All-electric magnetization switching and Dzyaloshinskii–Moriya interaction in WTe 2 /ferromagnet heterostructures

All-electric magnetization manipulation at low power is a prerequisite for a wide adoption of spintronic devices. Materials such as heavy metals 1 – 3 or topological insulators 4 , 5 provide good charge-to-spin conversion efficiencies. They enable magnetization switching in heterostructures with either metallic ferromagnets or with magnetic insulators. Recent work suggests a pronounced Edelstein effect in Weyl semimetals due to their non-trivial band structure 6 , 7 ; the Edelstein effect can be one order of magnitude stronger than it is in topological insulators or Rashba systems. Furthermore, the strong intrinsic spin Hall effect from the bulk states in Weyl semimetals can contribute to the spin current generation 8 . The Td phase of the Weyl semimetal WTe 2 (WTe 2 hereafter) possesses strong spin–orbit coupling 6 , 9 and non-trivial band structures 10 with a large spin polarization protected by time-reversal symmetry in both the surface and bulk states 9 – 11 . Atomically flat surfaces, which can be produced with high quality 12 , facilitate spintronic device applications. Here, we use WTe 2 as a spin current source in WTe 2 /Ni 81 Fe 19 (Py) heterostructures. We report field-free current-induced magnetization switching at room temperature. A charge current density of ~2.96 × 10 5 A cm −2 suffices to switch the magnetization of the Py layer. With the charge current along the b axis of the WTe 2 layer, the thickness-dependent charge-to-spin conversion efficiency reaches 0.51 at 6–7 GHz. At the WTe 2 /Py interface, a Dzyaloshinskii–Moriya interaction (DMI) with a DMI constant of −1.78 ± 0.06 mJ m −2 induces chiral domain wall tilting. Our study demonstrates the capability of WTe 2 to efficiently manipulate magnetization and sheds light on the role of the interface in Weyl semimetal/magnet heterostructures.