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

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 3 mu(B), whereas Mg doped 4H-GaN has the lowest magnetic moment of 0.75 mu(B). 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. (C) 2016 Elsevier B.V. All rights reserved.