JPH05298768A - Magneto-optical recording and reproducing method - Google Patents

Abstract

PURPOSE:To realize ultra-high resolution and simplified recording without necessity of erasing process by utilizing a magneto-optical recording medium comprising a multilayer magnetic film which can be formed by sequentially stacking a reproducing layer, a memory layer and a recording layer. CONSTITUTION:A magneto-optical recording medium 5 is formed by depositing a multilayer magnetic film 3 and a protection film 4 on a substrate such as light transmissive glass substrate, resin substrate or the like through a dielectric material film 2. For reproduction of recorded information, magnetization of reproducing layer is arranged uniformly in the reproducing magnetic field direction disabling readout operation of recorded information within the high temperature region due to temperature distribution in the reproducing light spot and limitedly recorded information can be read in a low temperature region. Thereby, recording can be simplified because the process which once erases total magnetic layer is no longer necessary.

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.

[0002]

2. Description of the Related Art In the case of a magneto-optical recording / reproducing method in which information recording pits or bubble magnetic domains are formed by light irradiation, for example, a laser beam, and the recorded information is read out by magneto-optical interaction, that is, Kerr effect or Faraday effect. In order to increase the recording density, the recording pits must be miniaturized. In this case, the resolution during reproduction is the wavelength λ of the read light and the numerical aperture N.V. of the objective lens. A. Depends on

In order to improve the resolution beyond such a limitation (hereinafter referred to as super resolution), Japanese Patent Application Laid-Open No. 1-143042 filed by the applicant of the present invention discloses a method of sequentially magnetically coupling each other at room temperature. First, second and third magnetic films,
That is, by using a magnetic recording medium having a multilayer film structure of a reproducing layer, a memory layer, and a recording layer, at the time of reproduction, the magnetic domains are eliminated or reduced at a high temperature portion generated in the laser beam spot of the reproduction light, and only at a low temperature portion. The magnetic domains are generated in a limited manner and read out to improve the resolution at the time of reproduction and thus the recording density.

However, the recording method for the magnetic recording medium to which such a reproducing method is applied is not a special consideration, and once the conventional method, that is, the rewriting of the recording is performed, the all magnetic film is once used. A general method is to erase the previous record over the entire period of time, and then perform the record based on the next new information. In this case, there still remain problems such as the time for erasing and the complexity of the device.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a magnetic recording medium having a multi-layer structure of magnetic films is used to achieve high resolution during reproduction, and at the time of recording, information previously recorded is erased once. It is possible to perform so-called overwriting in which a record based on new information is rewritten on a previous record without adopting the recording mode.

[0006]

In the present invention, as shown in FIG.
As shown in the configuration diagram, a magneto-optical recording medium having a multilayer magnetic film in which at least a reproducing layer 31, a memory layer 32, and a recording layer 33, which are sequentially magnetically coupled at room temperature, are sequentially laminated is used.

Information is recorded on the magneto-optical recording medium by light intensity modulation recording, and the reproducing layer 31 and the memory layer 32 are magnetized to the recording layer 33 by irradiation with low light intensity (low power P _L ). the first recording performed by magnetization by the transfer state, the magnetization of high light intensity (of high power P _H) 3 layers of the reproducing layer 31 and the memory layer 32 and the recording layer 33 by irradiation is performed by an external recording magnetic field 2 And the record of.

Further, the reproduction of the recorded information is performed in the reproduction layer 31 in the high temperature region due to the temperature distribution in the reproduction light spot.
The magnetization is aligned in the direction of the reproducing magnetic field, making it impossible to read the recorded information, and the recorded information is read out only in the low temperature region.

In another embodiment of the present invention, as shown in the configuration diagram of FIG. 11, at least a reproducing layer 31, a cutting layer 34, a memory layer 32, and an intermediate layer 3 which are magnetically coupled sequentially at room temperature.
A magneto-optical recording medium having a multilayer magnetic film formed by sequentially stacking 5 and a recording layer 33 is used.

Information is recorded on the magneto-optical recording medium by light intensity modulation recording, and the reproduction layer 31 and the memory layer 32 are magnetized by transferring the magnetization state of the recording layer with low light intensity irradiation. The first recording and the second recording in which at least the reproducing layer 31 and the recording layer 33 are magnetized by irradiation with high light intensity by an external recording magnetic field are performed.

The reproduction of the recorded information is limited in the low temperature region because the magnetization of the reproducing layer 31 is aligned in the reproduction magnetic field direction in the high temperature region due to the temperature distribution in the reproduction light spot and the recorded information cannot be read. The recorded information is read to.

