Evidence for a vortex-liquid–vortex-glass transition in epitaxialBi2Sr2

Evolution of the transport critical current density and irreversibility field as a function of heat treatment and pressing pressure during processing of Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox tapes

“…6 A/cm 2 at 77 K, 0 T͒ can be up to two orders of magnitude higher than for the best polycrystalline tapes, [13][14][15] even though the irreversibility temperatures of the films and tapes are rather similar. 15 Thus, lack of connectivity in polycrystals, whether produced by misaligned grains, lower T c phase intergrowths, insulating phases, or cracks, is still a very important current-limiting mechanism in tapes, whatever the flux pinning capability of individual grains.…”

“…15 Thus, lack of connectivity in polycrystals, whether produced by misaligned grains, lower T c phase intergrowths, insulating phases, or cracks, is still a very important current-limiting mechanism in tapes, whatever the flux pinning capability of individual grains. In attempting to distinguish the role of all of these various mechanisms, we believe that measurement of H* seems to be the best diagnostic for distinguishing the flux pinning component from the connectivity component in BSCCO tapes.…”

Thermally activated energy and critical magnetic fields of SmFeAsO0.9F0.1

“…YBa 2 Cu 3 O 7−δ (YBCO), and suggests that the anisotropy is similar to YBCO. The so-called apparent activated energy −∂ ln ρ(T, H)/∂T −1 data were generally used to analyze TAE [22,23], and the derivative ∂T / ln ρ(T, H) data is always used to analysis the vortex glass transition boundary [32,33,34,35]. Below, we will present our analysis.…”

“…According to the vortex glass transition theory, the linear (ohmic) resistivity ought to linearly vanish in a form ρ ∝ (T − T g ), where T g is the vortex glass transition temperature [32,33]. Accordingly, ∂T /∂ ln ρ ∝ (T − T g ) [34,35]. In figure 1(b), one will easily find that ∂T /∂ ln ρ(T, H) curves show approximately linear curvatures in regime (iv).…”

Significantly enhanced critical current density in Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3Ox composite conductors prepared by overpressure processing in final heat treatment

“…Typical critical current density J c ͑self-field-SF, 77 K͒ for the more widely studied 2223 tapes ranges from 30 to 40 kA/cm 2 and J c ͑0.1 T, 77 K͒ from 14 to 20 kA/cm 2 for the best commercial 2223 tape produced by the oxide-powder-in-tube ͑OPIT͒ method. 1-3 However, current reconstructions of magneto-optical images show local regions of 2223 tape with J c as high as 300 kA/cm 2 , 4 while J c up to 1000 kA/cm 2 has been achieved in 2223 thin films, 5,6 suggesting there is still much headroom to improve J c ͑SF, 77 K͒ in 2223 tape.…”