Tunnel magnetoresistance of ferrocene molecules

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.

Theoretical Studies of the Spin-Dependent Electronic Transport Properties in Ethynyl-Terminated Ferrocene Molecular Junctions

The spin-dependent electron transport in the ferrocene-based molecular junctions, in which the molecules are 1,3-substituted and 1,3′-substituted ethynyl ferrocenes, respectively, is studied by the theoretical simulation with nonequilibrium Green’s function and density functional theory. The calculated results suggest that the substitution position of the terminal ethynyl groups has a great effect on the spin-dependent current-voltage properties and the spin filtering efficiency of the molecular junctions. At the lower bias, high spin filtering efficiency is found in 1,3′-substituted ethynyl ferrocene junction, which suggests that the spin filtering efficiency is also dependent on the bias voltage. The different spin-dependent transport properties for the two molecular junctions originate from their different evolutions of spin-up and spin-down energy levels.