  This work reports theoretical and experimental study of the X-ray absorption
near-edge structure (XANES) at the Mn K-edge in (Ga,Mn)As diluted magnetic
semiconductors. The spectra have been calculated from the first-principles
using FLAPW including the core-hole effect, a special attention has been paid
to consequences of coexistence of Mn impurities in substitutional and
tetrahedral interstitial positions. We have performed quantitative component
analysis of experimental spectra collected on the (Ga,Mn)As samples
before/after annealing and etching, with the aim to determine the proportion of
Mn impurity configurations. Comparison of the experimental data with
theoretical computations indicates that even after annealing and etching some
Mn atoms still reside in interstitial sites, although the concentration of
interstitial defects has been reduced by annealing.
