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US5094925A
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US
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Opto-magnetic recording medium
Assignee: Sharp Corp
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Filing: 1990-06-27
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Granted: 1992-03-10
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Expires: 2010-06-27
Abstract
Abstract An opto-magnetic recording medium having a perpendicularly magnetized film of a dual layer structure comprising a first layer composed of a rare earth-transition metal amorphous thin alloy film and a second layer composed of a rare earth-transition metal amorphous thin alloy film of a composition different from that of the first layer and having a lower curie point and a larger coercive force as compared with that of said first layer, and being capable of transferring bits recorded at a curie point in said second layer to the first layer by exchange-coupling force, said first layer being composed of a GdDyFeCo film in which the sublattice magnetization for transition metal is predominant at a room temperature, the second layer being composed of TbFeCo series film in which sublattice magnetization for rare earth is predominant at a room temperature, and the directions of predominant magnetization between the first layer and the second layer being opposed to each other.
Inventors
- 👤 Tomokazu Ise
- 👤 Tkeo Takase
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:17
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; G11B11/10589; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
201 words
An opto-magnetic recording medium having a perpendicularly magnetized film of a dual layer structure deposited on a substrate comprising, in order, a first layer composed of a rare earth-transition metal amorphous thin alloy film and a second layer composed of a rare earth-transition metal amorphous thin alloy film of a composition different from that of the first layer and having a lower Curie point and a larger coercive force as compared with that of said first layer, said medium being capable of transferring bits recorded at a Curie point in said second layer to the first layer by an exchange-coupling force between said first and second layers, said first layer being composed of a GdDyFeCo film which is made of an alloy represented by the formula: (Gd.sub.100-X Dy.sub.X).sub.Z (Fe.sub.100-Y Co.sub.Y).sub.100-Z in which X=5-25 atm %, Y=18-30 atm % and Z=16-24 atm %, wherein the sublattice magnetization for the transition metal in said film is predominant at a room temperature, the second layer being composed of TbFeCo series film in which sublattice magnetization for the rare earth is predominant at a room temperature, and the directions of predominant magnetization between the first layer and the second layer are opposed to each other.
Claim 2
Dependent Claim
201 words
An opto-magnetic recording medium having a perpendicularly magnetized film of a dual layer structure deposited on a substrate comprising, in order, a first layer composed of a rare earth-transition metal amorphous thin alloy film and a second layer composed of a rare earth-transition metal amorphous thin alloy film of a composition different from that of the first layer and having a lower Curie point and a larger coercive force as compared with that of said first layer, said medium being capable of transferring bits recorded at a Curie point in said second layer to the first layer by an exchange-coupling force between said first and second layers, said first layer being composed of a GdDyFeCo film which is made of an alloy represented by the formula: (Gd.sub.100-X Dy.sub.X).sub.Z (Fe.sub.100-Y Co.sub.Y).sub.100-Z in which X=5-25 atm %, Y=18-30 atm % and Z=16-24 atm %, wherein the sublattice magnetization for the transition metal in said film is predominant at a room temperature, the second layer being composed of TbFeCo series film in which sublattice magnetization for the rare earth is predominant at a room temperature, and the directions of predominant magnetization between the first layer and the second layer are opposed to each other.
Claim 3
Dependent Claim
38 words
The recording medium of claim 1 in which the TbFeCo series film is made of TbFeCo or TbFeCo based alloy in which Tb is partially substituted with another rare earth element such as Gd, Dy, Nd or Ho.
Claim 4
Dependent Claim
20 words
The recording medium of claim 1 in which the total thickness of the magnetized film is 15 to 300 nm.
Claim 5
Dependent Claim
22 words
The recording medium of claim 1 in which the thickness of the second layer is greater than that of the first layer.
Claim 6
Dependent Claim
27 words
The recording medium of claim 1 in which the magnetized film is formed over a transparent substrate selected from the group consisting of glass and resin substrates.
Claim 7
Dependent Claim
20 words
The recording medium of claim 5 in which the magnetized film is interposed between a pair of dielectric material layers.
Claim 8
Dependent Claim
17 words
The recording medium of claim 1 which shows a Kerr rotation angle θK of more than 0.48°.
Claim 9
Dependent Claim
19 words
The recording medium of claim 1 which has a saturation magnetization Ms of less than 250 emu/cm 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) | 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 |