Abstract: This invention provides techniques for producing unique cobalt-phosphorus (Co-P) particles. The Co-P particles produced by this technique are novel as to both size and morphology. Their size is uniformly less than about 300 A, with average sizes being about 150 A. This is substantially smaller than Co-P particles previously known or reported in the literature. Their morphology is unique, as shown by x-ray and electron diffraction, in that they are amorphous. All known prior art Co-P particles have been crystalline. In addition, these Co-P particles have the capability of being manufactured with selectively controlled magnetic coercivity.The new reaction system utilized to produce these unique materials provides a substantial departure from art known systems.

Abstract: The problem of characterizing metallic magnetic particles as suitable or unsuitable for use in a high density magnetic recording media is believed to have been solved by use of a figure of merit designated as "W/H.sub.c ", and defined herein.It has been found that metallic magnetic particles which exhibit a W/H.sub.c of about 1.2 or less offer the most desirable magnetic recording characteristics for high density magnetic recording media. With this characterization technique available, it has been determined that most quantities of metallic magnetic cobalt-phosphorus particles produced by chemical reduction have W/H.sub.c 's greater than 1.2, and are unsuitable for use in high density magnetic recording media. Using W/H.sub.c, it has been possible to recognize those metallic particles which are suitable for use in high density recording media, and to engage in experimentation to determine what methods of manufacturing are required for the production of suitable high density recording particles.