PHASE-TRANSITION AND MAGNETIC-PROPERTIES OF RAPIDLY SOLIDIFIED ND-FE ALLOYS

Abstract

The magnetic phase transition taking place in melt-spun NdFe2 alloys during annealing is discussed. The high intrinsic coercive force ((i)H(c) = 2-3.5 kOe) of NdFe7 phase exhibiting a Curie temperature of 230-235-degrees-C was found to form in the melt-spun NdFe2 alloy. The NdFe7 phase transforms into Nd5Fe17 plus Nd2Fe17 in association with a Nd-rich phase under a vacuum atmosphere. Under an oxygen-controlled atmosphere, the NdFe7 + (Nd-rich) phases transform directly into Nd2O3 plus alpha-Fe. The Nd5Fe17 phase is observed to be magnetically soft ((i)H(c) = 0.18 kOe) and exhibits a rather higher Curie temperature (T(C) = 240-245-degrees-C) than that of the NdFe7 phase. The melt-spun NdFe2 alloy shows a magnetic anomaly at 325-350 K indicating the spin reorientation in NdFe7 crystals.