Accurate analysis for harmonic Hall voltage measurement for spin-orbit torques

An accurate method is developed to extract the spin-orbit effective fields through analysis of the results of harmonic Hall voltage measurements by deriving detailed analytical equations, in which both the z-component of the applied magnetic field and the second-order perpendicular magnetic anisotropy are taken into account. The method is tested by analyzing the results of a macrospin simulation. The spin-orbit effective fields extracted from the analysis are found to be in excellent agreement with the input spin-orbit effective fields used for the macrospin simulation over the entire range of the polar magnetization angle and a wide range (0-2) of the ratio of the planar to the anomalous Hall voltage considered in this study. The accuracy of the proposed method is demonstrated more clearly via a systematic study involving a comparison of its results with those of the conventional analytical method.