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Utilizes rapid thermal processing to sinter and anneal phase-pure and copper oxide-rich YBa[sub2]Cu[sub3]O[sub7] fibers and woven fibers formed by melt spinning a powder. Analysis of the optimum temperature for sintering the powders; Obstacle to the utilization of polycrystalline high-temperature superconductors; Significance of rapid thermal processing.

Describes a study on a technique to monitor the adsorption of mercury vapor on optically thin gold films. Experimental apparatus and methods; Detection of mercury vapor; Behavior of the reflectivity of semitransparent metal films as a function of thickness.

We have measured for the first time the temperature-dependent anisotropic resistivity of several Tl2Ca2Ba2Cu3Ox single crystals. The resistivity ratio between the c axis and the a-b plane orientations in the best crystals is approximately 60 at room temperature. Resistivity data indicate substantial differences in both Tc and the transition width of nominal Tl2Ca2Ba2Cu3Ox plates grown from two different melt compositions. A Tl-O and CuO-rich flux yielded approximately stoichiometric plates with sharp transitions beginning near 113 K, while a Tl-O-rich flux produced plates containing more Tl and less Ba with broad transitions starting near 103 K. These data demonstrate the extreme sensitivity of the superconductivity to cation site disorder in the Tl-Ca-Ba-Cu-O system. [ABSTRACT FROM AUTHOR]

Flux creep data are reported which clearly demonstrate a dramatic enhancement in the pinning potential for magnetic vortices (fluxoids) in a Tl2Ca2Ba2Cu3Oy single crystal upon irradiation with 4.5 MeV protons. The creep rate is markedly reduced between 5 and 80 K, and the effective pinning potential is quadrupled from ≊100 to ≊400 meV at 20 K in a field of 50 mT. This stronger pinning enhances the magnetization hysteresis and hence the inferred low-field critical current density by a factor of 5 at 40 K. [ABSTRACT FROM AUTHOR]

The in-plane structure of single-crystal samples of Tl2Ba2CaCu2O8 has been imaged at room temperature using a scanning tunneling microscope. Atomic-resolution surface images exhibit areas in which the structure has tetragonal symmetry (peak spacing 2.5±0.2 Å) and regions in which the structure is distorted from tetragonal symmetry. The lattice spacing indicates that the observed structure corresponds to the in-plane thallium and oxygen positions. The observation of both sites also suggests that the Tl-O band makes a significant contribution to the density of states near the Fermi level. In addition, a weak one-dimensional superlattice (period 10±0.5 Å) which shows short-range order has been observed. [ABSTRACT FROM AUTHOR]

Thin unoriented polycrystalline films in the Tl-Ca-Ba-Cu-O system were prepared by sequential electron beam evaporation of multiple Tl, Ca, Ba, and Cu layers and a two-stage anneal under controlled Tl and oxygen overpressures. These films show zero resistance as high as 97 K and transport critical current densities at 76 K up to 110 000 A/cm2 with typical values of 50 000 A/cm2. The critical currents exhibit a modest magnetic field dependence. Meissner effect data show an onset at 110 K and a superconducting fraction of 75%. Compositional and structural studies indicate that the films, although polyphase, are predominantly Tl2Ca1Ba2Cu2Oy. There is no evidence of other superconducting phases. [ABSTRACT FROM AUTHOR]

Optical Faraday rotation has been measured as a function of the frequency of an applied magnetic field in two compositions of the dilute magnetic semiconductor CdMnTe. A roll-off in response is observed with the roll-off frequency increasing with Mn concentration. The frequency dependence is fit well by a simple Debye relaxation model. This dependence is attributed to relaxation of the magnetization through interactions between the Zeeman and spin-spin energy reservoirs. [ABSTRACT FROM AUTHOR]