A few pA/\sqrt\mathbfH z current sensor based on magnetoelectric effect

Weak current sensors play a vital role in nuclear physics, quantum metrology, cryophysics, biomedicine, atmospheric measurement, and the semiconductor industry. In this paper, a weak current sensor based on the magnetoelectric (ME) effect is developed, consisting of a current-magnetic field conversion coil and an ME sensor composed of an ME sensing unit and a low-noise preamplifier. The equivalent magnetic field noise of the ME sensor at the resonant frequency of 15.96 kHz is 44.8 fT/\sqrt\rm Hz, and the conversion coefficient is improved by optimizing the current-magnetic field conversion coil to suppress the equivalent current noise introduced by the ME sensor and the external environment. The weak current sensor has excellent linearity and current sensitivity, and the equivalent current noise at the resonant frequency reaches 8.4 pA/\sqrt\rm Hz, which is 4 orders of magnitude lower than that of conventional ME current sensors.