US3974246A
Expired / Lapsed
US
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Method of improving the magnetic properties of cobalt substituted magnetite
Assignee: Corning Glass Works
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Filing: 1974-02-11
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Granted: 1976-08-10
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Expires: 1994-02-11
Abstract
Abstract A method of improving the magnetic properties of cobalt substituted magnetite by magnetizing the material to the saturation level in the desired direction, and then removing the magnetizing field. The material will retain a level of magnetization normally referred to as the remanent state of magnetization or simply remanence. The magnetized material is then subjected to a heat treatment to anneal the material. The above process significantly improves coercivity, hysteresis loop squareness ratio, and resistance to remanence loss due to external forces.
Inventors
- 👤 Shih-Lu Chen
- 👤 James A. Murphy
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 18:26
CPC Classifications
H; H01; H01F; H01F10/00; H01F10/08; H01F10/10; H01F10/18; H01F10/20; Y; Y10; Y10S; Y10S264/00; Y10S264/58
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
122 words
A method of improving magnetic properties of a magnetic material comprising the steps of providing a quantity of magnetic material comprising at least one phase thereof cobalt substituted magnetite material having a cobalt to iron ratio of between about 0.0345 and about 0.665, subjecting said material to a magnetic field having sufficient field strength and an orientation to magnetize said material in a desired direction, removing said material from said magnetic field, said material retaining a remanent level of magnetization in said desired direction, and thereafter annealing said magnetized material at a temperature between about 95°C and about 200°C in an atmosphere non-reactive with said material for a period of time sufficient to increase the hysteresis loop squareness ratio of said material.
Claim 2
Independent Claim
122 words
A method of improving magnetic properties of a magnetic material comprising the steps of providing a quantity of magnetic material comprising at least one phase thereof cobalt substituted magnetite material having a cobalt to iron ratio of between about 0.0345 and about 0.665, subjecting said material to a magnetic field having sufficient field strength and an orientation to magnetize said material in a desired direction, removing said material from said magnetic field, said material retaining a remanent level of magnetization in said desired direction, and thereafter annealing said magnetized material at a temperature between about 95°C and about 200°C in an atmosphere non-reactive with said material for a period of time sufficient to increase the hysteresis loop squareness ratio of said material.
Claim 3
Dependent Claim
24 words
The method of claim 1 wherein said cobalt substituted magnetite material has a cobalt to iron ratio of between about 0.1 and about 0.25.
Claim 4
Dependent Claim
20 words
The method of claim 1 wherein said magnetic field strength is sufficient to magnetize said material to the saturation level.
Claim 5
Dependent Claim
19 words
The method of claim 1 wherein said annealing is performed at a temperature between about 150°C and about 160°C.
Claim 6
Dependent Claim
16 words
The method of claim 1 wherein said material is annealed for at least about two hours.
Claim 7
Dependent Claim
23 words
The method of claim 1 wherein said material is annealed for a period of time bertween about 2 hours and about 147 hours.
Claim 8
Dependent Claim
12 words
The method of claim 1 wherein said annealing is performed in air.
Claim 9
Dependent Claim
64 words
The method of claim 1 wherein said cobalt substituted magnetite material has a cobalt to iron ratio of between about 0.3 and about 0.5, said magnetic field strength is sufficient to magnetize said material to the saturation level, and said annealing is performed at a temperature between about 150°C and about 160°C for a period of time between about 2 hours and 147 hours.
Claim 10
Independent Claim
114 words
A method of improving the magnetic properties of a cobalt substituted magnetite material comprising the steps of providing a quantity of cobalt substituted magnetite material having a cobalt to iron ratio of at least 0.0345, subjecting said material to a magnetic field having sufficient field strength and an orientation to magnetize said material in a desired direction, removing said material from said magnetic field, said material retaining a remanent level of magnetization in said desired direction, and thereafter annealing said magnetized material at a temperature between about 95°C and about 200°C in an atmosphere non-reactive with said material for a period of time sufficient to increase the hysteresis loop squareness ratio of said material.
Claim 11
Independent Claim
114 words
A method of improving the magnetic properties of a cobalt substituted magnetite material comprising the steps of providing a quantity of cobalt substituted magnetite material having a cobalt to iron ratio of at least 0.0345, subjecting said material to a magnetic field having sufficient field strength and an orientation to magnetize said material in a desired direction, removing said material from said magnetic field, said material retaining a remanent level of magnetization in said desired direction, and thereafter annealing said magnetized material at a temperature between about 95°C and about 200°C in an atmosphere non-reactive with said material for a period of time sufficient to increase the hysteresis loop squareness ratio of said material.
Claim 12
Dependent Claim
16 words
The method of claim 9 wherein said material is annealed for at least about 2 hours.
Claim 13
Dependent Claim
20 words
The method of claim 10 wherein said magnetic field strength is sufficient to magnetize said material to the saturation level.
References Cited (Backward Citations)
US3700500A
Cited
US3748270A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-08-10 | 1980-02-09 | 1980-08-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-10 | 1984-02-09 | 1984-08-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-10 | 1988-02-09 | 1988-08-10 | $7700.00 | Window Closed / Lapsed |