Amorphous-crystalline dual-layer structures resulting from metastable liquid phase separation in (Fe₅₀Co₂₅B₁₅Si₁₀)₈₀Cu₂₀ melt-spun ribbons

(Fe₅₀Co₂₅B₁₅Si₁₀)₈₀Cu₂₀ ribbons are prepared by the single-roller melt-spinning method. A dual-layer structure consisting of a (Fe, Co)-rich amorphous phase and a Cu-rich crystalline phase forms due to metastable liquid phase separation before solidification. The magnetic hysteresis loops of the as-quenched and annealed samples are measured at room temperature. It is indicated that the coercivity of the ribbon is almost zero in as-quenched state. The crystallization leads to the increase of coercivity and decrease of saturation magnetization.