Efficient organometallic spin filter based on Europium-cyclooctatetraene wire

Electronic structures, magnetic, and transport properties of organometallic sandwich molecular wire (SMW) constructed with altering europium (Eu) atoms and cyclooctatetraene (COT) rings have been studied by spin-polarized first-principles calculations and nonequilibrium Green's function method. The one-dimensional Eu-COT SMW is predicted to be a ferromagnetic semiconductor. The calculated average magnetic moment per Eu atom is about 7 μ_B. The total magnetic moment (TMM) of Eu_n (COT)_n+1 (n=1-4) sandwich clusters increases linearly with the number of Eu atoms and the linear relation TMM=7n-2 holds, which agrees nicely with experimental observations. The spin transportation calculations show that Eu-COT clusters coupled to gold electrodes are nearly perfect spin filters. In addition, we find that this large transmission spin polarization is very robust regardless of the contact configuration of the junctions, which is very important for the future molecular spintronics.