We have fabricated discrete Josephson vortex flow transistors from yttrium barium copper oxide thinfilms on 24 degree strontium titanate bicrystals. The devices have an asymmetric design with the control current fed through an independent control line. We have measured high current gains, in excess of 20 at 77K for a range of several devices, and substantially higher at lower temperatures. The performance at 77K has been studied and compared with theoretical simulations, which have included the effects of noise.

An integrated high Tc de-SQUID magnetometer is being developed. It has in total 10 layers of five different materials. Various materials aspects of the fabrication process will be discussed, especially the smoothness of the films and the techniques to obtain smooth edges. Cross-overs and superconducting window 9contacts were fabricated. The critical temperature of the window-contact is 84K (jc(77K)=2.10"A/cm -) and the resistivity of the insulating SrTiO 3 layer in the cross-over is 6-10 f~cm at 77K. The complete coil often shows a small resistive component down to about 50K. Ramp type and bi-epitaxial grain boundary de-SQUIDs show voltage modulation up to 65K and 79K, respectively. Efforts to fabricate an integrated high T e de-SQUID magnetometer will be discussed.

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