Process for producing cobalt-modified ferromagnetic iron oxide
US4581251A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 28, 1984 |
| Grant date | Apr 8, 1986 |
| Priority date | — |
| Expiry date | Jun 28, 2004 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11B5/70673
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A process for preparing cobalt-modified ferromagnetic iron oxide by modifying ferromagnetic .gamma.-Fe.sub.2 O.sub.3 particles with cobalt, wherein prior to cobalt modification treatment, the ferromagnetic .gamma.-Fe.sub.2 O.sub.3 is heat treated at a temperature in the range of from about -200.degree. C. to +30.degree. C. of the critical temperature at which partial transition of .gamma.-Fe.sub.2 O.sub.3 into .alpha.-Fe.sub.2 O.sub.3 occurs and which reduces the saturation magnetization to 99% of the saturation magnetization measured before the heat treatment, and the atomic ratio of Fe.sup.++ /Fe.sup.+++ after the cobalt modification is 0.00 to 0.10.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.