The effects of the combined substitution of Y and Ga on the crystallographic structure of Nd2−xYxFe17−yGay intermetallic compounds |
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Authors: | XF Liu SB Han JY Lv XJ Li ZB Hu DF Chen YJ Xue JH Li |
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Affiliation: | aCollege of Chemistry and Chemical Engineering, Graduate School, Chinese Academy of Sciences, 100049 Beijing, China bChina Institute of Atomic Energy, 102413 Beijing, China |
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Abstract: | The effects of the combined substitution of Y and Ga on the crystallographic structure of Nd2?xYxFe17?yGay compounds with x = 0, 0.5, 1.0, 1.5 and y = 0, 1, 2, 3 have been investigated using X-ray and neutron powder diffractions. Rietveld refinements of the diffraction data indicate that all the samples crystallize in the rhombohedral Th2Zn17-type structure with only small amounts of alpha iron. It is found that the addition of Ga atoms lessens the decreasing rates of the a-axis and unit cell volume V on the Y content but almost does not affect the decreasing rates of the c-axis. However, the substitution of Y has a positive effect on the increasing rates of the a-axis and unit cell volume V on the Ga content but has a very slight effect on the increasing rate of the c-axis. The c/a ratio of Nd2?xYxFe17?yGay as a function of Ga content exhibits a different increase for different Y content owe to the combined effects of Y and Ga on the crystallographic structure. The substitution of Y is found to have little effect on the site occupancy of Ga in Nd2?xYxFe17?yGay. The combined effects of Y and Ga on the bond lengths and ASBL of Nd2?xYxFe17?yGay indicate that more bonds detrimental to ferromagnetic exchange can be modulated into the desirable ferromagnetic exchange distance range through suitable combined substitution, which provides a valuable way to improve the magnetic properties of rare earth-transition intermetallic compounds. |
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Keywords: | Intermetallics Crystal structure X-ray diffraction Neutron diffraction |
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