Two-dimensional Mn structure on the GaN growth surface and evidence for room-temperature spin ordering

A class of striped superstructures with local hexagonal ordering has been obtained by depositing submonolayer Mn on the GaN(0001) surface. Combining scanning tunneling microscopy and first-principles theory, we find that Mn atoms incorporate into the surface and form a high-density two-dimensional MnxGa1-x structure. The highly spin-polarized Mn d electrons are found to dominate the surface electronic states. For the narrowest stripes, we calculate a row-wise antiferromagnetic ground state, which is observed in real space at room temperature as a spin-induced asymmetry in the density of states. These two-dimensional magnetic structures on GaN can also be considered model systems for wide-band-gap magnet/semiconductor spin injectors.