Evidence of magnetoresistance for nanojunction-controlled transport in heavily doped polyacetylene

We have investigated magnetotransport in ClO₄^-- and FeCl₄^--doped-polyacetylene at magnetic fields from 0 T up to 30 T. The observed magnetoresistance follows a linear law starting from H∼6-7 T up to the highest measured value of H=30 T, with no sign of a crossover to a weaker magnetic field dependence. We attribute this anomalous behavior to weak localization arising from the inherently nonhomogeneous character of transport in polymers. We demonstrate that the linear magnetoresistance indicates that current transport is mainly controlled by a network of point (interfibrillar) contacts between "bulk volumes" with higher conductance.