Magnetic properties of Fe-Si-Al alloy films fabricated by DC magnetron sputtering are systematically examined. A large relaxation in coercive force, H//c, by annealing is found around 300 to approximately 400 degree C. Mechanisms of this sudden relaxation are discussed in connection with phase transformations from disordered alpha phase (as-deposited) to ordered DO//3 structure. The precise composition dependence of H//c in films is clarified. Excellent soft magnetic properties, H//c equals 0. 5 Oe and mu eff greater than 1000 at 5 MHz, are 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 is found to be nearly the same as that of bulk Sendust alloy, while the latter is completely different. The composition dependence of H//c is discussed on the basis of magnetocrystalline anisotropy, and magnetostriction in bulk single crystals.
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