We have fabricated and tested high-Tc magnetometers based on DC superconducting quantum interference device (SQUID). The SQUID was made from YBa2Cu3O7-δ thin film deposited on SrTiO3 bicrystal substrate. The noise spectrum was characterized at 77 K and showed that above 5 Hz, the magnetometer sensitivity is limited by a white noise level of around 2 × 10-5 Φ0/Hz1/2, which corresponds to a magnetic field sensitivity of 100 fT/Hz1/2. Below 5 Hz, the noise is dominated by 1/f noise. The magnetometer was used for non-destructive evaluation (NDE) of conducting aluminum structures by performing eddy current testing. By mapping out the field distribution with the SQUID magnetometer, flaws 10 mm below the surface can be clearly identified. The system can operate in a magnetically unshielded laboratory environment.
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