Ferromagnetism in 4H-GaN polytype doped by non-magnetic light elements Li, Be, B, C, O, F, Ne, Na, and Mg: Ab-initio study

• The partial densities of states of 4H-GaN polytype doped light nonmagnetic elements have been investigated.
• We found that 4H-GaN:Ne is half metallic.
• We found that N atoms induced strong local magnetic.
• We found that doping with half-filled X-s impurity states promotes ferromagnetism.
• We found that doping with full-filled X-s impurity annihilates ferromagnetism.

Using density-functional theory within the generalized-gradient approximation, we explore the magnetic behavior induced by nonmagnetic impurity X atoms, such as Li, Be, B, C, O, F, Ne, Na, and Mg on cation site in 4H-GaN polytype. The results reveal that Ne doped 4H-GaN has the highest magnetic moment of 3µB, whereas Mg doped 4H-GaN has the lowest magnetic moment of 0.75µB. Among the systems studied 4H-GaN doped Ne has been found to be half-metallic, whereas 4H-GaN doped F and Na are found to be nearly half-metallic. The partial density of states evidence that magnetism is achieved through a p-p like coupling between the impurity and the host 2p states.Furthermore, we inspect whether there exists a relationship between the spin-polarization and the local structure around the doping X atoms. It is found that for all the compounds studied, the total magnetic moment increases with increasing the X–N bond lengths. Interestingly, 4H-GaN:Be becomes ferromagnetic with increasing the Be–N bond length, whereas 4H-GaN:Na and 4H-GaN:F become half-metallic with increasing Na–N and F–N bond lengths.