Weak-field polaron dynamics in organic ferromagnets

With nonadiabatic dynamical method the polaron dynamics in organic ferromagnets with spin radicals is investigated under weak electric fields. The results reveal two novel phenomena different from normal polymers due to the existence of the spin radicals. One is that the velocity of the polaron is asymmetric upon the reverse of the applied electric field, which is explained from the intrinsic dipole moment of the polaron induced by the asymmetric charge density of the polaron. The other is the ‘intermittent rebound’ of the polaron, where the polaron intermittently moves against the electric field force during a short time interval behaving like a negative current. The mechanism is attributed to the scattering of the polaron by the staggerred potention generated by the spin radicals. We further find that there exists different critical fields for the above two phenomena. With the increase of the electric field, the ‘intermittent rebound’ of the polaron vanishes firstly and subsequent the asymmetric polaron velocity. This work demonstrates the unique property of polaon transport in organic ferromagnets, which will be helpful in the further design of organic ferromagnetic devices.