An integrated dc 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 mm×8.6 mm pickup coil coupled inductively to a small washer‐type SQUID with 9 Ω bicrystal junctions via an integrated 101/2‐turn input coil. Using simple direct‐coupled read‐out electronics with additional positive feedback, a noise level of 9.7 fT/√Hz at 1 kHz and 53 fT/√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.

Topics
Superconducting quantum interference device, High temperature superconductors, Magnetic equipment, Transition metal oxides, Neuroanatomy
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