Resonant spin-filtering in cobalt decorated nanotubes

We study by means of first-principles calculations within the Landauer formalism the transport properties of carbon nanotubes filled with cobalt clusters. We show that in the limit of small cluster sizes, a significant spin polarization of the incoming pi-pi(*) wave packets can be obtained on a large energy range around the Fermi level. However, in the limit of increasing cluster size, both the spin polarization and total conductance decrease dramatically, suggesting that strategies to limit the diffusion of magnetic adatoms must be found for applications in spintronics.