US4544591A
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Perpendicular magnetic recording medium
Assignee: Hitachi Ltd
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Filing: 1983-09-30
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Granted: 1985-10-01
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Expires: 2003-09-30
Abstract
Abstract In a perpendicular magnetic recording medium comprising a high permeability film and a perpendicular magnetization film which are laminated on a non-magnetic substrate, a perpendicular magnetic recording medium is provided wherein a permanent magnet film is further sandwiched between the non-magnetic substrate and the high permeability film, thereby eliminating a spike noise.
Inventors
- 👤 Yasutaro Uesaka
- 👤 Sadao Hishiyama
- 👤 Masahiro Kitada
- 👤 Noboru Shimizu
- 👤 Hideo Tanabe
- 👤 Hideo Fujiwara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:59
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/62; G11B5/64; G11B5/66; G11B5/676; G11B5/68; G11B5/70; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/24; Y10T428/24942; Y10T428/2495; Y10T428/24967; Y10T428/24975
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
111 words
A perpendicular magnetic recording medium comprising a non-magnetic substrate; a permanent magnet film formed on said non-magnetic substrate, said permanent magnet film having a thickness from 0.02 μm and up to 1/5 the width of a track on said medium, and a coercive force of at least 100 Oe; a high permeability film formed on said permanent magnet film, said high permeability film having a thickness of 0.1-5 μm; and a perpendicular magnetization film formed on said high permeability film, said perpendicular magnetization film having a thickness of 0.03-0.3 μm, whereby said permanent magnet film formed on said non-magnetic substrate acts to eliminate occurrence of spike noise in said recording medium.
Claim 2
Dependent Claim
111 words
A perpendicular magnetic recording medium comprising a non-magnetic substrate; a permanent magnet film formed on said non-magnetic substrate, said permanent magnet film having a thickness from 0.02 μm and up to 1/5 the width of a track on said medium, and a coercive force of at least 100 Oe; a high permeability film formed on said permanent magnet film, said high permeability film having a thickness of 0.1-5 μm; and a perpendicular magnetization film formed on said high permeability film, said perpendicular magnetization film having a thickness of 0.03-0.3 μm, whereby said permanent magnet film formed on said non-magnetic substrate acts to eliminate occurrence of spike noise in said recording medium.
Claim 3
Dependent Claim
30 words
A perpendicular magnetic recording medium according to claim 1, wherein said permanent magnet film is a γ-Fe 2 O 3 film containing Co, Co-Pt alloy film, or Al-Ni-Co alloy film.
Claim 4
Dependent Claim
29 words
A perpendicular magnetic recording medium according to claim 2, wherein said Co-Pt alloy film which contains Pt whose content is within a range of 2-43 weight percent is used.
Claim 5
Dependent Claim
29 words
A perpendicular magnetic recording medium according to claim 2, wherein said Co-Pt alloy film which contains Pt whose content is within a range of 15-25 weight percent is used.
Claim 6
Dependent Claim
58 words
A perpendicular magnetic recording medium according to claim 1, wherein the thickness of said perpendicular magnetization film is within a range of 0.1-0.2 μm, and wherein after said perpendicular magnetization film has been produced, said recording medium is subjected to heat treatment in a vacuum, inert gas or reducing gas at temperatures in the range of 400°-500° C.
Claim 7
Dependent Claim
33 words
A perpendicular magnetic recording medium according to claim 1, wherein said permanent magnet film has a thickness of 0.1 μm or more, up to 1/5 the width of a track on said medium.
Claim 8
Dependent Claim
48 words
A perpendicular magnetic recording medium according to claim 1, wherein said perpendicular magnetization film is formed of a material selected from the group consisting of a Co-Ru alloy, a Co-V alloy, a Co-W alloy, and a Co-Cr alloy having another element, other than Co and Cr, incorporated therein.
Claim 9
Dependent Claim
19 words
A perpendicular magnetic recording medium according to claim 1, wherein said medium is in the form of a disk.
Claim 10
Dependent Claim
35 words
A perpendicular magnetic recording medium according to claim 1, wherein said permanent magnet film is magnetized by applying magnetic fields in the same direction as the direction of track width in said perpendicular magnetization film.
