Crystallographic and M?ssbauer studies of sintered Nd-Fe-B magnet

摘要

Nd-Ga-Fe_(bal).-Nb-B alloy with Nd_2Fe_(14)B structure was synthesized by using the strip casting method. The Nd-Ga-Fe_(bal).-Nb-B alloy retains the tetragonal structure with lattice constants a _0 = 8.802, and c _0 = 12.215 ?. M?ssbauer spectra were recorded at various temperatures ranging from 4.2 to 620 K. The Curie temperature (T _C), and Debye temperature (Θ_D) were determined to be T _C = 613, and Θ_D = 471.4 K, respectively. Each spectrum below T _C was fitted with six subspectra of Fe sites (8j _1, 8j _2, 16k _1, 16k _2, 4c, and 4e) based on the occupancy of Fe ions probability distribution. The area ratios of subspectra at 4.2 K are 12.8, 12.8, 29.6, 29.1, 6.8, and 9.1%, respectively. The magnetic hyperfine fields (H _(hf)) for the Fe sites decrease in the order H _(hf)(8j _2) > H _hf)(16k _2) > H _(hf)(4c) > H _(hf)(16k _1) > H _(hf)(8j _1) > H _(hf)(4e).