High temperature ferromagnetism of (Co,N)-codoped 3C-SiC investigated by density functional theory calculations

The electronic structure and magnetic properties of (Co,N)-codoped cubic silicon carbide (3C-SiC) are investigated by performing first-principles calculations based on density functional theory. Our studies suggest that the Co-Si impurities introduce magnetic moments due to the unpaired d electrons, and the C atoms play the important roles for mediating the ferromagnetic (FM) coupling between Co impurities by p-d exchange interaction. The magnetic moments introduced by the Co-Si-N-C defect complexes are much more energetically favourable than those of the Co-Si impurities in 3C-SiC. The lattice distortion contributed by Co-Si impurities is partially compensated by substituting N atoms at the nearest neighboring carbon sites, which results in the formation energy of the defect complex Co-Si-Nc is significantly decreased. The Curie temperature of Co-Si and Co-Si-N-C doped 3C-SiC is predicted to reach the room temperature.