JPH0547057A - Information recording and reproducing system for magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To reproduce a signal whose pitch is narrower than the spot diameter of a light source by completing the magnetization of the recording and reproduction layers in one direction before recording and completing the magnetization direction of the reproduction layer in one direction without applying the external magnetic field accompanied by the cooling after reading. CONSTITUTION:A powerful enough magnetic field, and then, laser beam and a magnetic field are applied to the reproduction layer, and the magnetization of the recording layer is completed with that of the reproduction layer in one direction. Then, a magnetic field is applied in the reverse direction while irradiating with the laser beam, the holding power of a recording layer with relatively low curie temperature disappears previously, and the external magnetic field is fixed to the recording layer accompanied by the cooling. Thus, the inversion magnetic domain is formed to record a signal. When a reproducing light irradiates, the holding power of the irradiated part is reduced in the reproduction layer, and the magnetization, that is, the information on the reproduction layer is transferred in the same direction as the recording layer just above it. The reading of this signal is performed by the Kerr effect influenced on the reflection light of the reproduction light. At this time, the holding power of the only left side irradiated for a long time deteriorates among the spot parts of the reproduction light, and the effective spot diameter is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording / reproducing system for a magneto-optical recording medium for the purpose of increasing the recording density, and more specifically, it can reproduce a signal having a recording pitch narrower than the spot diameter of a light source. The present invention relates to an information recording / reproducing system for a magneto-optical recording medium.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION Transition metals such as iron and cobalt,
An amorphous alloy thin film made of an alloy with a rare earth element such as terbium (Tb) or cadolinium (Gd) has an easy axis of magnetization in a direction perpendicular to the film surface, and is entirely magnetized in one direction on a film surface. It is known that it is possible to form a small inverted magnetic domain that is opposite to the entire magnetization direction. By making the presence or absence of this inversion magnetic domain correspond to "1" and "0", it becomes possible to record a digital signal on the above amorphous alloy thin film.

A magneto-optical recording medium using such an amorphous alloy thin film has already reached the stage of practical application. Further, the magneto-optical recording medium is required to be further improved in terms of recording density and the like.

Increasing the recording density of the magneto-optical recording medium has been promoted from both aspects of recording and reproduction. As the recording technology, technology for increasing the density by pit edge recording or duobinary recording has been developed. However, if a recording pit written at a pitch narrower than the spot diameter of the reproduction light is read by the current reproduction method, two or more pits are irradiated with the spot light at the same time, and the reproduction signal is mixed and reproduction becomes impossible. .. Therefore, at the time of reproduction, it has been attempted to reduce the spot diameter of the reproduction light by shortening the wavelength of the laser light used for reproduction, and reproduce the information recorded at high density. It is necessary to shorten the wavelength of laser light. On the other hand, as the wavelength of laser light becomes shorter, the Kerr rotation angle becomes smaller. Therefore, about 0.74 μm is currently the limit of the wavelength of laser light that can be used for reproduction. It had been.

As a reproducing method for high-density recording, a method of using a magnetic film having a two-layer structure, one film being exclusively used for holding recorded information and the other film being used only for reproducing recorded information, has recently been available. Proposed. According to this playback method,
It is said that information of minute pits, which could not be reproduced by a laser beam having a wavelength of 0.74 μm or more, can be reproduced, and that the recording density can be further increased.

In this new reproducing system, one film (recording layer) is a magnetic film made of a TbFeCo alloy having a large coercive force. The Curie temperature is almost the same as that of the magnetic film of a normal magneto-optical recording medium. That is, when the semiconductor laser is irradiated with the power for recording, it loses the magnetization over the Curie temperature and is magnetized in the direction of the external magnetic field for recording as the temperature decreases. After returning to normal temperature, the direction of magnetization is maintained.

The other film (reproducing layer) is a magnetic film made of a GdFeCo alloy. The Curie temperature of the reproducing layer is lower than that of the recording layer, the coercive force is small, and the magnetization reversal occurs when the laser light intensity during reproduction is applied for a sufficient time. Further, the magnetization direction of the reproducing layer can be reversed by the initializing magnetic field.

