JPH06302030A - Magneto-optical recording medium and magnetooptical recording method - Google Patents

Abstract

PURPOSE:To provide a magneto-optical recording medium capable of overwriting with high reliability without applying an initializing magnetic field. CONSTITUTION:A laminated structure consisting of a 1st magnetic layer 3, a 2nd magnetic layer 4 and a 3rd magnetic layer 5 is imparted to a recording layer. When the saturation magnetization, coercive force, Curie temp. and thickness of the 1st magnetic layer are expressed by Ms1, Hc1, Tc1, and t1, respectively, the saturation magnetization, coercive force, compensation temp., Curie temp. and thickness of the 2nd magnetic layer are expressed by Ms2, Hc2, Tcomp., Tc2 and t2, respectively, the coercive force, compensation temp. and Curie temp. of the 3rd magnetic layer are expressed by Hc3, Tcomp, and Tc3, respectively, room temp. is expressed by Troom and the interfacial magnetic wall energy between the 1st and 2nd magnetic layers and that between the 2nd and 3rd magnetic layers are expressed by sigmaw1 and sigmaw2, respectively, magnetic materials are selected so as to satisfy conditions represented by Troom< Tcomp3 Tc3Tc1<Tcomp2<Tc2, Hc1<Hc2>Hc3, Hc1>sigmaw1/2Ms1t1 and Hc2<sigmaw2/2Ms2t2.

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 medium and a magneto-optical recording method capable of overwriting without using an initializing magnetic field.

[0002]

2. Description of the Related Art In recent years,
As a rewritable optical recording medium, a magneto-optical recording medium utilizing the magneto-optical effect has been vigorously researched and developed, and has already been put to practical use. This magneto-optical recording medium has the advantages of large-capacity and high-density recording, non-contact recording / reproduction, and easy access, and in addition, it is possible to overwrite (overwrite) document information files, video / still image files, computer use. It is expected to be used for memory etc. In order to make a magneto-optical recording medium a recording medium having a performance equal to or higher than that of a magnetic disk, there are some technical problems, and one of the main ones is an overwrite technique. The currently proposed overwrite technology is
The recording method is roughly classified into a magnetic field modulation method and an optical modulation method (multi-beam method, two-layer film method, etc.).

The magnetic field modulation method is a method of recording by reversing the polarity of an applied magnetic field according to recording information. In this method, since the reversal of the magnetic field must be performed at high speed, it is necessary to use a flying type magnetic head, and it is difficult to exchange the medium.

On the other hand, the optical modulation method is a method of performing recording by turning on / off or irradiating the irradiation laser beam in accordance with recording information. Among these methods, the multi-beam method is a pseudo-overwrite method in which the direction of the magnetic field is reversed every rotation and recording / erasing is performed for each track by using two or three laser beams, but the device configuration is complicated. However, there are drawbacks such as increase in cost and increase in cost. Further, the two-layer film system is one in which the recording layer of the magneto-optical recording medium is a two-layer film to achieve overwriting.
It is disclosed in Japanese Patent No. 175948. The system described in the publication uses a magneto-optical recording medium having a two-layer recording layer including, for example, a memory layer made of TbFe and an auxiliary layer made of TbFeCo, and after initialization, an external magnetic field of It is intended to realize overwriting by irradiating laser beams having different powers and applied powers. That is,
In this method, the magnetization of the auxiliary layer is aligned in one direction by a magnetic field for initialization in advance of recording, and the medium temperature T is T> Tc ₂ (Tc ₂ is the Curie temperature of the auxiliary layer) by irradiation with a high-power laser beam. Recording is performed by raising the temperature to a temperature, applying a recording magnetic field (direction opposite to the initialization magnetic field) to reverse the magnetization of the auxiliary layer, and transferring the magnetization to the memory layer when the medium is cooled. In addition, the medium temperature is raised to a temperature of Tc ₁ <T <Tc ₂ (Tc ₁ is the Curie temperature of the memory layer) by irradiating a low power laser beam, and the magnetization direction of the auxiliary layer is transferred to the memory layer. To erase. Therefore, this method has a problem that an initialization magnet is required.

