A two-field-scan harmonic Hall voltage analysis for fast, accurate quantification of spin-orbit torques in magnetic heterostructures

We report on the development of a “two-field-scan” harmonic Hall voltage (HHV) analysis, which collects the second HHV as a function of a swept in-plane magnetic field at 45° and 0° relative to the excitation current, for the determination of the spin-orbit torques of transverse spins in magnetic heterostructures without significant perpendicular spins, longitudinal spins, and longitudinal/perpendicular Oersted fields. We demonstrate that this two-field-scan analysis is as accurate as the well-established but time-consuming angle-scan HHV analysis even in the presence of considerable thermoelectric effects but takes more than a factor of 7 less measurement time. We also show that the fit of the HHV data from a single field scan at 0°, which is commonly employed in the literature, is not reliable because the employment of too many free parameters in the fitting of the very slowly varying HHV signal allows erroneous conclusion about the spin-orbit torque efficiencies.