Effect of microstructure on the magnetic properties of mold-cast and melt-spun Nd-Fe-Co-Al amorphous alloys

Abstract In this paper, we discuss the role of quenched-in crystallites and amorphous matrix for the large coercivity of Nd-Fe-Co-Al bulk cylinders. The present investigations of mold-cast and melt-spun Nd60FexCo30-xAl10 0≤x≤10 samples show that the Fe-rich as-cast (x=7.5, 10) bulk cylinders exhibit a partially crystalline structure, whereas the melt-spun ribbons and Co-rich as-cast x≤5 bulk cylinders are amorphous. Spherulite-like regions consisting of Nd-rich and metastable (≈Nd36Fe32Co28Al4) crystallites along with an amorphous matrix were observed in the as-cast Fe-rich bulk cylinders. The Co-rich ribbons and bulk cylinders with x≤5 show a distinct endothermic peak in the DSC traces due to a glass transition in the range of 477–489 K. With further increasing Fe content the glass transition is masked by the crystallization. The effect of the Fe/Co ratio on the magnetic properties and the glass transition is discussed.