DOPING-INDUCED MAGNETIC PHASE-TRANSITION IN POLY(3-ALKYLTHIOPHENES)

The dopant-agent-pi system magnetic interactions in FeCl4-doped poly(3 -alkylthiophenes) (PAT's) have been studied. In particular, PAT's were subjected to magnetic susceptibility and magnetization measurements. The main goal of the experiments was to obtain temperature and magneti c-field dependencies of the above-mentioned magnetic quantities. The P AT samples were doped with ferric trichloride to different doping leve ls. The susceptibility and magnetization studies have shown that in th e doped conjugated system the transition from a paramagentic phase to an ordered phase occurs as the temperature is lowered. The magnetic in teractions observed are associated with the dopant-agent-charge-carryi ng-species antiferromagnetic coupling. The coupling is stabilized by a retro or forward virtual charge transfer between the impurity molecul e and the polymer chain.