The present invention has been made in view of the above circumstances of the prior art, and provides a magneto-optical recording medium and a magneto-optical recording method which can be overwritten with high reliability without applying an initializing magnetic field and have good reproduction characteristics. The purpose is to do.

[0006]

In order to achieve the above object, according to the present invention, a first magnetic film exhibiting perpendicular magnetic anisotropy is formed.
The magnetic layer, the second magnetic layer, and the third magnetic layer are laminated, and the saturation magnetization of the first magnetic layer is Ms ₁ , the coercive force is Hc ₁ , the Curie temperature is Tc ₁ , the film thickness is t ₁ , and the second magnetic layer is the second magnetic layer. The saturation magnetization of the layer is Ms ₂ ,
Coercive force is Hc ₂ , compensation temperature is Tcomp ₂ , Curie temperature is Tc
₂ , the film thickness t ₂ , the coercive force of the third magnetic layer is Hc ₃ , the compensation temperature is Tcomp ₃ , the Curie temperature is T ₃ , the room temperature is Troom, and the domain wall energy between the first magnetic layer and the second magnetic layer is σw. _1st and 2nd
A magneto-optical recording medium satisfying the following conditions when the interfacial domain wall energy between the magnetic layer and the third magnetic layer is σw ₂ . _{Troom <Tcomp 3 ≒ Tc 3 <} Tc 1 <Tcomp 2 <Tc 2 Hc 1> Hc 2> Hc 3 Hc 1> σw 1 / 2Ms 1 t 1 Hc 2 <σw 2 / 2Ms 2 t 2 is provided.

Further, according to the present invention, in the above structure, an exchange coupling force between the first magnetic layer and the second magnetic layer and / or between the second magnetic layer and the third magnetic layer is applied. There is provided the magneto-optical recording medium described above, which is provided with an intermediate layer for adjustment.

Further, according to the present invention, there is provided a magneto-optical recording medium having the above-mentioned structure, wherein the first magnetic layer and the second magnetic layer are each made of an amorphous magnetic film represented by the following general formula 1. To be done.

[Chemical 1] (However, RE1 is at least one heavy rare earth metal element of Tb, Gd, Dy, Ho and Er, and RE2 is C
e, Pr, Nd, Pm, Sm, and at least one light rare earth metal element of Eu, and 0.15 ≦ x ≦
0.35, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.5)

Further, according to the present invention, in the above structure, the following general formula showing the perpendicular magnetic anisotropy which is adjacent to the light incident side of the first magnetic layer and has a smaller coercive force and a higher Curie temperature than the first magnetic layer is given. There is provided a magneto-optical recording medium comprising a reproducing layer made of an amorphous magnetic film represented by Chemical Formula 2.

[Chemical 2] (However, RE3 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er, and RE4 is C
e, Pr, Nd, Pm, Sm, and at least one kind of light rare earth metal element of Eu, and 0.15 ≦ a ≦
0.35, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.5)

Further, according to the present invention, there is provided a magneto-optical recording medium having the above structure, wherein a heat conducting layer is provided adjacent to the surface of the second magnetic layer opposite to the light incident side. To be done.

Further, according to the present invention, any one of the above magneto-optical recording media is used, and Tc ₁ is applied without applying an initializing magnetic field.
There is provided a magneto-optical recording method characterized in that erasing is carried out by raising the temperature to the vicinity and recording is conducted by raising the temperature to the vicinity of Tc ₂ .

