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Patent US5094897A successfully refreshed from Google Patents.
US5094897A
Expired / Lapsed
US
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Magnetic recording medium comprising a glass substrate and a gamma Fe2 3 magnetic thin film with specified X-ray diffraction and surface roughness
Assignee: TDK Corp
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Filing: 1990-04-26
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Granted: 1992-03-10
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Expires: 2010-04-26
Abstract
Abstract A magnetic recording disk comprising a rigid substrate and a magnetic layer of the continuous thin film type is durable and exhibits good electromagnetic properties when the magnetic layer predominantly composed of γ-Fe 2 O 3 has specific peak area ratios in an X-ray diffraction chart thereof. Inclusion of α-Fe 2 O 3 in the magnetic layer is also effective. Reliable recording/reproduction can be conducted on the magnetic recording disk using a flying magnetic head.
Inventors
- 👤 Haruyuki Morita
- 👤 Monjiro Momoi
- 👤 Kazumasa Fukuda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 15:07
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/65; G11B5/658; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/31
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
137 words
A magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising γ-Fe 2 O 3 , characterized in that said magnetic layer meets the following conditions: 0≦P(400)/P(311)≦1.0 and 0≦P(222)/P(311)≦0.5 wherein P(311), P400), and P222) are peak areas at indexes of plane (311), (400) and (222) of γ-Fe 2 O 3 , respectively, in an X-ray diffraction chart of the magnetic layer, and said substrate has a surface roughness Rmax in the range of from 10 to 100 Å on at least one of the pair of major surfaces and said medium has a surface roughness Rmax in the range of from 50 to 200 Å on an outer surface adjacent to the magnetic layer.
Claim 2
Dependent Claim
137 words
A magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising γ-Fe 2 O 3 , characterized in that said magnetic layer meets the following conditions: 0≦P(400)/P(311)≦1.0 and 0≦P(222)/P(311)≦0.5 wherein P(311), P400), and P222) are peak areas at indexes of plane (311), (400) and (222) of γ-Fe 2 O 3 , respectively, in an X-ray diffraction chart of the magnetic layer, and said substrate has a surface roughness Rmax in the range of from 10 to 100 Å on at least one of the pair of major surfaces and said medium has a surface roughness Rmax in the range of from 50 to 200 Å on an outer surface adjacent to the magnetic layer.
Claim 3
Dependent Claim
21 words
The magnetic recording medium of claim 1 which further comprises a lubricating layer containing an organic compound on the magnetic layer.
Claim 4
Independent Claim
195 words
A method for recording and reproducing information in a magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising γ-Fe 2 O 3 , wherein said magnetic layer meets the following conditions 0≦P(400)/P(311)≦1.0 and 0≦P(222)/P(311)≦0.5 wherein P(311), P(400), and P(222) are peak areas at indexes of plane (311), (400) and (222) of γ-Fe 2 O 3 , respectively, in an X-ray diffraction chart of the magnetic layer, and wherein said substrate has a surface roughness Rmax in the range of from 10 to 100 Å on at least one of the pair of major surfaces and said medium has a surface roughness Rmax in the range of from 50 to 200 Å on an outer surface adjacent to the magnetic layer, the method comprising the step of rotating the magnetic recording medium in close proximity to a flying magnetic head, characterized in that said magnetic recording medium is a rotating magnetic disk and the flying magnetic head is kept at a spacing of up to 0.2 μm from the rotating magnetic disk.
Claim 5
Independent Claim
195 words
A method for recording and reproducing information in a magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising γ-Fe 2 O 3 , wherein said magnetic layer meets the following conditions 0≦P(400)/P(311)≦1.0 and 0≦P(222)/P(311)≦0.5 wherein P(311), P(400), and P(222) are peak areas at indexes of plane (311), (400) and (222) of γ-Fe 2 O 3 , respectively, in an X-ray diffraction chart of the magnetic layer, and wherein said substrate has a surface roughness Rmax in the range of from 10 to 100 Å on at least one of the pair of major surfaces and said medium has a surface roughness Rmax in the range of from 50 to 200 Å on an outer surface adjacent to the magnetic layer, the method comprising the step of rotating the magnetic recording medium in close proximity to a flying magnetic head, characterized in that said magnetic recording medium is a rotating magnetic disk and the flying magnetic head is kept at a spacing of up to 0.2 μm from the rotating magnetic disk.
Claim 6
Dependent Claim
52 words
A magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising γ-Fe 2 O 3 , characterized in that said magnetic layer further comprises α-Fe 2 O 3 .
Claim 7
Dependent Claim
52 words
A magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising γ-Fe 2 O 3 , characterized in that said magnetic layer further comprises α-Fe 2 O 3 .
Claim 8
Dependent Claim
36 words
The magnetic recording medium of claim 4 wherein in said magnetic layer, the content of α-Fe 2 O 3 is higher on a side remote from the substrate than on a side adjacent to the substrate.
Claim 9
Dependent Claim
66 words
The magnetic recording medium of claim 4 wherein the magnetic layer meets the following conditions: 0.02≦P(104)/P(311)≦0.20, 0≦P(400)P(311)≦1.0, and 0≦P(222)P(311)≦0.5 wherein P(311), P(400), and P(222) are peak areas at indexes of plane (311), (400) and (222) of γ-Fe 2 O 3 and P(104) is a peak area at an index of plane (104) of α-Fe 2 O 3 in an X-ray diffraction chart of the magnetic layer.
Claim 10
Dependent Claim
64 words
The magnetic recording medium of any one of claims 4 to 6 wherein said substrate has a surface roughness Rmax in the range of from 10 to 100 Å on at least one of the pair of major surfaces and said medium has a roughness Rmax in the range of from 50 to 200 Å on an outer surface adjacent to the magnetic layer.
Claim 11
Dependent Claim
26 words
The magnetic recording medium of any one of claims 4 to 6 which further comprises a lubricating layer containing an organic compound on the magnetic layer.
Claim 12
Independent Claim
109 words
A method for recording and reproducing information in a magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising α-Fe 2 O 3 , wherein the magnetic layer further comprises α-Fe 2 O 3 , the method comprising the step of rotating the magnetic recording medium in close proximity to a flying magnetic head, characterized in that said magnetic recording medium is a rotating magnetic disk and the flying magnetic head is kept at a spacing of up to 0.2 μm from the rotating magnetic disk.
Claim 13
Independent Claim
109 words
A method for recording and reproducing information in a magnetic recording medium comprising a rigid substrate, formed of glass, having a pair of opposed major surfaces and a layer of continuous magnetic thin film on at least one major surface predominantly comprising α-Fe 2 O 3 , wherein the magnetic layer further comprises α-Fe 2 O 3 , the method comprising the step of rotating the magnetic recording medium in close proximity to a flying magnetic head, characterized in that said magnetic recording medium is a rotating magnetic disk and the flying magnetic head is kept at a spacing of up to 0.2 μm from the rotating magnetic disk.
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) | 1995-03-10 | 1995-09-09 | 1996-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-03-10 | 1999-09-09 | 2000-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-03-10 | 2003-09-09 | 2004-03-10 | $7700.00 | Window Closed / Lapsed |