▎ 摘　　要

By using non-equilibrium Green's functions (NEGF) and density functional theory (DFT), we investigate the spin-dependent electronic transport properties of two heterojunctions based on zigzag-edged graphene nanoribbons and graphitic carbon nitride nanoribbons. The only difference is the scattering region, i.e., one is zigzag-edged graphene nanoribbons (ZGNRs) and the other is graphitic carbon nitride (g-C3N4) nanoribbons. The I-V curves in the ferromagnetic and antiferromagnetic states for both devices are demonstrated. Our results show that the heterojunctions are promising multifunctional devices in molecular spintronics due to their nearly perfect spin-filtering efficiency (SFE) and high rectification ratio (RR). Spin negative differential resistance (SNDR) properties at low biases can also be found in the two devices. The mechanisms are proposed for these phenomena. The spin polarizations in the transmission spectra result in the nearly perfect SFE, the asymmetry in the structures gives rise to the high RR. Moreover, for the SNDR, the suppression of the transmission spectra is mainly caused by the localization in the total density of states.