NDR and spin-polarized transport properties of magnetic Fe sandwiched C60-GNR single molecule devices: theoretical insight

Abstract

Encouraged by the promising performance of C₆₀-graphene single-molecule transistors observed in experiments, two types of Fe_n/C₆₀-GNR (n = 2 and 4 and GNR = graphene nanoribbon) molecules with Fe atoms sandwiched between the upper and lower GNR layers were designed and their electronic and transport properties were investigated by employing density functional theory (DFT) and nonequilibrium Green's function (NEGF) methods. Adding the Fe atoms induces high spin magnetism in the systems. Within the considered bias, almost all Fe₂/C₆₀-GNR devices generate double NDR peaks, and some of the Fe_n/C₆₀-GNR devices (n = 2 and 4) possess a large peak-to-valley current ratio R = I_peak/I_valley (>400), implying potential applications in developing on–off–on/off–on–off current switches. The NDR character originates from the crossing of the frontier molecular orbitals. In addition, these systems show distinct spin-polarized transport characteristics, with up-spin channels displaying higher conductivity than down-spin pathways. The spin filter efficiency (SFE) oscillates up and down as bias is scanned for almost all devices, suggesting the possibility of designing on–off–on/off–on–off current switches as well as up–down spin switches. All these findings provide guidance for exploring single molecular devices with promising properties combined with graphene, fullerenes, and transition metals.