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US 5,626,956 AGranted
Hexagonal magnetic ferrite pigment for high density magnetic recording applications
AssigneeImation Corp.
InventorsDavid M. Hopstock, John S. Roden, Gunther H. Dierssen, Ronald S. Sapieszko
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Abstract
The present invention provides a hexagonal magnetic ferrite pigment suitable for high density magnetic recording applications. The pigment is characterized by small particle size, a modified magnetoplumbite structure, and relatively high magnetic moment. The pigment is capable of being prepared by firing suitable precursor particles in air at temperatures below 850.degree. C.
Claims11
A magnetic recording medium comprising:
- (a) a nonmagnetizable substrate;
- and
- (b) a magnetizable layer disposed on the substrate, said magnetizable layer comprising a magnetic pigment dispersed in a binder, wherein the magnetic pigment comprises hexagonal, platelet-shaped magnetic ferrite particles having a modified magnetoplumbite structure and having approximately the formula:
- B(II)M(II).sub.u M(III).sub.v M(IV).sub.x M(V).sub.y M(VI).sub.z Fe(III).sub.w O.sub.p
- wherein
- B(II) is at least one metal ion selected from the group consisting of Ba, Sr, Pb, and Ca;
- M(II) is at least one divalent metal ion other than Ba, Sr, Pb, Fe(II), and Ca;
- M(III) is at least one trivalent metal ion other than Fe(III);
- M(IV) is at least one tetravalent metal ion;
- M(V) is at least one pentavalent metal ion;
- M(VI) is at least one hexavalent metal ion;
- Fe(III) is trivalent iron ion;
- p is 19+4u-4x-8y-12z;
- u satisfies the relationships 0.5+x+2y+3z.ltoreq.u.ltoreq.2+x+2y+3z and u>0.5v+2x+3.5y+5z;
- v is 0 to 0.1;
- x is 0 to 0.7;
- y is 0 to 0.7;
- z is 0 to 0.7;
- w is greater than 12 and is 90% to 115% of the value given by 12+2u-v-4x-7y-10z;
- and
- .ltoreq. x+y+z.ltoreq.0.7.
18 more elements
Dependencies are inferred from the claim text.