Emmanuel B. Nyeanchi

Electric resistance of single-walled carbon nanotubes under hydrostatic pressure

The electric resistance of single-walled nanotube mats has been studied systematically under both ambient and high hydrostatic pressures up to 1.5 GPa. Both the temperature dependence of the resistance and the magnetoresistance indicate that electrical transport occurs by variable range hopping, apparently in 2D. We suggest that this unexpected dimensionality arises from a fractal network of tubes and bundles. Under hydrostatic pressure (HP) the resistance still shows 2D variable range hopping and decreases with increasing HP. An irreversible increase in localization length and DOS is induced below 0.5 GPa. The behavior is reversible and due to strong interaction of tubes from 0.5 GPa up to 1.05 GPa. These results indicate that 2D variable range hopping occurs within bundles.

Semimetallic and semiconductor properties of some superhard and ultrahard fullerites in the range 300-2 K

Electrical resistivity and magnetoresistance were measured on samples with disordered structures synthesized from pure C60 and C70 at pressures in the range 8–12.5 GPa and temperatures of 900–1500 ...

Structure and pressure effect on the properties of La0.7Ca0.3−xSrxMnO3 manganites

We report a study of the structure and pressure effects on magnetic and transport properties of a lanthanum manganite, La0.7Ca0.3–xSrxMnO3 (0<=x<=0.3, Deltax = 0.03). The pressure coefficient ...

Crystal symmetry and pressure effects on the properties of mixed-valence manganites

A lattice structure effect on the magnetic and magnetotransport properties of La0.7Ca(0.3-x)SrxMnO3 lanthanum manganites have been studied. The Curie temperature pressure coefficient increased almo ...

La0.7Ca0.3-xSrxMnO3 manganites: Effect of structure on the magnetic and transport properties.

The effect of lattice structure on the magnetic and transport properties of La0.7Ca0.3-xSrxMnO3 (x= 0; 0.03; 0.06; ...; 0.3) lanthanum manganites have been studied. Curie temperature pressure coeff ...

Pressure effects in granular La0.7Ca0.3-xSrxMnO3.

This paper discusses the effect of hydrostatic pressure up to 0.8 GPa on magnetic properties of manganites La0.7Ca0.3 - xSrxMnO3 (0 x 0.3, x = 0.03) and magnetoresistance data in an applied magne ...

Low-Temperature Magnetoresistive Effect in Bulk La0.7Ca0.3-xSrxMnO3 Perovskites.

The temperature and field dependencies of the magnetoresistivity (MR) were studied and analysed for two series of polycrystalline samples of La0.7Ca0.3-xSrxMnO3 (0 <x <0.3) obtained by the ni ...

2D POLYMERIZATION AND DOPING OF FULLERENES UNDER PRESSURE

Abstract Tetragonal polymeric C60 has been studied by Raman spectroscopy and other methods. Attempts have been made to transform samples from the tetragonal to the orthorhom-bic phase and vice versa. The results suggest that the transformation is direct with no intermediate stage with free molecules. Tetragonal C60 has also been intercalated by potassium metal.

Electric resistivity and magnetoresistance of some superhard and ultrahard fullerites in the range 300-2K

Electric resistivity and magnetoresistance were measured on samples with disordered structure synthesized from pure C60 and C70 at pressure in the range 8–12.5 GPa and temperature 900–1500 K. Different types of behavior were observed: semimetallic and semiconducting, depending on the particular short-range order of the structure.