Ultrathin All‐in‐One Spin Hall Magnetic Sensor with Built‐In AC Excitation Enabled by Spin Current

Abstract

Abstract Magnetoresistance (MR) sensors provide cost‐effective solutions for diverse industrial and consumer applications, including emerging fields such as internet‐of‐things (IoT), artificial intelligence, and smart living. Commercially available MR sensors such as anisotropic magnetoresistance (AMR) sensors, giant magnetoresistance (GMR) sensors, and tunnel magnetoresistance (TMR) sensors typically require an appropriate magnetic bias for both output linearization and noise suppression, resulting in increased structural complexity and manufacturing cost. Here, an all‐in‐one spin Hall magnetoresistance (SMR) sensor with built‐in AC excitation and rectification detection is demonstrated, which effectively eliminates the requirements of any linearization and domain stabilization mechanisms separated from the active sensing layer. This is made possible by the coexistence of SMR and spin–orbit torque (SOT) in ultrathin NiFe/Pt bilayers. Despite the simplest possible structure, the fabricated Wheatstone bridge sensor exhibits essentially zero DC offset, negligible hysteresis, and a detectivity of around 1 nT Hz −1/2 at 1 Hz. In addition, it also shows an angle dependence to external field similar to those of GMR and TMR, though it does not have any reference layer (unlike GMR and TMR). The superior performances of SMR sensors are evidently demonstrated in the proof‐of‐concept experiments on rotation angle measurement, and vibration and finger motion detection.