  The emerging all-van der Waals (vdW) magnetic heterostructure provides a new
platform to control the magnetization by the electric field beyond the
traditional spintronics devices. One promising strategy is using unconventional
spin-orbit torque (SOT) exerted by the out-of-plane polarized spin current to
enable deterministic magnetization switching and enhance the switching
efficiency. However, in all-vdW heterostructures, large unconventional SOT
remains elusive and the robustness of the field-free switching against external
magnetic field hasn't been examined, which hinder further applications. Here we
demonstrate the field-free switching in an all-vdW heterostructure combining a
type-II Weyl semimetal TaIrTe4 and above-room-temperature ferromagnet Fe3GaTe2.
The fully field-free switching can be achieved at 2.56 x 10^10 A per m2 at 300K
and a large SOT efficiency of the out-of-plane polarized spin current generated
by TaIrTe4 is determined to be 0.37. Moreover, we find that the switching
polarity cannot be changed until the external in-plane magnetic field reaches
252mT, indicating a robust switching against the magnetic field. The numerical
simulation suggests the large unconventional SOT reduces the switching current
density and enhances the robustness of the switching. Our work shows that
all-vdW heterostructures are promising candidates for future highly efficient
and stable SOT-based devices.
