| 摘要 |
PURPOSE:To obtain magnetic powder having narrow grain size distribution, and to improve signal to noise ratio by mixing specific amounts of compounds of individual elements forming a hexagonal ferrite represented by a specific formula and specific amounts so other specific compounds, melting the mixture, and quickly cooling it. CONSTITUTION:Compounds of elements for forming a hexagonal ferrite represented by a general formula, and R2O2 (R: at least one type selected from Li, Na, k, Rb, Cs), AO) and B2O3 as the other components are so mixed that the compounds of R, A and B satisfy the relation:1.0<B2O3/(AO+R2O)<1.5, 0.0<AO<1.0 by mol ratio; the mixture is then melted; and quickly cooled to be brought into an amorphous state. Then, It is heat-treated, and hexagonal ferrite is extracted. Thus, magnetic powder having narrow grain size distribution is obtained, noise due to magnetic powder having large grain size is reduced, and its recording density and signal to noise ratio are improved. |
