Exchange Interaction in Iron Dimers on GaAs (110) Surface

Substitutional dopants in semiconductors such as transition metal Fe, Mn, and Co in III-V compounds offer excellent platforms to study magnetic phenomena for future applications in spintronics, optoelectronics, and quantum information processing. The main subjects of this study are single Fe and Fe-dimers on (110) GaAs surfaces. Based on the density functional theory we first calculate the electronic structure and orbital projected density of states for the single iron on the surface and in the bulk of the GaAs. We compare these results with previous studies in the literature, find an excellent agreement in the bulk calculations, and discuss agreements and dissimilarities for the surface calculations especially in the electronic states appearing in the bandgap. Next, we calculate the density of states, orbital projected densities, and electronic band structures of the Fe dimers on the surface. We also calculate the strength of the Fe-Fe exchange interactions in dimers as a function of the distance and direction. Finally, we include a variable Hubbard U term to show how the ground state alters between ferromagnetic and antiferromagnetic configurations with changing U.