Ultrathin All-in-one Spin Hall Magnetic Sensor with Built-in AC Excitation Enabled by Spin Current

TL;DR

This paper introduces an ultrathin all-in-one spin Hall magnetoresistance sensor with built-in AC excitation that simplifies design and improves performance by eliminating the need for external biasing mechanisms.

Contribution

It presents a novel SMR sensor with integrated AC excitation and detection, leveraging coexistence of SMR and SOT in ultrathin NiFe/Pt bilayers, reducing complexity and cost.

Findings

Zero DC offset and negligible hysteresis in the sensor.

Detectivity around 1nT/√Hz at 1Hz.

Effective in rotation, vibration, and finger motion detection.

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) sensor, giant magnetoresistance (GMR) sensor 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, we demonstrate an all-in-one spin Hall magnetoresistance (SMR) sensor with built-in AC excitation and rectification detection, which effectively eliminates the requirements of any linearization and domain stabilization mechanisms separate from the active sensing layer. This was 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 1nT/sqrt(Hz) at 1Hz. In addition, it also shows an angle dependence to external field similar to those of GMR and TMR, though it does 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.