The structure and magnetic properties of melt-spun Fe₅₅Pt ₂₅B₁₈M₂ (M C, P, Si) alloys

The effects of additional C, P or Si on the structure and magnetic properties of melt-spun Fe₅₅Pt₂₅B₂₀ alloy have been investigated. The mixed structure consisting of amorphous and fcc-FePt phases was formed for the Fe₅₅Pt₂₅B₁₈M ₂ (M=B, C or Si) alloys. Addition of 2at.% of P increased the amorphous-forming ability of the Fe-Pt-B alloy, leading to the formation of an amorphous phase in the M=P alloy. A homogeneous nanocomposite structure consisting of hard L1₀-FePt and soft Fe₂B magnetic phases with average grain sizes of ∼ 40 nm was formed in all the melt-spun alloys annealed at 825 K for 900 s. The good hard magnetic properties with high coercivity of over 540 kA /m were obtained for the M C or P nanocomposite alloys.