To reproduce information recorded on a magneto-optical recording medium having a recording layer and a reproducing layer as described above, (1) first, by applying an initializing magnetic field before reproduction, all magnetic domains in the reproducing layer are By reversing the magnetization in the same direction and erasing all the magnetic signals in the vicinity of the detection signal from the reproduction layer, (2) by irradiating the reproduction layer from which the signal has been erased with laser light, only the high temperature part of the reproduction layer This is performed by transferring a signal from the recording layer and detecting this signal. With this technique, it is possible to obtain the same effect as if the light spot area was reduced, and it is possible to detect information recorded at high density with reproduction light having a wavelength equivalent to that of conventional laser light.

However, the present inventors have found that there is a point to be improved even in such a reproducing system. For example, in the above reproducing method, the signal transferred to the reproducing layer is retained in the reproducing layer unless the initializing magnetic field is applied again. This means that a signal exists on the track adjacent to the track being reproduced. In other words, two pits are lined up at a track pitch. When the radius of the spot diameter of the reproduction light is smaller than the track pitch, the signal of the track being reproduced and the signal of the adjacent track are not mixed. However, if the track pitch is reduced, the signal of the track being reproduced and the signal of the adjacent track are mixed up unless the spot diameter of the reproduction light is narrowed down. Reducing the track pitch is one of the effective means for increasing the recording density. In order to narrow down the spot diameter of the reproduction light, it is necessary to use a short wavelength laser as described above, and there is still room for improvement in this respect.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an information recording / reproducing system for a magneto-optical recording medium capable of reproducing a signal having a recording pitch narrower than the spot diameter of a light source.

[0011]

SUMMARY OF THE INVENTION An information recording / reproducing system for a magneto-optical recording medium according to the present invention records information on a magneto-optical recording medium having at least a reproducing layer and a recording layer, and reproduces the recorded information. In the method, information is recorded on the recording layer,
An information recording / reproducing method in which the information recorded in the recording layer is transferred to the reproducing layer by heating the reproducing layer and the information transferred in the reproducing layer is read out, and the magnetization direction of the reproducing layer is aligned in one direction in advance.
Before recording, the magnetization direction of the recording layer is aligned in one direction, information is recorded in the recording layer, the reproducing layer is heated, the information recorded in the recording layer is transferred to the reproducing layer, and the information transferred to the reproducing layer is recorded. It is characterized in that the magnetization direction of the reproducing layer is aligned with the above-mentioned magnetization direction without applying an external magnetic field in accordance with the reading and the cooling after the reading.

According to the information recording / reproducing system for the magneto-optical recording medium according to the present invention, after the reading, the magnetization direction of the reproducing layer is the same as in the initialized state, so that it is adjacent to the reproducing track. Since no signal is recorded in the track, even if a signal with a recording pitch narrower than the spot diameter of the light source is reproduced, only a single signal can be reproduced, and high density recording is possible. is there.

[0013]

DETAILED DESCRIPTION OF THE INVENTION An information recording / reproducing system for a magneto-optical recording medium according to the present invention will be specifically described below with reference to the drawings.

The magneto-optical recording medium 10 used in the present invention.
Is the reproduction layer 1 on the substrate 11 as shown in FIG.
3 and the recording layer 12 are formed in this order, but the structure is not particularly limited. For example, when the reproducing light is irradiated from the opposite side of the substrate 11, the recording layer 12 and the reproducing layer 13 may be formed on the substrate 11 in this order. Further, in the present invention, it is preferable that an intermediate layer is provided between the recording layer 12 and the reproducing layer 13. Further, an enhancement film (protective film) or the like may be provided between the substrate 11 and the recording layer 12 or the reproduction layer 13.

As the structure of such a magneto-optical recording medium 10, when the surface of the substrate 11 is irradiated with reproducing light, (A) substrate / reproducing layer / intermediate layer / recording layer (B) substrate / enhancement Film (protective film) / reproducing layer / intermediate layer / recording layer (C) substrate / reproducing layer / intermediate layer / recording layer / metal layer (D) substrate / enhancement film (protective film) / reproducing layer / intermediate layer / recording layer Examples include a structure such as / metal layer (E) substrate / enhancement film (protective film) / reproducing layer / intermediate layer / recording layer / enhancement film (protective film) / metal layer.

