Browsing by Author "Schilling, James S."

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    Magnetic susceptibility of α and β phases of di[bis(ethylenediothiolo)tetrathiafulvalene] tri-iodide [(BEDT-TTF)2I3] under pressure
    (1986) Rothaemel, Bernd; Forró, Laszlo; Cooper, John R.; Schilling, James S.; Weger, Meir; Bele, Petra; Brunner, Hermann; Schweitzer, Dieter; Keller, Heimo J.
    We report static magnetic susceptibility data, χ(T), for the α and β phases of the organic conductor di[bis(ethylenediothiolo)tetrathiafulvalene] tri-iodide [(BEDT-TTF)2I3] both at ambient pressure and under applied pressures of up to 10 kbar. Ambient pressure ESR data for both phases below 300 K are also presented. The temperature dependence of the spin susceptibility χsβ(T) for the superconductor β-(BEDT-TTF)2I3 is unusually small for organic conductors; the pressure derivative ∂lnχsβ/∂P is found to be only moderate in magnitude (-3.3% per kbar) and independent of temperature below 300 K. For the αq phase, ∂lnχsα/∂P≃-2.0%/Kbar at ambient temperature.
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    Magnetic susceptibility under pressure and anisotropy of electrical conductivity in quasi-one-dimensional (perylene)2(AsF 6)0.75(PF6)0.35 × 0.85CH2Cl2
    (1983) Moritz, I.; Shaheen, Salem A.; Hardebusch, U.; Schilling, James S.; Weger, Meir; Bender, Klaus; Schweitzer, Dieter; Keller, Heimo J.
    The magnetic susceptibility and electrical conductivity of the quasi-one-dimensional organic metal (Perylene)2(AsF6)0.75(PF6)0.35 × 0.85CH2Cl2 was studied in the temperature range 3–300 K. The measured susceptibility can be separated into its defect χd, core χc and enhanced paramagnetic spin susceptibility χp components. χp is found to decrease upon lowering the temperature or applying pressure, in analogy with results on charge transfer compounds such as TTF-TCNQ. The conductivity ratio σdouble vertical bar/σperpendicular also decreases with falling temperature. The present results are discussed within the context of a model which takes into account band-narrowing (electron localization) due to strong electron-phonon coupling.
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    Pressure effect on the magnetic susceptibility of low dimensional organic conductors α-, β-(BEDT-TTF)2I3 and (TMTSF)2X (X=ClO4, PF6, ReO4)
    (1987) Forró, Laszlo; Cooper, John R.; Rothaemel, Bernd; Schilling, James S.; Weger, Meir; Schweitzer, Dieter; Keller, Heimo J.; Bechgaard, Klaus
    The pressure dependence of the static susceptibility of the α and β phases of (BEDT-TTF)2I3 and of (TMTSF)2X for X = CI04, PF6, Re04 was measured using a Faraday balance up to a pressure of 10 kbar. The fractional pressure dependence σ InXs/σP is -2.0%/kbar and -3.3%/kbar for the α- and β-(BEDT-TTF)2I3 respectively and it is temperature independent. For (TMTSF)2X σ1nXs/σP is about -3.0%/kbar at room temperature and increases to -4.8%/kbar on cooling. Both the magnitude and temperature dependence of the fractional pressure dependence in those two families are in contrast with the behaviour in TTF-TCNQ, where the magnitude is -8.%kbar and decreases with decreasing temperature.
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    ItemOpen Access
    Static and ESR susceptibilities of the ambient pressure superconductors β- and αt-(BEDT-TTF)2I3 and (BEDT-TTF)2Cu(SCN)2
    (1988) Klotz, Stefan; Schilling, James S.; Gärtner, Stephan; Schweitzer, Dieter
    Whereas the static spin-susceptibility χ(T) of β- and αt-(BEDT-TTF)2I3 at 5.7 tesla increases in a slow monotonic manner with temperature, χs(T) for the organic superconductor (BEDT-TTF)2Cu(SCN)2 displays a markedly structured temperature dependence. This gives evidence for two or more phase transitions in the metallic phase at temperatures near 100 K and 50 K, in addition to the onset of superconductivity at 5.7 tesla below not, vert, similar 8 K. Good agreement is found between the absolute magnitudes of static and ESR susceptibility results, thus confirming that orbital susceptibility contributions are of negligible importance here. Cooling in low magnetic fields reveals that superconductivity in (BEDT-TTF)2Cu(SCN)2 sets in at a temperature near 8.5 K, with a 7.6% Meissner effect in 14 G field.