Magnetoresistance of a copolymer: FeCl3-doped poly(2,5-dioctyloxy-p-phenylene vinylene-alt-3,4-ethylenedioxythiophene vinylene)

• A copolymer film composed of EDOT and phenylene is synthesized.
• The film was doped by FeCl3 and the conductivity increased 10 million times.
• MR of the FeCl3 doped copolymer was measured up to 35 T at T < 7 K.
• At low field, MR was negative and at high field, MR crossed over to positive.
• Positive and negative hopping MR models were applied to explain the MR behavior.

An experimental study of the low temperature magnetoresistance (MR) in a FeCl3-doped copolymer in which ethylenedioxythiophene and phenylene are alternatively linked by vinylene units is reported. The temperature dependence of conductivity followed characteristics of Coulomb gap variable range hopping (VRH) at low temperatures. The MR showed a crossover from negative to positive values. The crossover was explained by competition of negative and positive contributions which originated from quantum interference and shrinkage of wave function, respectively.

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