When the surface opposite to the substrate 11 is irradiated with reproducing light, (F) substrate / recording layer / intermediate layer / reproducing layer (G) substrate / enhancement film (protective film) / recording Layer / intermediate layer / reproducing layer (H) substrate / metal layer / recording layer / intermediate layer / reproducing layer (I) substrate / enhancement film (protective film) / metal layer / recording layer / intermediate layer / reproducing layer (J) substrate The following structures can be mentioned: / enhancement film (protective film) / metal layer / recording layer / intermediate layer / reproducing layer / enhancement film (protective film).

Further, a structure having a protective coat or a protective label for imparting scratch resistance to the outermost layer of these magneto-optical recording media is possible. As the substrate 11,
In addition to inorganic materials such as glass and aluminum, acrylic resins, polycarbonates, polymer alloys of polycarbonate and polystyrene, amorphous ethylene-cyclic olefin copolymers such as those shown in US Pat. No. 4,614,778 such as ethylene and 1, 4,5,8-Dimethano-
Copolymer with 1,2,3,4,4a, 5,8,8a-octahydronaphthalene (tetracyclododecene), ethylene and 2-methyl-1,4,5,8-dimethano-1,
A copolymer of 2,3,4,4a, 5,8,8a-octahydronaphthalene (methyltetracyclododecene), ethylene and 2-ethyl-1,4,5,8-dimethano-1,
Organic materials such as copolymers with 2,3,4,4a, 5,8,8a-octahydronaphthalene, poly-4-methyl-1-pentene, epoxy resin, polyether sulfone, polysulfone, polyetherimide, etc. Etc. can be used. The thickness of the substrate 11 is not particularly limited, but is preferably 0.5 mm to 5 mm, particularly preferably 1 mm to 2 mm.

As the recording layer 12, a magnetic film having large perpendicular magnetic anisotropy is used. As such a magnetic film,
An example is an alloy film of 3d transition metal and rare earth element. Here, as the 3d transition element, specifically, for example, T
i, Cr, Mn, Fe, Co, Ni, Cu are used,
Fe and Co are preferably used. As the rare earth element, specifically, Gd, Tb, Dy, Ho, Er,
Yb, Lu, La, Ce, Pr, Nd, Pm, Sm, E
u is used, and Gd, Tb, Nd, and Dy are preferably used.

More specific examples of the magnetic film used in the recording layer 12 include Tb _x Fe _1-x alloy and Tb.
_x (FeCo) _1-x alloy, (GdTb) _x Fe _1-x alloy,
Examples thereof include (GdTb) _x (FeCo) _1-x alloy. Note that x is in the range of 0.1 to 0.3.

The Curie temperature (Tc) of the recording layer 12 used in the present invention is lower than the Tc of the reproducing layer and T of the intermediate layer.
It is higher than c, specifically in the range of 100 to 300 ° C, preferably 150 to 200 ° C. The coercive force (Hc) of the recording layer 12 is in the range of 2 kOe or more, preferably 10 kOe or more at room temperature (20 to 25 ° C.).

The recording layer 12 is the magnetic film 1 as described above.
It may be formed of only layers, or may be a laminated body formed by laminating two or more magnetic films. The thickness of the recording layer 12 is 100 to 2000Å, preferably 20.
It is in the range of 0 to 800Å.

The reproducing layer 13 has a large perpendicular magnetic anisotropy, and even if a magnetic domain is formed, if the radius of the magnetic domain is less than a certain value, it cannot exist stably at room temperature and disappears. A magnetic film having the characteristic of being used is used. Here, the critical radius at which the magnetic domain disappears is 1 μm or more,
It is preferably 2 μm or more.

More specific examples of the magnetic film used for the reproducing layer 13 are Gd _x Co _1-x alloy and Gd.
_x Fe _1-x alloy, Gd _x (FeCo) _1-x alloy, (GdT
b) _x Co _1-x alloy, (GdTb) _x (FeCo) _1-x alloy and the like. Note that x is in the range of 0.1 to 0.3.

The Curie temperature (Tc) of the reproducing layer 13 used in the present invention is higher than the Tc of the recording layer, specifically in the range of 200 ° C. or higher, preferably 300 ° C. or higher.
The coercive force (Hc) of the reproducing layer 13 is 1 at room temperature.
It is in the range of kOe or more, preferably 5 kOe or more, and is required to be smaller than the coercive force of the recording layer at the temperature during reproduction.

