Origin of high-temperature ferromagnetism in (Ga,Mn)N layers grown on 4H-SiC(0001) by reactive molecular-beam epitaxy

We report on the growth, structural as well as magnetic characterization of (Ga,Mn)N epitaxial layers grown directly on 4H-SiC(0001) by reactive molecular-beam epitaxy. We focus on two layers grown under identical conditions except for the Mn/Ga flux ratio. Structural characterization reveals that the sample with the lower Mn content is a uniform alloy, while in the layer with the higher Mn content, Mn-rich clusters are found to be embedded in the (Ga,Mn)N alloy matrix. Although the magnetic behavior of both the samples is similar at low temperatures, showing antiferromagnetic characteristics with a spin-glass transition, the sample with higher Mn content additionally exhibits ferromagnetic properties at and above room temperature. This ferromagnetism most likely originates from the Mn-rich clusters in this sample. (C) 2003 American Institute of Physics.