2014/11/01 by Mitsuru Ohtake, Akira Itabashi, Masaaki Futamoto +2
Physics and Astronomy · Materials Science · #Magnetic properties of thin films #Magnetic and transport properties of perovskites and related materials #Physics of Superconductivity and Magnetism
paper · doi:10.1109/tmag.2014.2328624
L1 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ordering. The order degrees of FePt, CoPt, and FePd films with and without cap layers, (S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w/</sub> , S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">w/o</sub> ), 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 <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (100) crystal and possesses a high-order degree.