Magnetic Properties of Fe-Si-Al Sputtered Films

Magnetic properties of Fe-Si-Al alloy films fabricated by dc magnetron sputtering were systematically examined. A remarkable relaxation in coercive force, H
_C
, by annealing was found around 300~400°C. Mechanisms of this sudden relaxation were discussed in connection with phase transformations from disordered a phase (as-deposited) to ordered DO
₃
structure. Precise composition dependence of H
_c
in films was clarified. Excellent soft magnetic properties, H
_c
= 0.5 Oe and μ
_eff
≫ 1000 (at 5 MHz), were obtained at two different compositions: 9.0 wt%Si, 5.7 wt% Al, bal. Fe., and 8.0 wt%Si, 4.2 wt%Al, bal. Fe. The former composition was found to be nearly the same as that of bulk Sendust alloy, while the latter is completely different from bulk Sendust composition. The descussion was further developed on the composition dependence of H
_c
, based on the composition dependence of magnetocrystal 1ine anisotropy, K
₁
, and magnetostriction in bulk single crystals.