ON THE NATURE OF THE SPIN EXCHANGE INTERACTION IN POLY(M-ANILINE)

The energy spectra of two infinite 1D models of the poly(meta-aniline) (PMA) namely the neutral and cationic radical forms are theoretically investigated. The band structure is characterized by a wide energy gap with a half-filled band of nearly degenerate molecular orbitals. Different contributions (potential, kinetic, and indirect exchange) to the effective spin exchange between the unpaired electrons in the half-filled band are calculated. The PMA exhibits a net spin exchange of ferromagnetic nature, i.e. the ground state of the PMA is characterized by maximum spin multiplicity. The ferromagnetic interaction is due to the predominant contribution of the direct (potential) Coulomb exchange.