Noise characterization of STT-based Nanoscale magnetic tunnel junction magnetic sensors

Recently, the trend towards electrification has led to the widespread use of magnetic sensors in various applications. Magnetic tunnel junction (MTJ)-based magnetic sensors exhibiting very high sensitivity, compactness, and small dimensions could offer significant advantages over existing technologies such as conventional Hall effect sensors. New sensor concepts have been explored such as spin transfer torque (STT)-based MTJ magnetic sensors which have the potential to enable magnetic field detection with fine spatial resolutions of 50 to 100 nm and micro-Tesla resolution. This paper analyzes and describes the noise characteristics of STT-based MTJ sensors. Calculations and experimental results demonstrate that the signal-to-noise ratio (SNR) of the STT-based MTJ sensor is proportional to the square of the thermal stability factor, which is the ratio of the energy barrier of magnetization reversal and the thermal energy. This finding opens the way for future advances through predictive modelling of the sensing element and a deeper understanding of the noise sources in the proposed device.