Magnetic recording medium
AssigneeTDK Electronics Co., Ltd.
InventorsShinji Umeki, Kazuaki Onuki, Fumio Maruta
Life of this patent
Estimating the term…
Abstract
A magnetic recording medium having more than 550 Oersted of a coercive force, less than 1.8 of a ratio of a coercive force at -196.degree. C. to a coercive force at 25.degree. C., less than 1.0 wt. % of a content of Fe.sup.2+ is prepared by incorporating a magnetic powder obtained by dispersing acicular .gamma.-Fe.sub.2 O.sub.3 in an aqueous solution of a cobalt salt and reducing it with a reducing agent to deposit a cobalt compound on the acicular .gamma.-Fe.sub.2 O.sub.3.
Claims3
A magnetic recording medium having a coercive force greater than 550 Oersteds, a ratio of the coercive force at -196.degree. C. to the coercive force at 25.degree. C. less than 1.8 and having an Fe.sup.+2 content of less than 1.0 wt.%, comprising:
- a magnetic powder obtained by dispersing acicular iron oxide in an aqueous solution of a cobalt salt and a reducing agent selected from the group consisting of hydrosulfite, sodium borohydride, hydrazine, hydrazine derivatives, and sodium hypophosphite, said solution being free of a chelating agent;
- and reacting said cobalt salt with said reducing agent thereby depositing a cobalt compound on the iron oxide base.
Dependencies are inferred from the claim text.