Low-Frequency Magnetic Field Detection Using Magnetoelectric Sensor With Optimized Metglas Layers by Frequency Modulation

It is an important engineering challenge to detect a weak magnetic field
${H}_{AC}$
at low frequencies (1-100 Hz) due to large noise. In this work, a magnetoelectric (ME) sensor using single-crystal quartz material as the piezoelectric phase and optimized magnetostrictive layers has been presented to sense the low-frequency magnetic field signals. Firstly, the ME response properties of the bulk Metglas/quartz/Metglas laminate sensor were studied and a high ME coefficient of 3038 V/(cm
$\cdot $
Oe) has been attained in its electromechanical resonance frequency. With frequency modulation technique, which a magnetic low-frequency signal can be transferred to around resonance frequency of the sensor, the proposed sensor was used to detect the low frequency magnetic field signals under zero bias conditions. It is experimentally found that the absolute resolution with respect to a 1 Hz magnetic field can be decreased as low as 44 pT ± 1.41 pT with 20 layers of Metglas. More importantly, the ME coefficients with different layers under zero bias and the effect of Metglas layers on the limit of the detection at 1 Hz also have been investigated. The results show that the limit of the detection at 1 Hz can be decreased to 10 pT ± 0.32 pT with 14 layers of Metglas which indicates an enhancement by 4.4 times in comparison with 20 layers. This simple bulk Metglas/quartz/Metglas laminate sensor with optimized layers has a great potential to be used for low-frequency bio-magnetic signals measurement at room temperature.