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

Abstract

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.