Flux motion, proximity effect, and critical current density inYBa2Cu3

Energy gap and tunneling

“…Radousky (1992) reviewed the superconducting and normal-state properties of the Y 12x Pr x Ba 2 Cu 3 O 72δ system. Proximity junctions are (SÀNÀS) Josephson junctions in which the Cooper pair and quasiparticle transfer arises from the proximity effect (Agrait et al, 1992;Braginski, 1991;Claassen et al, (1991); Gijs et al, 1990;Han et al, 1990;Harris et al, 1991;Jung et al, 1990;Kleion and Aharony 1992;Yu et al, 1991). Studies have also been carried out on S-Semicond-S or S-Semicond junctions (Furusaki et al, 1991(Furusaki et al, , 1992Kastalsky et al, 1991;Kleiner et al, 1992;Van Wees et al, 1991) and arrays Kwong et al, 1992;Lerch et al, 1990;Sohn et al, 1992).…”

“…The proximity effect can cause two superconductors with different T c that are in contact with each other to exhibit the same intermediate T c . Theoretical treatments of this effect, such as the tunneling approach of McMillan (DiChiara et al, 1991Kadin, 1990;McMillan, 1968;Maritato and Noce (1989); Stephan and Carbotte 1991) have been published.…”

“…Current flows through and between the Josephson junctions, and sometimes the intrajunction phases are favorable for the formation of complete circuits, which can produce flux shielding (Jung et al, 1990; see Doyle and Doyle, 1993). There is a grain-decoupling (or phase-locking) temperature T g below which the Josephson junction network exhibits coherent properties, as well as a grain depairing (or critical) temperature T c below which individual grains superconduct, where T g , T c (Sergeenkov and Ausloos, 1993).…”

Type II superconductivity

“…A pinning force F p is a short-range force that holds the core of a vortex in place at, inter alia, a point defect (Giapintzakis et al, 1992;Hylton and Beasley, 1990), columnar defect (Nelson and Vinokur, 1992;Prost et al, 1993), screw dislocation (Ivlev and Jin et al, 1991), oxygen vacancy (Chudnovsky, 1990;, inclusion (Murakami et al, 1991;Sagdahl et al, 1991;Shi et al, 1989Shi et al, , 1990a, grain boundary (Muller et al, 1991b), twin boundary (Kwok et al, 1990a;Lairson et al, 1990a,b;Liu et al, 1991b;Svensmark and Falicov, 1990), intragranular or intergranular nonsuperconducting region Jung et al, 1990), or praseodymium (Pr) doping (Paulius et al, 1993;Radousky, 1992). The density of pinning centers can be high, with average separations of 100 Å or less (Martin et al, 1992;Tessler et al, 1991).…”

Synthesis and characterization of Pr substituted Gd-123 high-Tc superconductors

“…The stoichiometry δ = 0.00 is only reached if samples are slowly cooled at ambient temperature in oxygen atmosphere [20,21]. The oxygen content for all the samples calculated using the formula [22]:…”