Enhanced low-frequency magnetic field sensitivity in magnetoelectric composite with amplitude modulation method

It is an important scientific and engineering challenge to sense a weak magnetic field H-AC at extremely low-frequency (LF) below 1 Hz due to the large LF noise. In this work, we presented an amplitude modulation method (AMM) for quasi-static magnetic field detection based on a magnetoelectric (ME) sensor and a lock-in amplifier. Different from previously reported frequency conversion technology, the weak LF magnetic signal is demodulated directly from the output response of a ME sensor driven at its resonance frequency. Experimental results demonstrated that the absolute resolution with respect to a 100 mHz H-AC is as low as 100 pT, indicating an enhancement by a factor of 50% in comparison with previous reports. This proposed AMM should pave another route for LF weak H-AC detection. Published under license by AIP Publishing.