水銀系高温超伝導体を用いた高性能dc-SQUID

概要

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Josephson junctions and two types of dc-SQUID (superconducting quantum interference device) were fabricated by using films of a rhenium-doped mercurybased superconductive material [(Hg, Re) Ba_2CaCu_2O_y], which has high critical temperature (T_c) and stability. The films were grown on SrTiO_3 bicrystal substrates by annealing precursor films in mercury vapor. Josephson junctions formed on a boundary of the substrate showed resistively shunted junction type currentvoltage characteristics. Field-induced modulation was observed up to 113 K, and a large I_0Rn product of 400-460 μV was also observed. A stripline-type SQUID exhibited a voltage modulation depth ΔV as large as 90 μV. These results indicate that Hg-based SQUIDs are promising not only for applications at high temperatures, but also temperatures as low as 77 K. A washertype SQUID with a feedback line for flux locked loop operation exhibited flux noise of 10^<-3> Φ_0/Hz^<1/2> at 1 Hz, and 77 K. This noise property will be improved by using high-J_c films.
社団法人日本磁気学会の論文
1999-04-01