Nd-Fe-B薄膜におけるNd₂Fe₁₄B/Nd-Rich界面組織と保磁力

抄録

  This study provides the relationship between phase change of Nd-rich and microstructural changes of Nd₂Fe₁₄B/Nd-rich interface in Nd-Fe-B films with different coercivity values. In as-deposited Nd-Fe-B film, flat interface of Nd₂Fe₁₄B/dhcp Nd is mainly observed. After oxidation, oxidized region was observed at the surface of Nd₂Fe₁₄B phase, and Nd₂Fe₁₄B/fcc NdO_x interface were observed. In the Nd-Fe-B film subsequently annealed at 350℃ after oxidation, the coercivity of which decreases to around 20% of the value of as-deposited film, and the hcp Nd₂O₃ phase exists dominantly at the surface of Nd₂Fe₁₄B phase. In addition, there are some damaged regions at the surface of Nd₂Fe₁₄B phase. On the contrary, both the metastable C-Nd₂O₃ and amorphous phases existed dominantly at the Nd₂Fe₁₄B/Nd-rich interface of the film annealed at 650℃. The coercivity of this film recovered to the same value of as-deposited film.
   These results indicate that the crystallization of hcp Nd₂O₃ phase include some damages to neighboring Nd₂Fe₁₄B phase decrease coercivity. During annealing at 550 to 650℃, Nd-rich liquid phase appears and modifies the surface of Nd₂Fe₁₄B, and the coercivity recovers. After cooling, this liquid phase seems to crystallize into a C-Nd₂O₃ or an amorphous phases at the surface of Nd₂Fe₁₄B phase. In other words, the C-Nd₂O₃ or amorphous phases can exist without decreasing coercivity.