The reduction process and change of the magnetic properties have been investigated for a mixture comprising Co(OH)2 and metallic Al as a function of mechanical milling. Dehydration and apparent thermit reaction by milling are detected by thermal analyses (TGDTA). With increasing the milling time, the magnetization, M, becomes temperature-independent above 50K, whereas M at 5K rapidly decreases. At above 100K, M shows a maximum after milling for12h due to reduction to form metallic Co. Zero-field 59Co-spin echo NMR signals are detected for the milled mixture. Marked negative Knight shift of 27Al NMR by milling is induced by the polarization of 3d spins of neighboring Co atoms. At the later stage of milling partial re-oxidation of Co and compounding with aluminum takes place. The neighboring structure of cobalt atoms is widely distributed, as confirmed by the separate 59Co NMR signals.
|ジャーナル||Materials Science Forum|
|出版ステータス||Published - 1998 1 1|
ASJC Scopus subject areas
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering