Magnetism of 3d Transition Metals Doped 2H, 4H and 6H-GaN Polytypes

Abstract

We present spin-polarized density-functional theory study of substitutional 3d transition metal (TM) atoms (Sc → Ni) in various host polytypes of GaN. For the structural parameters, we found that a(c) decreases (increases) from Sc to Ni. Additionally, calculations reveal decreasing (increasing) of the lattice constants a (c/a ratio) with increasing hexagonality h. In spite of the small cell used, TM atoms doped GaN polytypes with Ti, Cr, Mn, Fe, Co, and Ni show ferromagnetic character; whereas Sc and V dopant systems show, respectively, semiconducting and metallic behavior. The origin behind magnetism in 3d transition metal atoms doped 2H, 4H, and 6H-GaN polytypes is clarified through the ordering of spin-up (t+, e+) and spin-down (t-, e-) states.