Field-like Torque Measured via a Wheatstone Bridge

In this study, a square Wheatstone bridge (WB) geometry is proposed to measure the field-like spin-orbit torque (FL-SOT) via 2^nd harmonic anisotropic magnetoresistance (AMR) measurements. This design yields 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.