[0012]

As is apparent from the above description, in the method of the present invention, the reading is performed in an area smaller than the spot of the reproduction light at the time of reproduction, so that the resolution is increased, and at the time of recording, the overwrite can be performed by the light intensity modulation. ..

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a magneto-optical recording medium 5 used in a magneto-optical recording method according to the present invention has, for example, a dielectric film 2 formed on a light-transmissive substrate 1 such as a glass substrate or a resin substrate. A multi-layer magnetic film 3 and a protective film 4 are adhered via the above.

The dielectric film 2 is made of, for example, a SiN film or the like, and is formed for the purpose of protecting the multilayer magnetic film 3 and car enhancement.

The protective film 4 can also be made of SiN or the like.

As shown in FIG. 2, the multilayer magnetic film 4 includes at least a reproducing layer 31, a memory layer 32, and a recording layer 3 each composed of, for example, a rare metal-transition metal from the substrate 1 side.
3 has a structure in which they are sequentially deposited.

FIG. 3 is a schematic view of an apparatus for carrying out magneto-optical recording according to the present invention, in which the disk-shaped magneto-optical recording medium 5 having the configuration described in FIGS. 1 and 2 rotates about its central axis. Irradiation light, for example, laser light L _B is irradiated from the substrate 1 side of the medium (disk) 5 in FIG.

The magneto-optical recording / reproducing head can move the irradiation position of the light L _{B in} the radial direction of the disk-shaped magneto-optical recording medium 5 by an actuator (not shown), that is, the irradiation light L _{B on} the medium 5. The irradiation locus is formed so as to draw a spiral or concentric circle around the rotation center of the medium 5.

Further, the first magnetic field generating means 11 for applying a predetermined recording magnetic field H _rec to the light irradiation portion of the irradiation light L _B with respect to the magneto-optical recording medium 5 and the predetermined initialization magnetic field H at other positions. Second magnetic field generating means 12 for applying _ini is provided. These first and second magnetic field generating means 11 and 12
Can be constituted by a permanent magnet or an electromagnet.

Then, with respect to the magneto-optical recording medium 5,
Binary light intensity modulation recording, that is, binary light intensity (power) P _H
And P _L with high temperature and low temperature binary spot heating T
_{By using H} and _TL , it is possible to newly rewrite the recorded information regardless of the presence or absence of the already recorded information recording pit.

Example 1 In this case, the multilayer magnetic film 3 has a three-layer structure of a reproducing layer 31, a memory layer 32, and a recording layer 33 as shown in FIG. 2, in the following order, in this case: A recording / reproducing method according to the present invention will be described. A ₁ initialization B ₁ playback C ₁ recording

A ₁ Initialization In FIG. 3, the rotation of the magneto-optical recording medium 5 causes the initialization magnetic field H _{ini of} the second magnetic field generating means 12 to magnetize the reproducing layer 31 and the recording layer 32 in this magnetic field direction. Therefore, the following conditions (Equation 1) to (Equation 5) are satisfied.

[0023]

[Equation 1] H _C1 <H _W1

[0024]

[Equation 2] H _C1 + H _W1 > H _ini

[0025]

[ _Equation 3] H _C2 + H _W21 −H _W23 ＞ H _ini

[0026]

[Equation 4] H _C3 + H _W3 <H _ini

[0027]

[Equation 5] H _C3 ＞ H _W3

Here, M _S , H _C , H _W , and h represent the respective saturation magnetization, coercive force, exchange coupling force, and film thickness. The subscripts 1, 2 and 3 represent the reproducing layer, the memory layer and the recording layer, respectively. H _W1 is the exchange coupling force that the reproducing layer 31 receives from the memory layer 32, H _W3 is the exchange coupling force that the recording layer 33 receives from the memory layer 32, and H _W21 and H _w23 are the reproducing layer 31 and the recording layer in the memory layer 32, respectively. The exchange coupling force received from the layer 32.

Each conversion coupling force is given by the following (Equation 6).

[0030]

[Equation 6]

Σ _{w12 and} σ _w23 are interfacial domain wall energies formed between the reproducing layer 31 and the memory layer 32 and between the memory layer 31 and the recording layer 33, respectively.

