Tuning the magnetic and transport properties of boron-nitride nanotubes via oxygen-doping

Using density functional theory we show that both magnetic and transport properties become chirality-dependent once a nitrogen atom is substituted by an oxygen atom in boron-nitride nanotubes (BNNTs). As chirality increases, the dispersion width of the doping induced impurity state decreases continuously, and this yields progressively larger exchange field and stronger spin polarization. Stronger chirality favors a larger magnetic moment and band insulator while weaker chirality favors a non-magnetic metallic state. In the case of oxygen substitution for a boron atom, the deep in-gap states always yield fully spin-polarized flat-bands and saturated magnetic moment of 1 μ B per oxygen atom.