SINGLE-LAYER HIGH-T-C SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE MAGNETOMETER WITH DOUBLE-PICKUP-COIL CONFIGURATION

We propose a new configuration for direct-coupling-type high-T-c super conducting quantum interference device (SQUID) magnetometers consistin g of two pickup coils per SQUID on a bicrystal substrate. The SQUID an d pickup coils can be arranged symmetrically without covering the bicr ystal line on the substrate. This configuration should produce a large coupling coefficient from the pickup coil to the SQUID, and thus a la rge effective pickup area. First, we optimized the structure and dimen sions of the pickup coils using an analogous model made of normal meta l. Second, we fabricated SQUIDS for this configuration, in which the s litlike holes were located parallel to the bicrystal line. We also fab ricated magnetometers consisting of pickup coils and SQUIDs of this co nfiguration from YBCO film on bicrystal 10 mm x 10 mm SrTiO3 substrate s. An effective area of 0.42 mm(2) has been achieved, which was measur ed by applying an external magnetic field.