High-Tc rf SQUIDs with large inductance of quantization loop

Abstract Experimental data on signal and noise characteristics of high- T c rf SQUIDs with large inductance are presented. The SQUIDs were fabricated by the thick-film technique of painting Y 2 BaCuO 5 substrates. For the first time, stable quantum interference is observed in an rf SQUID with inductance as large as L S =6.6 nH, that is, 60 times higher than the fluctuation inductance L F ≃10 −10 H at liquid nitrogen temperatures. A new method is offered to evaluate a sensitivity of rf SQUIDs with optimum inductance.