硬X線ナノビームによる焼結磁石材料の解析

概要

Understanding and controlling of the magnetization re-versal process is a key to develop a new permanent magnet ma-terial with an increased coercivity. To this goal, an effective mi-croscopy technique is required for studying the nucleation pro-cess of magnetic domains in bulk magnets. In this paper, we used a scanning hard-X-ray nanoprobe to study Nd-Fe-B sinteredmagnet. The technique provides a reasonable spatial resolution of 100 nm, element-selectivity, and non-destructive observations under a variable magnetic field up to 1750 kA/m. It also allows bulk-sensitive observations of non-flat specimens, with a prob-ing depth of ～2 μm, such that magnetic and chemical imag-ing at a fractured surface of a sintered magnet would be feasi-ble. Evolution of the magnetic domain structure in the demagne-tization process of an Nd14:0Fe79:7Cu0:1B6:2 sintered magnet has been demonstrated. We found a process that initial reversed mag-netic domains are created in particular grains of Nd2Fe14B main phase,　followed by intergranular domain propagation through the grain boundaries in a reproducible manner. Correlation between magnetic domain properties with the elemental distribution in the grain textures is discussed.