High temperature operation of YBa/sub 2/Cu/sub 3/O/sub 7-x/ DC SQUID

Using a YBa/sub 2/Cu/sub 3/O/sub 7-x/ thin film deposited by MOCVD, a DC SQUID which is operated at 77 K has been fabricated. The SQUIDs with microbridges are patterned by chemical and laser etching processes. The SQUIDs operate stably without hysteresis in quite a wide range of temperature, within several periods of Phi /sub 0/. At 4.2 K, the voltage modulation of 80 mu V and the intrinsic energy sensibility of 4.0*10/sup -31/J/Hz were obtained for the SQUID with an inductance of 70 pH. The flux noise of the SQUID operating at 77 K in FLL mode was 1.8*10/sup -4/ Phi /sub 0// square root Hz at 10 Hz.