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. 2021 Mar 18;11(1):6347.
doi: 10.1038/s41598-021-85713-5.

Determination of Dy substitution site in Nd2-xDyxFe14B by HAADF-STEM and illustration of magnetic anisotropy of "g" and "f" sites, before and after substitution

Syed Kamran Haider #  1   2   3 , Min-Chul Kang #  4 , Jisang Hong  5 , Young Soo Kang  6 , Cheol-Woong Yang  7 , Dongsoo Kim  8   9
Affiliations

Determination of Dy substitution site in Nd2-xDyxFe14B by HAADF-STEM and illustration of magnetic anisotropy of "g" and "f" sites, before and after substitution

Syed Kamran Haider et al. Sci Rep. .

Abstract

Nd2Fe14B and Nd2-xDyxFe14B (x = 0.25, 0.50) particles were prepared by the modified co-precipitation followed by reduction-diffusion process. Bright field scanning transmission electron microscope (BF-STEM) image revealed the formation of Nd-Fe-B trigonal prisms in [- 101] viewing zone axis, confirming the formation of Nd2Fe14B/Nd2-xDyxFe14B. Accurate site for the Dy substitution in Nd2Fe14B crystal structure was determined as "f" site by using high-angle annular dark field scanning transmission electron microscope (HAADF-STEM). It was found that all the "g" sites are occupied by the Nd, meanwhile Dy occupied only the "f" site. Anti-ferromagnetic coupling at "f" site decreased the magnetic moment values for Nd1.75Dy0.25Fe14B (23.48 μB) and Nd1.5Dy0.5Fe14B (21.03 μB) as compared to Nd2Fe14B (25.50 μB). Reduction of magnetic moment increased the squareness ratio, coercivity and energy product. Analysis of magnetic anisotropy at constant magnetic field confirmed that "f" site substitution did not change the patterns of the anisotropy. Furthermore, magnetic moment of Nd2Fe14B, Nd2-xDyxFe14B, Nd ("f" site), Nd ("g" site) and Dy ("f" site) was recorded for all angles between 0° and 180°.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
(a) XRD patterns of Nd2Fe14B and Nd2−xDyxFe14B particles (b) crystal parameters “a” and “c” of Nd2Fe14B and Nd2−xDyxFe14B. BSE-SEM images of (c) Nd2Fe14B (d) Nd1.75Dy0.25Fe14B and (e) Nd1.5Dy0.5Fe14B particles. Particle size distribution of (f) Nd2Fe14B (g) Nd1.75Dy0.25Fe14B and (h) Nd1.5Dy0.5Fe14B particles.
Figure 2
Figure 2
(a) LAADF-STEM image of Nd1.5Dy0.5Fe14B, (b) HAADF-STEM image and corresponding EDS line profile taken from blue circle in (a). (c) EDS line profile of (b).
Figure 3
Figure 3
(a) TEM image of the Nd1.5Dy0.5Fe14B, (b) SAED pattern taken from the red circle in (a), (c) Nd2Fe14B trigonal prism in the [− 101] viewing zone axis, (d) high resolution BF-STEM image of Nd1.5Dy0.5Fe14B at [− 101] zone axis and (e) simulation of arrangement of the atoms by JEMS software.
Figure 4
Figure 4
(a) Standard Nd2Fe14B unit cell with [100] zone axis (b) HADDF-STEM image of Nd1.5Dy0.5Fe14B at [100] zone axis, (c) intensity histogram for the atoms in the red dotted panel in (b).
Figure 5
Figure 5
HADDF-STEM image of Nd1.5Dy0.5Fe14B at [100] zone axis, with intensity histogram. Light grey circles in the center indicate Fe atoms.
Figure 6
Figure 6
(a) M–H curves, Mr, Ms, Magnetic moment, Hc, energy density and squareness ratio of Nd2Fe14B, Nd1.75Dy0.25Fe14B and Nd1.5Dy0.5Fe14B particles. (b) Schematic illustration to explain the ferro and anti-ferromagnetic coupling between Nd, Dy and Fe (c) Explanation of coupling and hybridization between Nd, Dy and Fe.
Figure 7
Figure 7
(a) Sample preparation for the measurement of magnetic anisotropy (b) Magnetic moment of Nd2Fe14B, Nd1.75Dy0.25Fe14B and Nd1.5Dy0.5Fe14B particles as a function of rotation angle. Magnetic moment at the “f” and “g” sites in (c) Nd2Fe14B (d) Nd1.5Dy0.5Fe14B (e) Nd1.75Dy0.25Fe14B as a function of rotation angle.
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