S. I. Pesotskii

Resistance and magnetoresistance anomaly in a new stable organic metal (ET)2TlHg(SCN)4

Abstract A new organic metal (ET) 2 TlHg(SCN) 4 has been synthesized. The X-ray study shows the compound to be isostructural to (ET) 2 MHg(SCN) 4 salts with M = K, NH 4 and Rb. The resistance and magnetoresistance measurements show anomalous behaviour at low temperature which may be attributed to spin-density-wave instability. Shubnikov-de Haas oscillations have also been observed at low temperature.

New BETS based molecular conductors with bromomercurate anions

Five BETS-based salts with different bromomercurate anions have been isolated. Some of these compounds ungergo the M-I transition with the temperature decrease, the others behave as metals. Among them a salt of nonstoichiometric composition BETS 4 Hg 2.84 Br 8 has been found with κ-type packing of organic layers.

Shubnikov-de Haas oscillations and magnetoresistance in the semi-metallic state of (TSeT)2Cl

Abstract Measurements of the magnetoresistance of the tetraselenotetracene derivatives (TSeT) 2 Cl and (TSeT) 2 Br have been performed at temperatures between 1.4 and 6 K in magnetic fields up to 15 T. At 1.4 K Schubnikov-de Haas oscillations have been observed for fields higher than 4 T in (TSeT) 2 Cl single crystals, indicative of the existence of small hole pockets, as suggested formerly. From the zero-field resistance of the low-temperature semi-metallic state and from the field action, it is deduced that (TSeT) 2 Cl and (TSeT) 2 Br probably exhibit the Kondo effect.

Competing types of quantum oscillations in the two-dimensional organic conductor ( B E D T − T T F ) 8 Hg 4 Cl 12 ( C 6 H 5 Cl ) 2

The interlayer magnetoconductance of the quasi-two-dimensional organic metal (BEDT-TTF) 8 Hg 4 Cl 1 2 (C 6 H 5 Cl) 2 has been investigated in pulsed magnetic fields extending up to 36 T and in the temperature range from 1.6 to15 K. A complex oscillatory spectrum, built on linear combinations of three basic frequencies only, is observed. These basic frequencies arise from the compensated closed hole and electron orbits and from the two orbits located in between. The field and temperature dependences of the amplitude of the various oscillation series are studied within the framework of the coupled-orbits model of Falicov and Stachowiak. This analysis reveals that these series result from the contribution of either the conventional Shubnikov-de Haas effect or quantum interference (QI), both of them being induced by magnetic breakthrough. Nevertheless, discrepancies between experimental and calculated parameters indicate that these phenomena alone cannot account for all of the data. Due to its low effective mass, one of the QI oscillation series-which corresponds to the whole first Brillouin zone area-is clearly observed up to 13 K.

The preparation of (BEDO-TTF)2Cl·3H2O salt in Bu4NHgX3 + Bu4NX + 1,2-dichloroethane system. Shubnikov-de Haas oscillations

Abstract Electrochemical oxidation of BEDO-TTF (bis(ethylenedioxo)tetrathiafulvalene) in 1,2-dichloroethane in the presence of Bu 4 NHgX 3 + Bu 4 NX (X = I, Br, Cl) as a supporting electrolyte at low current density results in the isolation of (BEDO-TTF) 2 Cl · 3H 2 O salt. Its composition has been established by a chemical analysis (Cl, C, H), electron probe microanalysis and X-ray analysis. The temperature dependence of the resistance has been studied down to 1.5 K at a pressure up to 30 kbar and at room temperature up to 80 kbar. Field and angular dependences of magnetoresistance have been investigated.

A mixed κ-(ET)2Cu[N(CN)2]Br0.9I0.1 salt: synthesis, structure and superconductivity

Abstract Crystals of κ-(ET) 2 Cu[N(CN) 2 ]Br 0.9 I 0.1 (ET = bis(ethylenedithio)tetrathiafulvalene) salt have been prepared, and their structure and conducting properties have been studied. The crystals have been found to undergo a superconducting transition at 3.5 K ( T c ) when coated with Apiezon N grease to provide a very low pressure (about 0.3 kbar). With the application of quasihydrostatic pressure, the T c increases up to 5.9 K at about 3.0 kbar.

Superconducting transitions in β-(bedt-TTF)2I3

Abstract The investigation of superconducting transitions in some crystals of β-(BEDT-TTF) 2 I 3 points to the existence in the (BEDT-TTF)-I system of other superconducting phases, with T c s of ∼ 4 K and ∼ 7 K, respectively.

de Haas-van Alphen oscillations and angular magnetoresistance oscillations in the organic metal κ-(BETS)2GaCl4

Quantum de Haas-van Alphen oscillations and semiclassical angular magnetoresistance oscillations are observed in the quasi-two-dimensional organic metal κ-(BETS)2GaCl4. The behavior of these oscillations attests to the existence of two cylindrical Fermi surface sheets with axes perpendicular to the conducting plane. The cross-sectional areas of these cylinders in the conducting plane are equal to about 20 and 100% of the corresponding cross section of the Brillouin zone. It is shown that the many-particle interaction can be suppressed significantly in this compound.

A new stable organic metal in the well known family of radical cation α-salts: α-(BETS)2TlHg(SeCN)4. Synthesis, structure and properties

The stable organic metalα-(BETS)2TlHg(SeCN)4 has been obtained by means of electrochemical oxidation of bis(ethylenedithio)tetraselenafulvalene (BETS) in 1,1,2-trichloroethane (TCE) with the addition of absolute ethanol in the presence of an electrolyte consisting of 18-crown-6, TlSeCN and Hg(SeCN)2 . The salt is isostructural with the ET-based salt with the same anion and ET and BETS salts with KHg(SCN)4 as well. The number of the side-by-side Se‥Se, Se‥S and S‥S contacts in each radical cation layer was twice that in comparison with the corresponding ET salt. Reflectivity spectra and magnetoresistance were studied. The Shubnikov–de Haas effect and angular oscillations of the magnetoresistance were observed. Optical and transport properties of α-(BETS)2TlHg(SeCN)4 were compared with those of the analogous ET salt.

On the possibility of a radical decrease in the strength of many-body interactions in the organic metal α-(BETS)2 KHg(SCN)4

Behavior of the de Haas-van Alphen (dHvA) oscillations depending on the angle between the magnetic field direction and the perpendicular to conducting layers in the quasi-two-dimensional organic metal α-(BETS)2 KHg(SCN)4 was studied in detail. The angular dependence of the dHvA oscillation amplitude exhibits a series of minima (at ±43.2°, ±64.6°, and ±72.0°) related to the “zero spin” effect, through which it is possible to estimate the splitting factor. An analysis of this value suggests that many-body interactions in the compound studied are either absent or at least radically weakened.