Interlayer exchange coupling in GaN-based diluted magnetic semiconductor multilayers studied by first-principles calculations

Interlayer exchange coupling (IEC) in a series model diluted magnetic semiconductor (DMS) multilayer consisting of two magnetic (Ga, M) N (M Mn or Cu) layers separated by non-doped or Mg-doped GaN non-magnetic spacers has been studied by first-principles calculations. The effects of the spacer thickness and of the hole doping to the IEC were studied systematically. It is observed that (1) without Mg doping, the IEC between two magnetic (Ga, M) N (M Mn or Cu) layers is always ferromagnetic, which is clarified as an intrinsic character of the Ruderman-Kittle-Kasuya-Yoshida interaction in a two dimensional gaped system; (2) with Mg doping into the GaN spacer, the IEC is tunable from ferromagnetic to antiferromagnetic by varying the spacer's thickness and the dopant's site. It is found that the significant hybridization between the Cu and Mg dopants contributes considerable density of states around the Fermi energy level and thus enhances the magnetic interaction between the Cu-doped magnetic layers, indicating that Cu is a better dopant for device application of the GaN-based DMS multilayers. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3602992]