Crystallization and Mossbauer studies of melt-spun NdFe10.7TiB0.3Nδ alloys

Magnetic properties of melt-spun NdFe10.7TiB0.3Ndelta ribbons have been investigated as functions of quenching rate and nitriding period. NdFe10.7TiB0.3 were prepared with substrate velocity v(s) less than or equal to 18 m/s and were nitrogenated at 500 degrees C for 15 min. The NdFe10.7TiB0.3Ndelta retains the ThMn12-type tetragonal structure with lattice constants a(0) = 8.640 Angstrom and c(0) = 4.811 Angstrom, but with an increase in the unit cell volume. The NdFe10.7TiB0.3Ndelta was confirmed to have uniaxial anisotropy by x-ray diffraction. Mossbauer spectra were taken at various temperatures ranging from 13 to 855 K. The Curie and Debye temperatures are determined to be T-c = 833 K and Theta = 390 K, respectively. Each spectrum below T-c was fitted with six subspectra of Fe sites (8i(1), 8i(2), 8j(2), 8j(1), 8f, and alpha-Fe). The area fraction of the subspectra at 13 K are 10.2%, 8.2%, 16.5%, 17.5%, 44.3%, and 3.3%, respectively. The magnetic hyperfine fields for the Fe sites decrease in the order, H-hf(8i) >H-hf(8j)>H-hf(8f). (C) 1998 American Institute of Physics.