Effect of charge distribution at nitrogen atoms of polyaniline copolymers on spin-dependent transport: experimental analysis and density functional theory calculations

Abstract

The understanding of spin-dependent transport in semiconducting polymers is significant in the field of organic spintronics. However, fully elucidating this phenomenon is challenging when relying solely on experimental data or theoretical analysis. Typically, the spin-dependent transport is associated with the magnetoresistance (MR) and charge distributions at N atoms of polyaniline. Herein, by combining density functional theory (DFT) calculations with experimental analysis, we investigate the spin-dependent transport of polyaniline copolymers by altering the charge distribution at nitrogen atoms through introduction of electron withdrawing (nitrile group) and electron donating (methyl group) groups on the benzene ring. The results show that the charge distribution induced by the methyl group on the benzene ring exhibits more pronounced influence on the spin-dependent transport of polyaniline copolymers than that of the nitrile group, which is affirmed by the zero-bias spin-revolved transmission spectra and the triple change of the gradient Δy/Δx of MR versus doping degree for copolymers with a methyl group relative to that of copolymers with a nitrile group. The gradient Δy/Δx of MR versus doping degree for copolymers with the methyl group and the nitrile group reaches 0.109 and 0.034, respectively. This research provides a novel perspective to figure out the spin-dependent transport of semiconducting polymers.