(Equation 1) is a condition under which the recording pits of the memory layer 32 are constantly transferred to the reproducing layer 31 at room temperature. (Equation 2) and (Equation 3) are conditions under which the recording pits of the reproducing layer 31 and the memory layer 32 are not erased in the initializing magnetic field. (Equation 4) is a condition that the magnetization of the recording layer 33 is aligned in the direction of the initialization magnetic field, that is, a condition for initialization. (Equation 5) is a condition for keeping the recording layer 33 in the initialized state even in the zero magnetic field.

B ₁ reproduction The recording pit (magnetic domain) in the reproduction layer 31 is read. In this case, as shown in FIG. 4, a laser beam L _B of, for example, 3.5 mW having a reproduction power P _R of _{2 to 4} mW which is lower than the low power P _L at the time of recording, that is, has the relationship of
Is used to cause rotation of polarized light due to the Kerr effect or the Faraday effect, and the information is read by detecting the rotation of the polarized light.

[0034]

[Equation 7] P _R <P _L <P _H

In this reproduction, as shown in FIG. 3, the reproduction magnetic field H _R is generated by the first magnetic field generating means 11.
The initialization magnetic field H _ini is applied in the same direction or in the opposite direction.

In this case, the relationship between the laser beam spot SP and the temperature on the magneto-optical recording medium 5 is that the temperature is high in the leading direction and low in the trailing direction with respect to the spot SP of the medium, as shown in FIG. Become. In the figure, the broken line is the spot SP
Shown is an isotherm at a predetermined temperature T _R in the inside, and the temperature T is a low temperature part of T <T _{R in} the region I and a high temperature part of T> T _{R in the} region II.

FIG. 6 is a schematic diagram for explaining the reproducing operation. The magnetization directions of the reproducing layer 31, the memory layer 32 and the recording layer 33 of the multilayer magnetic film 3 are indicated by arrows in the layers 31, 32 and 33. The recording pits BP in the reproducing layer 31 are read out in the initialized state with the downward direction and the recording pits with the recording information of “1” due to the upward magnetization, for example. In FIG. 6, the reproducing magnetic field H _{R is set} to the initialization magnetic field H _R.
This is the case when they are given in the same direction as _ini . A schematic top view at this time is shown in FIG. At this time the light spot SP
The temperature T inside becomes readable in the low temperature region I where T <T _R , and the information pits in the reproducing layer 31 disappear in the spot SP in the high temperature region II where T ≧ T _R shown by hatching in FIG. Then, the area becomes undetectable (reproduction).

That is, in order to be able to detect (reproduce) in the low temperature region I in the spot SP, it is necessary to satisfy the conditions of (Equation 8) and (Equation 10).

[0039]

[Equation 8] H _C1 + H _W1 > H _R

[0040]

[Equation 9] _{H C2 + H W21 -H W23>} H R

That is, (Equation 8) and (Equation 9) are reproduction magnetic fields.
H_RRecording pits BP in playback layer 31 and memory layer 32
Is a condition for being held. This makes the temperature
Is T _RThe low temperature region I below is the detection region.

On the other hand, in the high temperature region where the temperature is T _R or higher, it functions as a so-called optical mask for erasing the recording pits in the reproducing layer 31, but the following conditions (Equation 10) and (Equation 11) must be satisfied. Although the magnitude relation between the coercive force of the reproducing layer 31 and the exchange coupling force is not shown, this relation may be either.

[0043]

[Equation 10] H _C1 + H _W1 <H _R

[Number 11] _{H C2 -H W21 -H W23> H} R

(Equation 10) shows that the magnetization of the reproducing layer 31 is aligned in the direction of the reproducing magnetic field H _R regardless of the direction of magnetization of the memory layer 32. As a result, super-resolution reproduction is performed in which a high temperature area cannot be detected, that is, an optical mask serves as detection (reproduction) in a part of the light spot SP.

Furthermore, (Equation 11) is a condition for keeping the recording pits in the memory layer 32 even at such a temperature. The magnitude relationship between the coercive force of the reproducing layer 31 and the exchange coupling force is not shown here either, but this relationship may be either.

Further, the magnitude relation between the coercive force and exchange coupling force of the recording layer 33 and the reproducing magnetic field (corresponding to (Equation 4) at the time of initialization) is not shown in both the low temperature region and the high temperature region during reproduction, but this is not shown. Either can be adopted in the design of the membrane.

C₁Record This record is a binary value such as "0", "1", low power P
_L, High power P_HWith the laser beam. That
In this recording, the recording magnetic field H_recInitializing magnetic field H _iniWhen
Gives in the opposite direction.

