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US6017620A
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Magneto-optical recording medium
Assignee: TDK Corp
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Filing: 1998-04-07
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Granted: 2000-01-25
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Expires: 2018-04-07
Abstract
Abstract The invention is directed at a magneto-optical recording medium which is directly overwritable by light intensity modulation, does not require an initializing magnet, and has on the surface side of a substrate four magnetic layers, a memory layer M 1 , a writing layer W 2 , a switching layer S 3 , and an initializing layer I 4 . The magnetic layers each contain a rare earth element and a transition element, have perpendicular magnetic anisotropy at room temperature, and satisfy the relationships: Tc.sub.I4 >Tc.sub.W2 >Tc.sub.M1 and Tc.sub.I4 >Tc.sub.W2 >Tc.sub.S3 wherein Tc M1 , Tc W2 , Tc S3 and Tc I4 are the Curie temperatures of M 1 , W 2 , S 3 and I 4 , respectively. Writing layer W 2 is composed mainly of dysprosium, iron and cobalt, contains from 29-35 atomic percent of rare earth elements, and has an atomic ratio Fe/(Fe+Co) of from 0.40 to 0.58. This medium has an improved CNR, minimizes deterioration in the CNR with repeated overwriting, enhances storage reliability, and has an increased output.
Inventors
- 👤 Jiro Yoshinari
- 👤 Shinji Miyazaki
- 👤 Hiroyasu Inoue
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 18:20
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; G11B11/10502; G11B11/10517; G11B11/10519; G11B11/10521; G11B11/10584; Y; Y10; Y10S; Y10S428/00; Y10S428/90
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
200 words
A light intensity-modulation direct overwrite magneto-optical recording medium comprising a magnetic multilayer stack on a surface side of a substrate, which magnetic multilayer stack includes four magnetic layers, these being, in order from the substrate side, a memory layer M 1 , a writing layer W 2 , a switching layer S 3 , and an initializing layer I 4 , each of said magnetic layers containing a rare earth element and a transition element and having perpendicular magnetic anisotropy at room temperature, with neighboring magnetic layers being coupled to each other by exchange coupling, wherein said magnetic layers satisfy: Tc.sub.I4 >Tc.sub.W2 >Tc.sub.M1 and Tc.sub.I4 >Tc.sub.W2 >Tc.sub.S3 ; and wherein Tc M1 is the Curie temperature of the memory layer M 1 , Tc W2 is the Curie temperature of the writing layer W 2 , Tc S3 is the Curie temperature of the switching layer S 3 , and Tc I4 is the Curie temperature of the initializing layer I 4 , and the writing layer W 2 is composed mainly of dysprosium, iron, and cobalt, has a rare earth element content of 29 to 35 atomic percent, and has an atomic ratio Fe/(Fe+Co) of from 0.40 to 0.58.
Claim 2
Dependent Claim
200 words
A light intensity-modulation direct overwrite magneto-optical recording medium comprising a magnetic multilayer stack on a surface side of a substrate, which magnetic multilayer stack includes four magnetic layers, these being, in order from the substrate side, a memory layer M 1 , a writing layer W 2 , a switching layer S 3 , and an initializing layer I 4 , each of said magnetic layers containing a rare earth element and a transition element and having perpendicular magnetic anisotropy at room temperature, with neighboring magnetic layers being coupled to each other by exchange coupling, wherein said magnetic layers satisfy: Tc.sub.I4 >Tc.sub.W2 >Tc.sub.M1 and Tc.sub.I4 >Tc.sub.W2 >Tc.sub.S3 ; and wherein Tc M1 is the Curie temperature of the memory layer M 1 , Tc W2 is the Curie temperature of the writing layer W 2 , Tc S3 is the Curie temperature of the switching layer S 3 , and Tc I4 is the Curie temperature of the initializing layer I 4 , and the writing layer W 2 is composed mainly of dysprosium, iron, and cobalt, has a rare earth element content of 29 to 35 atomic percent, and has an atomic ratio Fe/(Fe+Co) of from 0.40 to 0.58.