Further, according to the present invention, in the above structure, the recording bias magnetic field Hb satisfying the following conditions is used in the process of increasing the temperature of the second magnetic layer to near Tc _1. A magneto-optical recording method is provided. Hc ₁ ± σw ₁ / 2Ms ₁ t ₁ >Hb> Hc ₃ + σw ₂ / 2Ms ₃ t ₃ (where Ms ₃ is the saturation magnetization of the third magnetic layer and t ₃ is the thickness of the third magnetic layer)

The present invention will be described below in detail with reference to the drawings. Figure 1
An example of the structure of the magneto-optical recording medium according to the present invention is shown in FIG. In this configuration example, SiO ₂ , SiO, Si ₃ N ₄ , Al is formed on the transparent substrate 1 made of glass, plastic, ceramic or the like.
A protective layer (film thickness 100 to 5000Å) 2 made of N or the like is provided, and a first magnetic layer, a second magnetic layer 4 and a third magnetic layer 4 each made of an amorphous magnetic film exhibiting perpendicular magnetic anisotropy are provided thereon.
A magnetic layer 5 is provided in that order, and SiO ₂ and S are further formed thereon.
Protective layer made of iO, Si ₃ N ₄ , AlN, etc. (film thickness 10
0-5000Å) 6 is provided. Each film can be formed by a sputtering method, a vapor deposition method, an ion plating method, or the like.

As a constituent material of the first magnetic layer 3, a rare earth-transition metal type amorphous alloy represented by the following formula 1 is preferably used.

[Chemical 1] (However, RE1 is at least one heavy rare earth metal element of Tb, Gd, Dy, Ho, and Er, and RE2 is at least one light rare earth metal element of Ce, Pr, Nd, Pm, Sm, and Eu. And 0.15 ≦ x ≦
0.35, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.5)

Specifically, Tb-Fe, Gd-Fe, G
d-Tb-Fe, Tb-Dy-Fe, Gd-Dy-F
e, Tb-Fe-Co, Gd-Fe-Co, Dy-Fe
-Co, Tb-Dy-Fe-Co, Gd-Tb-Fe-
Co, Gd-Dy-Fe-Co, Tb-Ho-Fe-C
o, Tb-Er-Fe-Co, etc. which satisfy the above conditions, and those to which at least one light rare earth metal element of Ce, Pr, Nd, Pm, Sm and Eu is added are used. It In particular, when a material having a composition containing a light rare earth metal element is used, there is an advantage that the deterioration of reproduction characteristics is small when reproduction is performed using a light source of a short wavelength range. A suitable film thickness t ₁ of the first magnetic layer 3 is 100 to 2000Å.

As the constituent material of the second magnetic layer 4, a rare earth-transition metal type amorphous alloy represented by the following general formula 1 is preferably used as in the first magnetic layer 3.

[Chemical 1] (However, RE1 is at least one heavy rare earth metal element of Tb, Gd, Dy, Ho, and Er, and RE2 is at least one light rare earth metal element of Ce, Pr, Nd, Pm, Sm, and Eu. And 0.15 ≦ x ≦
0.35, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.5)

Specifically, Tb-Fe, Gd-Fe, G
d-Tb-Fe, Tb-Dy-Fe, Gd-Dy-F
e, Tb-Fe-Co, Gd-Fe-Co, Dy-Fe
-Co, Tb-Dy-Fe-Co, Gd-Tb-Fe-
Co, Gd-Dy-Fe-Co, Tb-Ho-Fe-C
o, Tb-Er-Fe-Co, Tb-Nd-Fe-C
o, Tb-Sm-Fe-Co, Tb-Eu-Fe-Co
Etc., and those to which at least one kind of light rare earth metal element selected from Ce, Pr, Nd, Pm, Sm and Eu is added are used. Also in this case, in particular, when a material having a composition containing a light rare earth metal element is used, there is an advantage that the deterioration of the reproduction characteristic is small when the reproduction is performed using a light source of a short wavelength range. The film thickness t ₂ of the second magnetic layer 4 is 100 to 30.
00Å is suitable.

As the constituent material of the third magnetic layer 5, a rare earth-transition metal type amorphous alloy represented by the following general formula 1 is preferably used, like the first magnetic layer 3 and the second magnetic layer 5.

