Observation of strong-coupling effects in a diluted magnetic semiconductor Ga1-xFexN

The giant Zeeman splitting of free excitons is measured in Ga1-xFexN. Magneto-optical and magnetization data imply the ferromagnetic sign and a reduced magnitude of the effective p-d exchange energy governing the interaction between Fe3+ ions and holes in GaN, N-0 beta((app))=+0.5 +/- 0.2 eV. This finding corroborates the recent suggestion that the strong p-d hybridization specific to nitrides and oxides leads to significant renormalization of the valence band exchange splitting.