4,723 research outputs found

    module-lab-1.3-Cancellation and Shutdown

    Get PDF
    Practice & La

    module-lab-2.3-Basic Building Blocks for Synchronization

    Get PDF
    Practice & La

    module-lab-1.1-Concurrent Programming in Java - Overview

    Get PDF
    Practice & La

    module-1.1-Basic Concepts

    Get PDF

    module-lab-2.2-GUI Frameworks and Concurrency

    Get PDF
    Practice & La

    The Tetragonal to Orthorhombic structural phase transition in multiband FeAs-based superconductors

    Full text link
    We report the temperature dependent x-ray powder diffraction of the FeAs-based superconductors in the range between 300 K and 95 K. In the case of NdOFeAs we have detected the structural phase transition from the tetragonal phase, with P4/nmm space group, to the orthorhombic phase,with Cmma space group, over a broad temperature range from 150 K to 120 K, centered at T0 137K. This transition is reduced, by about 30K, by the internal chemical pressure going from LaOFeAs to NdOFeAs. On the contrary the superconducting critical temperature increases from 27K to 51 K going from LaOFeAs to NdOFeAs doped samples. The FeAs layers in all undoped 1111 and 122 systems suffer a tensile misfit strain. The tensile misfit strain is reduced in 1111 and in 122 samples and at optimum doping the misfit strain is close to zero. This result shows that the normal striped orthorhombic Cmma phase competes with the superconducting tetragonal phase. In the orthorhombic clusters the charges can move only along the stripes in the b direction and are localized by the magnetic interaction.Comment: 9 pages and 2 figures. accepted by Journal of Superconductivity and novel magnetis
    • …
    corecore