Local environment surrounding ferromagnetically ordered Mn in Mn/GaAs digital alloys and (Mn, Ga)As random alloys

The local environment surrounding ferromagnetically ordered Mn in Mn/GaAs digital layers and (Ga, Mn)As random alloys has been selectively probed using a combination of local structural information obtained by x-ray magnetic circular dichroism (XMCD) and extended x-ray absorption fine structure (EXAFS) techniques. The Mn/GaAs digital layers and (Ga, Mn)As random alloys exhibit an exceptionally large XMCD of 42% ± 2% and 39% ± 2% at the Mn L₃ absorption edge, indicating that a high percentage of at least 71% and 66% Mn atoms with robust local magnetic moments actually participate in the ferromagnetic ordering, respectively. The observed Mn L₃-edge XMCD spectra and Mn K-edge EXAFS spectra are very similar for the Mn/GaAs digital layers and (Ga, Mn)As random alloys, but clearly different from those found in a reference MnAs film. These results provide direct evidence that the ferromagnetism observed in the Mn/GaAs digital layers and (Ga, Mn)As random alloys is mainly due to the Mn atoms occupying the Ga sites in the GaAs host instead of possible MnAs magnetic clusters.