Using first-principles density functional calculations, we show that hexagonal metallic silicon nanotubes can be stabilized by doping with $3d$ transition metal atoms. Finite nanotubes doped with Fe and Mn have high local magnetic moments, whereas Co-doped nanotubes have low values and Ni-doped nanotubes are mostly nonmagnetic. The infinite ${\mathrm{S}\mathrm{i}}_{24}{\mathrm{F}\mathrm{e}}_4$ nanotube is found to be ferromagnetic with nearly the same local magnetic moment on each Fe atom as in bulk iron. Mn-doped nanotubes are antiferromagnetic, but a ferrromagnetic state lies only 0.03 eV higher in energy with a gap in the majority spin bands near the Fermi energy. These materials are interesting for silicon-based spintronic devices and other nanoscale magnetic applications.

• Received 19 February 2003

DOI:https://doi.org/10.1103/PhysRevLett.91.146802