Structure and magnetic properties of chill-cast and melt-spun Nd_x(Fe₃Al)_100-x and Nd₃₃(Fe_yAl)₆₇ alloys

The magnetic properties of chill-cast Nd-Fe-Al rods have been studied as a function of Nd and Al concentrations. High coercivities were obtained in Nd₆₀(Fe₃Al)₄₀, Nd₅₀(Fe₃Al)₅₀ and Nd₃₃(Fe₁₀Al)₆₇ alloys. The study on the melt-spun ribbons of these alloys has shown that coercivity is dependent on the quenching rate, and high coercivity could only be obtained in alloys prepared after a relatively low quenching rate. Several crystalline Nd-Fe-Al phases have been investigated in this work. A metastable tetragonal phase existed as nearly the single phase in Nd₃₃(Fe_yAl)₆₇ with y = 2-4. The tetragonal phase is antiferromagnetic with a Néel temperature of 260 K. Metamagnetism and magnetoresistivity have been observed. The study on the annealed Nd₃₃(FeAl)₆₇ alloy has shown that a hexagonal phase and an unknown were formed and these two Fe-containing phases, among which one is an antiferromagnetic with a Néel temperature of 280 K and the another is ferromagnetic below 130-140 K.