Tunnel magnetoresistance in polyaniline

The single-molecule electric current in polyaniline was investigated by first-principles calculation with a focus on tunnel magnetoresistance (TMR). The electric current in an aniline oligomer contacting two ferromagnetic electrodes was calculated by alternating the relative magnetic direction of the electrodes from parallel to antiparallel alignments. The oxidized state with imine instead of amine enhanced tunnelling between the electrodes under the parallel alignment. The electronic delocalization by π-conjugation upon varying the oxidation state of polyaniline increased the transmission at the Fermi level to induce the TMR effect under a low applied bias voltage between the electrodes.