Field-like torque measured via a Wheatstone bridge

Abstract

In this study, a square Wheatstone bridge geometry is proposed to measure the field-like spin–orbit torque (FL-SOT) via second harmonic anisotropic magnetoresistance measurements. This design yields an enhanced signal over the conventional Hall bar due to a geometric enhancement. In addition, the square Wheatstone bridge allows for in situ calibration without the need for additional patterns. The FL-SOT coefficient is extracted from the square Wheatstone bridge patterned on a Py(=Fe80Ni20)/Pt bilayer. This extrapolated torque is then compared against an elongated Wheatstone bridge and a Hall bar to demonstrate efficacy in studying the field-like torque.