Glass-forming ability and magnetic properties of Nd70-xFe20Al10Cox alloys

The influence of Co addition on the glass-forming ability of slowly cooled Nd70-xFe20Al10Cox alloys (0 less than or equal to x less than or equal to 1 0) was studied by x-ray diffraction, constant-rate heating calorimetry, and magnetic measurements. Without addition of Co, the as-cast Nd70Fe20Al10 cy linders of 3-mm diameter show a mixture of amorphous and crystalline phases after copper mold casting. Increasing the Co content promotes amorphizatio n, and bulk amorphous specimens can be obtained for Nd60Fe20Al10Co10. No gr ass transition or supercooled liquid region before crystallization was obse rved for the bulk Nd60Fe20Al10Co10 alloy. The bulk amorphous alloy exhibits hard magnetic behavior with a remanence (J(r)) of 0.09 T, a magnetization (J(1500)) of 0.13 T, and a coercivity (H-c) of 298 kAm(-1). The Curie tempe rature for the as-cast Nd70-xFe20Al10Cox cylinders increases from 480 K for x = 0 to 487 K for x = 10. The enhanced glass-forming ability for the Nd-F e-Al-based alloys upon Co addition will be critically discussed with respec t to classical nucleation theory and the formation of metastable ordered cl usters upon solidification.