Hard magnetic bulk amorphous alloys

An amorphous phase in Ln-Fe-Al (Ln=Nd and Pr) systems is formed in wide composition ranges of 0 to 90 at% Fe and 0 to 93 at% Al by melt spinning. Ferromagnetic Ln_90-xFe_xAl₁₀ bulk amorphous alloys with high coercive force (_lH_c) at room temperature are obtained by copper mold casting. The maximum diameter of the cylindrical amorphous samples is 12 mm for the Nd-30%Fe-Al alloy and 3 mm for the Pr-30%Fe-Al alloys and decreases with deviating Fe content The extremely high T_x/T_m and small ΔT_m(=T_m-T_x), which are evaluated by the crystallization (T_x) temperature (T_x) and melting temperature (T_m) , are the reason for the achievement of large glass-forming ability in these systems. The bulk amorphous Ln₆₀Fe₃₀AJ₁₀ alloys are ferromagnetic with the Curie temperature of 515 to 600 K which are higher than those for Nd-Fe and Pr-Fe binary amorphous ribbons. The remanence and _lH_c are 0.089 to 0.122 T and 277 to 321 kA/m, respectively, and the crystallization to Ln+Al₂Ln+δ causes a ferromagnetic- to -paramagnetic transition. Thus, the hard magnetic properties are achieved only in the amorphous state.