Molecular beam epitaxy growth of Mn4−xNixN thin films on MgO(0 0 1) substrates and their magnetic properties

• Published in: Journal of crystal growth 2019-02, Vol.507, p.163-167
• Main Authors: Komori, Taro, Anzai, Akihito, Gushi, Toshiki, Toko, Kaoru, Suemasu, Takashi
• Format: Article
• Language: English
• Subjects: A1. Crystal structure; A3. Molecular beam epitaxy; B1. MgO; B1. Mn4N; B1. Ni4N; B2. Magnetic materials; Crystal structure; Decomposition; Domain walls; Electron diffraction; Epitaxial growth; High energy electrons; Lattice parameters; Magnesium oxide; Magnetic anisotropy; Magnetic properties; Magnetic saturation; Magnetism; Manganese; Materials substitution; Memory devices; Molecular beam epitaxy; Nickel base alloys; Substrates; Thin films; X ray reflection; X-ray diffraction
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2018.11.019

•Mn4−xNixN films were grown on MgO(0 0 1) by molecular beam epitaxy.•The saturation magnetization (MS) and perpendicular magnetic anisotropy diminished with a small amount of Ni substitution.•The MS value was remarkably decreased from 86 emu/cm3 (Mn4N) to 19 emu/cm3 (Mn3.75Ni0.25N).•Magnetic anisotropy constants of 0.94 and 0.027 Merg/cm3 were obtained, respectively. We grew Mn4−xNixN epitaxial thin films on MgO(0 0 1) by molecular beam epitaxy, as well as studied their crystalline qualities and magnetic properties. The films were decomposed into Ni8N or Mn-Ni alloys when x ≥ 2, as confirmed by X-ray diffraction and reflection high-energy electron diffraction, but this decomposition was mitigated by reducing the substrate growth temperature. The lattice constants decreased with increased Ni substitution except when the Mn ratio was high, while the crystal orientation tended to degrade. The magnetic properties were measured via vibrating sample magnetometer, and it was found that the saturation magnetization (MS) and perpendicular magnetic anisotropy (PMA) diminished with a small amount of Ni substitution. Specifically, the MS value was remarkably decreased from 86.3 ± 1.1 emu/cm3 (Mn4N) to 19.0 ± 0.5 emu/cm3 (Mn3.85Ni0.25N), and the magnetic anisotropy constant was decreased from approximately 0.94–0.027 Merg/cm3, respectively. The PMA vanished with further Ni substitution. Ultimately, a small MS and a PMA were simultaneously achieved with a small amount of Ni substitution. These properties support spin transfer torque, which can be applied to the emerging non-volatile memory devices using domain wall motion.