Electrically Tunable Magnetic Properties of Defective Metallic Carbon Nanotubes*

We present a first-principles study of the magnetic properties of metallic carbon nanotubes with various defects under a homogeneous transverse electric field. Single carbon adatoms, hydrogen passivated single carbon adatoms, and the various vacancies in (10,10) nanotubes are shown to play the role of magnetic impurities. The relative energy levels of quazi-localized states of such magnetic impurities with respect to the Fermi level are changeable with the application of a transverse electric field so that the corresponding magnetic ground states are shown to be tunable. Our results suggest that a pure organic nanomagnet could be realizable and their magnetic properties are controllable by electric fields.