High Curie temperatures in ferromagnetic Cr-doped AlN thin films

Al1-xCrxN thin films with $0.02\le x \le 0.1$ were deposited by reactive co-sputtering onto c-plane (001) sapphire. Room-temperature ferromagnetism with a coercive field of 85 Oe was observed in samples with chromium contents as low as x = 0.027 (2.7%). With increasing Cr content the mean magnetic moment is strongly suppressed, with a maximum saturation moment of 0.62 and 0.71 $\mu_B$ per Cr atom at 300 and 50 K respectively. We show that the Curie temperature of Al1-xCrxN for x = 0.027 is greater than 900 K.