Magnetic properties of transition metal atoms doped in silicon nanotubes with hexagonal prism structure

Magnetic properties of magnetic transition metals doped in the infinite Si nanotubes (SiNTs) with hexagonal prism structure (Si₁₂M_n, M=Fe, Co, Ni, n=1, 2) have been investigated for two different numbers of dopants per hexagonal prism by using the localized basis calculational method. The decrease (increase) of spin-down (spin-up) electrons for the n=2 case results in the increase of magnetic moments compared with the n=1 case. The calculated magnetic moment per dopant Fe atom (2.39 μ_B) is larger than both of the bulk value (2.22 μ_B) and previous result for finite nanotube (1.7 μ_B). For Co and Ni atoms doped in the tube, the magnetic moments are smaller than those of bulk metals. The Si-Si bond lengths for the hexagonal prisms decrease compared with that of the nanotube without transition metals, but there is no dependency on different dopants. The distances between the transition metals and Si atoms decrease as the atomic number of transition metals increases, which is the same trend for the atomic radii of transition metal atoms. The doping of transition metal atoms leads to the increase of the binding energy (BE).