Highly Efficient Spin–Orbit Torque and Switching of Layered Ferromagnet Fe₃GeTe₂

TLDR

Fe₃GeTe₂ is a van der Waals layered ferromagnet with metallicity, strong perpendicular anisotropy, a Curie temperature near 225 K, and gate tunability, making it a promising candidate for high‑efficiency spin‑orbit torque in monolayer heterostructures. The study aims to quantify the spin‑orbit torque effect by measuring second‑harmonic Hall responses while rotating the FGT magnetization in the plane. Spin current generated in Pt exerts a damping‑like torque on FGT, and the authors quantify this by recording second‑harmonic Hall signals as the magnetic field rotates the magnetization. At a current density of ~2.5×10¹¹ A m⁻², the torque switches FGT magnetization, yielding a spin‑orbit torque efficiency comparable to the best 3D ferromagnet heterostructures and exceeding that of 3D ferrimagnetic insulators, attributed to the atomically flat FGT/Pt interface and indicating high potential for vdW spintronic devices.

Abstract

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.