N.D. Kushch

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.

Slow oscillations of magnetoresistance in quasi-two-dimensional metals.

Slow oscillations of the interlayer magnetoresistance observed in the layered organic metal beta-(BEDT-TTF)(2)IBr(2) are shown to originate from the slight warping of its Fermi surface rather than from independent small cyclotron orbits. Unlike the usual Shubnikov-de Haas effect, these oscillations are not affected by the temperature smearing of the Fermi distribution and can therefore become dominant at high enough temperatures. We suggest that the slow oscillations are a general feature of clean quasi-two-dimensional metals and discuss possible applications of the phenomenon.

Novel organic superconductor κ-(ET)2Cu[N(CN)2]Cl0.5Br0.5 with Tc∼11.3 K

κ-(ET)2Cu[N(CN)2]Cl0.5Br0.5, a new organic superconductor (Tc ∼ 11.3 K at ambient pressure) has been synthesized. Its X-ray study has been undertaken.

Angle-dependent magnetoresistance in the weakly incoherent interlayer transport regime in a layered organic conductor.

We present comparative studies of the orientation effect of a strong magnetic field on the interlayer resistance of alpha-(BEDT-TTF)2KHg(SCN)4 samples characterized by different crystal quality. We find striking differences in their behavior, which is attributed to the breakdown of the coherent charge transport across the layers in the lower quality sample. In the latter case, the nonoscillating magnetoresistance background is essentially a function of only the out-of-plane field component, in contradiction to the existing Fermi-liquid theories.

Anomalous beating phase of the oscillating interlayer magnetoresistance in layered metals

We analyze the beating behavior of the magnetic quantum oscillations in a layered metal under the conditions when the cyclotron energy h ω c is comparable to the interlayer transfer energy t. Using a simple semiclassical model, we show that the positions of the beats in the interlayer resistance are considerably shifted from those in the magnetization oscillations. The shift is determined by the ratio h ω c /t that may lead to significant deviations from the conventional periodicity of the heats in the scale of inverse magnetic field. A comparative study of the Shubnikov-de Haas and de Haas-van Alphen oscillations in the layered organic metal β-(BEDT-TTF) 2 IBr 2 is performed and shown to be consistent with the theoretical prediction.

New cation-radical salts of BEDT-TTF with the octahedral metal complex anions PtCl62−, PtBr62−, TeCl62− and SnCl62−. Synthesis, structure and properties

Abstract A new series of isostructural cation-radical salts of bis(ethylene)dithiotetrathiafulvalene (BEDT-TTF) with the octahedral metal complex dianions PtCl62−, PtBr62−, TeCl62− and SnCl62− have been obtained. The crystal structure of the (BEDT-TTF)4PtCl6C6H5CN salt has been determined. Although it should be attributed to the k-type of BEDT-TTF metallic salts due to the packing arrangement of the BEDT-TTF molecules, it undergoes a first-order transition into the insulating state at 250 K. Application of a pressure higher than 6 kbar results in a new conducting state. The complexes of (BEDT-TTF) with the anions PtBr62−, TeCl62− and SnCl62− exhibit semiconducting properties.

Optical study of the electronic structure and electron-molecular vibrational coupling in a novel organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Cl0.5Br0.5

Abstract Reflectance spectra of a new ambient-pressure superconductor, κ-(BEDT-TTF) 2 Cu[N(CN) 2 ]Cl 0.5 Br 0.5 ( T c = 11.3 K), where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene, are measured in the range from 750 to 5500 cm −1 and from 9000 to 40 000 cm −1 for different polarizations. The detailed analysis of the infrared conductivity, obtained after a Kramers-Kronig transformation, is performed in the framework of the approach, based on the ‘phase phonons’ theory of M.J. Rice, with the help of special transformation of the experimental data. Parameters of the electronic subsystem and electron-molecular vibration coupling are determined. The determined ‘total’ dimensionless coupling constant (λ) is compared with those of the organic superconductors κ-(BEDT-TTF) 2 Cu(NCS) 2 ( T c = 10.4 K) and (BEDT-TTF) 4 Hg 2.89 Br 8 ( T c = 4.3 K). It is found that a larger λ produces a larger T c in accordance with the known Bardeen-Cooper-Schriffer formula for T c .

π-Donor BETS Based Bifunctional Superconductor with Polymeric Dicyanamidomanganate(II) Anion Layer : κ-(BETS)2Mn[N(CN)2]3

Crystals of the bis(ethylenedithio)tetraselenafulvalene (BETS) radical cation salt with dicyanamidomanganate(II) anion, kappa-(BETS)2Mn[N(CN)2]3, were synthesized, which combine conducting and magnetic properties at ambient pressure and are superconducting (Tc approximately/= 5 K) at a moderate pressure of 0.3 kbar.

Transport properties and giant Shubnikov-de Haas oscillations in the first organic conductor with metal complex anion containing selenocyanate ligand, (ET)2 T1Hg(SeCN)4

Abstract Temperature dependence of the resistivity in various crystallographic directions and high pulsed field magnetoresistance of organic metal α-(ET) 2 TlHg(SeCN) 4 have been studied at temperatures down to 80 mK. Giant Shubnikov-de Haas oscillations, which are attributed to the two-dimensional nature of the cylindrical Fermi surface with a very small warping along the direction of the lowest conductivity have been observed. Four harmonics of the fast oscillations with fundamental frequency F 0 = 653 ± 3 T and slow frequency oscillations with F s = 38 ± 5 T have been revealed.

Magnetic field induced coherence-incoherence crossover in the interlayer conductivity of a layered organic metal

The angle-dependent interlayer magnetoresistance of the pressurized (to the normal metallic state) layered organic metal