Magneto-optic effect of the ferromagnetic diluted magnetic semiconductor Ga1−xMnxAs

Magnetic circular dichroism (MCD) of a ferromagnetic diluted magnetic semiconductor ${\mathrm{Ga}}_{\text{1−x}}{\mathrm{Mn}}_x\mathrm{As}$ films was measured to clarify their electronic structure. Strong enhancement of MCD by Mn substitution indicated a strong $\mathrm{sp–d}$ hybridization. The $\mathrm{p–d}$ exchange interaction was concluded to be antiferromagnetic, which was in contrast with the reported ferromagnetic $\mathrm{p–d}$ exchange in very diluted paramagnetic GaAs:Mn bulk crystals. The change of the character of the $\mathrm{p–d}$ exchange interaction is due to the unique feature of ${\mathrm{Ga}}_{\text{1−x}}{\mathrm{Mn}}_x\mathrm{As}$ that the relative abundance of the neutral and ionized Mn acceptors controls the $\mathrm{p–d}$ exchange.