C _1-a , low power recording As shown in FIG. 4, this low power recording is performed by irradiating a laser beam with a power P _L higher than the above-mentioned reproduction power P _R , for example, 6 to 10 mW. In this case,
2), (Equation 13), and (Equation 14) must be satisfied.

[0049]

[ _Equation 12] H _C2 + H _W21 + H _rec <H _W23

[0050]

[Equation 13] H _C3 −H _W3 > H _rec

[0051]

[Equation 14] H _C3 ＞ H _W3

As shown in FIG. 8, the memory layer 32 and the reproducing layer 31 are erased by the laser beam irradiation of the low power P _L.
Since the temperature at this time is sufficiently higher than that at the time of reproduction, the reproduction layer 3
The coercive force of 1 and the exchange coupling force between the reproducing layer 31 and the memory layer 32 are smaller than those at room temperature.

However, the magnitude relationship between these two quantities, or the magnitude relationship between the sum of these two quantities and the applied recording magnetic field H _rec can be selected depending on the selection of the magnetic film. Whether to follow H _rec or the direction of magnetization of the memory layer 32 cannot be specified here (FIG. 8 shows the case of following a recording magnetic field). In either case, if only the erasing operation of the memory layer 32 is taken into consideration, only the exchange coupling force from the recording layer 33 is originally necessary.

However, in the case of the present invention, the exchange coupling force from the reproducing layer 31 for reproducing super resolution and the recording magnetic field H _rec for high power recording function to prevent correct operation in some cases.

(Equation 12) shows that, regardless of which the magnetization of the reproducing layer 31 follows, the memory layer 32 moves in the direction of the magnetization of the recording layer 33 against the extra force (magnetic field) at the recording pit portion. This is the minimum requirement to have all of them. (Equation 13) is a condition for the initialized recording layer 33 not being aligned in the direction of the recording magnetic field, and (Equation 14) is a condition for maintaining the initialized state. When the magnetization state of the reproducing layer 31 follows the recording magnetic field, the magnetization state of the recording layer 33 is transferred to the memory layer 32 and at the same time the reproducing layer 3 is transferred.
It is not transferred to 1. However, even in such a case, since (Equation 1) is satisfied at room temperature,
Transfer to the reproducing layer is performed in the cooling process after laser irradiation.

C _1-b High Power Recording High power P _{H When} irradiated with laser light at, for example, 20 mW, all the magnetic layers 31 to 33 rise above the Curie temperature or above the coercive force sufficiently smaller than the recording magnetic field H _rec. As it is heated, the magnetization of each layer is changed to the recording magnetic field H as shown in FIG.
_{Align in} the direction of _rec .

In order to perform high density recording including low power, it is necessary to form a recording magnetic domain smaller than the spot SP of the laser beam. For this purpose, the recording power may be set so that only the narrow regions of high temperature in the temperature distribution within the spot SP as shown in FIG. 10 satisfy the conditions of low power and high power, respectively. Further, in the case of high power, there are regions around which low power conditions are satisfied. Therefore, even if there is some unerased portion, that portion is erased and sharp recording can be performed.

In the first embodiment described above, the multilayer magnetic film 3 has three layers.
Although it is due to the layer structure, there are actually the following problems.

1) Ideally, it is desirable that the exchange coupling force between the reproducing layer and the memory layer be zero in a step function at the temperature T _R , but it is difficult to realize the three-layer structure.

2) In the temperature range from room temperature to low power, the domain wall must exist stably between the memory layer 32 and the recording layer 33, but in order to satisfy such a condition in the three-layer structure, the film thickness is required. Must be thickened and the initializing magnetic field must be very large.

3) When erasing the memory layer 32 with low power, the three-layer structure is easily affected by the exchange coupling force from the reproducing layer, and the degree of freedom (margin) in designing the film is narrowed.

There is another method of the present invention to deal with this. An embodiment in this case will be described as a second embodiment.

Example 2 In this case, in addition to the reproducing layer 31, the memory layer 32, and the recording layer 33, a cutting layer 34 and an intermediate layer 35 are interposed therebetween to form a five-layer structure.

The magnetic materials of each layer are all amorphous without a crystal structure, and are ferrimagnetic materials in which the magnetic moments of the transition metal and the rare earth metal are antiferromagnetically coupled. Also,
All layers except the recording layer may be transition metal rich or rare earth metal rich over the entire operating temperature range.

Since the reproducing layer 31 plays a role of reproducing, it is made of, for example, a GdFeCo system having a high Curie temperature and a large magneto-optical effect.

