Magnetotransport properties of iodine doped helical polyacetylene

The temperature dependence of resistivity and the magnetoresistance up to H=17Tesla were measured for the helical polyacetylene films doped with iodine. For R-polyacetylene films, the magnetoresistance at low fields changes systematically from negative to positive as the resistivity ratio, ρ(1.2K)/ρ(300K), increases. In the high field region, the magnetoresistance is negative and linearly dependent on the magnetic field. For S-polyacetylene films, much bigger positive magnetoresistance appears at low fields than in the R-type samples. The results were discussed in terms of the degree of helicity and the effect of the well-defined fiber structure of helical polyacetylene.