EP0509836A2
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EP
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Magneto-optical recording medium
Assignee: Sharp Corp
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Filing: 1992-04-16
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Granted: —
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Expires: 2012-04-16
Abstract
Abstract A magneto-optical recording medium has a recording layer whereon information is magneto-optically recorded. A readout layer is provided on the recording layer. The readout layer has a compensating temperature that is located between room temperature and the Curie temperature. In the readout layer, upon an application of a light beam, the in-plane magnetization occurs at room temperature and a transition from the in-plane magnetization to vertical magnetization occurs as the temperature of the irradiated area of the readout layer rises above a predetermined temperature. By employing this magneto-optical recording medium, with an application of a light beam that is intensity modulated into two levels, only a spot having a temperature not less than a predetermined temperature is involved in the reproduction; therefore, a recorded bit with a size smaller than the diameter of the light beam can be reproduced, thereby greatly increasing the recording density. Further, the level of the reproduced signals is increased, and crosstalk from the adjoining tracks is reduced; thus, information recording and overwriting can be conducted more easily.
Inventors
- 👤 Akira Takahashi
- 👤 Yoshiteru Murakami
- 👤 Junsaku Nakajima
- 👤 Kenji Ohta
- 👤 Junichiro Nakayama
- 👤 Hiroyuki Katayama
- 👤 Michinobu Mieda
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-10 01:12
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10582; G11B11/10586; G11B11/10589; G11B11/10593; G11B11/10502; G11B11/10504; G11B11/10506; G11B11/10515; G11B11/10517; Y; Y10; Y10S; Y10S428/00; Y10S428/90; Y10T; Y10T428/00; Y10T428/26; Y10T428/263; Y10T428/264; Y10T428/265
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
69 words
A magneto-optical recording medium comprising: a recording layer whereon information is magneto-optically recorded; and a readout layer having a compensation temperature between room temperature and the Curie temperature, wherein in-plane magnetization occurs at room temperature and upon an application of a light beam, a transition from the in-plane magnetization to vertical magnetization occurs as the temperature of the irradiated area of the readout layer rises above a predetermined temperature.
Claim 2
Dependent Claim
96 words
The magneto-optical recording medium as set forth in claim 1, wherein the readout layer is constituted of a thin film of rare-earth-transition-metal alloy, a content of the rare-earth metal being greater in comparison with a compensating composition at room temperature whereat magnetic moments of the rare-earth metal and the transition-metal balance each other, the readout layer exhibiting in-plane magnetization at room temperature without showing vertical magnetization and, as temperature rises, the magnetic moment of the transition metal becoming,relatively greater until it balances the magnetic moment of the rare-earth metal, thereby providing vertical magnetization as a whole.
Claim 3
Dependent Claim
25 words
The magneto-optical recording medium as set forth in claim 2, wherein the transition from the in-plane magnetization to the vertical magnetization occurs at substantially 100°C.
Claim 4
Dependent Claim
25 words
The magneto-optical recording medium as set forth in claim 2, wherein the transition from the in-plane magnetization to the vertical magnetization occurs at substantially 70°C.
Claim 5
Dependent Claim
33 words
The magneto-optical recording medium as set forth in claim 1, wherein the readout layer is constituted of Gd 0.28 (Fe 0.8 Co 0.2 ) 0.72 whose Curie temperature positions between 300°C and 400°C.
Claim 6
Dependent Claim
33 words
The magneto-optical recording medium as set forth in claim 5, wherein the recording layer is constituted of Dy 0.23 (Fe 0.82 Co 0.18 ) 0.77 whose Curie temperature positions between 150°C and 250°C.
Claim 7
Dependent Claim
30 words
The magneto-optical recording medium as set forth in claim 6, wherein the readout layer has a thickness of 50 nm while the recording layer has a thickness of 20 nm.
Claim 8
Dependent Claim
31 words
The magneto-optical recording medium as set forth in claim 1, wherein the readout layer is a thin film of a rare-earth-transition-metal alloy whose magnetization directions substantially lie in-plane at room temperature.
Claim 9
Dependent Claim
26 words
The magneto-optical recording medium as set forth in claim 8, wherein the readout layer is constituted of Dy 0.3 (Fe 0.7 Co 0.3 ) 0.7 .
Claim 10
Dependent Claim
20 words
The magneto-optical recording medium as set forth in claim 1, further comprising a reflective film for enhancing the magneto-optical effect.
Claim 11
Dependent Claim
97 words
The magneto-optical recording medium as set forth in claim 10, wherein the readout layer is constituted of a thin film of rare-earth-transition-metal alloy, a content of the rare-earth metal being greater in comparison with a compensating composition at room temperature whereat magnetic moments of the rare-earth metal and the transition-metal balance each other, the readout layer exhibiting in-plane magnetization at room temperature without showing vertical magnetization and, as temperature rises, the- magnetic moment of the transition metal becoming relatively greater until it balances the magnetic moment of the rare-earth metal, thereby providing vertical magnetization as a whole.
Claim 12
Dependent Claim
25 words
The magneto-optical recording medium as set forth in claim 11, wherein the transition from the in-plane magnetization to the vertical magnetization occurs at substantially 70°C.
Claim 13
Dependent Claim
33 words
The magneto-optical recording medium as set forth in claim 10, wherein the readout layer is constituted of Gd 0.28 (Fe 0.8 Co 0.2 ) 0.72 whose Curie temperature positions between 300°C and 400°C.
Claim 14
Dependent Claim
33 words
The magneto-optical recording medium as set forth in claim 10, wherein the recording layer is constituted of Dy 0.23 (Fe 0.82 Co 0.18 ) 0.77 whose Curie temperature positions between 150°C and 250°C.
