Abstract: The present invention is a method for making highly stable magnetic alloy particles with high coercivities and high saturation magnetization comprising the steps of:a) providing a precursor selected from the group consisting of iron oxide hydroxide particles and iron oxide particles, wherein the precursor particle comprises from about 15 to about 45 atomic % Co based on amount of Fe present,b) reducing the precursor particles to magnetic alloy particles,c) passivating the magnetic alloy particles in an oxygen-containing atmosphere at a temperature between about 20.degree. and 100.degree. C.,d) annealing the passivated magnetic alloy particles in an inert atmosphere at a temperature from about 120.degree. to about 450.degree. C., ande) further oxidizing the annealed magnetic alloy particles in an oxygen-containing atmosphere.

Abstract: Spindle-shaped goethite particles are produced by oxidizing a ferrous carbonate intermediate in the presence of a growth modifier, or alternatively by changing the flowrate of oxidizing gas during oxidation. The goethite particles thus produced have a narrow size distribution, high aspect ratio and are substantially dendrite-free. These properties make the inventive goethite particles suitable for use in preparation of high density magnetic recording media.

Abstract: Beta cobaltous hydroxide is synthesized by decomposing the complex formed between cobaltous ions and a suitable complexing agent under hydrothermal conditions. Cobaltous ion and complexing agent are combined in an aqueous medium, wherein the molar ratio of the cobaltous ion to the complexing agent is about one or more. Hydroxide ion is added, wherein the molar ratio of hydroxide ion to cobaltous ion is more than about 2. The resulting admixture is heated under hydrothermal conditions for precipitating beta cobaltous hydroxide. The method provides improved control over the size and shape of the beta cobaltous hydroxide reaction product. The beta cobaltous hydroxide can be reduced to form magnetic particles of cobalt metal.

Abstract: Beta cobaltous hydroxide is synthesized by decomposing the complex formed between cobaltous ions and a suitable complexing agent under hydrothermal conditions. Cobaltous ion and complexing agent are combined in an aqueous medium, wherein the molar ratio of the cobaltous ion to the complexing agent is about one or more. Hydroxide ion is added, wherein the molar ratio of hydroxide ion to cobaltous ion is more than about 2. The resulting admixture is heated under hydrothermal conditions for precipitating beta cobaltous hydroxide. The method provides improved control over the size and shape of the beta cobaltous hydroxide reaction product. The beta cobaltous hydroxide can be reduced to form magnetic particles of cobalt metal.