Magnetic alloy particle compositions and method of manufacture

TLDR: In this article, the preparation of high coercivity, finely divided magnetic alloy particles for use in recording media by reduction of salts of cobalt, and mixtures of salt of iron and cobalt in a bath containing hypophosphite and amine borane reducing agents is described.

Abstract: This invention relates to the preparation of magnetic recording media including finely divided magnetic particles. It especially relates to the preparation of high coercivity, finely divided magnetic alloy particles for use in recording media by reduction of salts of cobalt, and mixtures of salts of cobalt and iron, mixtures of salts of cobalt and nickel, in a bath containing hypophosphite and amine borane anion reducing agents. Sodium hypophosphite and dimethyl amine borane or any soluble salts which provide hypophosphite and amine borane anions in solution are reacted with soluble metal salts of cobalt alone, or cobalt with iron, or nickel dissolved in the bath. After separating and drying, the precipitate is found to consist of non-pyrophoric magnetic alloy particles, including about 0.1-5% phosphorus and about 0.1-1.5% boron, which are generally spherical in shape and which vary in size from about 0.01 micron to 3.0 microns in diameter. These particles are dispersed in a binder, the dispersion coated on a substrate, and dried to form a recording media.