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  • Author or Editor: H. Yoshino x
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Abstract  

We have developed a system to measure electrical resistivity, thermopower and thermal conductivity of tiny fragile organic conductors simultaneously. Figure of merit Z has been successfully determined from these transport coefficients for a two-dimensional organic conductor τ-(EDO-S,S-DMEDT-TTF)2(AuBr2)1+y, (y≤0.875), where EDO-S,S-DMEDT-TTF is ethylenedioxy-S,S-dimethylethylenedithio-tetrathiafulvalene, for the first time.

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Abstract  

A study of xNa2O·5Fe2O3·(95-x)B2O3 glasses(x = 10–35) by Mössbauer spectroscopy was carried out in order to elucidate the effect of non-bridging oxygen (NBO) on Mössbauer parameters for Fe3+ ions. From the change of the isomer shift and quadrupole splitting, it was found that the Fe3+ ions in these borate glasses constitute FeO4 tetrahedra and play a role of network former. These Mössbauer parameters reflect well the formation of NBO when N2O contents is larger than 20 mol%. From the measurements of absorption area at low temperature, the D values for Fe3+ ions in 10Na2O·5Fe2O3·85B2O3 and 35Na2O·5Fe2O3·60B2O3 glasses were determined to be 320 and 289 K, respectively. The decrease of D value from 320 to 289 K is ascribed to the NBO which was formed by the breaking of -B-O-B- bonds.

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Abstract  

The effect of thermal treatment on the electrical conductivity was studied for a quasi-one-dimensional organic conductor, (DIMET)2I3 (DIMET=dimethyl(ethylenedithio)tetrathiafulvalene). After heating the samples up to a temperature between 340 and 370 K, the electric resistivity was measured at low temperature down to 2 K and under pressure up to 1.6 Gpa. (DIMET)2I3 shows irreversible decrease in the electric resistivity between 350 and 356 K on heating. It was found that the heating above 350 K suppresses the spin-density-wave transition at 40 K and another metal-insulator transition appears at 18 K.

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