Preparation of Bulk Pr–Fe–Al Amorphous Alloys and Characterization of Their Hard Magnetic Properties

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Abstract
The amorphous phase in the Pr–Fe–Al system is formed in an extremely wide composition range of 0 to 90 at% Fe and 0 to 93 at% Al by melt spinning. Ferromagnetic Pr90−xFexAl10 bulk amorphous alloys with high coercive force at room temperature are obtained by a copper mold casting method. The maximum diameter of the cylindrical amorphoussamples with a length of 50 mm is 3 mm for the 30%Fe alloy and 1 mm for the 20%Fe, 40%hFe and 50%hFe alloys. Neither the glass transition nor the supercooled liquid region is observed in the temperature range before crystallization (T<Tx), which is different from other bulk amorphous alloys exhibiting wide supercooled liquid regions. The extremely high Tx⁄Tm and small ΔTm(=Tm−Tx) values are the reason for the achievement of large glass-forming ability in this system. The bulk amorphous Pr60Fe30Al10 alloy is ferromagnetic with the Curie temperature (Tc) of 515 K which is higher than the highest Tc of 470 K for Pr–Fe binary amorphous ribbons. The remanence (Br) and intrinsic coercive force (iHc) are 0.089 T and 300 kA/m, respectively, and the crystallization to Pr+Al2Pr+δ phases causes a ferromagnetic-to-paramagnetic phase transition. Thus, the hard magnetic properties are achieved only in the amorphous state.