A systematic Mn $L$-edge x-ray absorption and magnetic circular dichroism study is carried out on ${\mathrm{Ga}}_{1-x}{\mathrm{Mn}}_x\mathrm{As}$ ferromagnetic semiconductors with $x$ ranging from 0.021 to 0.081. The dichroism lineshape of the $L_3$ peak is found to be independent of $x$, indicating an identical average local ferromagnetic Mn configuration across the Mn concentration range and the absence of significant second ferromagnetic phase formation. Further first-principles calculations suggest that the single-peak spectroscopic features stem from the presence of a significant amount of dimers composed of substitutional Mn coupled with interstitial Mn.

• Received 10 November 2004

DOI:https://doi.org/10.1103/PhysRevB.71.153310