Ferrite magnetic material for magnetic recording and process for the preparation thereof
AssigneeFuji Photo Film Co., Ltd.
InventorKouzi Kamiyama
Life of this patent
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Abstract
A magnetoplumbite type ferrite magnetic material having the formula: RFe.sub.12-2x M.sub.x M'.sub.x O.sub.19 wherein 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.
Claims4
A process for the preparation of a magnetoplumbite type ferrite magnetic material having the formula
- RFe.sub.12-2x M.sub.x M'.sub.x O.sub.19
- wherein 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 from 1 to 1,000 ppm of platinum and/or gold therein, said process comprising the steps of
- (1) melting a starting material mixture containing a basic component for hexagonal ferrite comprising Fe.sub.2 O.sub.3 and at least one oxide selected from the group consisting of BaO, SrO and PbO or compounds convertible into said oxides during melting, a coercive force-reducing component including M and M', and 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 ferrite crystals from the material resulting from said heat-treatment;
- characterized in that from 1 to 2,000 ppm of platinum and/or gold is contained in said starting material mixture, said magnetoplumbite type ferrite magnetic material having a narrower particle size distribution than said ferrite prepared as above, absent platinum and gold.
A magnetoplumbite type ferrite magnetic material having the formula:
- RFe.sub.12-2x M.sub.x M'.sub.x O.sub.19
- wherein R is at least one metal atom selected from the group consisting of barium, strontium and lead, M is at least one diavalent 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 ot titanium, zirconium and hafnium, and x is a number ranging from 0.6 to 1.0 and further containing from 1 to 1,000 ppm of platinum and/or gold, produced by the process comprising the steps of
- (1) melting a starting material mixture containing a basic component for hexagonal ferrite comprising Fe.sub.2 O.sub.3 and at least one oxide selected from the group consisting of BaO, SrO and PbO or compounds convertible into said oxides during melting, a coercive force-reducing component including M and M', and 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 ferrite crystals from the material resulting from said heat-treatment;
- characterized in that from 1 to 2,000 ppm of platinum and/or gold is contained in said starting material mixture, said magnetoplumbite type ferrite magnetic material having a narrower partizle size distribution than said ferrite prepared as above, absent platinum and gold.
Dependencies are inferred from the claim text.