Browsing by Author "Roussel, M"

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    The role of multilayering in the significant improvement of structural and superconducting properties in high-Tc films
    (Australian Institute of Physics, 2006-02-07) Pan, AV; Pysarenko, SV; Roussel, M; Dou, SX; Ionescu, M
    By introducing multilayered structures to YBa2Cu3O7 (YBCO) films, significant improvement of superconducting and structural properties in the obtained multilayers has been obtained. A sandwich-like system with three main YBCO layers of ~300 nm thick and two additional NdBCO layers of about ~50 nm thick in between the YBCO layers exhibits much smoother surface compared to the YBCO films of the same thickness. It has critical current density (Jc) which is not only significantly larger (by a factor > 3) than that obtained in YBCO films with the same thickness (1 μm), but also larger than Jc in mono-layer YBCO films of any smaller thickness. The Jc enhancement is observed in both low field and high field regions, which attributed to a larger filling factor of the multilayer, better grain alignment and additional formation of dislocations at the interfaces between the layers.
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    Superconducting and microstructural properties of two types of MgB/sub 2/ films prepared by pulsed laser deposition
    (Institute of Electrical and Electronics Engineers, 2005-06) Zhao, Y; Ionescu, M; Roussel, M; Pan, AV; Horvat, J; Dou, SX
    Significant differences in superconducting and microstructural properties between two types of MgB2 films prepared by pulsed laser deposition were determined. A very high Hc2 - T slope of 1.1 T/K was achieved in the in situ film. The Jc - H curves of the in situ film also show a much weaker field dependence than that of the ex situ film. The magneto-optical (MO) images show that at 4 K the flux penetrates the in situ MgB2 film through random paths, while for the ex situ film, the flux penetration pattern is mostly repeatable, indicating a defect-controlled flux penetration. Microstructural study (transmission electron microscopy and atomic force microscopy) revealed a relatively big grain size in the ex situ film. The correlation between the superconducting properties, microstructure and preparation conditions is discussed with regard to the two types of films. © 2005 IEEE.