Single-Layer High-TcSuperconducting Quantum Interference Device Magnetometer with Double-Pickup-Coil Configuration

We propose a new configuration for direct-coupling-type high- T c superconducting quantum interference device (SQUID) magnetometers consisting of two pickup coils per SQUID on a bicrystal substrate. The SQUID and pickup coils can be arranged symmetrically without covering the bicrystal line on the substrate. This configuration should produce a large coupling coefficient from the pickup coil to the SQUID, and thus a large effective pickup area. First, we optimized the structure and dimensions of the pickup coils using an analogous model made of normal metal. Second, we fabricated SQUIDs for this configuration, in which the slitlike holes were located parallel to the bicrystal line. We also fabricated magnetometers consisting of pickup coils and SQUIDs of this configuration from YBCO film on bicrystal 10 mm × 10 mm SrTiO 3 substrates. An effective area of 0.42 mm 2 has been achieved, which was measured by applying an external magnetic field.