Patent US1984604A successfully refreshed from Google Patents.
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US4156037A
Expired / Lapsed
US
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Process for producing a magnetic recording medium
Assignee: Fujitsu Ltd
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Filing: 1977-03-03
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Granted: 1979-05-22
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Expires: 1997-03-03
Abstract
Abstract A thin film of ferrite for use as a magnetic recording medium contain (a) Cu, (b) both Cu and Co, or (c) Cu, Co and Nb. The inclusion of Cu increases the temperature range for reduction from α-Fe 2 O 3 to one of the ferrites, i.e. Fe 3 O 4 , and also lowers the above-mentioned reducting temperature. The addition of Co improves the magnetic properties of the ferrite. The simultaneous addition of Cu, Co and Nb provides γ-Fe 2 O 3 with excellent magnetic properties, which are stable over wide temperature range for oxidizing the Fe 3 O 4 to the γ-Fe 2 O 3 .
Inventors
- 👤 Seizi Hattori
- 👤 Takehiko Nakagawa
- 👤 Kazuo Kobayashi
- 👤 Koichi Makino
- 👤 Wakatake Matsuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 10:23
CPC Classifications
H; H01; H01F; H01F41/00; H01F41/14; G; G11; G11B; G11B5/00; G11B5/84
Claims Analysis
Total Claims: 50
Claim 1
Independent Claim
98 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, and reducing said thin film of α-Fe 3 O 4 , characterized in that said thin film of α-Fe 2 O 3 is formed containing copper in an amount from 1 to 15 atomic % of copper, and said reduction step is performed by heating said α-Fe 2 O 3 containing said copper in a reducing atmosphere at a temperature of from 200° to 300° C.
Claim 2
Dependent Claim
98 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, and reducing said thin film of α-Fe 3 O 4 , characterized in that said thin film of α-Fe 2 O 3 is formed containing copper in an amount from 1 to 15 atomic % of copper, and said reduction step is performed by heating said α-Fe 2 O 3 containing said copper in a reducing atmosphere at a temperature of from 200° to 300° C.
Claim 3
Dependent Claim
18 words
A process according to claim 1, wherein said amount of copper is from 1 to 10 atomic %.
Claim 4
Dependent Claim
145 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, reducing said thin film of α-Fe 2 O 3 , to Fe 3 O 4 , and oxidizing said Fe 3 O 4 to γ-Fe 2 O 3 characterized in that said film of α-Fe 2 O 3 is formed containing copper in an amount from 1 to 15 atomic %, said reduction step is performed by heating said α-Fe 2 O 3 containing said copper in a reducing atmosphere at a temperature of from 200° to 300° C., and said oxidizing step is performed by heating said thin film of Fe 3 O 4 containing said copper at a temperature of from 150° to 400° C. in an atmosphere which contains oxygen.
Claim 5
Dependent Claim
145 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, reducing said thin film of α-Fe 2 O 3 , to Fe 3 O 4 , and oxidizing said Fe 3 O 4 to γ-Fe 2 O 3 characterized in that said film of α-Fe 2 O 3 is formed containing copper in an amount from 1 to 15 atomic %, said reduction step is performed by heating said α-Fe 2 O 3 containing said copper in a reducing atmosphere at a temperature of from 200° to 300° C., and said oxidizing step is performed by heating said thin film of Fe 3 O 4 containing said copper at a temperature of from 150° to 400° C. in an atmosphere which contains oxygen.
Claim 6
Dependent Claim
16 words
A process according to claim 4, wherein said oxidizing temperature is from 250° to 350° C.
Claim 7
Dependent Claim
18 words
A process according to claim 4, wherein said amount of copper is from 1 to 10 atomic %.
Claim 8
Dependent Claim
110 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 , characterized in that said film of α-Fe 2 O 3 is formed containing copper from 1 to 15 atomic % and cobalt in an amount from 1 to 6 atomic %, and said reduction step is performed by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature of from 200° to 300° C.
