  We report a theoretical and experimental investigation of Cr-doped AlN.
Density functional calculations predict that the isolated Cr t2 defect level in
AlN is 1/3 full, falls approximately at midgap, and broadens into an impurity
band for concentrations over 5%. Substitutional Al1-xCrxN random alloys with
0.05 <= x <= 0.15 are predicted to have Curie temperatures over 600 K.
Experimentally, we have characterized and optimized the molecular beam epitaxy
thin film growth process, and observed room temperature ferromagnetism with a
coercive field, Hc, of 120 Oersted. The measured magnetic susceptibility
indicates that over 33% of the Cr is magnetically active at room temperature
and 40% at low temperature.
