Growth and magnetic property of ζ-phase Mn2N1±x thin films by plasma-assisted molecular beam epitaxy

ζ-phase manganese nitride films were directly grown on sapphire substrates using plasma-assisted molecular beam epitaxy. Mn2N1.06, Mn2N0.98, and Mn2N0.86 films were synthesized by controlling the temperature of the effusion cell filled with highly pure manganese powder. The composition, structure, and morphology of the films were identified by x-ray photoelectron spectroscopy, x-ray diffraction and atomic force microscopy, and the magnetic properties of the films were characterized by a superconducting quantum interference device magnetometer at 5 and 300 K. The magnetic measurements reveal that Mn2N1±x exhibits weak ferromagnetism at 5 K, which is mainly ascribed to the weak interaction among the Mn cations induced by the nitrogen vacancies. Furthermore, the Mn2N0.86 single-crystalline films are found to have room-temperature ferromagnetism, which is attributed to the strain of the Mn2N0.86 films raised from lattice mismatch between the Mn2N0.86 films and the substrates.