US4631612A
Expired / Lapsed
US
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Magnetic recording and reproducing system
Assignee: Hitachi Ltd
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Filing: 1983-07-14
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Granted: 1986-12-23
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Expires: 2003-07-14
Abstract
Abstract A magnetic recording and reproducing system comprising (i) a magnetic head including a first magnetic pole whose saturation flux density is at least 7 kG and whose edge face is 0.15-0.5 mu m thick, and a second magnetic pole which lies on the same side as the first magnetic pole with respect to a recording medium and whose edge face is at least 10 times thicker than that of the first magnetic pole, and (ii) the perpendicular magnetic recording medium including a perpendicular magnetization layer which has a coercive force of 250-600 Oe. in a direction perpendicular to a plane thereof and which is 0.1-0.5 mu m thick.
Inventors
- 👤 Kazuo Shiiki
- 👤 Yoshihiro Shiroishi
- 👤 Isamu Yuito
- 👤 Kiminari Shinagawa
- 👤 Yasutaro Uesaka
- 👤 Hideo Fujiwara
- 👤 Hitoshi Nakamura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 11:52
CPC Classifications
G; G11; G11B; G11B5/00; G11B5/127; G11B5/1278; G11B5/62
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
194 words
A magnetic recording and reproducing system comprising a perpendicular magnetic recording and reproducing head and a perpendicular magnetic recording medium, said head having a first magnetic pole and a second magnetic pole, in which said first magnetic pole, for magnetic recording and reproduction, is made of a magnetic material having a saturation flux density of at least 7 kG, and an edge face of the first magnetic pole confronting the recording medium, is 0.15-0.5 μm thick, while an edge face of the second magnetic pole, confronting the recording medium, the second magnetic pole lying on the same side as the first magnetic pole with respect to the recording medium, is at least 5 times thicker than the first magnetic pole, and the perpendicular magnetic recording medium comprises a magnetic thin film which is formed on a magnetic layer of high magnetic permeability directly or through an intermediate layer, which magnetic thin film has an easy magnetization axis in a direction nearly perpendicular to the plane of the film, and which magnetic thin film has a thickness of 0.1-0.5 μm and a coercive force in the direction perpendicular to the film plane of 250-600 Oe.
Claim 2
Dependent Claim
194 words
A magnetic recording and reproducing system comprising a perpendicular magnetic recording and reproducing head and a perpendicular magnetic recording medium, said head having a first magnetic pole and a second magnetic pole, in which said first magnetic pole, for magnetic recording and reproduction, is made of a magnetic material having a saturation flux density of at least 7 kG, and an edge face of the first magnetic pole confronting the recording medium, is 0.15-0.5 μm thick, while an edge face of the second magnetic pole, confronting the recording medium, the second magnetic pole lying on the same side as the first magnetic pole with respect to the recording medium, is at least 5 times thicker than the first magnetic pole, and the perpendicular magnetic recording medium comprises a magnetic thin film which is formed on a magnetic layer of high magnetic permeability directly or through an intermediate layer, which magnetic thin film has an easy magnetization axis in a direction nearly perpendicular to the plane of the film, and which magnetic thin film has a thickness of 0.1-0.5 μm and a coercive force in the direction perpendicular to the film plane of 250-600 Oe.
Claim 3
Dependent Claim
26 words
A magnetic recording and reproducing system as defined in claim 1, wherein a magnetic material forming the second magnetic pole is an Mn--Zn ferrite single crystal.
Claim 4
Dependent Claim
48 words
A magnetic recording and reproducing system as defined in claim 1, wherein the magnetic thin film having the easy magnetization axis in the direction nearly perpendicular to the plane of said perpendicular magnetic recording medium is of an alloy which contains Co and Cr as its main components.
Claim 5
Dependent Claim
48 words
A magnetic recording and reproducing system as defined in claim 2, wherein the magnetic thin film having the easy magnetization axis in the direction nearly perpendicular to the plane of said perpendicular magnetic recording medium is of an alloy which contains Co and Cr as its main components.
Claim 6
Dependent Claim
51 words
A magnetic recording and reproducing system as defined in claim 1, wherein the edge face of the first magnetic pole is 0.2-0.3 μm thick and the edge face of the second magnetic pole is at least 10 times greater than the thickness of the edge face of the first magnetic pole.
Claim 7
Dependent Claim
44 words
A magnetic recording and reproducing system as defined in claim 1, wherein said head further comprises a coil for causing a signal current to flow therethrough and an insulator layer for magnetically and electrically isolating the first and second magnetic poles and said coil.
Claim 8
Dependent Claim
37 words
A magnetic recording and reproducing system as defined in claim 2, wherein the first magnetic pole is made of a material selected from the group consisting of Co amorphous alloys, Ni--Fe polycrystalline alloys, and Fe--Si polycrystalline alloys.
Claim 9
Dependent Claim
40 words
A magnetic recording and reproducing system as defined in claim 1, wherein the second magnetic pole is constructed of a plurality of layers, with insulator layers interposed between adjacent ones of the plurality of layers of the second magnetic pole.
Claim 10
Dependent Claim
48 words
A magnetic recording and reproducing system as defined in claim 8, wherein the insulator layers interposed between adjacent ones of the plurality of layers of the second magnetic pole are made of a material selected from the group consisting of SiO 2 and Al 2 O 3 .
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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) | 1989-12-22 | 1990-06-23 | 1990-12-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-12-22 | 1994-06-23 | 1994-12-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-12-22 | 1998-06-23 | 1998-12-23 | $7700.00 | Window Closed / Lapsed |