Low frequency excess noise source investigation of off-diagonal GMI-based magnetometers

International audienceThe impact of low frequency magnetization fluctuations on the equivalent magneticnoise of GMI sensors has recently been investigated [1]. It appears that this noise source mayexplain the low frequency excess noise exhibited by such sensors [2], in the 1/f regime. As aconsequence, we propose to extend the noise model of off-diagonal GMI-basedmagnetometers presented in [2], to this regime. The model, based on classical GMI equations,includes magnetization fluctuation noise sources. The equivalent magnetic noise level is thencomputed from the sensitivity of each term of the sensing element impedance matrix to themagnetization angle at the static working point (for both axial and circumferential staticmagnetic field) and to conditioning circuitry. We have obtained new criteria for optimizing theconditioning of the sensor signals. We highlight key parameters of the intrinsic properties ofthe sensing element responsible for the ultimate equivalent magnetic noise performance.Preliminary results lead to an expected equivalent magnetic noise (cf. figure 1), at 1 Hz, in therange of 10 pT/√Hz, for physical GMI properties and conditioning parameters similar tothose employed in [2].-----------------------------------------References:[1] C. Dolabdjian, B. Dufay, S. Saez, A. Yelon and D. Menard, Is low frequency excess noiseof GMI induced by magnetization fluctuations?, International Conference on Materials andApplications for Sensors and Transducers, ICMAST, 2013.[2] B. Dufay, S. Saez, C. Dolabdjian, A. Yelon and D. Menard, Characterization of anoptimized off-diagonal GMI-based magnetometer, IEEE Sensors Journal, vol. 13, no. 1(2013), pp. 379—388