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

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Abstract
Magnetic properties of melt-spun NdFe10.7TiB0.3Nδ ribbons have been investigated as functions of quenching rate and nitriding period. NdFe10.7TiB0.3 were prepared with substrate velocity vs⩽18 m/s and were nitrogenated at 500 °C for 15 min. The NdFe10.7TiB0.3Nδ retains the ThMn12-type tetragonal structure with lattice constants a0=8.640 Å and c0=4.811 Å, but with an increase in the unit cell volume. The NdFe10.7TiB0.3Nδ was confirmed to have uniaxial anisotropy by x-ray diffraction. Mössbauer spectra were taken at various temperatures ranging from 13 to 855 K. The Curie and Debye temperatures are determined to be Tc=833 K and Θ=390 K, respectively. Each spectrum below Tc was fitted with six subspectra of Fe sites (8i1, 8i2, 8j2, 8j1, 8f, and α-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, Hhf(8i)>Hhf(8j)>Hhf(8f).