Comparison of Electronic and Magnetic Properties of Fe, Co, and Ni Nanowires Encapsulated in Boron Nitride Nanotubes

The electronic and magnetic properties of the three types of ferromagnetic nanowires (FN4's), Fe-4, Co-4, and Ni-4, encapsulated in boron nitride nanotubes (BNNTs) have been investigated systematically using the first-principles projector-augmented wave potential within the density functional theory under the generalized gradient approximation. We find that all three types of the FN4 encapsulated into the narrower (6,6) BNNT are endothermic, whereas if they are encapsulated into the broader (8,8) BNNT, they are exothermic. Both the spin polarization and the magnetic moment of the FN4@(8,8) systems are larger than those of the FN4@(6,6) systems due to weaker restriction of the broader (8,8) BNNT, but those of these two combined systems are smaller than those of the corresponding freestanding FN4. The spin polarization of the Co-4@(8,8) system is larger than that of either the Fe-4@(8,8) system or the Ni-4@(8,8) system, which means that the Co-4@(8,8) system can be used as a spin valve in spin-dependent transport nanodevices.