Impurity distribution and ferromagnetism in Mn-doped GaAs nanowires: A first-principle study

Using first-principles calculations, we investigate the effect of surface passivation on the impurity distribution and magnetic properties in Mn-doped GaAs nanowires. A comparative analysis for the zinc-blend and wurtzite structures is made. Our results show that when the Mn-doped position shifts from the center to the edge, the Mn formational energy is reduced in the bare nanowire, while this behavior is reversed in the nanowire with surface dangling bonds passivated by pseudo-H. For the zinc-blend structured nanowire, a noticeable transformation from the antiferromagnetic to ferromagnetic coupling by surface passivation can be observed. However, for the wurtzite structured nanowire, the transformation cannot be observed, and the magnetic order exhibits the larger ferromagnetic coupling compared to that of the zinc-blend structure. A brief analysis of these results is given.