M.I.Faley¹, U.Poppe¹, K.Urban¹, V. Yu. Slobodchikov², Yu. V. Maslennikov², A. Gapelyuk³, B. Sawitzki³, and A. Schirdewan^3
1 Institut für Festkörperforschung, FZ-Jülich GmbH, D-52425 Jülich, Germany
² Institute of Radio Engineering & Electronics, 101999 Moscow, Russia
³ Franz-Volhard Hospital, D - 13125 Berlin, Germany

We have investigated the noise properties of do superconducting quantum interference device flip-chip magnetometers with submicrometer wide bicrystal junctions operating at 77.4 K. The magnetometers demonstrated a modulation voltage VPP up to about 80 pV compared with VPP up to about 30 IN for the magnetometers with 1.5 gm junctions. This increases the slew rate of the magnetometers and improves stability of their operation in noisy environment. The noise of the magnetometers with electronics was about 6 ff/4Hz at frequencies above 100 Hz increasing up to about 20 fT/4Hz at 1 Hz. The operation of the magnetometers was characterized in a HTS dc-SQUID electronic axial first order gradiometer system, which was employed for biomagnetic measurements. The system demonstrated a gradient resolution of about 1 ff/cm4Hz at 77.4 K and a stable operation in a standard magnetically shielded room under clinical conditions'.