Reducing equivalent magnetic noise by electrode design and magnetic annealing in Quartz/Metglas magnetoelectric sensors

Magnetoelectric (ME) composites are promising for the development of high-performance magnetometers due to their high sensitivity, low cost, low power consumption, and small size. Enhancing the ME coefficient while reducing the background noise is an effective method to improve the performance of ME sensors, which remains challenging. In this work, we propose a method to reduce the equivalent magnetic noise by optimizing the electrode design and the magnetic annealing process in magnetoelectric quartz/Metglas composites. Compared with the non-optimized ME composites, the ME coefficient increases by 1.38 times while the background noise decreases by about 0.78 times, resulting in a LoD of 10 fT at resonance. Due to the high ME coefficient and low background noise, the equivalent magnetic noise from 20 kHz to 50 kHz was less than 6.10 pT/Hz^1/2. The results show that proper annealing treatment of Metglas is beneficial for improving the soft magnetic properties. Meanwhile, the hollow electrode of quartz can reduce the equivalent capacitance and enhance the quality factor of the piezoelectric layer. This work demonstrates a feasible way to enhance the performance of ME magnetic field sensors.