Magnetic resonance of (FA)2X type organic conductors (original) (raw)
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Synthetic Metals - SYNTHET METAL, 1988
Abstract A comprehensive approach to the analysis of the infrared data of a quarter-filled, slightly dimerized organic molecular conductor characterized by narrow optical gaps is proposed. It is based on a model for a one-dimensional molecular chain system with twofold-commensurate charge-density-waves. Analysis of the room temperature infrared spectra of (TMTSF) 2 ClO 4 indicates the presence of electronic correlations strong enough as to effectively exclude the double occupancy of the electronic states. Other important ...
Structural investigation of the (TMDTDSF)2X series of organic conductor
Synthetic Metals, 1991
We present an X-ray study of a new series of organic conductors (TMDTDSF)2X based on an hybrid molecule of TMTSF and TMTTF. An analysis of the Laue diffuse scattering shows that in crystals with small anions X like CIO4, BF4, PF 6 and AsF 6, the unsymmetrical molecule TMDTDSF is orientationaly disordered, in contrast with (TMDTDSF)2ReO 4 where a weak disorder is found. The temperature behavior of (TMDTDSF)2ReO 4 and (TMDTDSF)2BF 4 is then presented. We show that in the former compounds the anion ordering (A.O.) transition still occurs at the q1=(1/2,1/2,1/2) reduced wave vector, at a temperature Tc=165 K intermediate between that of the A.O. transitions of (TMTSF)2ReO 4 (177 K) and of (TMTTF)2ReO 4 (154. K). In the BF 4 salt a local ql A.O. appears below ~22 K instead of the transitions observed at 36 K and 40 K in the Se-and S-based salts respectively. This reveals the essential r61e of the chains of molecules in these ql A.O. transitions.
Structural investigation of new 2 : 1 series of organic conductors
Synthetic Metals, 1991
We report on the relation between the structural and physical properties of 3 new series of 2 : 1 salts isomorphous to the Bechgaard salts, but based on the unsymmetrical molecules BCPTTF, tTTF and TMDTDSF. In the two first series the orientation of the molecules is ordered. With octahedral anions, (BCPTTF)2X and (tTTF)2X exhibit respectively spin-Peierls and antiferromagnetic ground states at critical temperatures sizeably higher than for the (TMTTF)2X series. In (TMDTDF)2X when the anions are small the orientation of the TMDTDSF molecule is found to be disordered. This disorder has dramatic effects on the anion ordering (A.O.) transition occuring when X is non-centrosymmetric. These effects are analyzed in the light of our present understanding of the A.O. mechanism and compared with previous results obtained with the (TMTSF)2_ x (TMTTF)x CIO 4 and (TMTSF)2 (CIO4) l_x (ReO4)x solids solutions.
Physical Review B, 2001
We present an electrical transport study of the 2-dimensional (2D) organic conductor τ -(P-(S,S)-DMEDT-TTF) 2 (AuBr) 2 (AuBr 2 ) y (where y ∼ 0.75) at low temperatures and high magnetic fields. The inter-plane resistivity ρ zz increases with decreasing temperature, with the exception of a slight anomaly at 12 K. Under a magnetic field B, both ρ zz and the in-plane resistivity plane ρ xx show a pronounced negative and hysteretic magnetoresistance. In spite of a negative residual resistivity ratio in zero field, Shubnikov de Haas (SdH) oscillations are observed in some (high quality) samples above 15 T. Furthermore, contrary to the single closed orbit Fermi surface predicted from band structure calculations (where a single star-shaped FS sheet with an area of ∼ 12.5% of A F BZ is expected), two fundamental frequencies F l and F h are detected in the SdH signal. These orbits correspond to 2.4% and 6.8% of the area of the first Brillouin zone (A BZ ), with effective masses µ l = 4.0 ± 0.5 and µ h = 7.3 ± 0.1 respectively. The angular dependence, in tilted magnetic fields, of F l and F h , reveals a 2D character of the FS, but no evidence for warping along the k z direction ( e.g., the absence of a beating effect in the SdH signal) is observed. Angular dependent magnetoresistance (AMRO) fur-
Organic conductors in high magnetic fields: model systems for quantum oscillations physics
2012
Even though organic conductors have complicated crystalline structure with low symmetry and large unit cell, band structure calculations predict multiband quasi-two dimensional electronic structure yielding very simple Fermi surface in most cases. Although few puzzling experimental results are observed, data of numerous compounds are in agreement with calculations which make them suitable systems for studying magnetic quantum oscillations in networks of orbits connected by magnetic breakdown. The state of the art of this problematics is reviewed.