The reproducing layer 13 is the magnetic film 1 as described above.
It may be formed of only layers, or may be a laminated body formed by laminating two or more magnetic films. The thickness of such a reproducing layer 13 is 100 to 2000Å, preferably 20.
It is in the range of 0 to 600Å.

The intermediate layer provided between the recording layer 12 and the reproducing layer 13 has a function of alleviating magnetic interaction between the magnetic domains of the recording layer and the reproducing layer and stably holding each magnetic domain. Have As the intermediate layer, a magnetic film having a smaller perpendicular magnetic anisotropy than the recording layer or the reproducing layer, for example, a film having a large in-plane magnetic anisotropy is used.

More specific examples of the magnetic film used for such an intermediate layer include Gd _x Fe _1-x alloy and Tb _x F.
e _1-x alloy, (GdTb) _x Fe _1-x alloy, Gd _x Co _1-x
Alloy, Gd _x (FeCo) _1-x alloy, (GdTb) _x Co
_1-x alloy, (GdTb) _x (FeCo) _1-x alloy, Tb
Examples include _x (FeCo) _1-x alloys. Note that x is 0
It is 0.1 or in the range of 0.3 or more.

The Curie temperature (Tc) of the intermediate layer used in the present invention is lower than the Tc of the recording layer, specifically, 60.
To 250 ° C, preferably 80 to 150 ° C.
The intermediate layer may be formed of only one magnetic film as described above, or may be a laminated body formed by laminating two or more magnetic films.

The enhance film (protective film) may be any one as long as its refractive index is larger than that of the substrate, and may be either organic or inorganic material. Specific examples of the enhance film (protective film) include TiO ₂ , SiO,
TiO, ZnO, ZrO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , Ce
O ₂ , SnO ₂ , TeO _{2 and} other oxides, Si ₃ N ₄ , Si
Nx (0 <X ≦ 4/3) nitride such as AlN or BN, Zn
There are sulfides such as S and CdS, ZnSe, SiC, and Si. Further, a transparent material having a Faraday effect such as ferrites typified by cobalt ferrite and garnets typified by Bi-substituted garnet may be used as the enhancement film.

As the metal layer, for example, an aluminum alloy (Al alloy) or a nickel alloy (Ni alloy) is used. This metal layer has a function as a heat conduction layer or a reflection layer, and is, for example, A
The l-based alloy layer has a function as a heat conduction layer, and the Ni-based alloy layer has a function as a reflection layer.

Next, a method of manufacturing the above magneto-optical recording medium will be described. While maintaining the substrate temperature at about room temperature, a composite target in which chips composed of the respective elements constituting the recording layer and the reproduction layer of the magneto-optical recording medium are arranged in a predetermined ratio, an alloy target composed of a predetermined composition or a target of each element, etc. A substrate which is combined and placed at a predetermined position, and which revolves around its own axis by adopting conventionally known film forming conditions such as a sputtering method, an electron beam vapor deposition method, or a vacuum simultaneous vapor deposition method (the substrate may be fixed. (In this case, the shutter on each target is alternately opened and closed), and a recording layer and a reproducing layer of the magneto-optical recording medium can be formed by sequentially depositing a thin film having a predetermined composition on the target.

Such a recording layer and a reproducing layer can be formed at room temperature, and it is not necessary to perform a heat treatment such as an annealing process after the film formation in order to have an easy axis of magnetization perpendicular to the film surface.

If necessary, the substrate temperature may be set to 50-6.
The recording layer and the reproducing layer can be formed on the substrate while heating to 00 ° C or cooling to -50 ° C. It is also possible to bias the substrate to a negative potential during sputtering. By doing so, the inert gas ions such as argon accelerated by the electric field will hit not only the target material but also the recording layer and the reproducing layer which are being formed, so that a magneto-optical recording medium having excellent characteristics can be obtained. May be obtained.

As described above, the recording layer and the reproducing layer of the magneto-optical recording medium have the easy axis of magnetization perpendicular to the film surface. In the information recording / reproducing system for the magneto-optical recording medium according to the present invention,
Using the magneto-optical recording medium as described above, information is recorded in the recording layer, the reproducing layer is heated to transfer the information recorded in the recording layer to the reproducing layer, and the information transferred in the reproducing layer is read.

