An integrated dc superconducting quantum interference device (SQUID) magnetometer has been fabricated using a YBa2Cu3O7minus;xndash;SrTiO3ndash;YBa2Cu3O7minus;xmultilayer process. The magnetometer consists of a 8.3 mmtimes;8.6 mm pickup coil coupled inductively to a small washerhyphen;type SQUID with 9 OHgr; bicrystal junctions via an integrated 101/2hyphen;turn input coil. Using simple directhyphen;coupled readhyphen;out electronics with additional positive feedback, a noise level of 9.7 fT/sqrt;Hz at 1 kHz and 53 fT/sqrt;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. copy;1996 American Institute of Physics.
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