Boundary conditions, solitons, and spin configuration in interchain coupled organic ferromagnetic polymers

With an extended Su-Schrieffer-Heeger Hamiltonian including Hubbard energy and intersite Coulomb repulsion, we study the effects of two kinds of bound ary conditions on the spin configuration and lattice distortion in organic ferromagnetic polymers with interchain coupling. It is shown that if the le ngth L of the lattice is even, there is dimerization along the main chain a nd uniform spin density along side radicals. If L is odd, there exist domai n wall solitons describing the displacement of the lattice along the main c hain, and spin soliton with envelope shape describing the localization of s pin at side radicals. Under the condition of strong interchain coupling, a great fluctuation of spin and distortion appear along the main chain and si de radicals, and the system transfers to two-dimensional one. The e-e corre lation reduces the amplitude of spin soliton and domain wall while electron -phonon coupling has the reverse effect. (C) 2000 American Institute of Phy sics. [S0021- 9606(99)50247-X].