INTEGRATED HIGH-TRANSITION TEMPERATURE MAGNETOMETER WITH ONLY 2 SUPERCONDUCTING LAYERS

We describe the fabrication and testing of an integrated YBa2Cu3O7-x t hin-film magnetometer consisting of a dc superconducting quantum inter ference device (SQUID), with biepitaxial grain boundary junctions, int egrated with a flux transformer on a single substrate. Only two superc onducting layers are required, the SQUID body serving as the crossunde r that completes the multiturn flux transformer. The highest temperatu re at which any of the magnetometers functioned was 76 K. At 60 K the magnetic field gain of this device was 63, and the magnetic field nois e was 160 fT Hz-1/2 at 2 kHz, increasing to 3.4 pT Hz-1/2 at 1 Hz.