Half-metallic behavior in ruthenium-cyclopentadienyl organometallic sandwich molecules

We have theoretically investigated spin transport properties of one-dimensional ruthenium-cyclopentadienyl sandwich molecules, Ru_n(Cp)_n+1, between two gold electrodes. Calculations were performed based on the non-equilibrium Green's function formalism and density functional theory. The results clearly reveal that for n = 1, no spin-polarized behavior is observed due to the fully occupied valence shell of ruthenocene molecule, while for the higher n values, the total magnetic moments increase with increasing size of the cluster and a half metallic behavior has been achieved. This can be attributed to the altered ligand field of π-conjugate systems generated by metal centers. Interestingly, for n values higher than 1, not only do the current-voltage curves exhibit an efficient spin-current generation but also a pronounced negative differential resistance behavior can be detected in the bias region. Our results will be strongly informative for the design and control of high-performance organometallic sandwich molecules based on spin-electronic devices.