Angle resolved second harmonic technique for precise evaluation of spin orbit torque in strong perpendicular magnetic anisotropy systems

Abstract

A low field second harmonic technique has been widely used for evaluation of spin orbit torque (SOT) despite it cannot distinguish SOT from various thermal effects such as the ordinary Nernst effect, anomalous Nernst effect, and spin Seebeck effect. In this paper, we show how thermal effects can lead to significant underestimation or overestimation of spin orbit torque from the low field second harmonic data. We propose a generalized angle resolved second harmonic technique to separate spin orbit torque from various contributions of thermal effects, which allows us to precisely estimate SOT in strong perpendicular magnetic anisotropy systems.