通过高角度环形暗场扫描透射电子显微镜（HAADF-STEM）确定钕铁硼（NdDyFeB）中镝（Dy）的取代位点，并说明取代前后“g”和“f”位点的磁各向异性。

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

作者信息

Haider Syed Kamran, Kang Min-Chul, Hong Jisang, Kang Young Soo, Yang Cheol-Woong, Kim Dongsoo

机构信息

Convergence Research Center for Development of Mineral Resources, Korea Institute of Geoscience and Mineral Resources, Daejeon, 34132, South Korea.

Powder and Ceramics Division, Korea Institute of Materials Science, Changwon, Gyeongnam, 51508, South Korea.

出版信息

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

DOI:10.1038/s41598-021-85713-5

PMID:33737675

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC7973419/

Abstract

NdFeB and NdDyFeB (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 NdFeB/NdDyFeB. Accurate site for the Dy substitution in NdFeB 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 NdDyFeB (23.48 μB) and NdDyFeB (21.03 μB) as compared to NdFeB (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 NdFeB, NdDyFeB, Nd ("f" site), Nd ("g" site) and Dy ("f" site) was recorded for all angles between 0° and 180°.

摘要

通过改进的共沉淀法随后进行还原扩散工艺制备了钕铁硼（NdFeB）和钕镝铁硼（NdDyFeB，x = 0.25，0.50）颗粒。明场扫描透射电子显微镜（BF-STEM）图像显示在[-101]观察区轴上形成了钕铁硼三角棱柱，证实了NdFeB/NdDyFeB的形成。通过使用高角度环形暗场扫描透射电子显微镜（HAADF-STEM）确定了Dy在NdFeB晶体结构中取代的精确位置为“f”位。发现所有的“g”位都被Nd占据，而Dy仅占据“f”位。与NdFeB（25.50 μB）相比，“f”位的反铁磁耦合降低了NdDyFeB（23.48 μB）和NdDyFeB（21.03 μB）的磁矩值。磁矩的降低增加了矩形比、矫顽力和能量积。在恒定磁场下对磁各向异性的分析证实“f”位取代没有改变各向异性的模式。此外，记录了NdFeB、NdDyFeB、Nd（“f”位）、Nd（“g”位）和Dy（“f”位）在0°至180°之间所有角度的磁矩。