Patent attributes
A method for making iron-based oxide magnetic particle powders having particular peak intensity and diffraction intensities, comprising neutralizing an aqueous solution containing a trivalent iron ion, alone or with a substituting metal (M), a step of adding hydroxycarboxylic acid to the neutralized solution to create a second solution including the hydroxycarboxylic acid D, another neutralizing step for the second solution, a coating step of silicon oxide coating iron oxyhydroxide with or without the substituted metal element found in the second neutralized solution, and heating the coated iron oxyhydroxide with or without the substituted metal element to form a silicon oxide coated iron oxide with or without the substituted metal element. After the second neutralization step, there is no water washing. As a result, the molar ratio D/(Fe+M) is between 0.125 and 1.0 and the silicon oxide coating can be uniform and the formation reaction of the hydroxide is not retarded.
