Search for Novel Carbon Based Nanonetwork Materials and their Properties

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(1) Intercalation processes of carbon nanotubes with alkali metalsOne of the possible application of single walled carbon nanotubes (SWNT) is the anode of the Li ion batteries. We have uncovered the intercalation processes by means of the spectroscopic methods, such as Raman, infrared, and XPS. First, alkali metals are inserted into interstitial sites surrounded by three tubes, followed by an insertion into the smaller site between two tubes, causing a serious expansion of the intertube distances. Until this state, A3C80, the concentration of alkali metals increases continuously, but displays a discontinuous jump to A9C80, above which the A concentration shows a continuous increase again.(2) Molecular orientations and magnetic structures in fullerene antiferromagnetsWe have systematically synthesized (NH_3)A_3C_<60>, by intercalating neutral ammonia molecules into A_3C_<60> superconductors, and found that all the monoammoniated compounds are antiferromagnetic insulators. (NH_3)A_3C_<60 … More > adopts an orthorhombic unit cell derived by a slight deformation of the fcc cell of A_3C60, and because of this deformation, the electron is localized on the C_<60> moiety. Furthermore, the magnetic structure and molecular orientations have been determined by NMR, and neutron scattering experiments, respectively. The correlation between these displays a nice analogy to the relation between the orbital and spin orderings in transition metal oxides magnets, which is known as Kanamori-Goodenough rule.(3) Novel dimer structure in rare earth metal doped fulleridesIntercalation of fullerenes with rare earth metals has been investigated. Among these, we succeeded in synthesizing single phase Sm_3C_<70>, and in determining the crystal structure in a electron density level, by means of MEM/Rietveld analysis. It was found that two neighboring C_<70> moieties are connected by the Sm ion, forming a new type of dimer structure. This dimer structure is considerably stable, because the structure is maintained at least up to 850K, in contrast to the bond breaking in the conventional fullerene polymers showing a bond breaking below 600K.(4) Dielectric properties of La@C_<82> thin filmsWe have fabricated thin films of the metallofullerene La@C_<82>, and measured dielectric constants as a function of temperature. The dielectric constant at room temperature is about 40, approximately one order larger than that of C_<60> (4.4). The considerably large dielectric constant is presumably due to the rotation of the molecules with a large dielectric moment. Such dipolar activity of La@C_<82> might suggest that the molecular rotation states could be controlled by the external electic field. Less