Effect of different deposition sequences on the magnetic properties of sintered Nd–Fe–B magnets diffused with multicomponent Tb–Cu films

Abstract

To further investigate the impact of layered deposition process on the magnetic properties of sintered Nd–Fe–B magnets, the multicomponent Tb–Cu films with different deposition sequences were designed through magnetron sputtering system. We first examined the effects of heat treatment, pure Cu and pure Tb diffusion on the magnetic properties of original magnets. For multicomponent Tb–Cu diffused magnets, we found that the deposition amount of Cu was an important factor in studying the diffusion mechanism of Tb–Cu films during grain boundary diffusion process. The deposition of Cu in moderation could significantly increase the diffusion depth of Tb due to the reduction in the enrichment of Tb near the surface. The deposition of excessive Cu reduced the diffusion efficiency of Tb, even lower than that of Tb in pure Tb diffused magnet. The results showed that the sequence of Tb deposition followed by Cu deposition in moderation was the optimal deposition order to achieve higher synthetical magnetic properties. Moreover, we investigated the negative impact of the Tb-rich zone on magnetic properties and proposed structural models for different diffused magnets.

Keywords

• Nd–Fe–B magnets
• Grain boundary diffusion process
• Layered deposition sequence
• Heavy rare earth