A systemic study was made of dilute magnetic semiconductors doped with rare-earth elements (La, Ce–Yb) using the full-potential linearized augmented plane wave method within the framework of density functional theory, and adding consideration of the electronic correlation and the spin-orbital coupling effects. A study was made of the electronic structures of DMSs, especially for the contribution from f electrons. The origin of magnetism, magnetic interaction and the possible mechanism of the colossal magnetic moment were explored. It was found that, for materials containing f electrons, electronic correlation was usually strong and the spin–orbital coupling was sometimes crucial in determining the magnetic ground state. It was found that GaN doped by La was non-magnetic. GaN doped by Ce, Nd, Pm, Eu, Gd, Tb and Tm were stabilized at antiferromagnetic phase, while GaN doped by other RE elements show strong ferromagnetism which was suitable materials for spintronic devices. Moreover, it was shown that the observed large enhancement of magnetic moment in GaN was caused mainly by Ga vacancies (3.0μB per Ga vacancy), instead of the spin polarization by magnetic ions or originating from N vacancies. Various defects, such as substitutional Mg for Ga, O for N under the RE doping were found to bring a reduction of ferromagnetism. In addition, intermediate bands were observed in some systems of GaN:RE and GaN with intrinsic defects, which possibly opens the potential application of RE-doped semiconductors in the third generation high efficiency photovoltaic devices.

Ga Vacancy Induced Ferromagnetism Enhancement and Electronic Structures of RE-Doped GaN. G.Zhong, K.Zhang, F.He, X.Ma, L.Lu, Z.Liu, C.Yang: Physica B, 2012, 407[18], 3818–27