Hg(Tl)BaCaCuO high-Tc thin film rf-SQUID operating above 115 K

Abstract An rf-SQUID has been fabricated on Hg 0.8 Tl 0.2 Ba 2 Ca 2 Cu 3 O 8+ δ thin film using natural grain boundary weak links. The film was prepared by the spray pyrolysis technique and had T c = 123 K. Voltage-flux modulation of the SQUID has been obsrved up to 117.5 K. The flux noise density, √S Ф of the rf-SQUID is ≈ 2.5 × 10 −3 Ф 0 /√ Hz at 1 Hz and 77 K. Th value of √S Ф remains almost the same when the operating temperature is increased from 77 to 112 K, and its value becomes ≈ 4 × 10 −3 Ф 0 /√ Hz at 114 K.