Single-device offset-free magnetic field sensing with tunable sensitivity and linear range based on spin-orbit torques

Abstract

We propose a novel device concept that uses spin-orbit torques to realize a magnetic field sensor, where we eliminate the sensor offset using a differential measurement concept. We derive a simple analytical formulation for the sensor signal and demonstrate its validity with numerical investigations using macrospin simulations. The sensitivity and the measurable linear sensing range in the proposed concept can be tuned by varying the effective magnetic anisotropy or the magnitude of the injected currents. We show that undesired perturbation fields normal to the sensitive direction preserve the zero-offset property and only slightly modulate the sensitivity of the proposed sensor. Higher harmonic voltage analysis on a Hall cross experimentally confirms the linearity and tunability via current strength. Additionally, the sensor exhibits a nonvanishing offset in the experiment, which we mostly attribute to the anomalous Nernst effect.