Superconductivity in polycrystalline pressed samples of organic metals

We report bulk superconductivity at ambient pressure in polycrystalline pressed samples of αt-(BEDT-TTF)2I3. As in single crystals of αt-(BEDT-TTF)2I3 the onset for superconductivity in the polycrystalline pressed samples lies at about 9K but the transition is broader. Zero resistivity is observed at 2.2K and the middle of the transition is found at 5K. The measurement of the ac susceptibility shows that at 2K about 50% of the sample is superconducting, but at this temperature the transition is still not saturated. The observation of bulk superconductivity in this polycrystalline pressed samples is of special interest because it demonstrates that organic superconductors can be used in principle as well for the production of electronic devices such as squids and superconducting cables. In addition the finding of bulk superconductivity in large pressed samples of crystallites of the typical diameter of 1μm of an organic metal indicates that the observation of superconductivity in organic polymers should be possible as well

Electrochemically prepared radical salts of BEDT-TTF: molecular metals and superconductors

The structural, electronic and superconducting properties of several electrochemically prepared BEDT-TTF radical salts are discussed

Superconductivity at 10 K and ambient pressure in the organic metal (BEDT-TTF)2Cu(SCN)2

We confirm the observation of superconductivity at ambient pressure above 10 K in the organic metal (BEDT-TTF)2Cu(SCN)2 as reported recently by Urayama et al [12]. In addition we have measured ESR, ac-susceptibility and thermopower in crystals of (BEDT-TTF)2Cu(SCN)2 and have shown that in contrast to other organic superconductors here a relatively sharp superconducting transition even in the ac-susceptibility can be observed which saturates already around 8 K. The thermopower measurements indicate a clear metal-metal phase transition at 100 K and a possible second phase transition at around 50 K, while from the temperature dependence of the resistivity and susceptibility (ESR) these phase transitions cannot be observed

Bulk superconductivity at ambient pressure in polycrystalline pressed samples of organic metals

Bulk superconductivity in polycrystalline pressed samples of αt-(BEDT-TTF)2I3 and βp-(BEDT-TTF)2I3 is reported. This finding shows that organic superconductors can be used in principle for the preparation of electronic devices and superconducting cables

Radical cation salts of an unsymmetrical BEDT-TTF derivative: molecular structure and physical properties of (DIMET)2ClO4xTHF

Sheets of cations with an average charge of 1/2+ are separated by sheets of anions and THF solvent molecules. Intermolecular S···S contacts result in two-dimensional physical properties. Electrical conductivity and thermopower measurements indicate two broad phase transitions at around 200 K and 80 K

Preparation, structure and investigations of BEDT-TTF trihalides

Crystals of the β-phases of (BEDT-TTF)2Br-I-Br (1) and (BEDT-TTF)2I-I-Br (2) have been isolated by electrocrystallization. The solids can be obtained using different tetrabutylammonium trihalides containing iodine and bromine as supponing electrolytes. Cyclovoltammetric results show clearly that the trihalide anions are involved in the oxidation reactions near the anode which finally lead to the crystals

Preparation, structure and physical properties of BEDT-TTF nitrates

Electrocrystallization of BEDT-TIF in THF with tetrabutylammonium nitrate as supporting electrolyte leads to the deposition of at least three different phases. Sheets of BEDT-TTF radical cations with short intermolecular S···S contacts (>3.315(4) A) are separated by anion layers. Two more BEDT-TrF nitrates have been characterized by their unit cell data. Resuhs of temperature dependent electrical conductivity and thermopower measurements on crystals of the a-phase are presented. They are metallic down to about 30 K

A stable superconducting state at 8K and ambient pressure in αt-(BEDT-TTF)2I3

We report bulk superconductivity at 8 K and ambient pressure in crystals of α t (BEDT-TTF)2I3. In contrast to the earlier observed metastable superconducting state at 8 K in crystals of β-(BEDT-TTF)2I3 here the superconducting state is stable and the crystals can be prepared by tempering α-(BEDT-TTF)2I3 above 70 °C for several days. ac-susceptibility measurements show that the observed superconducting state at 8 K is a bulk property of the crystals. Resistivity measurements indicate a sharp superconducting transition at 8 K with an onset temperature of about 9 K. The upper critical fields Hc2 at 1.3 K lie between 3 and 11 T depending on the direction of the magnetic field with respect to the crystal axes. ESR- as well as NMR-measurements indicate a total transformation of the α-phase crystals into the new superconducting α t -crystals after tempering

Radical cation salts of an unsymmetrical BEDT-TTF derivative: DIMET

A surprising fact in the structures of the organic superconductors (TMTSF)2 Cl04 and -β-(BEDT-TTF)2X (X=I3-, IBr2- and AuI2-) is that there exists a slight dimerisation of the donor molecules within the stacks of these radical cation salts. Therefore, the question arises whether a more pronounced dimerisation in organic radical salts of this type leads to stronger intra- and interstack interactions and to stronger couplings between the unpaired electrons. This might result in an increase of the transition temperature to superconductivity. A step in this direction is the preparation of "unsymmetrical" donors like DIMET, which was synthesized recently. This new donor was electrocrystallized by us in different solvents using tetrabutylammonium salts of various anions like ClO4-, ReO4-, NO3-, I3-, (AuI2)-, PF6-, ASF6- and SbF6- as electrolytes. With all these anions radical salts were obtained and in some cases even several crystallographic different phases

Superconductivity at 7.5 K and ambient pressure in polycrystalline pressed samples of βp-(BEDT-TTF)2I3

Recently, bulk superconductivity at ambient pressure in polycrystalline pressed samples of an organic metal - α-(BEDT-TTF)2I3 - was observed. This is a remarkable fact because this finding shows that organic superconductors can in principle be used for the production of electronic devices, such as squids, and might even be suitable for the preparation of superconducting cables similar to the high temperature superconductors of the copper oxides