  Among van der Waals (vdW) layered ferromagnets, Fe3GeTe2 (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 (Tc about 225 K) and electrostatic gate tunability offer
a tantalizing possibility of achieving the ultimate high SOT limit in monolayer
all-vdW nanodevices. The spin current generated in Pt exerts a damping-like SOT
on FGT magnetization. At about 2.5x1011 A/m2 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.
