Spin Filter Effect in Organic Polymers in the Presence of Local Magnetic Field

Using a nonadiabatic evolution method, we investigate the spin filter effect in organic polymers in the presence of a local magnetic field. Through a spin-dependent magnetic field, polarons (charge carrier) with different spins will feel repulsive or attractive force determined by their spins. Our simulations show that in a single-site magnetic field (affecting electrons at a single site), for example V₁₅₀=0.35eV, or V₁₅₀=0.45eV, a spin-up polaron accelerated to saturated velocity by an electric field can pass through the field while the spin-down polaron is trapped. When the local field extends over several sites (V_n ～ exp-(n-n_c) sup>2/n²_w), similar behaviour is also found. Simultaneously we find that it is more likely to realize the spin filter effect in a comparatively large field since the polaron which feels attractive force is easily trapped by a local magnetic field.