Study of Mn interstitials in (Ga, Mn)As using high-resolution x-ray diffraction

We present a method for the determination of the concentration of Mn ions in nonequivalent interstitial positions in the lattice of (Ga, Mn)As. The Mn ions occupy substitutional and/or interstitial positions in the GaAs lattice and the dependence of the structure factor on their concentration differs for various diffractions and for different positions in the lattice. We measured several diffractions including weak diffractions, which are very sensitive to the Mn content. All measured diffraction curves were simultaneously fitted to a theoretical model and the densities of Mn ions, in particular interstitial positions, were obtained. The method reported here allows us to determine the amount of interstitial Mn which, according to current understanding, affects the ferromagnetic properties including the Curie temperature in (Ga, Mn)As.