Effect of an electric field on the I-V curves of DyBa2Cu3-xOy/1 wt % PtHTSC ceramics

This paper reports on an experimental study of the effect of a magnetic fie ld, B less than or equal to 70 G, and an electric field, E = 120 MV/m, on t he critical current I-c and I-V curves of DyBa2Cu3-xOy HTSC ceramics (x = 0 and 0.2), both undoped and doped with 1 wt % Pt. It has been established t hat, in stoichiometric ceramics (x = 0) at 77 K, I-c drops sharply (by more than an order of magnitude) already at very low B less than or equal to 1 G. In copper-deficient ceramics (x = 0.2), I-c decreases with increasing B slowly, with Pt-doped samples exhibiting Con the dropping I-c(B) dependence ] a peak effect, i.e., an increase rather than decrease of I-c at B approxi mate to 10 G. As for the effect of an electric field on I-c and the I-V cur ves (the E effect), it is not observed in ceramics of a stoichiometric comp osition. DyBa2Cu2.8Oy samples acted upon by an electric field reveal a subs tantial increase in I-c and a decrease in the resistance R for I > I-c. In the case of DyBa2Cu2.8Oy/Pt, the electric field practically does not affect I-c but R decreases for I > I-c. In a sample placed in a magnetic field, t he magnitude of the E effect is observed to correlate with the I-c(B) depen dence. In particular, in Pt-doped samples, the E effect decreases with incr easing magnetic field B not gradually but with a maximum appearing at B app roximate to 10 G, i.e., in the region of the peak effect in the I-c(B) depe ndence. The data obtained suggest the conclusion that the electric-field ef fect in ceramics exhibiting weak links of the superconductor-insulator-supe rconductor (SIS) type correlates with magnetic vortex pinning. (C) 2001 MAI K "Nauka/Interperiodica".