Equivalent Magnetic Noise Analysis for a Tunneling Magnetoresistive Magnetometer

Tunneling magnetoresistive (TMR) magnetic sensors are broadly applied in various fields. However, to further improve the limit of detection (LOD), it is highly desirable to realize and calculate the noise limits of such sensor systems. Thus, techniques for noise elimination can be developed. In this paper, we propose an equivalent magnetic noise model to describe the LOD of a TMR magnetometer by considering intrinsic noise sources in the TMR sensing element and readout electronics. According to the model, the contribution of each noise source can be directly obtained. Therefore, the LOD of the magnetometer can be established theoretically. Moreover, the predicted detectivity of 390 pT/√Hz is also demonstrated by the experimental results. The model is applicable to all kinds of TMR sensors with a “Wheatstone bridge” configuration.