Claim 15
Dependent Claim
23 words
The magneto-optical recording medium as set forth in claim 14, wherein the readout layer and the recording layer are respectively 15 nm thick.
Claim 16
Dependent Claim
31 words
The magneto-optical recording medium as set forth in claim 10, wherein the readout layer is a thin film of a rare-earth-transition-metal alloy whose magnetization directions substantially lie in-plane at room temperature.
Claim 17
Dependent Claim
26 words
The magneto-optical recording medium as set forth in claim 10, wherein the readout layer is constituted of Dy 0.3 (Fe 0.7 Co 0.3 ) 0.7 .
Claim 18
Dependent Claim
22 words
The magneto-optical recording medium as set forth in claim 1, wherein the readout layer is constituted of Gd 0.25 Co 0.75 .
Claim 19
Dependent Claim
22 words
The magneto-optical recording medium as set forth in claim 10, wherein the readout layer is constituted of Gd 0.25 Co 0.75 .
Claim 20
Dependent Claim
120 words
A magneto-optical recording medium comprising: a transparent substrate; a first transparent dielectric member, between 10 nm and 80 nm thick, made of one of the group of AIN, SiN and AlSiN, which is formed on the transparent substrate; a readout layer, 50 nm thick, made of Gd 0.28 (Fe 0.8 Co 0.2 ) 0.72 or Gd 0.25 Co 0.75 , which is formed on the first transparent dielectric member; a recording layer, 20 nm thick, made of Dy 0.23 (Fe 0.82 Co 0.18 ) 0.77 , which is formed on the readout layer; and a second transparent dielectric member, 50 nm thick, made of a nitride, which is provided on the recording layer so as to protect the recording layer.
Claim 21
Dependent Claim
150 words
A magneto-optical recording medium comprising: a transparent substrate; a first transparent dielectric member, 80 nm thick, made of one of the group of AIN, SiN and AlSiN, which is formed on the transparent substrate; a readout layer, 15 nm thick, made of one of the group of Gd 0.28 (Fe 0.8 Co 0.2 ) 0.72 , Gd 0.25 Co 0.75 and Dy 0.3 (Fe 0.7 Co 0.3 ) 0.7 , which is formed on the first transparent dielectric member; a recording layer, 15 nm thick, made of Dy 0.23 (Fe 0.82 Co 0.18 ) 0.77 , which is formed on the readout layer; a second transparent dielectric member, 30 nm thick, made of a nitride, which is provided on the recording layer so as to protect the recording layer; and a reflective film, 50 nm thick, provided on the second transparent dielectric member so as to enhance the magneto-optical effect.
Claim 22
Dependent Claim
41 words
The magneto-optical recording medium as set forth in claim 1, wherein the readout layer is made of Gd x (Fe y Co 1-y ) 1-x , where a composition rate x is set to be within 0.20 < x < 0.35.
Claim 23
Dependent Claim
29 words
The magneto-optical recording medium as set forth in claim 1, wherein the compensating temperature of the readout layer is not lower than the Curie temperature of the recording layer.
Claim 24
Dependent Claim
20 words
The magneto-optical recording medium as set forth in claim 1, further comprising a cooling member provided on the recording layer.
Claim 25
Dependent Claim
20 words
The magneto-optical recording medium as set forth in claim 23, further comprising a cooling member provided on the recording layer.
Claim 26
Dependent Claim
20 words
The magneto-optical recording medium as set forth in claim 23, further comprising a reflective member provided on the recording layer.
Claim 27
Dependent Claim
189 words
A recording method for recording on a magneto-optical recording medium while applying a recording magnetic field, the magneto-optical recording medium including a recording layer, whereon information is magneto-optically recorded, and a readout layer having a compensating temperature between room temperature and the Curie temperature, wherein in-plane magnetization occurs at room temperature and upon an application of a light beam, a transition from the in-plane magnetization to vertical magnetization occurs as the temperature of the irradiated area of the readout layer rises above a predetermined temperature, the recording method comprising the steps of: applying onto the magneto-optical recording medium a first light beam so that a temperature thereof rises up to a point in the vicinity of the Curie temperature of the readout layer, whereat the coercive force of the readout layer is greater than that of the recording layer; and applying thereonto a second light beam so that the temperature of the readout layer is raised to a point within a range neither less than the temperature whereat a transition from the in-plane magnetization to the vertical magnetization occurs, nor more than the compensation temperature of the readout layer.
Claim 28
Dependent Claim
65 words
The recording method as set forth in claim 27, wherein the first light beam has a first-pulse section and a second-pulse section, and in projecting the first light beam onto the magneto-optical recording medium, the second-pulse section having a light intensity not more than that of the first-pulse section being applied thereonto after a predetermined time has elapsed since the application of the first-pulse section.
Claim 29
Dependent Claim
60 words
The recording method as set forth in claim 27, wherein the first light beam has a first-pulse section and a second-pulse section, and in projecting the first light beam onto the magneto-optical recording medium, the second-pulse section having a light intensity not more than that of the first-pulse section being successively applied thereonto after the application of the first-pulse section.
Claim 30
Dependent Claim
71 words
A magneto-optical recording medium comprising a recording layer in which information can be recorded by locally reversing the direction of a vertical magnetization of the recording layer, and a readout layer disposed adjacent the recording layer, said readout layer having a substantially in-plane magnetization at room temperature and being capable of reversibly undergoing a transition to vertical magnetization on the temperature of the readout layer being raised above a predetermined temperature.
References Cited (Backward Citations)
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