Influence of microstructure on soft magnetic properties of low coreloss and high B_s Fe₈₅Si₂B₈P ₄Cu₁ nanocrystalline alloy

Microstructure and magnetic properties of high B_s Fe ₈₅Si₂B₈P₄Cu₁ nano-crystalline alloy were tailored. The B_s ∼1.85T and low coercivity H_c ∼6A/m were obtained by conventional annealing (i.e., one step) at a heating rate of ∼400°C/min. While one step annealing process produces a fairly stable nanostructure, for short times at temperatures <425°C, the nanostructure and concomitant magnetic properties of this alloy are shown to be tunable by two step annealing process. Nanocrystalline ribbons with grain size (D) ranging from ∼15 to 32nm, H _c ∼6 to 140A/m and core-loss at 1.5T, 50Hz ∼0.39 ∼5.0W/kg were obtained. The H_c of Fe₈₅Si₂B ₈P₄Cu₁ alloy is shown to vary as D⁶, but a small deviation was noticed, which may be due to weak anisotropy.