Shao Qiming, Aldosary Mohammed, Su Tang, Fokwa Boniface P T, Shi Jing
Department of Physics and Astronomy , University of California , Riverside , California 92521 , United States.
Department of Chemistry , University of California , Riverside , California 92521 , United States.
Nano Lett. 2019 Jul 10;19(7):4400-4405. doi: 10.1021/acs.nanolett.9b01043. Epub 2019 Jun 14.
Among van der Waals (vdW) layered ferromagnets, FeGeTe (FGT) is an excellent candidate material to form FGT/heavy metal heterostructures for studying the effect of spin-orbit torques (SOT). Its metallicity, strong perpendicular magnetic anisotropy built in the single atomic layers, relatively high Curie temperature ( ∼ 225 K), and electrostatic gate tunability offer a tantalizing possibility of achieving the ultimate high SOT limit in monolayer all-vdW nanodevices. In this study, we fabricate heterostructures of FGT/Pt with 5 nm of Pt sputtered onto the atomically flat surface of ∼15-23 nm exfoliated FGT flakes. The spin current generated in Pt exerts a damping-like SOT on FGT magnetization. At ∼2.5 × 10 A/m current density, SOT causes the FGT magnetization to switch, which is detected by the anomalous Hall effect of FGT. To quantify the SOT effect, we measure the second harmonic Hall responses as the applied magnetic field rotates the FGT magnetization in the plane. Our analysis shows that the SOT efficiency is comparable with that of the best heterostructures containing three-dimensional (3D) ferromagnetic metals and much larger than that of heterostructures containing 3D ferrimagnetic insulators. Such large efficiency is attributed to the atomically flat FGT/Pt interface, which demonstrates the great potential of exploiting vdW heterostructures for highly efficient spintronic nanodevices.
在范德华（vdW）层状铁磁体中，FeGeTe（FGT）是形成用于研究自旋轨道扭矩（SOT）效应的FGT/重金属异质结构的理想候选材料。其金属性、单原子层中固有的强垂直磁各向异性、相对较高的居里温度（约225K）以及静电栅极可调性，为在单层全vdW纳米器件中实现最终的高SOT极限提供了诱人的可能性。在本研究中，我们制备了FGT/Pt异质结构，将5nm的Pt溅射在约15 - 23nm厚的剥离FGT薄片的原子平面表面上。在Pt中产生的自旋电流对FGT磁化施加类阻尼SOT。在约2.5×10 A/m的电流密度下，SOT导致FGT磁化翻转，这通过FGT的反常霍尔效应检测到。为了量化SOT效应，我们在施加的磁场使FGT磁化在平面内旋转时测量二次谐波霍尔响应。我们的分析表明，SOT效率与包含三维（3D）铁磁金属的最佳异质结构相当，并且远大于包含3D亚铁磁绝缘体的异质结构。如此高的效率归因于原子平面的FGT/Pt界面，这证明了利用vdW异质结构制造高效自旋电子纳米器件的巨大潜力。
