Mn-doped wurtzite GaN epilayers have been grown by nitrogen plasma-assisted molecular beam epitaxy. Correlated SIMS, structural and magnetic measurements show that the incorporation of Mn strongly depends on the conditions of the growth. Hysteresis loops which persist at high temperature do not appear to be correlated to the presence of Mn. Samples with up to 2% Mn are purely substitutional Ga1−xMnxN epilayers, and exhibit paramagnetic properties. At higher Mn contents, precipitates are formed which are identified as GaMn3N clusters by x-ray diffraction and absorption: this induces a decrease of the paramagnetic magnetisation. Samples co-doped with enough Mg exhibit a new feature: a ferromagnetic component is observed up to Tc∼175 K, which cannot be related to superparamagnetism of unresolved magnetic precipitates.
@article{arxiv.cond-mat/0307395,
title = {Ferromagnetic (Ga,Mn)N epilayers versus antiferromagnetic GaMn$_3$N clusters},
author = {R. Giraud and S. Kuroda and S. Marcet and E. Bellet-Amalric and X. Biquard and B. Barbara and D. Fruchart and D. Ferrand and J. Cibert and H. Mariette},
journal= {arXiv preprint arXiv:cond-mat/0307395},
year = {2007}
}