STRUCTURAL AND MAGNETIC-PROPERTIES OF ND2(FE,TI)19

Alloys with the composition Nd2(Fe,Ti)19 can exist in two crystal structures depending on the preparation technique. Melt-spun material has a hexagonal TbCu7-type structure (a = 4.902 angstrom, c = 4.248 angstrom) for a range of quenching speeds. Alloys prepared by arc melting, annealing at 1373 K and then water quenching have a complex monoclinic structure derived from a TbCU7 superlattice (a = 10.644 angstrom, b = 8.585 angstrom, c = 9.755 angstrom, beta = 96.92-degrees) and related to those of other intermetallics such as tetragonal Nd(Fe,Ti)12 and rhombohedral Nd2Fe17. Magnetic ordering temperatures for annealed (monoclinic) and melt-spun (hexagonal) Nd2(Fe,Ti)19 are 411 and 454 K, respectively. Fe-57 Mossbauer spectroscopy at 295 K demonstrates that the local environments of the Fe atoms in the two structural modifications of Nd2(Fe,Ti)19 are similar. The average Fe-57 magnetic hyperfine fields at 295 K for the monoclinic and hexagonal Nd2(Fe,Ti)19 are 20.8 and 22.3 T, corresponding to average Fe magnetic moments of 1.33 and 1.43mu(B), respectively.