Doped magnetic iron oxide particles and method of preparing the same
AssigneeMinnesota Mining and Manufacturing Company
InventorAlbena V. Blagev
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Abstract
A doped magnetic iron oxide particle suitable for use in magnetic recording media, and methods of preparing the doped magnetic iron oxide particle, are disclosed. The doped magnetic iron oxide particle has the general formula: Co.sub.x Fe.sup.+2.sub.1-x Fe.sub.2.sup.+3 O.sub.4, wherein O<x.ltoreq.1, wherein essentially all of the cobalt(II) and iron(II) dopants are present in a shell surrounding a core of a magnetic iron oxide particle. The doped magnetic iron oxide particle has a narrow switching distribution, high squareness, high coercivity and high remanence.
Claims4
A method of manufacturing a doped magnetic iron oxide particle having the general formula:
- Co.sub.x Fe.sup.+2.sub.1-x Fe.sub.2.sup.+3 O.sub.4, wherein O<x.ltoreq.1,
- comprising the steps of:
- (a) forming an aqueous mixture of a magnetic iron oxide and a base;
- (b) agitating the mixture of step (a) under high shear conditions such that there is turbulent flow with Reynolds number (N.sub.Re) of at least 10.sup.5, impeller discharge rate (Q) of at least 6.8 liters/second and velocity head (H) of at least 450 ergs/gram;
- (c) adding a dopant compound selected from the group consisting of cobalt(II) compounds, iron(II) compounds and mixtures thereof to the agitated mixture of step (b);
- (d) maintaining agitation under the high shear conditions of step (b) and heating the aqueous mixture of step (c) to a sufficient temperature and for a sufficient time for the dopant compound to react with the magnetic iron oxide and form the doped magnetic iron oxide particle;
- and
- (e) separating the doped magnetic iron oxide particle from the aqueous mixture of step (d).
Dependencies are inferred from the claim text.