JP2570777B2 - Recording method of magneto-optical recording - Google Patents

Description

The present invention relates to a recording system for a magneto-optical recording medium.

(Prior art) In recent years, as a high-density recording method using a laser, magneto-optical recording in which bits are written by irradiating a laser beam to locally heat a recording medium and read out by using a magneto-optical effect has been studied. Is being developed. As a recording medium, an amorphous magnetic thin film made of a rare earth-transition metal alloy has attracted attention. In the magneto-optical recording method, conventionally, a single recording layer,
Overwriting was not possible due to the light modulation method using a single beam. Therefore, as a method of enabling overwrite recording, a magnetic field modulation method, a pseudo-overwrite recording method using a multi-beam, a method using a two-layer film, and the like have been considered.

(Problems to be solved by the invention) In the magnetic field modulation method, it is necessary to generate a strong magnetic field at a high frequency, but this is difficult with a normal electromagnet.
This is made possible by bringing the medium and the electromagnet close together using a slider used for a hard disk or the like. However, this method has disadvantages such as sacrificing the non-contact property which is a characteristic of magneto-optical recording. In addition, the pseudo overwrite method using multiple beams has a disadvantage that the device becomes complicated. Overwrite method using a conventional two-layer film (Proceedings of the 34th JSAP Lecture Meeting, 28p-Z
L-3, in P721,1987), aligning the magnetization of the auxiliary layer in one direction in advance by the external magnetic field prior to recording, Kiyuri temperature T _CR memory layer, is applied in a direction opposite to the direction of the prior external magnetic field during recording When the temperature at which the magnitude of the external magnetic field is equal to the coercive force of the auxiliary layer is T _B , the medium temperature T is T _CR <T
When cooling after raising the temperature to the temperature of T _B, the magnetization direction of the auxiliary layer previously aligned in one direction is transferred to the recording layer, and when cooling the medium after raising the temperature to T _B or more, A method has been adopted in which the magnetization of the recording layer is oriented in the direction of the magnetic field applied during recording. For this reason, a prior external magnetic field for erasing the auxiliary layer before recording and two external magnetic fields to be applied at the time of recording are required, which has a drawback that the apparatus becomes complicated.

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording method of magneto-optical recording which enables overwriting with a single beam and a single magnetic field.

(Means to be Solved by the Invention) In order to achieve the above object, the present invention relates to a readout layer made of a perpendicular magnetic film and a write layer made of a ferrimagnetic material which is a perpendicular magnetic film as a recording layer of a magneto-optical recording medium. , The room temperature is T _r , the coercive force of the readout layer and the write layer at room temperature is H _CR and H _Cw , the Curie temperature of the read layer is T _CR , and the Curie temperature of the write layer is T _CW ,
When the compensation temperature of the write layer is T _{comp · w} , H _CW
<A H _CR, and satisfies _{T r <T comp · w <} T CR <T CW the relationship, after raising the medium temperature T up to T _CR <T, T _CR
In the magneto-optical recording medium in which the magnetization of the write layer is transferred to the read layer when cooled to just below, in the magneto-optical recording medium, H _CW <H _ext. <H
_When a temperature at which _CR and H _{ext. Are} equal to the coercive force of the readout layer is T _A , an external magnetic field is applied to the recording medium in a perpendicular direction so that T _{comp · w} <T _A , a compensation temperature T _{comp · w} temperature the magnitude of the external magnetic field and the coercive force of the writing layer is equal at the high temperature side of the writing layer is taken as T _B, heated recording medium by laser irradiation, the medium temperature T And cooling after raising the temperature to satisfy the relationship of T _A <T <T _CR and cooling after raising the temperature to a temperature of T _CR <T <T _B. It is.

(Function) In the present invention, a writing layer made of a ferrimagnetic material, which is a perpendicular magnetization film, whose compensation temperature exists between room temperature and the Curie temperature of the reading layer as a recording layer of a magneto-optical recording medium, and a magnetization of the writing layer. And a readout layer provided with a readout layer for transferring in the same direction. FIGS. 1A and 1B show the temperature characteristics of the coercive force of the writing layer and the reading layer required for this recording medium. In FIG. 1, 1,1 'are the temperature characteristics of the coercive force of the readout layer, and 2 is the temperature characteristic of the coercive force of the write layer. FIG. 1A shows the case where the compensation temperature of the readout layer does not exist at room temperature or higher, and FIG. 1B shows the case where the compensation temperature of the write layer exists at room temperature or higher. Need not be present to the temperature compensation temperature above room temperature of the readout layer in the present invention, exists between the compensation temperature of the writing layer is Kiyuri temperature of the readout layer, the layer reads the magneto-optical recording medium Kiyuri temperature T _CR upon cooling to T _CR just below the temperature was increased to above, it is important that the magnetization direction is copied to the readout layer becomes magnetized in the same direction as the direction of the writing layer.