Claim 9
Dependent Claim
110 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 , characterized in that said film of α-Fe 2 O 3 is formed containing copper from 1 to 15 atomic % and cobalt in an amount from 1 to 6 atomic %, and said reduction step is performed by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature of from 200° to 300° C.
Claim 10
Dependent Claim
21 words
A process according to claim 6, wherein said copper is contained in an amount of from 1 to 10 atomic %.
Claim 11
Dependent Claim
160 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 , and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 , characterized in that said film of α-Fe 2 O 3 is formed containing copper in an amount from 1 to 15 atomic % and cobalt in an amount from 1 to 6 atomic %, said reduction step is performed by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature of from 200° to 300° C., and said oxidizing step is performed by heating said thin film of Fe 3 O 4 containing said copper and cobalt at a temperature of from 150° to 400° C. in an atmosphere which contains oxygen.
Claim 12
Dependent Claim
160 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 , and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 , characterized in that said film of α-Fe 2 O 3 is formed containing copper in an amount from 1 to 15 atomic % and cobalt in an amount from 1 to 6 atomic %, said reduction step is performed by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature of from 200° to 300° C., and said oxidizing step is performed by heating said thin film of Fe 3 O 4 containing said copper and cobalt at a temperature of from 150° to 400° C. in an atmosphere which contains oxygen.
Claim 13
Dependent Claim
21 words
A process according to claim 8, wherein said copper is contained in an amount of from 1 to 10 atomic %.
Claim 14
Dependent Claim
16 words
A process according to claim 8, wherein said oxidizing temperature is from 250° to 350° C.
Claim 15
Dependent Claim
31 words
The process of claim 6 or 8 wherein said copper and cobalt are contained in said film of αFe 2 O 3 in total amount of up to 15 atomic %.
Claim 16
Dependent Claim
137 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, and, reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 , characterized in that said film of α-Fe 2 O 3 is formed containing niobium in an amount from 1 to 10 atomic %, copper in an amount from 1 to 15 atomic % and cobalt in an amount from 1 to 6 atomic %, and further said reduction step of said α-Fe 2 O 3 to said Fe 3 O 4 is performed by heating said α-Fe 2 O 3 containing said niobium, copper and cobalt in a reducing atmosphere at a temperature of from 225° to 400° C.
Claim 17
Dependent Claim
137 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate, and, reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 , characterized in that said film of α-Fe 2 O 3 is formed containing niobium in an amount from 1 to 10 atomic %, copper in an amount from 1 to 15 atomic % and cobalt in an amount from 1 to 6 atomic %, and further said reduction step of said α-Fe 2 O 3 to said Fe 3 O 4 is performed by heating said α-Fe 2 O 3 containing said niobium, copper and cobalt in a reducing atmosphere at a temperature of from 225° to 400° C.
Claim 18
Dependent Claim
48 words
A process according to claim 12, wherein said niobium is contained in an amount from 2 to 5 atomic %, said copper is contained in an amount of from 1 to 10 atomic %, and said cobalt is contained in an amount from 1 to 3 atomic %.
Claim 19
Dependent Claim
178 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate; reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 ; and, oxidizing said Fe 3 O 4 to α-Fe 2 O 3 , characterized in that said film of α-Fe 2 O 3 is formed containing niobium in an amount from 1 to 10 atomic %, copper in an amount from 1 to 15 atomic % and cobalt from 1 to 6 atomic %, said reduction step of said α-Fe 2 O 3 to said Fe 3 O 4 is performed by heating said α-Fe 2 O 3 containing said niobium, copper and cobalt at a temperature of from 225 to 400° C in a reducing atmosphere and said oxidation step is performed by heating said Fe 3 O 4 containing said niobium, copper and cobalt to a temperature of from 150° to 450° C. in an atmosphere which contains oxygen.
