First principles total-energy pseudopotential calculations have been
performed to investigate STM images of the (110) cross-sectional surface of
Mn-doped GaAs. We have considered configurations with Mn in interstitial
positions in the uppermost surface layers with Mn surrounded by As (IntAs)
or Ga (IntGa) atoms. The introduction of Mn on the GaAs(110) surface
results in a strong local distortions in the underlying crystal lattice, with
variations of interatomic distances up to 3% with respect to unrelaxed ones. In
both cases, the surface electronic structure is half-metallic (or \emph{nearly}
half metallic) and it strongly depends on the local Mn environment. The nearby
Mn atoms show an induced spin-polarization resulting in a ferromagnetic Mn--As
and antiferromagnetic Mn--Ga configuration. The simulation of the STM images
show very different pattern of the imaged Mn atom, suggesting that they could
be easily discerned by STM analysis.Comment: Typos correcte