Digital magnetic heterostructures based on GaN

Delta doped heterostructures based on GaN are possible wide band gap spintronic material with high temperature ferromagnetic transition [Hory et al, Physica B 324, 142 (2002); Reed et al, Appl. Phys. Lett. 79, 3473 (2001)]. They are formed by a thin magnetic layer or submonolayer, embedded into thick semiconductor layers [Marques et al, Phys. Rev. B 73, 224409 (2006)]. In this work we studied digital magnetic heterostructures with isolated magnetic monolayers of V, Cr, Mn, Fe, Co, Ni, or Cu embedded in GaN. We performed first-principles calculations within the density functional theory with self-energy, to account for excitation energies [Ferreira et al, Phys. Rev. B 78, 125116 (2008)]. The technique allowed us to calculate the GaN band gap as $E^{calculated}_{gap}=3.53eV$ with no adjustable parameters. GaN:V and GaN:Cr do have ferromagnetic ground states with high Curie temperatures, as predicted by a mean-field approximation. GaN:Cr presents a 2D half-metallic ground state with 100\% spin polarization. GaN:V has an unusual ground state, with a 2.0$\mu_B$ magnetic moment, no states at the Fermi energy, a minority spin gap of 3.0eV, and a majority spin gap of only 0.3eV.