Influences of microstructure on macroscopic crystallinity and magnetic properties of Sm-Fe-N fine powder produced by jet-milling

A variety of high performance Sm-Fe-N fine powders (the highest (BH)(max) = 43.6 MGOe (347 kJ/m(3))) were produced by jet-milling technique under very low oxygen atmosphere. The particle size distribution, the crystallinity and the microstructure of those jet-milled powders were systematically investigated. It was confirmed that the macroscopic crystallinity (estimated from XRD peaks) was significantly deteriorated with the decrease of particle size and found that this is attributed to the formation of nanocrystalline regions and dislocations introduced by jet-milling. Careful analyses however clarified that those nanocrystalline regions play a very undesirable role in dominating the degree of alignment of a batch of aligned powder and consequently lead to degradation of saturation magnetization and (BH)(max). (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

High performance Sm-Fe-N fine powders were produced through jet-milling technique under low oxygen atmosphere, showing deteriorated crystallinity with decrease in particle size due to the formation of nanocrystalline regions and dislocations. These nanocrystalline regions negatively affected the alignment degree of the powder batch, leading to degradation in saturation magnetization and (BH)(max).