ESR studies of AuCl3 doped polyacetylene: Metallic behaviour at low temperatures

Doped polyacetylene (PA) samples stored under vacuum at room temperature in ESR sample tubes reach after three months nearly a steady state in the temperature dependent intensity and linewidth behaviour. The ESR spectra show two lines with an equal g-factor. In particular the linewidth of the small line demonstrates a remarkable property. The temperature dependence of the linewidth indicates a maximum at 30 K, and has a value of about 0.17 mT above this temperature in the whole investigated region up to 300 K. The ESR data are dicussed in a two spin model of delocalized states at the PA chain and fixed spins in the dopants. The interpretation underlines the metallic behaviour of the doped PA at low temperatures.