We describe a direct observation of the excitonic giant Zeeman splitting in (Ga,Mn)N, a wide-gap III-V diluted magnetic semiconductor. Reflectivity and absorption spectra measured at low temperatures display the A and B excitons, with a shift under magnetic field due to s,p-d exchange interactions. Using an excitonic model, we determine the difference of exchange integrals between Mn^3+ and free carriers in GaN, N_0(alpha-beta)=-1.2 +/- 0.2 eV. Assuming a reasonable value of alpha, this implies a positive sign of beta which corresponds to a rarely observed ferromagnetic interaction between the magnetic ions and the holes.
@article{arxiv.cond-mat/0703041,
title = {Excitonic giant Zeeman effect in GaN:Mn^3+},
author = {W. Pacuski and D. Ferrand and J. Cibert and J. A. Gaj and A. Golnik and P. Kossacki and S. Marcet and E. Sarigiannidou and H. Mariette},
journal= {arXiv preprint arXiv:cond-mat/0703041},
year = {2008}
}