The 2nd harmonic signal analysis in Ca-doped Y-123 superconductors: Sensing DC-fields down to 0.5Â nT

We have investigated the DC-field sensing performances of a series of Ca-doped polycrystalline YBa2Cu3O7−δ superconductors. The second harmonic signal generated by applying the AC and DC fields was processed in the designed magnetic sensors. Optimal magnetic sensor properties were achieved on the Ca-doped sample with composition Y0.94Ca0.06Ba2Cu3O7−δ. Small DC-fields down to 0.5 nT could be detected with the transfer functions (dV/dB) of 23,300 V/T. The dynamical range of the sensor can be extended up to ∼0.5 Oe. The experiments were repeated to test the validity and reproducibility of the results presented.