Claim 11
Dependent Claim
34 words
A perpendicular magnetic recording medium according to claim 9, wherein the magnetic fields applied in the same direction as the direction of track width have a magnetic field strength of at least 2 Oe.
Claim 12
Dependent Claim
42 words
A perpendicular magnetic recording medium according to claim 1, wherein after said perpendicular magnetization film has been produced, said recording medium is subjected to heat treatment in a vacuum, inert gas or reducing gas at temperatures in a range of 350°-550° C.
Claim 13
Dependent Claim
34 words
A perpendicular magnetic recording medium according to claim 11, wherein said high permeability film is a magnetic alloy film, the crystallization temperature of said magnetic alloy film is higher than said heat treatment temperature.
Claim 14
Dependent Claim
38 words
A perpendicular magnetic recording medium according to claim 12, wherein the high permeability film is a magnetic alloy film that is amorphous, the crystallization temperature of the amorphous magnetic alloy film is higher than the heat treatment temperature.
Claim 15
Dependent Claim
26 words
A perpendicular magnetic recording medium according to claim 1, wherein a non-magnetic insulating film is sandwiched between said permanent magnet film and said high permeability film.
Claim 16
Dependent Claim
36 words
A perpendicular magnetic recording medium according to claim 14, wherein said permanent magnet film is magnetized by applying the magnetic fields in the same direction as the direction of track width in said perpendicular magnetization film.
Claim 17
Dependent Claim
58 words
A perpendicular magnetic recording medium according to claim 14, wherein the thickness of said perpendicular magnetization film is within a range of 0.1-0.2 μm, and wherein after said perpendicular magnetization film has been produced, said recording medium is subjected to heat treatment in a vacuum, inert gas or reducing gas at temperatures in a range of 400°-500° C.
Claim 18
Dependent Claim
32 words
A perpendicular magnetic recording medium according to claim 14, wherein said non-magnetic insulating film is made of material selected from the group consisting of SiO 2 and Al 2 O 3 .
Claim 19
Dependent Claim
22 words
A perpendicular magnetic recording medium according to claim 17, wherein said non-magnetic insulating film has a thickness of 20Å to 1 μm.
Claim 20
Dependent Claim
33 words
A perpendicular magnetic recording medium according to claim 14, wherein said permanent magnet film has a thickness of 0.1 μm or more, up to 1/5 the width of a track on said medium.
Claim 21
Dependent Claim
29 words
A perpendicular magnetic recording medium according to claim 19, wherein said Co-Pt alloy film which contains Pt whose content is within a range of 15-25 weight percent is used.
Claim 22
Dependent Claim
30 words
A perpendicular magnetic recording medium according to claim 19, wherein said permanent magnet film is a γ-Fe 2 O 3 film containing Co, Co-Pt alloy film, or Al-Ni-Co alloy film.
Claim 23
Dependent Claim
29 words
A perpendicular magnetic recording medium according to claim 21, wherein said Co-Pt alloy film which contains Pt whose content is within a range of 2-43 weight percent is used.
Claim 24
Dependent Claim
42 words
A perpendicular magnetic recording medium according to claim 14, wherein after said perpendicular magnetization film has been produced, said recording medium is subjected to heat treatment in a vacuum, inert gas or reducing gas at temperatures in a range of 350°-550° C.
Claim 25
Dependent Claim
35 words
A perpendicular magnetic recording medium according to claim 23, wherein when said high permeability film is a magnetic alloy film, the crystallization temperature of said magnetic alloy film is higher than said heat treatment temperature.
Claim 26
Dependent Claim
38 words
A perpendicular magnetic recording medium according to claim 24, wherein the high permeability film is a magnetic alloy film that is amorphous, the crystallization temperature of the amorphous magnetic alloy film is higher than the heat treatment temperature.
References Cited (Backward Citations)
US3515606A
Cited
US3929604A
Cited
US4075384A
Cited
US4210946A
Cited
US4277809A
Cited
US4410590A
Cited
US4391874A
Cited
US4438066A
Cited
JPS5829028A
Cited
US4454195A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-09-30 | 1989-04-01 | 1989-10-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-09-30 | 1993-04-01 | 1993-10-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-09-30 | 1997-04-01 | 1997-10-01 | $7700.00 | Window Closed / Lapsed |