Browsing by Author "Jerome, Denis"

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    The high-Tc superconducting state of β-(BEDT-TTF)2I3 at atmospheric pressure: bulk superconductivity and metastability
    (1986) Creuzet, Francois; Jerome, Denis; Schweitzer, Dieter; Keller, Heimo J.
    The AC susceptibility study of β-(BEDT-TTF)2I3 reveals that the high-Tc metastable superconducting state which can be stabilized at atmospheric pressure after a particular pressure-temperature cycling procedure, exhibits bulk superconductivity resembling very closely that of the high-Tc state, which is stabilized above 1 kbar. Annealing experiments show that the high-Tc state remains stable at low temperature as long as the annealing temperature does not exceed 125 K.
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    Homogeneous superconducting state at 8.1 K under ambient pressure in the organic conductor β-(BEDT-TTF)2I3
    (1985) Creuzet, Francois; Creuzet, Gerard; Jerome, Denis; Schweitzer, Dieter; Keller, Heimo J.
    We report the observation of the first narrow and complete superconducting transition yet obtained in β-(BEDT-TTF)2I3 at 8.1 K and ambient pressure after pressurization up to 1.5 kbar and a release of the helium gas pressure at low temperature. We show experimental evidences indicating that the metastable state giving rise to homogeneous superconductivity at ambient pressure is not stable above 250 K.
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    Proton NMR relaxation in the high-Tc organic superconductor β-(BEDT-TTF)2I3
    (1986) Creuzet, Francois; Bourbonnais, Claude; Jerome, Denis; Schweitzer, Dieter; Keller, Heimo J.
    We report the measurement of a striking enhancement of the proton spin-lattice relaxation rate occurring at the critical temperature in the high-Tc superconducting state of β(BEDT-TTF)2I3. The T1-1 behaviour is attributed to a logarithmic critical singularity whose amplitude is enhanced by the low-dimensional character of these conductors.
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    Temperature dependent resistivity under pressure and magnetoresistance data of the organic superconductor (BEDO-TTF)2ReO4(H2O)
    (1993) Kahlich, Siegfried; Schweitzer, Dieter; Auban-Senzier, Pascale; Jerome, Denis; Keller, Heimo J.
    The temperature dependence of the resistivity under pressure (up to 6 kbar) of the organic metal (BEDO-TTF)2ReO4(H20) is reported. An increase of the resistivity below 35 K, which is observed at ambient pressure, is already suppressed at 1 kbar. In addition at this pressure the superconducting transition sharpens and the onset temperature of 2.3 K is nearly the same as at ambient pressure. Magnetoresistance data, observed at 1.3 K and 6.7 Tesla show a strong angle dependence. In addition at 1.3 K first SdH -oscillations in the magnetoresistance are found already at such low fields as 5 Tesla.
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    Two superconducting phases in the organic conductor : β-(BEDT-TTF)2I3
    (1987) Creuzet, Francois; Bourbonnais, Claude; Creuzet, Gerard; Jerome, Denis; Schweitzer, Dieter; Keller, Heimo J.
    We have shown the first stabilization of homogeneous superconductivity in the β-phase of (BEDT-TTF)2I3 at high temperature and ambient pressure. We propose that the crystallographic transition occuring at 1 bar is responsible of the striking reduction of Tc if no pressure is applied. However, the phase corresponding to the room temperature structure (called β-H) is the only one giving rise to the high-Tc superconductivity and can be frozen at low temperature and atmospheric pressure after the Orsay process. It is worth noting that organic superconductivity is very sensitive to slight changes of physical parameters.
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    ItemOpen Access
    Two superconducting phases in the organic conductor: β-(BEDT-TTF)2I3
    (1986) Creuzet, Francois; Bourbonnais, Claude; Creuzet, Gerard; Jerome, Denis; Schweitzer, Dieter; Keller, Heimo J.
    We have investigated the nature and the stability of the high-Tc(∼8 K) and low-Tc (∼1.5 K)superconducting phases (respectively called β-H and β-L) of the organic conductor β-(BEDT-TTF)2I3. First, by resistivity measurements and following a well-defined temperature-pressure cycling process, we show that the β-H phase is stabilized at ambient pressure and low temperature, exhibiting a very sharp and complete superconducting transition at 8.1 K and 1 bar. Secondly, an AC-susceptibility study reveals that this state is stable and exhibits bulk superconductivity at high Tc and ambient P as long as the sample is not warmed above 125 K. Finally, we present NMR results on the 1H spin-lattice relaxation rate behaviour in both the β-H phase and the β-L phase.