TO ACHIEVE FERROMAGNETISM IN ORGANIC POLYMERS BY DOPING - QUANTUM-CHEMISTRY STUDIES

The ab initio-many body perturbation theory(MBPT) method has been applied to a number of conjugated charged diradicals, which can be regarded as model molecules of doped systems. The intra-molecular effective exchange integral(J) have been estimated by this method. In these diradicals, it is found that the J-value of two radical spins coupled through odd number of conjugated atoms is ferromagnetic, while that through even number of atoms is antiferromagnetic. According to this simple topological rule we have proposed some quasi one- and two-dimensional polymeric models which can potentially be oxidized(or reduced) to ferromagnetic states by doping. This proposal has been further reasoned by ab initio Unrestricted-Hartree-Fock(UHF) Crystal-Orbital calculation for one of the models. The Curie temperatures have also been estimated to be rather high for some two-dimensional models by Ising approximation.