Magnetic Dopants on GaAs (110) and ZnS (110) Surfaces

Magnetic dopants in bulk semiconductors and their surfaces, such as transition metals Fe, Co, Ni, and Cu, offer excellent platforms to study magnetic phenomena for future applications in spintronics, optoelectronics, and quantum information processing with a possibility of the coherent, room-temperature interface between spins and photons, robust exchange interactions of spin centers, and potential of inducing also enhancing of the ferromagnetic order by doping. In this study, we use first-principles calculations to focus on Fe, Co, Ni, and Cu defects on (110) surfaces of GaAs and ZnS. We first report the formation energies of these defects in the bulk crystal for differently charged configurations. We show the relaxed structures of these dopants on the surfaces. Next, we compute the total and projected density of states, electronic structure, and exchange interactions between pairs of the dopants. We show the trend of the exchange interactions between pairs as a function of the pair separation and the strength of the Hubbard U corrections. We also compare the ferromagnetic and antiferromagnetic ground states of the pairs.