279 research outputs found
Pressure dependence of the magnetoresistance oscillations spectrum of beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF
The pressure dependence of the interlayer magnetoresistance of the quasi-two
dimensional organic metal beta''-(BEDT-TTF)4(NH4)[Fe(C2O4)3].DMF has been
investigated up to 1 GPa in pulsed magnetic fields up to 55 T. The Shubnikov-de
Haas oscillations spectra can be interpreted on the basis of three compensated
orbits in all the pressure range studied, suggesting that the Fermi surface
topology remains qualitatively the same as the applied pressure varies. In
addition, all the observed frequencies, normalized to their value at ambient
pressure, exhibit the same sizeable pressure dependence. Despite this behavior,
which is at variance with that of numerous charge transfer salts based on the
BEDT-TTF molecule, non-monotonous pressure-induced variations of parameters
such as the scattering rate linked to the various detected orbits are observed.Comment: accepted for publication in Phys. Rev.
De Haas-van Alphen oscillations in the compensated organic metal alpha-'pseudo-kappa'-(ET)4H3O[Fe(C2O4)3].(C6H4Br2)
Field-, temperature- and angle-dependent Fourier amplitude of de Haas-van
Alphen (dHvA) oscillations are calculated for compensated two-dimensional (2D)
metals with textbook Fermi surface (FS) composed of one hole and two electron
orbits connected by magnetic breakdown. It is demonstrated that, taking into
account the opposite sign of electron and hole orbits, a given Fourier
component involves combination of several orbits, the contribution of which
must be included in the calculations. Such FS is observed in the strongly 2D
organic metal alpha-'pseudo-kappa'-(ET)4H3O[Fe(C2O4)3].(C6H4Br2), dHvA
oscillations of which have been studied up to 55 T for various directions of
the magnetic field with respect to the conducting plane. Calculations are in
good quantitative agreement with the data.Comment: European Physical Journal B (2014
Magnetic Transformations in the Organic Conductor kappa-(BETS)2Mn[N(CN)2]3 at the Metal-Insulator Transition
A complex study of magnetic properties including dc magnetization, 1H NMR and
magnetic torque measurements has been performed for the organic conductor
kappa-(BETS)2Mn[N(CN)2]3 which undergoes a metal-insulator transition at
T_MI~25K. NMR and the magnetization data indicate a transition in the manganese
subsystem from paramagnetic to a frozen state at T_MI, which is, however, not a
simple Neel type order. Further, a magnetic field induced transition resembling
a spin flop has been detected in the torque measurements at temperatures below
T_MI. This transition is most likely related to the spins of pi-electrons
localized on the organic molecules BETS and coupled with the manganese 3d spins
via exchange interaction.Comment: 6 pages, 5 Figures, 1 Table; Submitted to Phys.Rev.B (Nov.2010
Pressure dependence of the Shubnikov-de Haas oscillation pectrum of beta''-(BEDT-TTF)4(NH4)[Cr(C2O4)3].DMF
The Shubnikov-de Haas (SdH) oscillation spectra of the
beta''-(BEDT-TTF)4(NH4)[Cr(C2O4)\_3].DMF organic metal have been studied in
pulsed magnetic fields of up to either 36 T at ambient pressure or 50 T under
hydrostatic pressures of up to 1 GPa. The ambient pressure SdH oscillation
spectra can be accounted for by up to six fundamental frequencies which points
to a rather complex Fermi surface (FS). A noticeable pressure-induced
modification of the FS topology is evidenced since the number of frequencies
observed in the spectra progressively decreases as the pressure increases.
Above 0.8 GPa, only three compensated orbits are observed, as it is the case
for several other isostructural salts of the same family at ambient pressure.
Contrary to other organic metals, of which the FS can be regarded as a network
of orbits, no frequency combinations are observed for the studied salt, likely
due to high magnetic breakdown gap values or (and) high disorder level
evidenced by Dingle temperatures as large as about 7 K.Comment: To be published in European Physical Journal
Molecular solids containing BEDT-TTF and structurally related transition metal complexes
The special physical properties of BEDT-TTF salts, e.g. their two-dimensional behaviour, are caused by the typical geometry of this donor and the arrangement of the cations in the crystal lattice of its salts. In order to extend the range of physical properties produced by BEDT-TTF like compounds, we synthesized sulfur containing transition metal complexes with a molecular structure very similar to BEDT-TTF. The bis(5.6-dihydro-1.4-dithin-2.3-dithiolate)metallates of the nickel triad can be prepared in different oxidation states as anions and in neutral form. The anionic complexes can be reacted with BEDT-TTF cations
Indication for the coexistence of closed orbit and quantum interferometer with the same cross section in the organic metal (ET)4(H3O)[Fe(C2O4)3].C6H4Cl2: Persistence of SdH oscillations above 30 K
Shubnikov-de Haas (SdH) and de Haas-van Alphen (dHvA) oscillations spectra of
the quasi-two dimensional charge transfer salt
"-(ET)(HO)[Fe(CO)]CHCl have been
investigated in pulsed magnetic fields up to 54 T. The data reveal three basic
frequencies F, F and F, which can be interpreted on the basis
of three compensated closed orbits at low temperature. However a very weak
thermal damping of the Fourier component F, with the highest amplitude, is
evidenced for SdH spectra above about 6 K. As a result, magnetoresistance
oscillations are observed at temperatures higher than 30 K. This feature, which
is not observed for dHvA oscillations, is in line with quantum interference,
pointing to a Fermi surface reconstruction in this compound.Comment: published in Eur. Phys. J. B 71 203 (2009
A bi-TTF with a bipyridine spacer: 4,4âČ-bisÂ[(3,6,7-trimethylÂsulfanyltetraÂthiaÂfulvalen-2-yl)sulfanylmethÂyl]-2,2âČ-bipyridine
The title compound, C30H28N2S16, is a precursor to hybrid magnetic materials. The complete molecule is generated by a crystallographic inversion centre. In the crystal structure, the TTF core is not planar and adopts a chair conformation; the two C3S2 rings are folded around the SâŻS hinges, the dihedral angles being 17.14â
(8) and 13.46â
(7)°. There is a short SâŻS contact [3.4863â
(14)â
Ă
] in the crystal structure
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