Prior to recording, a sufficiently strong magnetic field is first applied to the reproducing layer so that at least the reproducing layer is magnetized in one direction as shown in FIG. 2 (hereinafter, this magnetizing direction is referred to as A direction, The magnetization direction opposite to this may also be referred to as the reverse A direction.). Note that heat may be applied at the same time when the magnetic field is applied.

Before recording, a laser beam is irradiated and a magnetic field is applied in the A direction to align the magnetization direction of the recording layer in one direction. Next, as shown in FIG. 3, for example, a magnetic field is applied in the reverse A direction while irradiating with laser light. At this time, by irradiating the laser beam from the side opposite to the substrate 11 or adjusting the focal depth of the laser beam to the depth of the recording layer,
It is also possible to selectively heat only the recording layer. The temperature of the portion irradiated with the laser light rises and the coercive force decreases. The coercive force of the recording layer having a relatively low Curie temperature (Tc) disappears first and is affected by the external magnetic field.
Then, with cooling, the external magnetic field is fixed to the recording layer, an inverted magnetic domain having a magnetization direction of the reverse A direction is formed in the recording layer as shown in FIG. 4, and a signal is recorded. Signal recording is performed by turning on / off the laser light intensity, turning on / off the applied magnetic field, or a combination of both. The irradiation intensity of the laser light, the irradiation time, and the intensity of the applied magnetic field differ depending on the type of the magnetic film forming the recording layer and the reproducing layer, but in general, the irradiation intensity of the laser light is about 3 to 50 mW, The irradiation time is about 1 × 10 ⁻⁹ seconds to 1 × 10 ⁻⁶ seconds, and the intensity of the applied magnetic field is 100 to 800 O.
It is preferably about e. The wavelength of laser light used for recording is about 400 to 2000 nm. In addition,
In addition to the light beam, any method such as a needle type magnetic head, a heating pen, and an electron beam can be used as the method of writing to the recording layer as long as it can supply the energy required to cause the magnetization reversal. Needless to say.

The information recorded on the recording layer is reproduced by heating the reproducing layer, transferring the information recorded on the recording layer to the reproducing layer, and reading the information transferred on the reproducing layer. As shown in FIG. 5, the portion irradiated with the reproducing light is locally heated and its coercive force is small. The magnetic domain with a reduced coercive force is magnetized in the same direction as the magnetic direction of the magnetic domain of the recording layer directly above it or by applying an external magnetic field, and the information of the recording layer is transferred to the reproducing layer. It To read the signal transferred to the playback layer,
This is performed by the Kerr effect that the reflected light of the laser light (reproduction light) irradiated on the reproduction layer receives (see FIG. 6). That is, the laser light (reproducing light) applied to the reproducing layer has a function of heating the reproducing layer and a function of reading light. The wavelength of such laser light (reproduction light) is 4
It is about 0.00 to 2000 nm, and its intensity is 0.
It is about 5 to 5 mW.

This reproducing system will be described again with reference to FIG. Focusing on the spot portion of the reproducing light, the reproducing light is irradiated for a long time, and the magnetization of the recording layer is transferred only to the reproducing layer in the left region where the coercive force is lowered. In the light spot, the recording pit in the right side area where the reproduction light is started to be irradiated is still covered with the reproduction layer. A portion of the spot of the reproduction light, which is not necessary for reading the recording pit, is covered with the magnetic domain in the direction A of the reproduction layer, which apparently reduces the effective light spot diameter. This apparent spot diameter corresponds to the detection area in FIG. As a result, the same effect as narrowing down the reproduction light is obtained, and it becomes possible to reproduce the signal recorded at high density.

The magnetic domain of the reproducing layer formed by transferring the magnetic domain of the recording layer is very small and its magnetization is weak. Therefore, due to the stray magnetic field from the surrounding magnetic domain or the movement of the magnetic domain wall, the magnetic domain of the reproducing layer disappears with cooling, and the magnetization direction of the reproducing layer comes to be aligned with the A direction again (FIGS. 7 and 8). reference). The cooling may be either standing cooling or forced cooling using a cooling device. As a result, the magnetic domain in the reverse A direction exists only in the detection region of the reproduction layer, and only the magnetic domain in the A direction exists in the reproduction layer of the adjacent track. Therefore, even if the track pitch is reduced in order to improve the recording density, the signal of the adjacent track will not be mixed with the signal of the track being reproduced.

