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

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% A1 by melt spinning. Ferromagnetic Pr 90-x Fe x Al 10 bulk amorphous alloys with high coercive force at room temperature are obtained by a copper mold casting method. The maximum diameter of the cylindrical amorphous samples with a length of 50 mm is 3 mm for the 30%Fe alloy and 1 mm for the 20%Fe, 40%Fe and 50%Fe alloys. Neither the glass transition nor the supercooled liquid region is observed in the temperature range before crystallization (T < T x ), which is different from other bulk amorphous alloys exhibiting wide supercooled liquid regions. The extremely high T x /T m and small ΔT m (= T m - T x ) values are the reason for the achievement of large glass-forming ability in this system. The bulk amorphous Pr 60 Fe 30 Al 10 alloy is ferromagnetic with the Curie temperature (T c ) of 515 K which is higher than the highest T c of 470 K for Pr-Fe binary amorphous ribbons. The remanence (B t ) and intrinsic coercive force ( 1 H c ) are 0.089 T and 300 kA/m, respectively, and the crystallization to Pr+Al 2 Pr+δ phases causes a ferromagnetic-to-paramagnetic phase transition. Thus, the hard magnetic properties are achieved only in the amorphous state.