Claim 20
Dependent Claim
178 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming a thin film of α-Fe 2 O 3 on a substrate; reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 ; and, oxidizing said Fe 3 O 4 to α-Fe 2 O 3 , characterized in that said film of α-Fe 2 O 3 is formed containing niobium in an amount from 1 to 10 atomic %, copper in an amount from 1 to 15 atomic % and cobalt from 1 to 6 atomic %, said reduction step of said α-Fe 2 O 3 to said Fe 3 O 4 is performed by heating said α-Fe 2 O 3 containing said niobium, copper and cobalt at a temperature of from 225 to 400° C in a reducing atmosphere and said oxidation step is performed by heating said Fe 3 O 4 containing said niobium, copper and cobalt to a temperature of from 150° to 450° C. in an atmosphere which contains oxygen.
Claim 21
Dependent Claim
16 words
A process according to claim 14, wherein said oxidation temperature is from 200° to 450° C.
Claim 22
Dependent Claim
50 words
A process according to claim 10, wherein said niobium is contained in an amount of from 2 to 4 atomic %, said copper is contained in an amount of from 1 to 15 atomic %, and said cobalt is contained in an amount of from 1 to 3 atomic %.
Claim 23
Dependent Claim
16 words
A process according to claim 16, wherein said oxidizing temperature is from 200° to 450° C.
Claim 24
Dependent Claim
82 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 containing copper in an amount from 1 to 15 atomic %, and reducing said α-Fe 2 O 3 to Fe 3 O 4 by heating said film in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.
Claim 25
Dependent Claim
82 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 containing copper in an amount from 1 to 15 atomic %, and reducing said α-Fe 2 O 3 to Fe 3 O 4 by heating said film in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.
Claim 26
Dependent Claim
29 words
The process of claim 18, wherein said amount of copper is from 3 to 15 atomic % and said reducing temperature range is between approximately 200° and 270° C.
Claim 27
Dependent Claim
27 words
The process of claim 18, wherein said amount of copper is approximately 5 atomic % and said reducing temperature range is between approximately 200° and 300° C.
Claim 28
Dependent Claim
17 words
The process of claim 18, wherein said amount of copper is from 2 to 5 atomic %.
Claim 29
Dependent Claim
130 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of forming on a substrate a thin film of α-Fe 2 O 3 containing copper in an amount from 1 to 15 atomic %, and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 containing said copper in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C; and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 by heating said thin film of Fe 3 O 4 containing copper at a temperature of from 150 to 400° C. in an atmosphere which contains oxygen.
Claim 30
Dependent Claim
130 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of forming on a substrate a thin film of α-Fe 2 O 3 containing copper in an amount from 1 to 15 atomic %, and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 containing said copper in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C; and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 by heating said thin film of Fe 3 O 4 containing copper at a temperature of from 150 to 400° C. in an atmosphere which contains oxygen.
Claim 31
Dependent Claim
17 words
The process of claim 22, wherein said amount of copper is from 2 to 5 atomic %.
Claim 32
Dependent Claim
28 words
The process of claim 22, wherein said amount of copper if from 3 to 15 atomic % and said reducing temperature is between approximately 200° and 270° C.
Claim 33
Dependent Claim
26 words
The process of claim 22, wherein said amount of copper is approximately 5 atomic % and said reducing temperature is between approximately 200° and 300° C.
Claim 34
Dependent Claim
103 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 comprising copper in a mount from 1 to 15 atomic % and cobalt in amount from 1 to 6 atomic %; and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.
Claim 35
Dependent Claim
103 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 comprising copper in a mount from 1 to 15 atomic % and cobalt in amount from 1 to 6 atomic %; and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.
Claim 36
Dependent Claim
17 words
The process of claim 26, wherein said amount of copper is from 2 to 5 atomic %.
