High-coercivity Nd-Fe-B thick films without heavy rare earth additions

N. M. Dempsey, T. G. Woodcock, H. Sepehri-Amin, Y. Zhang, H. Kennedy, D. Givord, K. Hono, O. Gutfleisch

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

The magnetic properties and microstructures of two Nd-Fe-B thick films with different Nd contents have been studied. The films were deposited in the amorphous state and were crystallized by post-deposition annealing. Both films show a strong 〈0 0 1〉 fibre texture out-of-plane. The film with the higher Nd content has a large room temperature coercivity of 2.7 T, while the one with the lower Nd content has a room temperature coercivity of only 0.7 T. The difference in coercivity may be explained by the fact that the film with the higher Nd content exhibits a continuous Nd-rich grain boundary phase, giving better isolation of the Nd2Fe14B grains with respect to magnetic exchange interactions. The extrusion of Nd-rich liquid to the top surface of the film with high Nd content during post-deposition annealing led to the formation of ripples in the Ta capping layer, indicating that the films are under compressive stress. This stress-induced flow of the Nd-rich material up through the film explains the excellent distribution of the Nd-rich grain boundary phase. Atom probe tomography has revealed the presence of Cu in the Nd-rich grain boundary phase, explaining the formation of the liquid phase at the relatively low temperature of 550 C due to the eutectic reaction of Nd and Cu.

Original languageEnglish
Pages (from-to)4920-4927
Number of pages8
JournalActa Materialia
Volume61
Issue number13
DOIs
Publication statusPublished - 2013 Aug 1
Externally publishedYes

Keywords

  • Coercivity
  • Hard
  • Magnets
  • Thick films

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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