  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.
