Low-temperature magnetoresistance of multi-walled carbon nanotubes withperfect structure

The magnetoresistance of multi-walled carbon nanotubes is studied in the temperaturerange 4.2–200 K and magnetic fields up to 9 T. The magnetoresistance is negative in thewhole temperature range. For small magnetic fields and low temperatures, the dependence ofthe relative conductivity on the magnetic field is quadratic. However, as the magneticfield increases, it becomes logarithmic, which may be described by weak localization andcharge carriers’ interaction models. We show that the addition to conductivity due to thecharge carriers’ weak localization significantly exceeds the addition due to the effect ofthe charge carriers’ interaction. The Fermi energy and the charge carriers’ interactionconstant were estimated in terms of these models using the experimental data on themagnetoresistance field and temperature dependences. Also, we determined the exact formfor the temperature dependence of the phase relaxation time of the charge carriers’ wavefunction.