The cutting layer 34 is mainly composed of TbFe, for example, and the Curie temperature can be lowered by adding a non-magnetic element or the like, and at room temperature, it is rich in transition metal and is close to the compensation composition. Is good.

Since the memory layer 32 is responsible for recording, it is made of, for example, TbFe (Co) having a large coercive force at room temperature. Also,
It is preferable that the composition ratio of the rare earth transition metal in the memory layer 32 be close to the compensation composition at room temperature. Further, since the memory layer 32 must have a higher Curie temperature than the cutting layer 34, the amount of Co added is increased. The coercive force at room temperature is preferably 1 T or more.

Since the intermediate layer 35 is a layer for stably holding the domain wall, it is made of GdFe having a small perpendicular magnetic anisotropy.

The coercive force of the recording layer 36 must be smaller than the initializing magnetic field at room temperature and larger than that of the memory layer 32 at low power. For this reason, GdTbFeCo is the main component, and the composition has a coercive force of about 0.4 to 0.6 T at room temperature when the transition metal is rich, and a compensation temperature near a low power temperature, and 0.2 to 0 at room temperature. It has a coercive force of about 6T. In this example, a rare earth metal-rich composition was used.

The second embodiment will also be described in the following order. A ₂ . Initialization B _2. Playback C ₂ . Record

Note that FIG. 12 mainly describes the reproducing operation, and FIGS. 13 and 14 show the magnetization states of the respective layers with arrows for explaining the low power recording and the high power recording, respectively. The dashed arrow in the white arrow indicates the transition metal sublattice magnetization, and the solid arrow indicates the rare earth metal sublattice magnetization. The magnitude of which indicates which of the two metals is rich (the longer is rich).

A ₂ .. Initialization In this example as well, the recording layer 33 is changed by the initialization magnetic field H _ini .
Only is initialized. Also in this case, all of the above (Equation 1) to (Equation 6) are satisfied.

However, in this case, the point different from the case of the first embodiment is that the domain wall is in the intermediate layer 35 in the initialized state. This is because the recording layer 33 has a domain wall in a film having small perpendicular magnetic anisotropy.
It is possible to reduce the exchange coupling force between the memory layer 32 and the recording layer 33 without increasing the film thickness. As a result, the coercive force of the recording layer at room temperature can be made smaller than in (Equation 5), and the initialization magnetic field can be further reduced in (Equation 4).

In the case of the second embodiment, since the recording layer 33 is rich in rare earth at this temperature, the magnetization direction of the recording layer 33 follows the direction of the rare earth sublattice magnetic moment (see FIG. 12). It is generally known that in the case of a heavy rare earth transition metal-based amorphous thin film, the coercive force becomes very large near the compensation point. As will be described later, the coercive force of the recording layer at room temperature can be reduced by setting the compensation temperature near the temperature at the time of low power irradiation, so that the magnitude of the initializing magnetic field can be further reduced.

B ₂ .. As with the regeneration temperature is initialized by T _R or less clogging recording pit detection region (8), (9) is satisfied. On the other hand, as shown in FIG. 12, when the temperature rises above T _R , the cutting layer 34
Since the Curie temperature is exceeded, the exchange coupling force does not work between the reproducing layer 31 and the memory layer 32. Therefore, in the first embodiment, the conditions in this state are (Equation 10) and (Equation 11), whereas in this Embodiment 2, H _W1 = H _W21 = 0. Therefore, the following ( _Equation 15), ( _Equation 15) 16).

[0076]

[Equation 15] H _C1 <H _R

[0077]

[ _Equation 16] H _C2 −H _W23 > H _R

In the case where the cutting layer of Example 1 is not provided, it is very difficult to sharply cut the exchange coupling force to some extent, but the temperature of the ideal step function exchange coupling force is set by installing the cutting layer 34. You can get a change.

C ₂ .. Recording In the second embodiment, since the recording layer 33 has a rare earth-rich composition having a compensation temperature above room temperature below a high power temperature, the recording magnetic field is equal to the initialization magnetic field as shown in FIGS. Must be applied in the direction.

C _2-a Low Power Recording In the case of low power P _L , the equations (12) to (14) must be satisfied. However, the temperature at which the erasing operation is performed exceeds the temperature T _R shown at the time of reproduction as shown in FIG. 13, so that the cutting layer 34 is at the Curie temperature or higher. Therefore, the memory layer 32 is not affected by the exchange coupling force from the reproducing layer 31. Therefore, in the case of the second embodiment (Equation 12), it is changed to the following (Equation 17).

