高分解能Kerr効果顕微鏡を用いたNd-Fe-B系微細結晶粒磁石の磁区観察と磁化過程解析

摘要

本稿でほ，紫外光を用いて分解能を向上させたKerr効果rn顕微鏡の原理および構成と，それを用いたNd-Fe-B系rnHDDR磁粉ホットプレス体の磁区構造および磁化過程の観rn察結果について概説した．ホットプレス温度に依存して保磁rn力の異なる2種類のHDDR磁粉ホットプレス体試料を磁区rn観察した結果から，保磁力と磁化反転の際の反転領域の大きrnさに相関があることを明らかにした．%A Kerr microscope that uses ultraviolet (UV) light for high-resolution magnetic domain observation was built, and the domain structure and magnetization process of hydrogenation-disproportionation-desorption-recombination (HDDR) magnets were examined. The UV Kerr microscope can observe nanometer-sized domain patterns. The coercivity of the HDDR magnet depends on the area of magnetization reversal during a reversal process. Magnetization reversal in a few grains simultaneously occurs in a low-coercivity magnet, because the Nd-rich phase along the grain boundaries is absent. On the other hand, magnetization reversal in a grain independently occurs owing to an adequate Nd-rich phase along the grain boundaries in a high-coercivity magnet. It follows that the high coercivity of an HDDR magnet is due to domain wall pinning at the grain boundaries.