Electronic structure and magnetism of Fe-doped SiC nanotubes

Abstract

The electronic structure and magnetic properties of Fe-doped SiC nanotubes are investigated by using the first-principles method based on density functional theory (DFT) in the local spin density approximation (LSDA). The calculation results indicate that the SiC nanotube of Fe substitution for C exhibits antiferromagnetism while ferromagnetism features prominently when Fe substitutes Si. This is a kind of half-metal magnetic material. The formation energy calculation results show that the formation energy of ferromagnetic structure is 3.2 eV lower than that of antiferromagnetic structure. Fe atoms are more likely to replace Si atoms. Spin-orbit coupling induces electron spin polarization in the ground state. Also, the doping Fe atoms make relaxation towards the outside of the tube to some extent and larger geometric distortion occurs when Fe substitutes C, but the whole geometric structure of SiC nanotubes is not damaged due to the doping. It is revealed in the calculation of energy band structure and density of states that more dispersed distribution of energy levels is produced near the Fermi level. For Fe substitution for Si, obviously there are spin-split and intense p-d hybrid effects by Si 3p electron spins and Fe 3d electron spins localized at the exchanging interactions between magnetic transitional metal (TM) impurities. Spin electronic density results indicate that system magnetic moments are mainly generated by the unpaired 3d electrons of Fe atoms. All these results show that the transition metal doping SiC nanotube could be a potential route to fabricating the promising magnetic materials.