Neutron Diffraction and Mössbauer Spectral Study of the Nd₂Fe₁₆TiCₓ Solid Solutions

Author

Gaya Kanishka Marasinghe
Peter C. Ezekwenna
William Joseph James, Missouri University of Science and TechnologyFollow
Gary J. Long, Missouri University of Science and TechnologyFollow
Oran Allan Pringle, Missouri University of Science and TechnologyFollow
Zhongbo Hu
William B. Yelon, Missouri University of Science and Technology
Fernande Grandjean, Missouri University of Science and TechnologyFollow

Abstract

Three samples of , with x equal to 0.0, 0.3, and 2.8, with the Th₂Zn₁₇-type rhombohedral structure, have been studied by powder x-ray and neutron diffraction, magnetic measurements, and Mössbauer spectroscopy. Nd₂Fe₁₆Ti and Nd₂Fe₁₆TiC_0.3 were synthesized by induction melting stoichiometric amounts of the constituent elements, whereas Nd₂Fe₁₆TiC_2.8 was synthesized by methane-derived gas phase insertion of carbon into finely ground Nd₂Fe₁₆Ti at 600 K. The neutron diffraction determined titanium site occupancies are similar in both Nd₂Fe₁₆Ti and Nd₂Fe₁₆TiC_2.8 in which titanium preferentially occupies the 6c transition metal site. In contrast, the titanium occupancies in Nd₂Fe₁₆TiC_0.3 are markedly different in that titanium avoids the 6c transition metal site and randomly occupies the other three transition metal sites. This difference in occupancies most likely occurs because the titanium diffusion rate during the quenching of Nd₂Fe₁₆TiC_0.3 is affected by the presence of carbon in the melt. Even though the unit cell volume of Nd₂Fe₁₆TiC^2.8 is larger than that of Nd₂Fe₁₇N₃, the 615 K Curie temperature of Nd₂Fe₁₆TiC_2.8 is much lower than the 746 K Curie temperature of Nd₂Fe₁₇N₃. This is an indication that the volume expansion, which occurs upon nitrogenation of R₂Fe₁₇, is not the only factor which contributes to the increase in the Curie temperature. The Mössbauer spectra of Nd₂Fe₁₆Ti confirm the high preferential titanium occupancy of the 6c site. At 85 K the weighted average hyperfine field of Nd₂Fe₁₆Ti is approximately 263 kOe, a value which is 33 kOe smaller than that in Nd₂Fe₁₇. The 85 K Mössbauer spectrum of Nd₂Fe₁₆TiC_0.3 is virtually identical to that of Nd₂Fe₁₇ and indicates an approximately random titanium occupancy of the four transition metal sites.

Recommended Citation

G. K. Marasinghe et al., "Neutron Diffraction and Mössbauer Spectral Study of the Nd₂Fe₁₆TiCₓ Solid Solutions," Journal of Applied Physics, vol. 79, no. 8 PART 2A, pp. 4587 - 4589, American Institute of Physics (AIP), Apr 1996.

The definitive version is available at https://doi.org/10.1063/1.361735

Department(s)

Chemistry

Second Department

Physics

International Standard Serial Number (ISSN)

0021-8979

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 1996 American Institute of Physics (AIP), All rights reserved.

Publication Date

01 Apr 1996