[0081]

[ _Expression 17] H _C2 + H _rec <H _W23

Thus, when designing the memory layer 32, the intermediate layer 36, and the recording layer 35 for overwriting, it can be considered separately from the cutting layer 34 and the reproducing layer 32 for super-resolution. Therefore, the degree of freedom in film formation is also increased.
The recording layer 33 has a compensation temperature near this temperature. For this reason, the coercive force of the recording layer 33 takes a maximum value near the low power temperature, so that the recording magnetic field and the exchange coupling force between the recording layer 33 and the memory layer 32 are controlled as shown in (Equation 13) and (Equation 14). The degree of freedom will increase.

C _2-b High Power Recording For high power P _H , all layers are heated above the Curie temperature or above the temperature at which the coercive force is sufficiently smaller than the recording magnetic field. Align with the direction of the recording magnetic field. At this temperature, the recording layer 33 is in a transition metal-rich state at least above the compensation temperature. Therefore, FIG.
As shown in FIG. 4, even if a recording magnetic field is applied in the same direction as in the initialization, paying attention to the sublattice magnetization, it is found that the magnetization is in the opposite direction to the low power.

[0084]

As is apparent from the above, according to the method of the present invention, the readout is performed in the area smaller than the spot of the reproduction light at the time of reproduction, so that the resolution is increased and the overwrite is possible at the time of recording. Since the erasing process, that is, the process of once erasing the entire magnetic layer is not required, the recording can be simplified.

[0085]

[Brief description of drawings]

FIG. 1 is a block diagram of a magneto-optical recording medium used in a method of the present invention.

FIG. 2 is a configuration diagram of a multilayer magnetic film.

FIG. 3 is a schematic view of an apparatus for carrying out an example of the method of the present invention.

FIG. 4 is an explanatory diagram of optical power.

FIG. 5 is a temperature distribution diagram on the magneto-optical recording medium.

FIG. 6 is an explanatory diagram of a reproduction operation.

FIG. 7 is an explanatory diagram of a reproduction operation.

FIG. 8 is an explanatory diagram of low power recording.

FIG. 9 is an explanatory diagram of high power recording.

FIG. 10 is a temperature distribution diagram in a light spot.

FIG. 11 is a constitutional view of a multilayer magnetic film of a magneto-optical recording medium used in another embodiment of the method of the present invention.

FIG. 12 is an explanatory diagram of a reproducing operation of another example of the method of the present invention.

FIG. 13 is an explanatory diagram of low power recording according to another example of the method of the present invention.

FIG. 14 is an explanatory diagram of high power recording according to another example of the method of the present invention.

[Explanation of symbols]

 3 multilayer magnetic film 31 reproducing layer 32 memory layer 33 recording layer 34 cutting layer 35 intermediate layer

Claims (2)

[Claims] 1. A magneto-optical recording medium having a multi-layer magnetic film in which at least a reproducing layer, a memory layer, and a recording layer, which are magnetically coupled sequentially at room temperature, are sequentially laminated, is used. Information recording is performed by light intensity modulation recording, with low light intensity irradiation, first recording performed by magnetization of the reproducing layer and the memory layer by transferring the magnetization state of the recording layer, and high light intensity irradiation. Magnetization of the three layers of the reproducing layer, the memory layer, and the recording layer is performed by the second recording performed by the external recording magnetic field, and the recording information is reproduced in the high temperature region due to the temperature distribution in the reproducing light spot. Is arranged in the direction of the reproducing magnetic field to make it impossible to read the recorded information, and the recorded information is read out only in a low temperature region. 2. At least magnetically coupled sequentially at room temperature.
A reproduction layer, a cutting layer, a memory layer, an intermediate layer, and a recording layer
Magneto-optical recording medium having a multilayer magnetic film formed by sequentially stacking
The body is used for recording information on the magneto-optical recording medium.
Recording, and with low light intensity irradiation, the reproduction layer and the memory layer
Is performed by the magnetization due to the transfer of the magnetization state of the recording layer.
When the first recording is performed and the high light intensity irradiation is performed, the reproduction layer and
Magnetization of the three layers, the memory layer and the recording layer, is performed by the external recording magnetic field.
The recorded information is reproduced by the second recording performed and the temperature distribution in the reproduction light spot.
In the high temperature region due to
Since it is impossible to read the recorded information because it is aligned, the low temperature area
Is characterized in that the recorded information is read out in a limited manner
Magneto-optical recording / reproducing method.