Spin-orbit torque (SOT) driven deterministic control of the magnetic state of a ferromagnet with perpendicular magnetic anisotropy is key to next generation spintronic applications including non-volatile, ultrafast, and energy efficient data storage devices. Due to the system symmetry, the spin polarization because of the spin-Hall effect and/or Rashba-Edelstein effect in conventional spin-source materials, such as heavy metals or topological insulators, is constrained to be in the plane of the film. This fundamental limitation in conventional spin-source materials has prevented the use of SOT to achieve field-free deterministic switching of ferromagnets with perpendicular magnetic anisotropy. To overcome this longstanding hurdle in the field of spintronics, one can exploit low-symmetry crystal structure and topological electronic structure in Weyl semimetals (WSMs), such as WTe2 and MoTe2, to efficiently generate out-of-plane oriented spin current. Importantly, WSMs host plethora of novel phenomena that are highly relevant for quantum spintronics, namely: Dirac type dispersion, strong spin-orbit coupling, Fermi arcs, and helical spin-momentum locked surface and bulk states. In this talk, I will discuss our experiments to realize field-free deterministic magnetic switching of a perpendicularly polarized van der Waals magnet employing an out-of-plane oriented spin current in layered WTe21, which is layered WSM candidate. Time permitting, I will also briefly discuss our experiments aimed at achieving field-free SOT switching of semiconducting and insulating ferromagnets using spin current in WSMs.

[1]. Kao, I-H et. al., Deterministic switching of a perpendicularly polarized magnet using unconventional spin–orbit torques in WTe2. Nature Materials (2022). https://doi.org/10.1038/s41563-022-01275-5