US3573980A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of making magnetic particles and recording tape
Assignee: 3M Co
•
Filing: 1968-02-19
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Granted: 1971-04-06
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Expires: 1988-02-19
Abstract
Abstract METHOD OF MAKING MAGNETIZABLE ACICULAR GAMMA-FE2O3 PARTICLES MODIFIED WITH AMOUNTS COBALT OXIDE, WHICH PARTICLES ARE USEFUL FOR MAKING MAGNETIC RECORDING TAPE OF HIGH COERCIVITY AFFORDING SUPERIOR ABILITY TO STORE HIGH FREQUENCY INFORMATION. EVEN HIGHER COERCIVITY MAY BE ATTAINED BY CONTROLLING THE HEATING STEPS IN MAKING THE NOVEL PARTICLES TO PROVIDE UP TO 20% FEO BY WEIGHT OF THE TOTAL IRON OXIDE.
Inventors
- 👤 Willis D Haller
- 👤 Raymond M Colline
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 18:53
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/68; G11B5/70; G11B5/706; G11B5/70626; G11B5/70642; G11B5/70678; G11B5/70684; G11B5/70694; G11B5/70652; G11B5/70668; G11B5/70673
Claims Analysis
Total Claims: 0
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References Cited (Backward Citations)
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-04-05 | 1974-10-05 | 1975-04-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-05 | 1978-10-05 | 1979-04-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-05 | 1982-10-05 | 1983-04-06 | $7700.00 | Window Closed / Lapsed |