Spin-dependent transport characteristics of Fe met-cars

Using non-equilibrium Green’s function and first-principles calculations we study structural, electronic, and transport properties of Fe₈C₁₂ met-car cluster sandwiched between two Au (1 0 0) electrodes. Several orientations were considered for the cluster attached to the gold surface and full structural optimization has been performed for the whole two-probe system. It was found a large current value for the present device and the molecular orientation plays an important role in the conducting behavior of the system. In energetically favorable case the I–V characteristic remains almost linear at low bias voltage (up to 1.5 V). This finding can be attributed to this fact that the transmission coefficient is almost flat around the gold Fermi level since the transmission is dominated by several broad molecular orbitals. We show that the electronic transmission is significantly spin-polarized while its size is large for the C atoms linkage. We also observe and discuss the NDR behavior of this novel molecular device in the range of 1.0–1.5 V for the energetically favorable configuration. The results are rationalized by analyzing the device transmission coefficient and density of states spectra.