Structural and magnetic properties of as-cast Nd-(Fe,Co)-Al alloys

Partially amorphous Nd60FexCo30-xAl10 (0 less than or equal to x less than or equal to 30) alloys were prepared by copper mold casting. The effect of transition metal content on the glass-forming ability and the magnetic properties was investigated. The Nd60Co30Al10 alloy exhibit's an amorphous structure shown by the corresponding diffraction pattern. A small substitution of Co by 2.5 at.% Fe results in the formation of Fe-rich crystallites embedded in the Nd-rich amorphous matrix. The Fe-rich crystallites show hard magnetic behaviour at room temperature with a coercivity value of about 4 kOe and a Curie temperature of 500 K. The magnetic behaviour and the composition of these crystallites were found to resemble those of the metastable A(1) (or mu) phase. The amount of hard magnetic phase and the remanence increase with increasing Fe content. However, the coercivity and the Curie temperature do not change significantly with Fe content indicating the formation of the same magnetic phase in the alloys. The presence of Co and Al in the present alloys suppresses the formation of Nd2Fe17 and Nd5Fe17 phases resulting in the formation of a large amount of hard magnetic phase in comparison to the corresponding as-cast Nd100-xFex binary alloys.