Phase and Hyperfine Structures of Melt-spun Nanocrystalline (Ce1-xNdx)16Fe78B6 Alloys

To reduce the cost of the Nd-Fe-B magnets, the Ce element was suggested to be used as a replacement of Nd element. In this paper, nanocrystalline (Ce1-xNdx)(16)Fe78B6 (x = 0-0.7) alloys were prepared by melt spinning. The X-ray diffraction (XRD) results indicate that the alloys are composed of (NdCe)(2)Fe14B (2:14:1) phase and (CeNd)Fe-2 (1:2) phase for 0 < 0.6, and the 1:2 phase was replaced by (NdCe)(1+epsilon)Fe4B4 (1:4:4) phase when x = 0.6 and 0.7. The hyperfine parameters characteristics of the 2:14:1 phases were estimated from 300 K Fe-57 Mossbauer spectra, as well as their contents and those of other intergranular phases. In addition to the 2:14:1, 1:2, and 1:4:4 phases, a small content of the rare earth-rich phase was also detected in all the alloys, which was not able to be observed by the XRD characterization. Based upon the hyperfine field, the average magnetic moment of Fe in 2:14:1 phase could be determined as 1.56, 1.62, 1.67, 1.73, 1.78, 1.83, 1.85, and 1.91 mu B for x = 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7, respectively. The minor change between the x = 0.5 (1.83 mu B) and x = 0.6 (1.85 mu B) is discussed. Both the present local and macroscopic magnetic parameters significantly contribute to understand the fundamental role of Ce in those nanocrystalline Nd-Ce-Fe-B permanent magnets.