Vector Magnetometer Based on a Single Spin-Orbit-Torque Anomalous-Hall Device

Abstract

In many applications, the ability to measure the vector information of a magnetic field with high spatial resolution and low cost is essential, but remains a challenge for existing magnetometers composed of multiple sensors. Here, we report a single-device based vector magnetometer, which is enabled by spin-orbit torque, capable of measuring a vector magnetic field using the harmonic Hall resistances of a ferromagnet (FM)/heavy metal (HM) bilayer with superparamagnetic behavior. Under an ac driving current, the first- and second-harmonic Hall resistances of the FM/HM bilayer show a linear relationship with the vertical and longitudinal component (along the current direction) of the magnetic field, respectively. By employing an L-shaped Hall device with two orthogonal arms, we can measure all the three field components simultaneously, thereby detecting both the amplitude and direction of magnetic field in a three-dimensional space. As proofs of concepts, we demonstrate both angular position sensing on the three coordinate planes and vector mapping of magnetic field generated by a permanent magnet, both of which are in good agreement with the simulation results. Crosstalk between vertical and longitudinal field components at large field is discussed using theoretical models.