High Curie temperatures in ferromagnetic Cr-doped AlN thin films

Al1−xCrxN thin films with 0.02⩽x⩽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 μB 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.