Spin-orbit Torques in Magnetron-Sputtered MoTe₂

Weyl semimetals can generate large current-induced spin-orbit torques (SOT) that can manipulate the magnetization dynamics in the ferromagnetic materials, and thus play an important role in spintronic devices. Due to their concomitant reduced symmetries, Weyl semimetals are also promising for generating novel SOT that may be able to efficiently switch perpendicular magnetic anisotropy thin films. Large spin-orbit torque efficiencies have already been reported for exfoliated and sputtered WTe₂ films[1]. Here we investigate magnetron-sputtered MoTe₂ films that are theoretically predicted to have even larger SOT efficiencies than WTe₂. We studied the effects of processing conditions on the stoichiometry and crystal structure of the magnetron-sputtered MoTe₂ films by using Rutherford backscattering and X-ray diffraction.  Furthermore we verified the presence of the 1T’ semimetal phase from Raman spectroscopy. SOT efficiencies of the MoTe₂ thin films were measured via angle-dependent Spin-Torque ferromagnetic resonance on MoTe₂/Ni₈₀Fe₂₀ heterostructures and we observed mixing voltage signals characteristic of large novel SOT in both the symmetric and anti-symmetric components of the lineshape.