A washer type high temperature superconducting dc-SQUID magnetometer with bicrystal junctions on SrTiO3 substrate

The c-oriented YBCO thin film was epitaxially grown on 10 × 10 mm2 SrTiO3 bicrystal substrate using pulsed laser deposition. The film has few outgrowths on the surface with the roughness of several nanometers in the scope of 20 μm. A washer type dc-SQUID magnetometer with bicrystal junctions was patterned using standard photolithography and wet-etching methods. The fabricated magnetometer with the effective area of 0.09 mm2 has a white noise of 333 fT/Hz1/2 without superconducting shield, and can be effectively applied in eddy current non-destructive evaluation. Flaws over 10 mm below the surface of the conducting aluminum plates can be clearly identified and located by mapping the magnetic field distribution in an unshielded magnetic environment.