Density matrix renormalization group studies on the stability of quasi-1-D undoped and doped polymer ferromagnets

We study the ferromagnetic ground state of the theoretical model proposed for quasi-one-dimensional organic polymer ferromagnets by using the density matrix renormalization group method. We find that the chain–radical interaction, the on-site electron–electron repulsion, and the electron–phonon coupling play important roles in the stability of the ferromagnetic state, whether in doped systems or not. We are convinced that when the system is doped by one electron, a polaron appears, diminishing the stability of the high-spin state.PACS No.: 75.10.Jm