|Budget Amount *help
¥1,900,000 (Direct Cost : ¥1,900,000)
Fiscal Year 1991 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1990 : ¥1,600,000 (Direct Cost : ¥1,600,000)
In 1990, an equipment for d. c. conductivity measurements was constructed by using a digital multimeter, a scanner, a constant current source, a personal computer and a cryostat, which were purchased with the grant. It is possible semi-automatically to measure electrical conductivity in the temperature range 4-300 K.
The crystals of charge-transfer salts of TTF derivatives were prepared to obtain compounds in that organic radicals form itinerant electron systems and transition-metal ions form localized electron spin systems. In these compounds, BEDT-TTF salts of CoCl_4 and MnCl_4 exhibit relatively high conductivity (2.5 S cm^<-1> at room temperature). Magnetization and electron paramagnetic resonance investigations reveal that there is weak but finite exchange coupling below 1 K between the itinerant and localized spin systems.
In 1991, two types of compounds were prepared to obtain organic radical complexes which form both itinerant and localized spin systems. One is TCNQ and TCNQF_4 complexes of the organic donor or cation having a nitronyl nitroxide moiety and the other is TCNQ and TCNQF_4 complexes of TTF linked with a nitroxide moiety. These compounds show low conductivity. Only the radical moieties contribute the paramagnetism of the compounds. This implies very small magnetic interaction between spins.
In the source of the investigation mentioned above, ferromagnetic intermolecular interaction is found in one of the nitronyl nitroxide derivatives of aromatic heterocycles, which are used to give electron donative characters. 3-quinolyl nitronyl nitroxide shows ferromagnetic coupling of 0.3 K.
It is worth noting that it is of great importance to increase magnetic intermolecular interactions in all the type of compounds shown here.