N. Hayashi, Y. Miyamoto, K. Machida
Feb 1, 2005
Journal of Magnetism and Magnetic Materials
Abstract The soft magnetic properties of Fe–Co–Al–O films deposited by sputtering (Fe 70 Co 30 ) 99 (Al 2 O 3 ) 1 on a variety of underlayers have been investigated. A remarkable reduction in coercivity, H c , was found in Fe–Co–Al–O films sputtered on underlayer materials, such as Au, Ag or Cu, that have a surface-free energy in the region of 1–2 J/m 2 . All underlayers induced a BCC-(1 1 0) preferred grain orientation in the Fe–Co–Al–O films, although this effect was weak for Au, Ag and Cu. When the surface free energy of the underlayer material is higher than 2 J/m 2 , as in the case of Hf, Fe–Co–Al–O films can be grown with a well-defined BCC-(1 1 0) crystallographic texture. The primary effect of varying the underlayer in Fe–Co–Al–O bilayer structures is to change the crystallographic texture of the Fe–Co–Al–O films due to the difference in surface-free energy. Transmission electron microscopy performed on cross-sections revealed the presence of clear columnar grains for all underlayers, with an average size of approximately 50 nm for Hf, dropping to 5–7 nm for Au, Ag and Cu. This allows us to explain qualitatively the reduction in H c using Hoffman's ripple theory.