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Article Dans Une Revue Acta Materialia Année : 2013

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

Résumé

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 h001i fibre texture outof- 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.

Dates et versions

hal-00969338 , version 1 (02-04-2014)

Identifiants

Citer

Nora Dempsey, T.G. Woodcock, H. Sepehri-Amin, Yuepeng Zhang, H. Kennedy, et al.. High-coercivity Nd-Fe-B thick films without heavy rare earth additions. Acta Materialia, 2013, 61, pp.4920-4927. ⟨10.1016/j.actamat.2013.04.055⟩. ⟨hal-00969338⟩

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