Temperature dependence of electric resistance and magnetoresistance of pressed nanocomposites of multilayer nanotubes with the structure of nested cones

TL;DR

This study investigates the temperature-dependent electrical and magnetoresistive properties of pressed nanocomposites made from multilayer nanotubes with nested cone structures, revealing two-dimensional variable-range hopping conduction behavior.

Contribution

It provides new insights into the transport mechanisms in nanotube nanocomposites, highlighting the role of the inter-wall space as a two-dimensional conducting medium.

Findings

Resistance follows ln ρ ~ (T_0/T)^{1/3} law at low temperatures.

Magnetoresistance is quadratic in magnetic field and linear in reciprocal temperature.

High density of electron states at the Fermi level (~5×10^{21} eV^{-1} cm^{-3}).

Abstract

Bulk samples of carbon multilayer nanotubes with the structure of nested cones (fishbone structure) suitable for transport measurements, were prepared by compressing under high pressure (~25 kbar) a nanotube precursor synthesized through thermal decomposition of polyethylene catalyzed by nickel. The structure of the initial nanotube material was studied using high-resolution transmission electron microscopy. In the low-temperature range (4.2 - 100 K) the electric resistance of the samples changes according to the law ln \rho ~ (T_0/T)^{1/3}, where T_0 ~ 7 K. The measured magnetoresistance is quadratic in the magnetic field and linear in the reciprocal temperature. The measurements have been interpreted in terms of two-dimensional variable-range hopping conductivity. It is suggested that the space between the inside and outside walls of nanotubes acts as a two-dimensional conducting medium. Estimates suggest a high value of the density of electron states at the Fermi level of about 5 10^{21} eV^{-1} cm^{-3}.