[Chemical 1] (However, RE1 is at least one heavy rare earth metal element of Tb, Gd, Dy, Ho, and Er, and RE2 is at least one light rare earth metal element of Ce, Pr, Nd, Pm, Sm, and Eu. And 0.15 ≦ x ≦
0.35, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.5)

Specifically, Tb-Fe, Gd-Fe, G
d-Tb-Fe, Tb-Dy-Fe, Gd-Dy-F
e, Tb-Fe-Co, Gd-Fe-Co, Dy-Fe
-Co, Tb-Dy-Fe-Co, Gd-Tb-Fe-
Co, Gd-Dy-Fe-Co, Tb-Ho-Fe-C
o, Tb-Er-Fe-Co, Tb-Nd-Fe-C
o, Tb-Sm-Fe-Co, Tb-Eu-Fe-Co
Etc., and those to which at least one kind of light rare earth metal element selected from Ce, Pr, Nd, Pm, Sm and Eu is added are used. Also in this case, in particular, when a material having a composition containing a light rare earth metal element is used, there is an advantage that the deterioration of the reproduction characteristic is small when the reproduction is performed using a light source of a short wavelength range. The thickness t ₃ of the third magnetic layer 4 is 100 to 30.
00Å is suitable.

Here, the first magnetic layer 3, the second magnetic layer 4, and the third magnetic layer 5 have a saturation magnetization Ms ₁ , a coercive force Hc ₁ , a Curie temperature Tc ₁ , and a film thickness of the first magnetic layer 3. Is t ₁ , the saturation magnetization of the second magnetic layer 4 is Ms ₂ , the coercive force is Hc ₂ , and the compensation temperature is Tcomp.
₂ , Curie temperature is Tc ₂ , film thickness is t ₂ , coercive force of the third magnetic layer 5 is Hc ₃ , compensation temperature is Tcomp ₃ , Curie temperature is T ₃ ,
Room temperature is Troom, interface domain wall energy between the first magnetic layer 3 and the second magnetic layer 4 is σ w ₁ , the second magnetic layer 4 and the third magnetic layer 5 are
When the interfacial domain wall energy between is σ w ₂ , the following conditions must be satisfied. _{Troom <Tcomp 3 ≒ Tc 3 <} Tc 1 <Tcomp 2 <Tc 2 ... (1) Hc 1> Hc 2> Hc 3 ... (2) Hc 1> σw 1 / 2Ms 1 t 1 ... (3) Hc 2 <σw ₂ / 2Ms ₂ t ₂ (4)

First, the condition (1) will be described. In order to transfer the magnetization of the second magnetic layer 4 to the first magnetic layer 3 and store the magnetization in the first magnetic layer 3, Tc ₂ is T.
Greater than c ₁ and of course Tc ₁ and Tc ₂ must be greater than Troom. Since recording and erasing are performed only by the recording bias magnetic field, Tcomp ₂ must be larger than Tc _{1 and} smaller than Tc ₂ . Furthermore, in order to ensure the initialization using the recording bias magnetic field, Tc ₃ and Tcomp ₃ are almost equal (| Tc ₃ −Tcomp ₃ | <20 ° C.), and naturally Tc ₃ and Tc
omp ₃ must be greater than Troom. Tc ₁ is 13
0 to 200 ° C is suitable, Tc ₂ is suitably 200 to 300 ° C, and Tc ₃ is suitably 70 to 130 ° C.

Next, the condition (2) will be described. When Hc ₁ ≤Hc ₂ , the magnetization of the first magnetic layer 3 is reversed by a bias magnetic field or an external magnetic field, so that Hc ₁ > Hc. Must be ₂ . Further, since the magnetization of the third magnetic layer 5 is used to surely initialize the second magnetic layer 4 using the recording bias magnetic field, Hc ₂ > Hc ₃ must be satisfied.

