  Density functional theory and nonequilibrium Green's function calculations
have been used to explore spin-resolved transport through the high-spin state
of an iron(II)sulfur single molecular magnet. Our results show that this
molecule exhibits near-perfect spin filtering, where the spin-filtering
efficiency is above 99%, as well as significant negative differential
resistance centered at a low bias voltage. The rise in the spin-up conductivity
up to the bias voltage of 0.4 V is dominated by a conductive lowest unoccupied
molecular orbital, and this is accompanied by a slight increase in the magnetic
moment of the Fe atom. The subsequent drop in the spin-up conductivity is
because the conductive channel moves to the highest occupied molecular orbital
which has a lower conductance contribution. This is accompanied by a drop in
the magnetic moment of the Fe atom. These two exceptional properties, and the
fact that the onset of negative differential resistance occurs at low bias
voltage, suggests the potential of the molecule in nanoelectronic and
nanospintronic applications.
