Control of } -Axis Orientation of }\textbf } Ordered FePt, CoPt, and FePd Alloy Thin Films Deposited on MgO(001) Substrates

• Published in: IEEE transactions on magnetics 2014-11, Vol.50 (11), p.1-4
• Main Authors: Ohtake, Mitsuru, Itabashi, Akira, Futamoto, Masaaki, Kirino, Fumiyoshi, Inaba, Nobuyuki
• Format: Article
• Language: English
• Subjects: Annealing; Crystals; Diffraction; Magnetism; Metals; Perpendicular magnetic anisotropy; Substrates; X-ray scattering
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2014.2328624

L1 0 films formed on (001)-oriented underlayers or substrates may involve (100) crystal with the c-axis lying in the film plane in addition to (001) crystal with the c-axis normal to the film surface. In this paper, FePt, CoPt, and FePd alloy films with L1 0 structure are prepared on MgO(001) single-crystal substrates. The c-axis orientation is accurately controlled to be perpendicular by introducing a thin MgO cap layer on magnetic films with disordered structure prepared by low-temperature deposition at 200 °C and by annealing the bilayer films at 600 °C. The phase transformation preferentially occurs along the perpendicular direction in the MgO/(FePt, CoPt, FePd)/MgO sandwich structures. Furthermore, the cap layer promotes L1 0 ordering. The order degrees of FePt, CoPt, and FePd films with and without cap layers, (S w/ , S w/o ), are (0.82, 0.58), (0.36, 0.30), and (0.72, 0.62), respectively. The FePt film with cap layer shows a strong perpendicular magnetic anisotropy and a very low in-plane coercivity because of which the film does not include L1 0 (100) crystal and possesses a high-order degree.