Disconnected zigzag carbon nanotube as spin valve and spin filter predicted by first-principles study

The first-principles study of the spin-polarized transport of a disconnected zigzag carbon nanotube is reported. We find that the tunnel magnetoresistance ratio continuously increases and has no trend of decrease. For magnetic parallel configuration, the spin-filter ratio also increases with bias and eventually reaches 99.37%. Our results indicate that the disconnected zigzag carbon nanotubes can be used as a perfect spin-filter or spin valve.