Manganese concentration and low-temperature annealing dependence of Ga_1-xMn_xAs by x-ray absorption spectroscopy

The Mn-site-projected electronic structure of the diluted magnetic semiconductors Ga_1-xMn_xAs (x =0.032, 0.038, 0.047, 0.052, 0.058) of as-grown and low-temperature-(LT) annealed samples are systematically studied using high-resolution Mn 2p absorption spectroscopy. The study exhibits coexistence of the ferromagnetic Mn²⁺ ion and the paramagnetic Mn-As complex that transforms into the ferromagnetic component with LT annealing. The ratio of ferromagnetic to paramagnetic components is directly related to the x dependence of the hole density and ferromagnetic critical temperature.