Next, the recording method of magneto-optical recording according to the present invention will be described. During recording, FIG. 1 (a), applies a (b), the external magnetic field 3 greater than the coercive force H _CW of but less than the coercive force H _CR of the readout layer at room temperature write layer. In FIGS. 1 (a) and 1 (b), the temperature at which the coercive force of the readout layer becomes equal to the external magnetic field is T _A , the temperature higher than the compensation temperature of the write layer, and the coercive force of the write layer becomes equal to the external magnetic field. Temperature to T _B. In a state where the external magnetic field 3 is applied, the medium is irradiated with a laser having a writing level 5 in FIG. 2 so that the medium temperature T in FIG.
When the temperature is raised to the temperature region A 'where T _A <T <T _CR , the coercive force of the readout layer becomes smaller than the external magnetic field, so that in the temperature region A', the magnetization of the readout layer always faces the direction of the external magnetic field. Become. Therefore, the magnetization direction of the readout layer when the medium is cooled to room temperature is directed to the direction of the external magnetic field in FIG. 1 (a), and the compensation temperature of the readout layer becomes higher than room temperature in FIG. 1 (b). Due to its presence, it will face in the opposite direction to the direction of the external magnetic field. Next, the external magnetic field 3 while applying a temperature T a T _CR <T in FIG. 1 <T _B of the magnetic medium by laser irradiation intensity of the write level 6 in FIG. 2
Consider a case where the temperature is increased to a certain temperature range A and cooled. Since the external magnetic field 3 is larger than the coercive force H _CW of the writing layer at room temperature, the magnetization of the writing layer at room temperature always points in the direction of the external magnetic field. However, the compensation temperature of the writing layer
Since T _CW exists between room temperature and the reading layer's Kyrie temperature, the magnetic medium is heated to a temperature range A where T _CR <T <T _B , and the medium temperature is raised to just above the reading layer's Kyuri temperature T _CR. Upon cooling, the magnetization direction of the writing layer is oriented in a direction opposite to the direction of the external magnetic field. Readout layer, a rare earth as a writing layer - When using a perpendicular magnetization film is ferrimagnetic material comprising a transition metal, for compensating the temperature of the writing layer is located below T _CR, the magnetization direction of the writing layer just above T _CR is ,
It is determined by the magnetization direction of the transition metal. In addition, the medium temperature
When than T _CR slightly lowered, but the magnetization of the readout layer is generated, because the compensation temperature of the readout layer is present below T _CR, the magnetization direction generated here is determined by the direction of magnetization of the transition metal. When the magnetization direction of the writing layer is copied to the readout layer, if the layers of the rare earth metals are, and the magnetization of the transition metal with each other to couple the same direction to each other, the magnetization of the readout layer just below T _CR is the writing layer It will be in the opposite direction to the magnetization. Therefore, the magnetization direction of the readout layer when the medium is cooled to room temperature is in the opposite direction to the external magnetic field in the case of FIG. 1A, and in the case of FIG. It will face the direction of the magnetic field. Thus, by changing the laser power applied to the magnetic medium in the external magnetic field in accordance with a desired recording pattern, overwriting of magneto-optical recording with a single beam and a single magnetic field becomes possible.

Reproducing process can be carried out by conventional same manner by laser irradiation of the read level 4 in the second drawing medium temperature T in no magnetic field is T <T _CR. Does not require an external magnetic field during reproduction, can be reproduced while the temperature of the readout layer by laser irradiation at the time of reproduction is increased, the temperature of the readout layer is by applying an external magnetic field to be not more than T _A.

In this method, the conventional single-beam, single-magnetic-field magneto-optical recording apparatus can be used as it is, and the prior external magnetic field required by the conventional overwriting method using the two-layer film is not required. Features.

