Structure and magnetism in Ga-rich MnGa/GaN thin films and unexpected giant perpendicular anisotropy in the ultra-thin film limit

• Published in: Applied surface science Vol. 367; no. C; pp. 312 - 319
• Main Authors: Mandru, Andrada-Oana, Corbett, Joseph P., Lucy, Jeremy M., Richard, Andrea L., Yang, Fengyuan, Ingram, David C., Smith, Arthur R.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 30.03.2016; Elsevier
• Subjects: Concentration (composition); Evolution; Ferromagnetic materials; Gallium nitride; Gallium nitrides; Magnetic properties; Magnetism; Manganese gallium; Molecular beam epitaxy; Perpendicular magnetic anisotropy; Scanning tunneling microscopy; Thin films; Manganese gallium; Scanning tunneling microscopy; Gallium nitride; Perpendicular magnetic anisotropy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2016.01.105

[Display omitted] •We investigate Ga-rich MnGa films grown by molecular beam epitaxy on GaN substrates.•The properties are explored as a function of film composition and thickness.•Scanning tunneling microscopy reveals highly epitaxial films with smooth surfaces.•All MnGa films exhibit ferromagnetism, including the very Ga-rich ones.•Giant perpendicular magnetic anisotropy is induced by decreasing the film thickness. We report structural, surface, and magnetic investigations of ferromagnetic Ga-rich MnGa thin and ultra-thin films grown on semiconducting GaN(0001) using molecular beam epitaxy. The Mn:Ga composition ratio is varied from ≈1 (stoichiometric) to ≈0.42 (very Ga-rich) for different samples. We find that the L10 MnGa phase is preserved down to a Mn:Ga ratio of ≈0.81. As the Ga concentration increases, we observe the coexistence of more Ga-rich phases, namely Mn3Ga5 and Mn2Ga5. Room temperature scanning tunneling microscopy imaging reveals highly epitaxial films, with atomically smooth and highly reconstructed surfaces. Magnetic characterizations show how the magnetic properties evolve with changing composition and that giant perpendicular magnetic anisotropy is induced by reducing the size of our films.