EPR studies of organic conductors (DMET)2X
Synthetic Metals, 1988
We have performed EPR studies on the family of organic conductors, (DMET)2X, [ X= PF6, BF 4, Au(CN) 2, 13 and AuBr 2 ]. In spite of large difference in conductive behaviors, the four salts, except the AuBr 2 salt, show similar magnitude aJnl temperature-dependence of the spin susceptibility as a whole. Below 20-25 K, the PF6, BF 4 and Au(CN) 2 salts exhibit an abrupt decrease of the susceptibility, suggesting some phase transitions. The AuBr 2 salt shows temperature-independent spin susceptibility, greater than those of other salts, and an anomalous temperature dependence of the linewidth. The physical implication of the results are dfscussed. iNTRODUCTION Recently, a new family of organic conductors, dimethyl(ethylenedithio)diselena-dithiafulvalene (DMET) salts, have been synthesized [i]. The DMET molecule is a hybrid between TMTSF and BEDT-TTF molecules: one half of the molecule is that of TMTSF and the other half BEDT-TTF. A schematic of the DMET molecule is shown in Fig. 1. This molecule forms 2:1 compounds (DMET)2X with a variety of monovalent anions X-, as TMTTF, TMTSF, and BEDT-TTF do. It has already been revealed that this family has a rich variation of transport properties, ranging from insulator to superconductor [2]; (DMET)2PF 6 is an insulator below, at least, room temperature [i]; (DMET)2BF 4 is metallic down to 37 K, at which a metalinsulator transition occurs [i]; (DMET)2Au(CN) 2 exhibits a metal-insulator transition at 25 K at ambient pressure, but a superconducting transition at 1 K when pressurized [3]; (DMET)2I 3 is an ambient-pressure superconductor with T c of 0.5 K, above which resistivity is metallic [4]; (DMET)2AuBr 2 exhibits a broad
Magneto-oscillations and field-induced phase transitions in organic conductors
Surface Science, 1996
We have made a systematic study of the temperature-and field-dependence of the quantum oscillations in the mag~etoresistance of the quasi-2D systems (BEDT-TYF)aMHg(SCN), (MffiK, Rb, TI, NI~) and the quasi-lD system (TMTSF)aCIO( at fields up to 51 T and temperatures down to 300 inK. Recent theoretical work can explain the high magnetic-field induced phase transitions observed in these systems.
Journal of Structural Chemistry, 2009
We analyze the specific features of the structure and properties of crystals that belong to the family of lowdimensional molecular conductors based on BEDT-TTF (ET) radical cation salts with [MNOX 5 ] 2-(M = Os, Ru; X = Cl, Br) mononitrosyl metal complexes as anions. It is shown that when the synthesis components are changed single crystals with , , , and -types of the conducting layers form. All radical cation salts of this family can be considered as pseudopolymorphous phases with a general formula of (ET) 4 [MNOX 5 ] 2-x G x (G is a guest solvent molecule, BN or NB). The studied crystals display a range of remarkable structural features such as conformational and charge ordering in the conducting ЕТ layers as well as commensurate and incommensurate structural modulations mainly related to the positional ordering of the components of complex anion layers.