Magnetoelectric intrinsic gradiometer with high detection sensitivity and ambient noise rejection

We report theoretically and experimentally the simultaneous realization of high detection sensitivity and high ambient noise rejection in an intrinsic gradiometer based on the giant magnetoelectric effect and the magnetic field gradient sensing technique in two specifically designed and arranged magnetoelectric magnetometers. The output voltage of the gradiometer is directly obtained from the intrinsic difference voltage between the two magnetoelectric magnetometers and is calibrated magnetic field gradient to give a high detection sensitivity of 3.2 mV/(Oe/m) and a high ambient noise rejection of 30 dB (equivalent to a noise level of 20 pT/root Hz at the natural resonance frequency of 120 kHz). The consistent characteristics of the magnetoelectric magnetometers result in almost zero non-linearity between the gradiometer output voltage and its magnetic field gradient over a broad range of frequency from 1 Hz to 170 kHz.