Claim 3
Dependent Claim
86 words
The magneto-optical recording medium of claim 1, wherein the memory layer M 1 is composed mainly of terbium, iron and cobalt, contains from 21 to 25 atomic percent of terbium, and has an atomic ratio Fe/(Fe+Co) of from 0.85 to 0.95; the switching layer S 3 is composed mainly of terbium and iron, and contains from 23 to 29 atomic percent of terbium; and the initializing layer I 4 is composed mainly of terbium and cobalt, and contains from 21 to 28 atomic percent of terbium.
Claim 4
Dependent Claim
61 words
The magneto-optical recording medium of claim 1, herein the memory layer M 1 has a thickness of 10 to 40 nm, the writing layer W 2 has a thickness of 15 to 40 nm, the switching layer S 3 has a thickness of 5 to 15 nm, and the initializing layer I 4 has a thickness of 15 to 50 nm.
Claim 5
Dependent Claim
28 words
The magneto-optical recording medium of claim 1 comprising an exchange coupling control layer C 12 between the memory layer M 1 and the writing layer W 2 .
Claim 6
Dependent Claim
33 words
The magneto-optical recording medium of claim 4, wherein the exchange coupling control layer C 12 is a magnetic layer comprised of an amorphous alloy containing a rare earth element and a transition element.
Claim 7
Dependent Claim
69 words
The magneto-optical recording medium of claim 5, wherein the axis of easy magnetization in the exchange coupling control layer C 12 is oriented in-plane at room temperature, and a temperature at which the axis of easy magnetization in the exchange coupling control layer C 12 becomes perpendicularly oriented exists within the range of from 100° C. to the Curie temperature of the exchange coupling control layer C 12 .
Claim 8
Dependent Claim
43 words
The magneto-optical recording medium of claim 5, wherein the exchange coupling control layer C 12 includes as primary components gadolinium, iron and cobalt, contains from 23 to 32 atomic percent of gadolinium, and has an atomic ratio Fe/(Fe+Co) of from 0.40 to 0.80.
Claim 9
Dependent Claim
24 words
The magneto-optical recording medium of claim 4, wherein the thickness of the exchange coupling control layer C 12 is from 5 to 30 nm.
Claim 10
Dependent Claim
58 words
The magneto-optical recording medium of claim 1 comprising a readout layer R 01 that is a magnetic layer between the substrate and the memory layer M 1 , said readout layer R 01 being comprised of an amorphous alloy containing as primary components gadolinium, iron and cobalt, and coupled with the memory layer M 1 by exchange coupling.
Claim 11
Dependent Claim
33 words
The magneto-optical recording medium of claim 9, wherein the readout layer R 01 contains from 23 to 27 atomic percent of gadolinium and has an atomic ratio Fe/(Fe+Co) of from 0.65 to 0.75.
Claim 12
Dependent Claim
21 words
The magneto-optical recording medium of claim 9, wherein the readout layer R 01 has a thickness of 5 to 20 nm.
Claim 13
Dependent Claim
17 words
The magneto-optical recording medium of claim 1, wherein the memory layer M 1 contains a nonmagnetic element.
Claim 14
Dependent Claim
34 words
The magneto-optical recording medium of claim 12, wherein the nonmagnetic element contained in the memory layer M 1 is at least one from among chromium, titanium, tantalum, molybdenum, tungsten, vanadium, zirconium, niobium, and aluminum.
Claim 15
Dependent Claim
78 words
The magneto-optical recording medium of claim 1 comprising a first dielectric layer on the back side of said magnetic multilayer stack and comprising a second dielectric layer and a heat dissipating layer, in this order, on the surface side of the magnetic multilayer stack, wherein the heat sink layer is comprised of metal, the second dielectric layer has a thickness of 13 to 30 nm, and the heat dissipating layer has a thickness of 30 to 60 nm.
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) | 2003-01-24 | 2003-07-26 | 2004-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2007-01-24 | 2007-07-26 | 2008-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2011-01-24 | 2011-07-26 | 2012-01-25 | $7700.00 | Window Closed / Lapsed |