E. E. Laukhina

Superconductivity in reticulate doped polycarbonate films, containing (BEDT-TTF)2I3

Abstract Electric properties of conducting reticulate doped polymeric films, containing ET polyiodide crystalline network, have been investigated. In order to improve their conducting properties they were annealed in iodine vapors. It was found, that certain conditions of thermal treatment lead to metal-like state, stable down to helium temperatures. The overall decrease of resistivity R 300K /R 4.2K reaches 45. At some conditions of the thermal treatment an accelerated decrease of resistivity is observed below 7 K, vanishing with application of magnetic field, thus giving the first evidence of the (incomplete) superconducting transition in polymeric organic composite material.

Endohedral metallofullerenes M@C82 (M=La, Y): synthesis and transport properties

Endohedral metallofullerenes M@C2n (M=La, Y) were synthesized by the arc-discharge method using optimum electric arc parameters. It was also shown that an organic solvent (N,N-dimethylformamide) is successfully used in selective extraction of M@C2n. We identified the resulting products by mass spectrometry, electron spectrophotometry, EPR and X-ray fluorescence spectroscopy. The resulting N,N-dimethylformamide extracts of La@C2n and Y@C2n are shown to be free of empty fullerenes and appear as a mixture of endometallofullerenes M@C2n whose main ingredient is M@C82 (∼80 wt%). Transport properties of the extracts of La@C82 and Y@C82 were studied using pressed pellets. It was found that oxygen and heat treatment affect conductivity of endometallofullerenes. Heat treatment results in a three-order increase of conductivity from 10−5 upto 10−2 Ohm−1 cm−1

EPR Study of Reactivity of Endohedral Metallofullerenes La@C82 and Y@C82

Abstract Reactivity of La@C82 in the mixture with C60 and C70 vs L2pto, phosphoryl radical ∗P(O)(OR)2, and CF3COOH has been studied using EPR spectroscopy. Whereas two former reagents did not change EPR spectrum, treatment with CF3COOH in toluene caused the disappearance of minor octet and a new signal was observed. Similar behaviour was found upon treatment of Y@C82 with CF3COOH. It is interpreted as selective protonation of one isomer of endohedral metallofullerene.

Microwave and d.c. conductivity of α-ET2I3 and βt-ET2I3 microcrystals in polymer films

Abstract Electrical properties of conducting polymer films containing an ET 2 I 3 (ET=bis(ethylenedithiolo)tetrathiafulvalene) polyiodide crystalline network have been investigated. It is shown that the conditions of preparation of these films, i.e., time of exposition to solvent iodine vapours, concentration of iodine in solvent, time and temperature of annealing, have a very strong influence on the conducting properties of the films. By choosing proper preparation conditions one can obtain conducting composites showing the conductivity behaviour characteristic of α-ET 2 I 3 or β t -ET 2 I 3 single crystals.

Some structural features of the conducting layer in the radical cation [Pt(dddt)2]2FeCl4 salt

Abstract The crystal structure and electrical conductivity of the cation metal complex [Pt(dddt)2]2FeCl4 are reported. The main characteristic feature of the crystal structure of [Pt(dddt)2]2FeCl4 is the absence of radical cation stacks in the conducting layer and the strong dimerization of the [ Pt(dddt) 2 ] 1 2+ cations.

Production of carbon soot with a high content of C60 and C70 fullerenes by electric arc

The effect of the parameters of the electric arc (helium pressure, current and voltage, clearance between electrodes) and of the peculiarities of the setup design (arrangement of electrodes, distance between the arc and the cooling surface, temperature of the soot condensation surface) on the yield of fullerenes has been studied. Conditions for producing soot with a C60 and C70 content up to 43% (toluene extract) have been found.

Conductivity of the ET Polyiodides Crystalline Networks Transformed into Superconducting Phase

The realization of new generation of devices taking advantages of the unusual electronic properties of organic molecular compounds will require the development of new processing methods and fabrication procedures. Since introduction of the concept of organic semiconductors by Akamatu and Inokuchi in 1950 [1], a large number of various conducting organic molecular solids has been elaborated. Superconductivity is the most fascinating phenomena discovered in organic crystals. However, while the supercon-ductivity transition critical temperature (Tc) is quickly growing with the discovery of new classes of organic superconductors [2], it is rather clear, that single crystals of such materials may have only limited application. It is therefore necessary to develop new materials comprising organic superconductors (composites, hybrid structures, multi-layers etc.) which can be used for fabrication of electronic circuits and devices.

Stability and mobility of the endohedral metallofullerene of La@C82 in polycarbonate polymer films

An La@C82-doped polymer (bisphenol-A polycarbonate) was prepared. EPR spectra of La@C82 in a solid polymer film and in a polycarbonate solution in o-dichlorobenzene were studied. The EPR spectrum shape of La@C82 was shown to be sensitive to the phase state of the polymer. La@C82 in the film was found to have a high chemical stability below the glass formation temperature, thus permitting one to use the polymer for the storage and study of endohedral metallofullerenes.

New EPR signals of endohedral metallofullerenes

The EPR spectra of endohedral metallofullerenes (EMF), La-EMF and Y-EMF, which were free of admixtures of C60 and of other empty fullerenes, were examined. Endohedral metallofullerenes were prepared by extraction of fullerene-containing soots with DMF. New signals withg factors close to those of fullerene radical anions were observed in the EPR spectra of solutions of EMF in DMF and DMSO. At −20 °C, these signals are observed as a doublet (ΔHpp≈0.04 mT) and singlet (ΔHpp≈0.01 mT) in solutions of La-EMF and Y-EMF, respectively. These EPR signals belong to solvated La@C82 and Y@C82 molecules and are characterized by small hyperfine interaction constantsaM due to a substantial decrease in the spin density of the unpaired electron at the metal atom.

Stability of the vortex lattice in ET superconductors studied by μSR

Abstract Muon-spin rotation (μSR) measurements have been used to study the vortex lattice and its instabilities in the organic superconductors κ-ET 2 Cu(SCN) 2 and β-ET 2 IBr 2 . We ascribe the field- and temperature-dependent destruction of the vortex lattice to the large anisotropy found in these materials.