| 摘要 |
Spindle-shaped goethite particles of the present invention contain Co of 8 to 45 atm %, calculated as Co, based on whole Fe, Al of 5 to 20 atm %, calculated as Al, based on whole Fe, and have an average major axial diameter of 0.05 to 0.18 mum, each of said spindle-shaped goethite particles comprising a seed portion and a surface layer portion, the weight ratio of said seed portion to said surface layer portion being 30:70 to 80:20 and the relationship of the Co concentration of the seed portion with that of the hematite particle being 50 to 95:100 when the Co concentration of the hematite particle is 100, and said Al existing in said surface layer portion. Such spindle-shaped goethite particles are fine particles and exhibit a good particle size distribution. Spindle-shaped hematite particles obtained form the spindle-shaped goethite particles, can be prevented as highly as possible from causing destruction of particle shape when subjected to a heat-reduction step for producing magnetic spindle-shaped metal particles and magnetic spindle-shaped metal particles containing iron as a main component produced from the spindle-shaped goethite particles or the spindle-shaped hematite particles as a starting material, exhibit a high coercive force, an excellent particle coercive force distribution, a large saturation magnetization and an excellent oxidation stability, and are excellent in a squareness (Br/Bm) of the sheet due to a good dispersibility in a binder resin.
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