A particularly preferred embodiment of the present invention will be described below. In the present invention, it is particularly preferable to use the following magnetic films as the recording layer, the intermediate layer and the reproducing layer.

The recording layer is (GdTb) _24.5 Fe _75.5
A magnetic film having a composition of (atomic%) is used. This magnetic film is a perpendicular magnetization film, and the Curie temperature Tc is 220.
The coercive force at 10 ° C and room temperature is 10 kOe or more, and the film thickness is about 1000Å.

A magnetic film having a composition of Gd ₅₅ Fe ₄₅ (atomic%) is used for the intermediate layer. This magnetic film is an in-plane magnetized film and has a Curie temperature Tc of 180 ° C. and a film thickness of about 75.
It is Å.

As the reproducing layer, a magnetic film having a composition of Gd ₂₁ Co ₇₉ (atomic%) is used. This magnetic film is a perpendicular magnetization film, the Curie temperature Tc is 300 ° C. or higher, the coercive force at room temperature is about 10 kOe, and the film thickness is about 400 Å.
Is.

A magnetic field of 300 Oe is applied in advance to raise the medium temperature and at least magnetize the reproducing layer in one direction (direction A). Before recording, a magnetic field of 300 Oe is applied and laser light (15 mW) is irradiated to align the magnetization direction of the recording layer in the A direction.

Recording is performed by applying a laser beam (15 m) according to the information to be recorded while applying a magnetic field of 300 Oe in the reverse A direction.
W) is irradiated to form magnetic domains in the recording layer. The reproduction is performed by irradiating the reproduction layer with laser light (3 mW) and transferring the magnetic domain of the recording layer to the reproduction layer only at the high temperature portion of the reproduction light spot.

At this time, the wavelength of the reproduction light is 830 nm, the NA of the objective lens is 0.55, and the CN ratio is 45 dB at a pit pitch of 0.8 μm.

[0047]

According to the information recording / reproducing system for the magneto-optical recording medium according to the present invention as described above, since the magnetization direction of the reproducing layer is the same as that in the initialized state after reading, No signal is recorded in adjacent tracks, so even when reproducing a signal with a recording pitch narrower than the spot diameter of the light source, it is possible to reproduce only a single signal, resulting in higher recording density. It is possible.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of a magneto-optical recording medium used in the present invention.

FIG. 2 is a diagram showing a recording layer and a reproducing layer which are initialized prior to recording.

FIG. 3 is a diagram showing a process of recording a signal on a recording layer.

FIG. 4 is a view showing a recording layer on which a signal is recorded.

FIG. 5 is a view showing a process in which a reproducing layer is irradiated with reproducing light and a heated magnetic domain loses magnetization.

FIG. 6 is a diagram showing a process in which a signal of a recording layer is transferred to a reproducing layer and reproduced.

FIG. 7 is a diagram showing an outline of a reproduction method.

FIG. 8 is a view showing a recording layer and a reproducing layer after being cooled through a reproducing process.

[Explanation of symbols]

 10 ... Magneto-optical recording medium 11 ... Substrate 12 ... Recording layer 13 ... Reproducing layer

Claims (1)

[Claims] 1. An information recording / reproducing system for recording information on a magneto-optical recording medium having at least a reproducing layer and a recording layer and reproducing the recorded information, wherein information is recorded on the recording layer and the reproducing layer is heated. An information recording / reproducing system in which the information recorded on the recording layer is transferred to the reproducing layer and the information transferred to the reproducing layer is read out. The magnetization direction of the reproducing layer is aligned in one direction in advance, and the recording layer is recorded before recording. The magnetization direction is aligned in one direction, information is recorded in the recording layer, the reproducing layer is heated, the information recorded in the recording layer is transferred to the reproducing layer, the information transferred to the reproducing layer is read, and after reading, An information recording / reproducing system for a magneto-optical recording medium, wherein the magnetization direction of a reproducing layer is aligned with the magnetization direction without applying an external magnetic field upon cooling.