We analyze the magnetic behavior of well-characterized, precipitate-free ${\text{Ga}}_{1-x}{\text{Mn}}_x\text{N}$ thin films containing Mn at higher levels than previously attained; up to $x=0.36$. This level is above the percolation threshold $x_c$ for nearest-neighbor cations, such that exchange between nearest neighbors will dominate the magnetic response. The susceptibility decreases as the Mn content increases up to and beyond $x_c$, as an increasing fraction of the Mn experiences antiferromagnetic exchange. The dominance of antiferromagnetic behavior at higher Mn concentrations and the total lack of evidence for ferromagnetic ordering even above $x_c$ demonstrates that the nature of the exchange between ${\text{Mn}}^{2+}$ ions in GaN is antiferromagnetic.

• Received 18 November 2009

DOI:https://doi.org/10.1103/PhysRevB.81.184425