THE CDW TRANSITION IN QUASI-ONE-DIMENSIONAL ORGANIC POLYMER FERROMAGNETS - EFFECTS OF NEXT-NEAREST-NEIGHBOR HOPPING INTERACTIONS

The next-nearest neighbor hopping interactions of pi-electrons in quas i-one-dimensional organic polymer ferromagnets are considered. Within the mean-field theory and allowing for full lattice relaxation, a set of self-consistent equations is established to study the system. It is found that with increasing of the next-nearest neighbor interaction a charge-density-wave (CDW) transition will happen. At the CDW state, a strong charge density distribution along the main chain will appear, and the spin density-wave (SDW) along the main chian will be tuned by the CDW. Consequently the ferromagnetic state, in which all the spins of the unpaired electrons at side free-radicals are arranged parallely , will be no longer the stable ground state of the system.