Spin-wave excitation in a quasi-one-dimensional organic ferromagnet

The spin-wave properties of a quasi-one-dimensional organic ferromagnet model are investigated. By unrestricted Hartree-Fock approximation, it is shown that the ferromagnetic ground state is stable due to topological structure of the system. The spin-wave excitation is investigated using the random-phase approximation. The typical spectrum of such a model is obtained, including an acoustic spin-wave mode and two optical modes below the Stoner gap. It is found that the excitation possesses the general feature of antiferromagnetic order. Especially, the acoustic spin-wave mode has rather large stiffness.