Integrated YBa2Cu3O7-x magnetometer for biomagnetic measurements

An integrated de superconducting quantum interference device (SQUID) magnetometer has been fabricated using a YBa2Cu3O7-x-SrTiO3-YBa2Cu3O7-x multilayer process. The magnetometer consists of a 8.3 mmX8.6 mm pickup coil coupled inductively to a small washer-type SQUID with 9 Ohm bicrystal junctions via an integrated 10 1/2-turn input coil. Using simple direct-coupled read-out electronics with additional positive feedback, a noise level of 9.7 fT/root Hz at 1 kHz and 53 fT/root Hz at 1 Hz was measured inside a magnetically shielded room. Due to the low noise level biomagnetic heart and brain signals with high quality and the very weak signals of the peripheral nerve system were recorded. (C) 1996 American Institute of Physics.