The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 05, 1985
Filed:
Jul. 24, 1984
Masanori Hayakawa, Ube, JP;
Noriaki Yamada, Ube, JP;
Hiromi Kawamoto, Onoda, JP;
Satoshi Nishimura, Ube, JP;
Central Glass Company Limited, Ube, JP;
Abstract
In preparing fine and plate-shaped particles of a ferrite having the magnetoplumbite structure by hydrothermal treatment of a powder of .gamma.-Fe.sub.2 O.sub.3 or (FeO).sub.x.Fe.sub.2 O.sub.3, where O<x.ltoreq.1, and a compound of Ba, Sr or Pb in an aqueous alkali solution, Sn.sup.4+, or Sn.sup.4+ and M.sup.2+ such as Fe.sup.2+, Cu.sup.2+ or Zn.sup.2+, are introduced into the reaction system of the hydrothermal treatment such that Fe.sup.3+ in the obtained ferrite are partly substituted by Sn.sup.4+ or M.sup.2+ -Sn.sup.4'. The substitution has the effect of lowering the coercive force of the ferrite powder to a level suitable for use in magnetic recording media of the perpendicularly magnetizing recording type. By using an iron oxide powder having a mean particle size not larger than 500 .ANG. with addition of a surface-active agent, the particle size of the ferrite powder can be reduced to about 0.2 .mu.m.