DC-SQUIDs and flux transformers in YBa/sub 2/Cu/sub 3/O/sub 7/ magnetometers at 77 K

For biomagnetic applications magnetometer devices are prepared in a multilayer process based on KrF-excimer laser deposition of superconductor and insulator layers as well as semiconducting barriers. For patterning conventional photolithography and argon-ion etching are used. In the DC-SQUIDs we employ Josephson junctions with artificial barriers of PrBa/sub 2/Cu/sub 3/O/sub 7/ in a ramp-type geometry. As insulating layers in the flux transformers we use SrTiO/sub 3/. Both, the DC-SQUIDs and the input-coils operate up to temperatures of 86 K. The characterisation of the devices is made by electrical transport and by noise measurements. For the use as sensitive magnetometers the DC SQUIDs are either used in inductively shunted magnetometers with galvanic coupling to a large pick-up coil or are coupled to flux transformers in a flip-chip arrangement.<>