Low-temperature magnetoresistance of multi-walled carbon nanotubes with perfect structure

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