Abstract: A process for the preparation of a ferrite magnetic particulate for magnetic recording which comprises steps of: (1) melting a starting material mixture containing a basic component for hexagonal ferrite, a coercive force-reducing component and a glass-forming component; (2) rapidly cooling the resulting molten mixture to obtain an amorphous material; (3) heat-treating said amorphous material to form ferrite crystals; and (4) removing components other than the ferrite crystals from the material resulting from said heat-treatment:characterized in that a step for pulverizing said amorphous material and/or a step of pulverizing said heat-treated amorphous material are included in advance of the above step (4).

Abstract: A magnetoplumbite type ferrite magnetic material having the formula:RFe.sub.12-2x M.sub.x M'.sub.x O.sub.19wherein R is at least one metal atom selected from the group consisting of barium, strontium and lead, M is at least one divalent metal atom selected from the group consisting of cobalt, nickel and zinc, M' is at least one tetravalent metal atom selected from the group consisting of titanium, zirconium and hafnium, and x is a number ranging from 0.6 to 1.0; and further containing 1 to 1,000 ppm of platinum and/or gold therein.A process for the preparation of the magnetoplumbite type ferrite magnetic material is also disclosed.

Abstract: A process for the preparation of a ferrite magnetic particulate for magnetic recording which comprises steps of: (1) melting a starting material mixture containing a basic component for hexagonal ferrite, a coercive force-reducing component and a glass-forming component; (2) rapidly cooling the resulting molten mixture to obtain an amorphous material; (3) heat-treating said amorphous material to form ferrite crystals; and (4) removing components other than the ferrite crystals from the material resulting from said heat-treatment:characterized in that said starting material mixture contains a glass-forming component comprising a B.sub.2 O.sub.3 component and a SiO.sub.2 component in which the amount of said SiO.sub.2 component has a value (in terms of SiO.sub.2) 0.05 to 0.8, the value being represented by a molar ratio of SiO.sub.2 /(B.sub.2 O.sub.3 +SiO.sub.2).

Abstract: An optical glass comprising in mole % 8 to 11% Al(PO.sub.3).sub.3, 0.5 to 5% MPO.sub.3, 5 to 25% BaF.sub.2, 10 to 35% SrF.sub.2, 5 to 30% CaF.sub.2 ; 5 to 20% MgF.sub.2, 13 to 30% AlF.sub.3, and 0 to 10% LaF.sub.3 +YF.sub.3, wherein the mole ratio of fluorine to phosphorus (F/P) in the composition is 6.5 or less and M represents Li, Na or K, which glass has a refractive index ranging from 1.47 to 1.53 and an Abbe's number ranging from 77 to 85.