Next, the conditions (3) and (4) will be described. Hc ₁ must satisfy equation (3) so that the magnetization of the first magnetic layer 3 at room temperature Troom does not face the magnetization direction of the second magnetic layer 4 due to the exchange coupling force. Also H
c ₂ must satisfy equation (4) so that the magnetization of the first magnetic layer 3 and the magnetization of the second magnetic layer 4 are always stable due to the exchange coupling force. Hc ₁ is suitably 5 KOe or less, Hc ₂ is suitably 0.5 to ₃ KOe, Hc ₃
0.5 KOe or less is suitable. Ms ₁ is 0 to 150e
mu / cc is suitable and Ms ₂ is 100 to 300 emu.
/ Cc is suitable. Those satisfying the above conditions (1) to (4) can change the magnetization direction of the second magnetic layer 4 by the laser irradiation temperature only by using the recording bias magnetic field, and the magnetization is changed to the first magnetic layer 3. Since the magnetization can be transferred by the exchange coupling force, the overwriting can be performed without the initialization magnetic field.

Although the recording layer has a two-layer structure in the above configuration example, according to the present invention, as shown in FIG. 2, the first magnetic layer 3 is formed.
For the purpose of controlling the exchange coupling force between the second magnetic layer 4 and the second magnetic layer 4 and / or the exchange coupling force between the second magnetic layer 4 and the third magnetic layer 5, an intermediate layer 7 and / or an intermediate layer 7 between these layers. The intermediate layer 8 may be provided. The material of the intermediate layers 7 and 8 is the first
A magnetic material that does not deteriorate the magnetic layer 3, the second magnetic layer 4, and the third magnetic layer 5 and has a small perpendicular magnetic anisotropy is preferable. Specifically, not only the rare earth metal-transition metal amorphous magnetic film, but also Si, Al, A
g, Au, Cu, Fe, Co, Ni, Cr, Si-N,
Al-N, Fe-N, SiO, SiO 2, Fe-Co,
Gd, Tb, Dy, Nd, etc. can be mentioned. If the film thickness of the intermediate layers 7 and 8 is too thin, the effect of adjusting the exchange coupling force cannot be obtained, and if it is too thick, the exchange coupling force between both magnetic layers becomes too small, which hinders recording and erasing.
Å About is appropriate. The intermediate layers 7 and 8 can be formed by a sputtering method, a vapor deposition method, an ion plating method, or the like.

In the magneto-optical recording medium of the present invention, as shown in FIG.
As shown in FIG. 3, a reproducing layer formed of an amorphous magnetic film adjacent to the light incident side of the first magnetic layer 3 and having a perpendicular magnetic anisotropy with a smaller coercive force Hc and a higher Curie temperature Tc than the first magnetic layer 3. 9 can be provided.

As the material of the reproduction layer 9, the following general formula 2
A rare earth-transition metal-based amorphous alloy having a large magneto-optical effect is preferably used.

[0027]

[Chemical 2] (However, RE3 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er, and RE4 is C
e, Pr, Nd, Pm, Sm, and at least one kind of light rare earth metal element of Eu, and 0.15 ≦ a ≦
0.35, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.5)

Specifically, Tb-Fe, Gd-Fe, G
d-Tb-Fe, Tb-Dy-Fe, Gd-Dy-F
e, Tb-Fe-Co, Gd-Fe-Co, Dy-Fe
-Co, Tb-Dy-Fe-Co, Gd-Tb-Fe-
Co, Gd-Dy-Fe-Co, Tb-Ho-Fe-C
o, Tb-Er-Fe-Co, etc., and Ce,
At least one of Pr, Nd, Pm, Sm, and Eu
The one to which the light rare earth element of the kind is added is used. The thickness of the reproducing layer needs to be thin enough to allow light to pass therethrough, and 600 Å or less is optimal. The reproduction layer 9 can be formed by a sputtering method, a vapor deposition method, an ion plating method, or the like. The reproduction layer 9 has a role of improving reproduction characteristics. In this case, the magnetization of the reproducing layer 9 must be in a state in which the magnetization information of the first magnetic layer 3 is transferred, so that the coercive force Hcr of the reproducing layer 9 is small and the condition of Hcr <Hc ₁ is satisfied. I have to. Hcr is 0.1-2
It is preferably KOe. Further, if the magnetization information of the reproducing layer 9 is lost before the magnetization information of the first magnetic layer 3 is lost, a read error occurs, so the Curie temperature Tcr of the reproducing layer 9 is increased.
Must satisfy the condition of Tcr> Tc ₁ .
Tcr is preferably 120 to 300 ° C. Reproduction layer 9
The magnetization information transferred to is read out by utilizing the magneto-optical effect using the reproduction laser light. At this time, since the reproducing layer 9 is made of a material having a large magneto-optical effect, and the film thickness of the reproducing layer 9 is thin enough to transmit light (600 Å or less), not only the Kerr effect but also the Faraday effect is obtained. Can be utilized, the magneto-optical effect is enhanced, and the reproducing characteristic can be improved.

