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Pulsed laser deposition on various single crystl substrates was used to fabricate epitaxial (rare earth)Ba2Cu3O7 films, RE123, with RE = Y, Er and Sm. Each material's deposition was optimized for T(sub c). An increase in ionic sized of the rare-earth element was observed in increased T(sub c) in RE123 films. In addition, the vortex pinning anisotropy was affected by the rare-earth element as shown by the study of field- and angle-dependent J(sub c).

Research was conducted to show the effects of proton-induced linear defects on the dissipationless flow of current in multifilamentary Ag-sheathed tapes of (Bi1Pb)2Sr2ca2Cu3O10 superconductors in the temperature range of 55-77 K. Substantial enhancement of critical currents of the tapes are provided by randomly oriented columnar defects of estimated areal density 5 X 10 (super 10)/cm2 produced by 800 MeV proton-induced fission fragments.

The magnetic field dependence of isothermal melt-processed Bi-2212/Ag round wires' critical current density was measured. Minimal dependence of critical current density was observed when the magnetic field direction was rotated normal to the wire axis. When the direction of the magnetic field was rotated parallel to the wire axis, critical current density at 64 K and 0.2 T rose by more than a factor of four.

A calorimeter is proposed for the measurement of meter-long high temperature superconducting power transmission cables' alternating current (AC) losses. The device is based on a temperature differential scheme and features 1 mW precision. It was designed for single, two-phase and three phase loss measurements. The calorimeter accurately measured coupling losses between phases.

The c-axis conduction characteristics of silver-clad Bi-2223 and Bi-2212 tapes were investigated. Specifically, transport, resistivity and critical current measurements were carried out under varying temperatures and magnetic fields. The measurements, which looked at the superconducting current path parallel and perpendicular to the tape plane, revealed that the critical currents flowing along and normal to the tape plane have similar field orientation and magnetic field dependences.

Ion beam assisted deposition is used to create textured yttria-stabilized-zirconia buffer layers on flexible nickel substrates prior to the preparation of high current YBa2Cu3O7-gamma thick films. This approach enables the formation of c-oriented thick films with strong in-plane textures. The films produced using this method also exhibit excellent resistance to high magnetic fields at cryogenic temperatures.

Magnetic relaxation measurements are conducted to study the zero field cooled, field cooled warming and field cooled cooling c-axis transport properties of Bi2Sr2CaCu2O8 single crystals. Bi-2212 cristals are used in the experiments which involve the application of a magnetic field along the c-axis. Results the c-axis transport properties of the crystals are strongly influenced by the flux profile.

The trend of flux pinning in the melt-powder-melt-growth (MPMG) process was examined. This involved the comparison of the magnetic hysteresis and magnetic relaxation of three MPMG samples having different nominal concentrations of 211 inclusions. A weak field dependence of critical current and an enhanced pinning strength were exhibited by the samples prepared by the MPMG process.

Silver-clad monofilament (Bi, Pb)SrCaCuO-2223 superconducting tapes manufactured by the oxide-powder-in-tube process were measured at magnetic fields from O T to 7 T and a temperature range of 7-75 K. The measurements obtained the tapes's transport critical current densities and magnetization currents at fields parallel and perpendicular to the sample's plane. These also provided information on the magnetic relaxation and flux pinning potentials.

The fabrication and characterization of silver-clad TlBa2Ca2Cu3O(8+x) (Tl-1223) films is presented. It details the procedures performed to synthesize superconductors from thalliated precursor powders. It also presents the measurements of transport and magnetization critical current densities which reveal its suitability for high-field and high-temperature applications.

We have performed measurements of the magnetic field dependence of the critical current density J/sub c/ of Bi-2212/Ag round wire produced by isothermal melt processing. In contrast to the case for flat tape, there is very little dependence of J/sub c/ on on the direction of the magnetic field as it is rotated normal to the wire axis which is the direction of the nominal current flow. However, when the angle of the magnetic field direction is rotated from normal to the wire axis to parallel to that axis, J/sub c/ at 64 K and 0.2 T increases by more than a factor of four. Again, this is in contrast to the results observed for Bi-2212/Ag and Bi-2223/Ag flat tapes, which show no anisotropy under similar experimental conditions. We can explain these differences in angular anisotropy by referring to the microstructure of these two conductor types, which have distinctly different types of grain alignment. We discuss the general behaviour of the dependence of J/sub c/ on the orientation of a magnetic field for high temperature superconductors. [ABSTRACT FROM PUBLISHER]

Examines the measurement of the anisotropic properties of Bi2223/Ag tapes with and without the silver sheath. Relationship between the resistivity anisotropy ratio and rolling plane; Use of the standard four-probe method in measuring anisotropic transport properties; Description of critical current scaling as a function of the angle theta.

Investigates ab-plane anisotropy of the critical currents in twinned YBa[sub 2]Cu[sub 3]O[sub 7-delta] superconductor films. Deposition of films on crystalline yttria-stabilized zirconia (YSZ); Effect of the alignment of the twin boundary mosaic diagonal; Nucleation of the YSZ buffer layer in large grains.

We argue that superconductor/ferromagnet multilayers of nanoscale period should exhibit strong pinning of vortices by the magnetic domain structure in magnetic fields below the coercive field when ferromagnetic layers exhibit strong perpendicular magnetic anisotropy. The estimated maximum magnetic pinning energy for single vortex in such a system is about 100 times larger than the pinning energy by columnar defects. This pinning energy may provide critical currents as high as 10[sup 6]-10[sup 7] A/cm[sup 2] at high temperatures (but not very close to T[sub c]) at least in magnetic fields below 0.1 T. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We use interlayer intrinsic tunneling resistivity to probe the pseudogap in Bi2Sr2CaCu2O8+y in magnetic fields up to 60 T. A map of the field–temperature (H–T) diagram of the pseudogap state reveals the pseudogap as a dominant feature up to very high levels of hole doping. The unconventionally large quantum fluctuation regime observed on the overdoped side is consistent with the pseudogap in the vortex cores. Unlike the characteristic fields of the superconducting state, the field that closes the pseudogap at low temperatures is temperature-independent. It is related to the pseudogap temperature T★ through a simple Zeeman energy scale, pointing to the pseudogap controlled by the spin rather than the orbital degrees of freedom. [Copyright &y& Elsevier]

A dense sample of MgB2 (Tc=38.5 K) was synthesized under 200 MPa pressure using a novel hot isostatic pressing (HIPing) technique, and a high-purity single crystal of YBa2Cu3O7−δ (Tc=93.5 K) was grown in a home-made BaZrO3 crucible. Electric field vs current density (E–J) isotherms of the MgB2 and YBa2Cu3O7−δ high-temperature superconductors were measured and analyzed in terms of the critical scaling model. E–J isotherm sets were taken at fields ranging from 2 to 90 kOe. Scaling and resistivity data reveal a smooth transition from a vortex glass to a vortex liquid state for the bulk MgB2 sample and the existence of both a vortex lattice melting line and a vortex glass to vortex liquid line in the YBa2Cu3O7−δ single crystal. The critical scaling exponents for both systems are presented. A more complete (H–T) phase diagram, containing the upper critical field Hc2(T), the vortex-glass transition line Hg(T), and the magnetic irreversibility line Hirr(T) was established for bulk MgB2. [Copyright &y& Elsevier]