Structural, electronic and magnetic properties of hcp Fe, Co and Ni nanowires encapsulated in zigzag carbon nanotubes

The structural, electronic and magnetic properties of hcp transition metal (TM = Fe, Co or Ni) nanowires TM4 encapsulated inside zigzag nanotubes C(m, 0) (m = 7, 8, 9, 10, 11 or 12), along with TM n (n = 4, 10 or 13) encapsulated inside C(12, 0), have been systematically investigated using the first-principle calculations. The results show that the TM nanowires can be inserted inside a variety of zigzag carbon nanotubes (CNTs) exothermically, except from the systems TM4@(7, 0) and TM13@(12, 0) which are endothermic. The charge is transferred from TM nanowires to CNTs, and the transferred charge increases with decreasing CNT diameter or increasing nanowire thickness. The magnetic moments of hybrid systems are smaller than those of the freestanding TM nanowires, especially for the atoms on the outermost shell of the nanowires. The magnetic moment per TM atom of TM/CNT system increases with increasing CNT diameter or decreasing nanowire thickness. Both the density of states and spin charge density analysis show that the spin polarization and the magnetic moments of all hybrid systems mainly originate from the TM nanowires, implying these systems can be applied in magnetic data storage devices.