(Embodiment) FIG. 3 shows a medium configuration diagram for implementing the present invention. In FIG. 3, 7 is a polycarbonate substrate (PC),
8 is a dielectric layer, 9 is a readout layer, 10 is a write layer, and 11 is a protective film layer.

The PC board 7 used as the board has an outer diameter of 130 mmφ and an inner diameter of 15 m
This is a substrate with a group of mφ. On this substrate, a dielectric layer 8, a reading layer 9, a writing layer 10, and a protective film layer 11 were continuously formed in a vacuum by a sputtering method. As the dielectric layer 8 and the protective film layer 11, 800 nm thick Si ₃ N ₄ was used. Each of the readout layer 9 and the write layer 10 has a thickness of 500 D Dy.
_0.21 Fe _0.79 film, (Gd _0.5 Tb _0.5 ) _0.25 (Fe _0.95 Co _0.5 )
_{A 0.75} membrane was used. FIG. 4 shows the temperature characteristic 12 of the coercive force of the readout layer and the temperature characteristic 13 of the coercive force of the write layer. The reading layer 9 and the writing layer 10 have a Curie temperature of 21
0 ° C. and 120 ° C., and the compensation temperature of the writing layer is 180 ° C.

An external magnetic field of 2KOe is applied vertically to this recording medium, and the linear velocity
The overwrite characteristics were measured at 10 m / s. First, a 1 MHz signal was recorded / reproduced under the conditions that the writing power level 5 in FIG. 2 was 4.5 mW, the laser irradiation level 6 during writing was 5.2 mW, and the laser irradiation level 4 during reading was 1 mW. A C / N ratio of 48 dB was obtained. When a 2MHz signal was overwritten under the same conditions, a C / N ratio of 47dB was obtained.

As described above, with the magneto-optical recording method according to the present invention, good overwrite characteristics could be obtained using a conventional magneto-optical recording apparatus having a single beam and a single magnetic field.

(Effects of the Invention) According to the present invention, overwriting can be performed on a magneto-optical recording medium only by modulating the laser irradiation intensity using a conventional single-beam, single-static-field magneto-optical recording apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram showing a temperature characteristic of a coercive force of a medium used for carrying out the present invention, FIG. 2 is an explanatory diagram of a laser power modulation method for carrying out the present invention, and FIG. FIG. 4 shows the temperature characteristics of the coercive force of the readout layer and the write layer used in the example. FIG. 1.1 '... The temperature characteristics of the coercive force required for the readout layer.
2. Temperature characteristics of coercive force required for writing layer, 3.
... External magnetic field level, 4 ... Laser irradiation level for reading, 5 ... Laser irradiation level for writing, 6 ...
Laser irradiation level at writing, 7 ... substrate, 8 ...
Dielectric layer, 9 ... Readout layer, 10 ... Write layer, 11 ...
... Protective film layer, 12 Temperature characteristics of coercive force of readout layer, 13
...... Temperature characteristics of coercive force of writing layer

Claims (1)

(57) [Claims] A recording layer of a magneto-optical recording medium has a two-layer film in which a reading layer made of a perpendicular magnetic film and a writing layer made of a ferrimagnetic material, which is a perpendicular magnetic film, are laminated.
T _r , the holding power at room temperature of the readout layer and the write layer are H _CR and H _Cw , the Curie temperature of the read layer is T _CR , the Curie temperature of the write layer is T _CW , and the compensation temperature of the write layer is T.
_{When comp · w} , H _CW <H _CR and T _r <T
_{comp · w} <T _CR <T _CW
After warming to _CR <T, when cooled to just below T _CR, in the magneto-optical recording medium in which the magnetization of the writing layer is copied to the readout _{layer, H CW <H ext. <} H CR next and,, H _ext. Assuming that T _A equals the coercive force of the read layer, an external magnetic field is applied to the recording medium in a perpendicular direction so that T _{comp · w} <T _A, and the compensation temperature T _{comp · w}
When the temperature at which the magnitude of the external magnetic field is equal to the coercive force of the write layer on the higher temperature side is T _B , the recording medium is heated by laser irradiation, and the medium temperature T is set to T _A <T <T _CR When the temperature is raised to satisfy the relationship before cooling,
A recording method for magneto-optical recording, comprising: cooling to a temperature satisfying _CR <T <T _B and then cooling.