Synthesis, characterization, and modeling of high quality ferromagnetic Cr-doped AlN thin films

We report a theoretical and experimental investigation of Cr-doped AlN. Density functional calculations predict that the isolated Cr t(2) 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 0.05less than or equal toxless than or equal to0.15 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, H-c, of 120 Oe. The measured magnetic susceptibility indicates that over 33% of the Cr is magnetically active at room temperature and 40% at low temperature.