EP0330394A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Two-layered type opto-magnetic recording medium having low-coercive force layer containing Gd and at least one of Tb and Dy
Assignee: Canon Inc
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Filing: 1989-02-20
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Granted: —
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Expires: 2009-02-20
Abstract
Abstract An opto-magnetic recording medium with higher stability of recorded information comprises a perpendicularly magnetizable first magnetic layer formed of a rare earth-ion amorphous alloy, and a perpendicularly magnetizable second magnetic layer formed of a rare earth-ion amorphous alloy having a higher Curie temperature and a lower coercive force than those of the first magnetic layer. The first and second magnetic layers are exchange-coupled. The second magnetic layer contains Gd and at least one of Tb and Dy. Further, in the relationship between the coercive force (H H ) of the first magnetic layer and the coercive force (H L ) of the second magnetic layer, the following equation is satisfied: where M s is the saturated magnetization of the second magnetic layer, h is the film thickness of the second magnetic layer, and σ w is the magnetic wall energy between the first and second magnetic layers.
Inventors
- 👤 Tadashi Kobayashi
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 13:19
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; G11B11/10589; G11B11/10591
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
132 words
An opto-magnetic recording medium comprising a perpendicularly magnetizable first magnetic layer of a rare earth-iron amorphous alloy, and a perpendicularly magnetizable second magnetic layer of a rare earth-iron amorphous alloy having a higher Curie temperature and a lower coercive force than those of said first magnetic layer, said first and second magnetic layers being exchange-coupled, characterized in that said second magnetic layer contains Gd and at least one of Tb and Dy, and satisfies: where H H is the coercive force of said first magnetic layer, H L is the coercive force of said second magnetic layer, M S is the saturated magnetization of said second layer, h is the film thickness of said second magnetic layer, and σ W is the magnetic wall energy between said first and second magnetic layers.
Claim 2
Dependent Claim
132 words
An opto-magnetic recording medium comprising a perpendicularly magnetizable first magnetic layer of a rare earth-iron amorphous alloy, and a perpendicularly magnetizable second magnetic layer of a rare earth-iron amorphous alloy having a higher Curie temperature and a lower coercive force than those of said first magnetic layer, said first and second magnetic layers being exchange-coupled, characterized in that said second magnetic layer contains Gd and at least one of Tb and Dy, and satisfies: where H H is the coercive force of said first magnetic layer, H L is the coercive force of said second magnetic layer, M S is the saturated magnetization of said second layer, h is the film thickness of said second magnetic layer, and σ W is the magnetic wall energy between said first and second magnetic layers.
Claim 3
Dependent Claim
39 words
A medium according to claim 1, wherein said second magnetic layer has a composition represented by: (Gd - Tb) W M 1-W where M is at least one element of Fe and Co, and 0.15 < W < 0.30.
Claim 4
Dependent Claim
39 words
A medium according to claim 1, wherein said second magnetic layer has a composition represented by: (Gd - Dy) W M 1-W where M is at least one element of Fe and Co, and 0.15 < W < 0.30.
Claim 5
Dependent Claim
33 words
A medium according to claim 1, wherein at least one element selected from the group consisting of Ni, Cr, Ti, Al, Si, Pt, In, and Cu is doped in said second magnetic layer.
Claim 6
Dependent Claim
18 words
A medium according to claim 1, wherein said first magnetic layer consists of one of TbFeCo and DyFeCo.
Claim 7
Dependent Claim
24 words
A medium according to claim 1, wherein said first magnetic layer has a compensation temperature between a room temperature and a Curie temperature thereof.
Claim 8
Dependent Claim
29 words
A medium according to claim 1, wherein said first magnetic layer has rare earth group sublattice magnetization superiority, and said second magnetic layer has iron group sublattice magnetization superiority.
Claim 9
Dependent Claim
23 words
A medium according to claim 1, wherein a thickness of said second magnetic layer falls in a range of 100 to 1,000 Å.
Claim 10
Dependent Claim
23 words
A medium according to claim 1, wherein a thickness of said first magnetic layer falls in a range of 100 to 2,000 Å.
Claim 11
Dependent Claim
26 words
A medium according to claim 1, wherein a total thickness of said first and second magnetic layers falls in a range of 500 to 2,000 Å.
Claim 12
Dependent Claim
24 words
A medium according to claim 1, wherein a thickness of said first magnetic layer is larger than a thickness of said second magnetic layer.
Claim 13
Dependent Claim
60 words
An opto-magnetic recording medium comprising a first magnetic layer of a rare earth-iron amorphous alloy and a second magnetic layer of a rare earth-iron amorphous alloy having a higher Curie temperature and a lower coercive force than those of the first magnetic layer, characterised in that the second magnetic layer contains Gd and at least one of Tb and Dy.
Claim 14
Dependent Claim
60 words
An opto-magnetic recording medium comprising a first magnetic layer of a rare earth-iron amorphous alloy and a second magnetic layer of a rare earth-iron amorphous alloy having a higher Curie temperature and a lower coercive force than those of the first magnetic layer, characterised in that the second magnetic layer contains Gd and at least one of Tb and Dy.
Claim 15
Dependent Claim
16 words
An opto-magnetic disk carrying a recording medium as claimed in any of claims 1 to 12.
References Cited (Backward Citations)
No citation records indexed.
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