Negative to Positive Magnetoresistance transition in Functionalization of Carbon nanotube and Polyaniline Composite

TL;DR

This study investigates the magnetoresistance behavior in polyaniline composites with carbon nanotubes, revealing a disorder-dependent transition from negative to positive MR explained by a polaron-bipolaron model.

Contribution

It demonstrates a disorder-induced transition in magnetoresistance in fCNT/PANI composites and explains it using a polaron-bipolaron framework.

Findings

Resistivity increases at low temperature with functionalized CNT.

Transition from negative to positive MR observed at 10wt% composite.

MR transition explained by increased Coulomb repulsion forming bipolarons.

Abstract

Electrical resistivity and magnetoresistance(MR) in polyaniline(PANI) with carbon nanotube(CNT) and functionalized carbon nanotube(fCNT) composites have been studied for different weight percentage down to the temperature 4.2K and up to magnetic field 5T. Resistivity increases significantly in composite at low temperature due to functionalization of CNT compare to only CNT. Interestingly transition from negative to positive magnetoresistance has been observed for 10wt% of composite as the effect of disorder is more in fCNT/PANI. This result depicts that the MR has strong dependency on disorder in the composite system. The transition of MR has been explained in the basis of polaron-bipolaron model. The long range Coulomb interaction between two polarons screened by disorder in the composite of fCNT/PANI, increases the effective on-site Coulomb repulsion energy to form bipolaron which leads to change the sign of MR from negative to positive.