In the magneto-optical recording medium of the present invention, as shown in FIG.
As shown in, the heat conduction layer 10 can be provided adjacent to the surface of the second magnetic layer 4 opposite to the light incident side. The heat conductive layer 10 has a role of reducing the spread of heat in the lateral direction and making the shape of the recording magnetic domain uniform to improve the reproducing characteristic. As the material of the heat conduction layer 10, Al, Cu, Au,
Examples thereof include Ag, Pt, SiC, AlN and the like. The thickness of the heat conduction layer 10 is preferably 100 to 3000 liters, and can be formed by a sputtering method, a vapor deposition method, an ion plating method, or the like. With such a configuration, the heat conduction layer 10 plays a role as a heat sink layer during recording, the lateral spread of the film temperature of each magnetic layer is reduced, and the leading edge shape and trailing edge of the recording magnetic domain are reduced. There is no problem that the shape of the magnetic recording medium is different or the length of the recording magnetic domain extends longer than the actual recording pattern, so that a uniform magnetic domain shape is obtained and the reproducing characteristic is improved. In addition, since there is no lateral spread of heat, it is possible to record minute magnetic domains, which is suitable for high density recording.

The layer structure of the magneto-optical recording medium used in the present invention is not limited to those shown in FIGS. 1 to 4, and various modifications and changes can be made.

Next, the magneto-optical recording method of the present invention will be described. In the method of the present invention, a bias magnetic field Hb satisfying the following conditions is applied in the process of increasing the temperature to around Tc ₁ , erasing is performed without applying an initializing magnetic field, and the temperature is raised to around Tc ₁ for recording. To do. Hc ₁ ± σw ₁ / 2Ms ₁ t ₁ >Hb> Hc ₃ + σw ₂ / 2Ms ₃ t ₃ (5)

FIG. 5 is a diagram for explaining recording and erasing by the method of the present invention. In the present invention, when erasing is performed, a low laser power (PL) is applied and the film temperature T
Up to near Tc ₁ (Tc ₁ −20 ≦ T ≦ Tc ₁ +20 [° C.]). Before laser irradiation, the magnetization is oriented in the previously recorded direction in the first magnetic layer 3, and in the second magnetic layer 4 in the energy stable direction by the exchange coupling force due to the magnetization of the first magnetic layer 3. The magnetization is oriented, and the magnetization of the third magnetic layer 5 is oriented in the same direction as the magnetization of the second magnetic layer 4 due to the exchange coupling force of the magnetization of the second magnetic layer 4. When the laser irradiation is performed there, the magnetization of the third magnetic layer 5 is oriented in the bias magnetic field Hb direction during the temperature rising process, and the magnetization of the second magnetic layer 4 is accordingly magnetized by the exchange coupling force. And the same direction (bias magnetic field Hb direction). Since Hc ₂ becomes very large near Tc ₁ , it is frozen as it is. At that time, the magnetization of the first magnetic layer 3 gradually decreases and becomes zero at Tc ₁ . Further, since the temperature of the third magnetic layer 5 is higher than Tc ₃ , its magnetization becomes zero. After that, when the laser irradiation ends and the film temperature drops, the second magnetic layer 4
Is transferred to the first magnetic layer 3 by the exchange coupling force, and when returning to the room temperature Troom, Hc ₁ is very large and is frozen as it is. On the contrary, since Hc ₂ of the second magnetic layer 4 is small, the magnetization is oriented in an energetically stable direction by the exchange coupling force with the magnetization of the first magnetic layer 3 near the room temperature Troom, and the temperature of the third magnetic layer 5 is lowered. Then, due to the exchange coupling force with the second magnetic layer 4, the magnetization is oriented in the same direction as the magnetization of the second magnetic layer 4. Erasing is performed as described above.

