NdN: An intrinsic ferromagnetic semiconductor

The rare-earth nitrides have recently regained attention due to findings that most members of the series are intrinsic ferromagnetic semiconductors, a class of materials that is crucial for the development of spintronics devices. Here we present a study of NdN thin films, with films grown via molecular beam epitaxy. Optical transmission measurements revealed a band gap of about 0.9 eV, while resistivity measurements confirmed semiconducting behavior with a negative temperature coefficient of resistance, though semimetallic behavior could not be ruled out. The room temperature resistivity of 0.6mΩ0.16em0excm indicates strong doping by nitrogen vacancies. Magnetization measurements show a ferromagnetic moment of 1.0±0.2μB below the Curie temperature TC of 43±1 K, strongly suppressed from the Hund's rules value of 3.27μB per ion. The ferromagnetic moment is strongly quenched and the TC is enhanced compared to previously studied bulk NdN, and crystal field calculations reveal that the quenched moment is likely due to lattice strain. X-ray magnetic circular dichroism measurements show that the magnetic moment is orbital dominant, placing NdN in the same category as SmN, an intrinsic ferromagnetic semiconductor with an orbital-dominant ferromagnetic moment.