Nearly Perfect Spin Filter Based on a Wire of Half-Metallic (η5-C5H5)Ti (η8-C8H8)Ti Units

Organic molecular devices show strong potential for future nanoelectronics applications, many of which require multifunction capability. Organometallic [(C_{5H5)Ti(C8H8)] n} clusters are one of the few molecular material clusters that have been synthesized experimentally. Here we present a theoretical study of the spin-polarized transport on the clusters of [(C_{5H5)Ti(C8H8)] n} by using nonequilibrium Green's functions combined with the density-functional theory. Results indicate that one-dimensional, organic (η⁵-C₅H₅)Ti (η⁸-C₈H₈)Ti wire has unique half-metallic properties with 100% spin polarization near the Fermi level in the ground state. We predict that finite-layer [(C_{5H5)Ti (C8H8)] n} clusters coupled to gold electrodes exhibit a near-perfect spin-filter effect. Furthermore, due to the large spin coherence originated from its organic nature, these devices possess a spin-valve effect with large magnetoresistance. Our findings suggest that such a multifunctional molecular device is an excellent candidate for future molecule-based spintronic applications.