[0033] when recording in the present invention, by irradiating a high laser power (PH), carried out by raising the film temperature T up to the vicinity of _{Tc 2 (Tc 2 -20 ≦ T} ≦ Tc 2 +30 [℃]).
When the film temperature T is increased to around Tc ₂ , the first magnetic layer 3 and the third magnetic layer 3
The magnetization of the magnetic layer 5 becomes zero, and the magnetization of the second magnetic layer 4 also approaches zero. Therefore, the second magnetic layer 4 has a bias magnetic field H
The magnetization is reversed (recorded) in the b direction and frozen during the cooling process. When the temperature drops and passes through Tcomp ₂ , the sublattice magnetization is T
Since the M dominant changes to the RE dominant, the entire magnetization is reversed again. Then, the temperature drops further and T
When passing near c ₁ , the magnetization is transferred from the second magnetic layer 4 to the first magnetic layer 3 by the exchange coupling force, and the magnetization of the first magnetic layer 3 is frozen at room temperature Troom. The magnetization of the second magnetic layer 4 is oriented in the energetically stable direction due to the exchange coupling force with the magnetization of the first magnetic layer 3 near room temperature Troom. The magnetization of the third magnetic layer 5 is oriented in the same direction as the magnetization of the second magnetic layer 3 due to the exchange coupling force with the second magnetic layer 4 during the temperature decrease process. The recording is performed as described above.

As described above, in the magneto-optical recording method of the present invention,
Recording and erasing can be performed without applying an initializing magnetic field, and the interface domain wall does not exist between the magnetic layers at room temperature Troom. Therefore, the stability of the recording magnetic domain is excellent.

[0035]

EXAMPLES Examples of the present invention will be described below.
The invention is not limited to the embodiments illustrated here.

Example 1 and Comparative Example Polycarbonate (PC) substrate with groove (diameter 13
0 mm) and the following films were successively laminated in vacuum by an rf magnetron sputtering method to prepare a magneto-optical recording medium. - layer structure of Comparative Example - protective _{layer:.. Si 3 N 4 (} 800Å) the first magnetic _{layer: Tb 0 21 (.. Fe} 0 9 Co 0 1) 0 79 (500
Å) second magnetic layer:..... (Gd 0 5 Tb 0 5) 0 19 (Fe 0 85 Co 0 15)
. _{0 81} (1500Å) protective _{layer: Si 3 N 4 (500Å)} - layer structure of Example 1 - protective _{layer:.. Si 3 N 4 (} 800Å) the first magnetic _{layer: Tb 0 21 (Fe 0 9} Co 0 . _{1) 0.79} (500
Å) second magnetic layer:..... (Gd 0 8 Tb 0 2) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (500Å) the third magnetic _{layer:.. Dy 0 27 (.} . Fe 0 9 Co 0 1) 0 73 (100
0 Å) Protective layer: Si ₃ N ₄ (500 Å)

The magnetic characteristics of the medium of the comparative example are shown in Table 1, and the magnetic characteristics of Example 1 are shown in Table 2.

[Table 1]

[0038]

[Table 2]

With respect to σw, the medium of the comparative example has 1.5 erg / cm ² , and the medium of Example 1 has σw ₁ = 1.
4 erg / cm ² , σw ₂ = 1.5 erg / cm ² ,
σw / 2Ms ₁ t ₁ is 4.4 KO in the medium of the comparative example.
is e, the medium of Example _{1 σw 1 / 2Ms 1 t 1} = 4.1
KOe, σw ₂ / 2Ms ₂ t ₂ = 1.2KOe.

