JPH05342677A - Magneto-optical recording / reproducing method - Google Patents

Abstract

(57) [Summary] [Object] To provide a magneto-optical recording / reproducing method capable of simultaneously improving the recording density and the transfer rate. A magneto-optical recording medium having a recording layer formed by sequentially laminating an exchange-coupled reproducing layer, a memory layer, and a memory auxiliary layer, and having magnetic characteristics satisfying a predetermined relationship is used. Recording is performed by applying a first initializing magnetic field in advance to align the magnetic field of the memory auxiliary layer in one direction, and irradiating a recording laser beam having a binary power with a bias magnetic field applied. By For reproduction, the magnetization of the reproducing layer is aligned in one direction by applying a second initializing magnetic field in advance, and the recorded information is magnetically transferred from the memory layer to the reproducing layer under the heating condition by irradiation of the reproducing laser beam. After that, a super-resolution reproducing method is used in which recorded information is read by the magneto-optical effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing method for simultaneously improving recording density and transfer rate.

[0002]

2. Description of the Related Art In a magneto-optical recording / reproducing method in which an information bit, that is, a magnetic domain is formed by irradiating a laser beam and is read out by utilizing a magneto-optical effect, an ultra high density recording is achieved. In order to achieve this, a super-resolution reproduction system is proposed in Japanese Patent Laid-Open No. 3-88156. In this method, a magneto-optical recording medium having a memory layer and a reproducing layer is used, an initializing magnetic field is applied to the reproducing layer prior to reproducing to align its magnetization in one direction, and the reproducing layer is heated in a memory state in the memory. This is a system in which recorded information on a layer is transferred by a magnetostatic force due to recording magnetization of a memory layer, and the transferred recorded information is read out by a magneto-optical effect. By doing so, it is said that the reproduction S / N can be improved together with the super high density recording.

However, according to the above conventional method, although the recording density can be improved, the transfer rate cannot be increased. Improving the transfer rate is a very important issue for speeding up information processing.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a magneto-optical recording / reproducing method capable of simultaneously improving the recording density and the transfer rate.

[0005]

To achieve the above object, according to the present invention, there is provided a recording layer formed by sequentially laminating a reproducing layer exchange-coupled from a laser light irradiation side, a memory layer and a memory auxiliary layer. , And the Curie temperatures of these are Tc ₁ , T
When c ₂ , Tc ₃ and coercive forces are Hc ₁ , Hc ₂ and Hc ₃ , T
c ₁ > Tc ₃ > Tc ₂ , Tc ₁ −Tc ₂ ≧ 100 ° C. and Hc ₂ > Hc ₃
Using a magneto-optical recording medium satisfying the relationship of> Hc ₁ , recording is performed by applying a first initializing magnetic field in advance to align the magnetic field of the memory auxiliary layer in one direction and applying a bias magnetic field. Is performed by a direct overwrite method in which a binary recording laser beam is irradiated, and reproduction is performed by applying a second initialization magnetic field in advance to align the magnetization of the reproducing layer in one direction and irradiating the reproducing laser beam. A magneto-optical recording / reproducing method is provided, which comprises magnetically transferring recorded information from a memory layer to a reproducing layer under heating and then performing the super-resolution reproducing method of reading the recorded information by a magneto-optical effect. It

[0006]

EXAMPLES The present invention will be described in detail below based on examples. FIG. 1 shows the structure of a recording layer of a magneto-optical recording medium used in the method of the present invention.
The reproduction layer 1, the memory layer 2, and the memory auxiliary layer 3 are sequentially laminated. The reproducing layer 1 and the memory layer 2, and the memory layer 2 and the memory auxiliary layer 3 are exchange-coupled to each other. The reproducing layer 1, the memory layer 2 and the memory auxiliary layer 3 have at least the relationship shown in FIG.
That is, when these Curie temperatures are Tc ₁ , Tc ₂ , Tc ₃ and coercive forces are Hc ₁ , Hc ₂ , Hc ₃ , Tc ₁ > Tc ₃ > Tc ₂ , Tc
It is necessary to satisfy the relations of c ₁ -Tc ₂ ≧ 100 ° C. and Hc ₂ > Hc ₃ > Hc ₁ .

The reproducing layer 1 has the highest Curie temperature (> 300 ° C.) and the lowest coercive force (10) among these three layers.
A magnetic material having a large Kerr rotation angle is used. GdFe is a magnetic material that satisfies these conditions.
Co, GdTbFeCo, or the like is used. Memory layer 2
Is a magnetic material having the highest coercive force (> 5 KOe) and the lowest Curie temperature (100 to 200 ° C.). Also, in order to obtain a sufficient high-level and low-level laser power margin at the time of overwriting, the memory layer 2 and the reproduction layer 1
The difference in the Curie temperature is 100 ° C. or more. Magnetic materials that satisfy such conditions include TbFe and Tb.
FeCo, TbDyFeCo, DyFeCo, etc. are used. A magnetic material having a Curie temperature in the memory auxiliary layer 3 between the Curie temperatures of the reproducing layer 1 and the memory layer 2 (200 to 250 ° C.) and a coercive force between the memory layer 2 and the reproducing layer 1 (about 1 KOe). , For example, TbFeCo, TbDyF
eCo, DyFeCo, etc. are used. The thickness of the reproducing layer 1 is 200 to 500Å, and the thickness of the memory layer 2 is 100 to 5
00 Å, the film thickness of the memory auxiliary layer 3 is preferably 200 to 700 Å. As a method for forming these films, a sputtering method,
Vacuum deposition or the like can be used.