Claim 37
Dependent Claim
28 words
The process of claim 26, wherein said amount of copper is from 3 to 15 atomic % and said reducing temperature is between approximately 200° and 270° C.
Claim 38
Dependent Claim
26 words
The process of claim 26, wherein said amount of copper is approximately 5 atomic % and said reducing temperature is between approximately 200° and 300° C.
Claim 39
Dependent Claim
143 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 comprising copper in amount from 1 to 15 atomic % and cobalt in amount from 1 to 6 atomic %; and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300 to 325° C; and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 by heating said thin film of Fe 3 O 4 containing said copper and cobalt at a temperature of from 150 to 400° C. in an atmosphere containing oxygen.
Claim 40
Dependent Claim
143 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 comprising copper in amount from 1 to 15 atomic % and cobalt in amount from 1 to 6 atomic %; and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 containing said copper and cobalt in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300 to 325° C; and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 by heating said thin film of Fe 3 O 4 containing said copper and cobalt at a temperature of from 150 to 400° C. in an atmosphere containing oxygen.
Claim 41
Dependent Claim
18 words
The process of claim 30, wherein the amount of said copper is from 2 to 5 atomic %.
Claim 42
Dependent Claim
28 words
The process of claim 30, wherein said amount of copper is from 3 to 15 atomic % and said reducing temperature is between approximately 200° and 270° C.
Claim 43
Dependent Claim
26 words
The process of claim 30, wherein said amount of copper is approximately 5 atomic % and said reducing temperature is between approximately 200° an 300° C.
Claim 44
Dependent Claim
30 words
The process of claim 26 or 30 wherein said copper and cobalt are contained in said film of α-Fe 2 O 3 in total amount up to 15 atomic %.
Claim 45
Dependent Claim
93 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 containg niobium, copper and cobalt in amount from 1 to 10, 1 to 15 and 1 to 6 atomic %, respectively; and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.
Claim 46
Dependent Claim
93 words
A process for producing a magnetic recording medium of a thin film of ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 containg niobium, copper and cobalt in amount from 1 to 10, 1 to 15 and 1 to 6 atomic %, respectively; and reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.
Claim 47
Dependent Claim
33 words
The process of claim 35, wherein said amounts of niobium, copper and cobalt are approximately 5, 5 and 2 atomic %, respectively, and said reducing temperature is approximately from 225° to 400° C.
Claim 48
Dependent Claim
135 words
A process for producing a magnetic recording medium of a thin film ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 containing niobium, copper and cobalt in amount from 1 to 10, 1 to 15 and 1 to 6 atomic %, respectively; reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.; and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 by heating said Fe 3 O 4 containing said niobium, copper and cobalt to a temperature of from 150° to 450° C. in an atmosphere containing oxygen.
Claim 49
Dependent Claim
135 words
A process for producing a magnetic recording medium of a thin film ferrite, said process comprising the steps of: forming on a substrate a thin film of α-Fe 2 O 3 containing niobium, copper and cobalt in amount from 1 to 10, 1 to 15 and 1 to 6 atomic %, respectively; reducing said thin film of α-Fe 2 O 3 to Fe 3 O 4 by heating said α-Fe 2 O 3 in a reducing atmosphere at a temperature in a range broader than and extending lower than the range from 300° to 325° C.; and oxidizing said Fe 3 O 4 to α-Fe 2 O 3 by heating said Fe 3 O 4 containing said niobium, copper and cobalt to a temperature of from 150° to 450° C. in an atmosphere containing oxygen.
Claim 50
Dependent Claim
34 words
The process of claim 37, wherein said amounts of niobium, copper and cobalt are approximately 5, 5 and 2 atomic %, respectively, and said reducing temperature range is approximatey from 225° to 400° C.
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) | 1982-05-21 | 1982-11-20 | 1983-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-05-21 | 1986-11-20 | 1987-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-05-21 | 1990-11-20 | 1991-05-22 | $7700.00 | Window Closed / Lapsed |