US3859129A
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: 1972-05-26
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Granted: 1975-01-07
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Expires: 1992-05-26
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
2026-10-31 19:28
CPC Classifications
H; H01; H01F; H01F10/00; H01F10/08; H01F10/10; H01F10/18; H01F10/20
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
109 words
A method of improving magnetic properties of a magnetic device comprising the steps of forming a cobalt substituted magnetite film having a cobalt to iron ratio of between about 0.0345 and about 0.665, said film being bonded to a non-magnetic substrate, thereafter subjecting said cobalt substituted magnetite film to a magnetic field having sufficient field strength and an orientation to magnetize said film in a desired direction, removing said film from said magnetic field, said film retaining a remanent level of magnetization in said desired direction, and thereafter annealing said magnetized film at a temperature of between about 95* C and about 200*C for at least about 2 hours.
Claim 2
Independent Claim
109 words
A method of improving magnetic properties of a magnetic device comprising the steps of forming a cobalt substituted magnetite film having a cobalt to iron ratio of between about 0.0345 and about 0.665, said film being bonded to a non-magnetic substrate, thereafter subjecting said cobalt substituted magnetite film to a magnetic field having sufficient field strength and an orientation to magnetize said film in a desired direction, removing said film from said magnetic field, said film retaining a remanent level of magnetization in said desired direction, and thereafter annealing said magnetized film at a temperature of between about 95* C and about 200*C for at least about 2 hours.
Claim 3
Dependent Claim
24 words
The method of claim 1 wherein said cobalt substituted magnetite film 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
23 words
The method of claim 1 wherein said film is annealed for a period of time between about two hours and about 177 hours.
Claim 7
Dependent Claim
12 words
The method of claim 1 wherein said annealing is performed in air.
Claim 8
Dependent Claim
65 words
The method of claim 1 wherein said cobalt substituted magnetite film has a cobalt to iron ratio of between about 0.1 and about 0.25, said magnetic field strength is sufficient to magnetize said film 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 about 147 hours.
Claim 9
Dependent Claim
25 words
The method of claim 1 wherein said non-magnetic substrate is formed of material selected from the group consisting of anodized aluminum, glass-ceramic, glass, and ceramic.
Claim 10
Dependent Claim
99 words
The method of claim 1 wherein forming a cobalt substituted magnetite film comprises the steps of heating said substrate to a temperature of between about 350*C and about 550*C, exposing a surface of said heated substrate to vapors of a cobalt containing compound and simultaneously to vapors of an iron containing compound, to form a film of non-magnetic cobalt-iron oxide chemically bonded to said substrate, and thereafter heating said film of non-magnetic cobalt-iron oxide to a temperature of between about 300*C and about 600*C in a reducing atmosphere to reduce the material of said film to cobalt substituted magnetite.
Claim 11
Dependent Claim
53 words
The method of claim 9 wherein said cobalt containing compound is selected from the group consisting of cobalt nitrosyltricarbonyl, cobaltocene, cobaltic acetylacetonate, cobaltous acetylacetonate, cobaltic hexafluoroacetylacetonate, and cobaltous hexafluoroacetylacetonate, and said iron containing compound is selected from the group consisting of iron pentacarbonyl, ferrocene, ferric acetylacetonate, ferrous acetylacetonate, ferric hexafluoroacetylacetonate, and ferrous hexafluoroacetylacetonate.
Claim 12
Dependent Claim
21 words
The method of claim 9 wherein said cobalt containing compound is cobalt chloride, and the iron containing compound is ferric chloride.
Claim 13
Dependent Claim
16 words
THE METHOD OF CLAIM 9 WHEREIN SAID NON-MAGNETIC SUBSTRATE IS MADE OF AN ION-EXCHAGE STRENGTHENED GLASS.
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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) | 1978-01-06 | 1978-07-08 | 1979-01-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-01-06 | 1982-07-08 | 1983-01-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-01-06 | 1986-07-08 | 1987-01-07 | $7700.00 | Window Closed / Lapsed |