The above-mentioned recording layer has the most basic structure, and an underlayer, an inorganic protective layer, a reflective layer, a cover layer, a heat insulating layer and the like can be appropriately provided. Further, an intermediate layer may be provided between the magnetic layers in order to adjust the exchange coupling force.

Next, the recording method according to the present invention will be described. During recording, the first initialization magnetic field Hini ₁ (Hc ₂ >
(Hini ₁ > Hc ₃ : 2 to 5 KOeOe) is applied to align the magnetizations of the reproducing layer 1 and the memory auxiliary layer 3 in one direction ((a)-(b) in FIG. 3), which is the opposite of Hini _1. A biasing magnetic field Hex: about 100 to 500) is applied in the direction to irradiate a recording laser beam having a binary power (low level Pl, high level Ph). More specifically, when the temperature of the memory layer 2 is raised to the Curie temperature Tc ₂ or higher or near the Curie temperature Tc ₂ by irradiating the laser beam of the low level Pl, the magnetization direction of the memory layer 2 becomes the memory auxiliary layer. 3, aligned in the magnetization direction of the reproducing layer 1 ((c)-
(D)). Therefore, the data can be erased by irradiating the laser beam of low level Pl. Further, by irradiating a laser beam of high level Ph under the same bias magnetic field Hex as described above, the magnetization of the memory auxiliary layer 3 is reversed, and then the memory layer 2 has the same magnetization as the memory auxiliary layer 3 in the process of cooling to room temperature. Direction ((e)-(f) in FIG. 3). Therefore, it becomes possible to record data by irradiating the laser beam of high level Ph. Data recording in this way (formation of recording marks)
The state (f) can be brought by irradiating the laser beam of the high level Ph for the purpose of carrying out, and the state (d) can be brought by the irradiation of the laser beam of the low level Pl for erasing the data. Yes, direct overwriting is possible. Even if the initial state is the state (a) ′, the state (c) is obtained by the initialization with the _first initializing magnetic field Hini ₁ .

Next, the reproducing method according to the present invention will be described. During reproduction, a second initialization magnetic field Hini ₂ is applied in advance by an initialization magnet to align the magnetization of the reproduction layer 1 in one direction ((a)-(b) in FIG. 4), which is lower than during recording. A reproducing laser beam of level Pr is irradiated. As a result, the recorded information in the memory layer 2 is magnetically transferred to the reproducing layer 1, and the information can be read out by utilizing the magneto-optical effect. The value of the second initialization magnetic field Hini ₂ is smaller than that of the first initialization magnetic field Hini ₁ at the time of recording, and Hc ₁ <Hini ₂ <H
The value that satisfies c ₃ is set. By doing so, since the state other than the reproduction area is in the state of FIG. 4B, crosstalk, intersymbol interference and the like can be eliminated, and the reproduction S / N is improved.

[0011]

As described above in detail, according to the present invention, since the magneto-optical recording medium having the recording layer having the three-layer structure as described above is used, the recording is performed by the direct overwrite method and the reproduction is performed. Since the super resolution reproduction method can be used, it is possible to improve the recording density and the transfer rate at the same time.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing the structure of a recording layer of a magneto-optical recording medium used in the present invention.

FIG. 2 is a diagram showing a relationship of magnetic characteristics of a reproducing layer, a memory layer, and a memory auxiliary layer.

FIG. 3 is an explanatory diagram of a recording method according to the present invention.

FIG. 4 is an explanatory diagram of a reproducing method according to the present invention.

[Explanation of symbols]

 1 reproduction layer 2 memory layer 3 memory auxiliary layer

Claims (1)

[Claims] 1. A recording layer having a reproducing layer, a memory layer, and a memory auxiliary layer, which are exchange-coupled from the laser beam irradiation side, are sequentially laminated, and the Curie temperatures of these layers are Tc ₁ , Tc ₂ , and Tc.
c ₃ and coercive forces Hc ₁ , Hc ₂ and Hc ₃ , Tc ₁ > T
c ₃ > Tc ₂ , Tc ₁ −Tc ₂ ≧ 100 ° C. and Hc ₂ > Hc ₃ > Hc ₁
Using a magneto-optical recording medium satisfying the following relationship, recording is performed by applying a first initializing magnetic field in advance to align the magnetic field of the memory auxiliary layer in one direction, and applying a bias magnetic field to a binary power. Is performed by the direct overwrite method of irradiating the recording laser beam, and the reproduction is preliminarily applied with the second initializing magnetic field so that the magnetization of the reproducing layer is aligned in one direction. A magneto-optical recording / reproducing method characterized in that the recorded information is magnetically transferred from a memory layer to a reproducing layer, and then the recorded information is read by a magneto-optical effect by a super-resolution reproducing method.