Strong current polarization and perfect negative differential resistance in few-FeN4-embedded zigzag graphene nanoribbons.

Ferromagnetic devices have special significance in spintronics. Here, we investigate the electronic structures and transport properties of the experimentally achievable FeN4-embedded armchair and zigzag graphene nanoribbons (FeN4-AGNR and FeN4-ZGNR). The first principles results show that FeN4 induces room-temperature stable ferromagnetic ground states in both AGNRs and ZGNRs, but only significant changes in the band structure of the latter, inducing strong current polarization (nearly 100%) and spin-dependent negative differential resistance (NDR) in the FeN4-ZGNR based devices. We find that the performance of the NDR can be easily enhanced by embedding more FeN4 structures. Its peak-to-valley current ratio (PVCR) rises rapidly and reaches 104 when only 4 FeN4 structures are used. It is revealed that the localized f electrons of the Fe atom and the p electrons of the C atoms at the ribbon edges have the same spin orientation, resulting in a ferromagnetic ground state with a larger magnetic moment, FeN4 induces conductive states around the Fermi level, which are responsible for the observed NDR, and the quite different conductivity of the frontier orbitals in the spin-down and spin-down systems contributes to the strong current polarization. Such intrinsic properties suggest prospective device applications of the FeN4-ZGNRs in spintronics.