LC resonant giant magneto-impedance sensor with high SNR for weak magnetic field detection

The Giant Magneto-Impedance (GMI) sensor offers excellent capabilities in detecting weak magnetic field, current measurement, and intelligent systems. However, traditional GMI sensors often face challenges such as instability, high power consumption, and complex circuits designs. Herein, we present an LC resonant GMI sensor utilizing a Co-based amorphous wire wound coil. By leveraging the strong dependence of impedance on the magnetic field at resonance, we significantly reduce both the excitation frequency and the equivalent magnetic noise. The resonant circuit, composed in series with a 560 pF capacitor, increases the impedance change ratio from 678% to 2203%. Optimization of the DC bias magnetic field and excitation frequency enables the sensor to achieve equivalent magnetic noise levels of 54 pT/Hz^1/2 at 1 Hz and 28 pT/Hz^1/2 at 10 Hz. Experimental results show that the series-resonant GMI sensor improves the limit of detection (LOD) by approximately 16 folds compared with that of the self-resonant one.