US4423114A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic powder for magnetic recording medium
Assignee: TDK Corp
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Filing: 1981-09-09
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Granted: 1983-12-27
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Expires: 2001-09-09
Abstract
Abstract A magnetic powder for a magnetic recording medium which is a cobalt-adsorbed magnetic iron oxide having a coercive force of 1000 Oe or more and a ratio of a coercive force at -196° C. to a coercive force at room temperature of 3 or less.
Inventors
- 👤 Hiroto Saguchi
- 👤 Masashi Hayama
- 👤 Keitaro Sakai
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 17:16
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70647; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/29; Y10T428/2982; Y10T428/2991
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
149 words
A magnetic powder for a magnetic recording medium which is a cobalt-adsorbed magnetic iron oxide comprising γ-Fe 2 O 3 , having a coercive force of at least 1000 Oe and a ratio of a coercive force at -196° C. to a coercive force at room temperature of 3 or less, which magnetic powder is obtained by coating said γ-Fe 2 O 3 in dispersion with a cobalt component by adding cobalt ion to γ-Fe 2 O 3 at a ratio of 6 wt. % or more, and then adding ferrous ion at a ratio of 20 wt. % or more as Fe 2+ based on γ-Fe 2 O 3 and at a ratio of said ferrous salt to said cobalt salt of 3.0 to 4.5 by weight so as to adsorb Fe 2+ and Co 2+ in a Fe 2+ /Co 2+ weight ratio of 2.0 to 3.5.
Claim 2
Dependent Claim
149 words
A magnetic powder for a magnetic recording medium which is a cobalt-adsorbed magnetic iron oxide comprising γ-Fe 2 O 3 , having a coercive force of at least 1000 Oe and a ratio of a coercive force at -196° C. to a coercive force at room temperature of 3 or less, which magnetic powder is obtained by coating said γ-Fe 2 O 3 in dispersion with a cobalt component by adding cobalt ion to γ-Fe 2 O 3 at a ratio of 6 wt. % or more, and then adding ferrous ion at a ratio of 20 wt. % or more as Fe 2+ based on γ-Fe 2 O 3 and at a ratio of said ferrous salt to said cobalt salt of 3.0 to 4.5 by weight so as to adsorb Fe 2+ and Co 2+ in a Fe 2+ /Co 2+ weight ratio of 2.0 to 3.5.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-12-26 | 1987-06-27 | 1987-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-12-26 | 1991-06-27 | 1991-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-12-26 | 1995-06-27 | 1995-12-27 | $7700.00 | Window Closed / Lapsed |