Regarding the mediums of the comparative example and the example 1 produced as described above, the initializing magnetic field of 4 KOe was applied to the medium of the comparative example, and the initializing magnetic field was not applied to the medium of the example 1 under the following conditions. Measure the overwrite characteristics with
Compared. Regarding the bias magnetic field Hb, a magnetic field of 0.5 KOe was applied in the direction shown in FIG. 5 so as to satisfy the above-mentioned expression (5). Further, the medium temperature was raised to about 280 ° C. by the laser irradiation of 12 mW, and the medium temperature was raised to about 180 ° C. by the laser irradiation of 6 mW. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s

With respect to the media of Comparative Example and Example 1, C / N when a 1 MHz signal was recorded and reproduced under the above conditions and C when a 2 MHz overwrite was performed on this
/ N is shown in Table 3.

[Table 3]

From the above results, it was found that the medium of Example 1 according to the present invention can obtain the overwrite characteristic equivalent to that of the medium of the comparative example using the initializing magnetic field without using the initializing magnetic field. It should be noted that the medium of the comparative example could not be overwritten when the initialization magnetic field was not used.

Example 2 Polycarbonate (PC) substrate with groove (diameter 13)
0 mm) and the following films were successively laminated in vacuum by an rf magnetron sputtering method to prepare a magneto-optical recording medium. Protective layer: Si ₃ N ₄ (800Å) the first magnetic _{layer:.. Tb 0 21 (.} . Fe 0 9 Co 0 1) 0 79 (500
Å) Intermediate _{layer:.... Gd 0 35} (Fe 0 85 Co 0 15) 0 65 (10
0 Å) second magnetic layer:..... (Gd 0 8 Tb 0 2) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (500Å) Intermediate _{layer:.. Gd 0 35 (.} . Fe 0 85 Co 0 15) 0 65 (50
Å) third magnetic _{layer:.... Dy 0 27} (Fe 0 9 Co 0 1) 0 73 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

The magnetic characteristics of the first magnetic layer, the second magnetic layer and the third magnetic layer were the same as in the case of Example 1, respectively.

The overwrite characteristics of this medium were evaluated under the following conditions without applying an initializing magnetic field. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Bias magnetic field Hb: 0.5 KOe

Under the above conditions, 1M for the medium of Example 2
C / N when recording and reproducing the Hz signal and 2 on this
Table 4 shows the C / N ratio when overwriting at MHz.
Shown in.

[Table 4]

From the above results, it is shown that when the intermediate layer is provided between the first magnetic layer and the second magnetic layer and between the second magnetic layer and the third magnetic layer, the intermediate layer is not provided (Examples). It was found that the overwrite characteristic was further improved as compared with (1).

Example 3 Polycarbonate (PC) substrate with groove (diameter 13)
0 mm) and the following films were successively laminated in vacuum by an rf magnetron sputtering method to produce a magneto-optical recording medium. Protective layer: Si ₃ N ₄ (800Å) the first magnetic _{layer:. (.. Nd 0 2} Tb 0 8) 0 22 (.. Fe 0 9 Co 0 1) 0.
₇₈ (500 Å) the second magnetic _{layer:. (.. Gd 0 8} Tb 0 2) 0 28 (.. Fe 0 85 Co 0 15)
. _{0 72} (500Å) the third magnetic _{layer:.. Dy 0 27 (.} . Fe 0 9 Co 0 1) 0 73 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

The magnetic characteristics of the first magnetic layer, the second magnetic layer and the third magnetic layer are as follows.

[Table 5]

The overwrite characteristics of the medium of Example 3 were evaluated under the following conditions without applying an initializing magnetic field.
Regarding the bias magnetic field Hb, a magnetic field of 0.5 KOe was applied in the direction shown in FIG. 5 so as to satisfy the above-mentioned expression (5). Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s

Under the above conditions, 1M of the medium of Example 3 was used.
Table 6 shows the C / N when recording and reproducing the Hz signal and the C / N when the 2 MHz overwrite is performed on the C / N.

[Table 6]

From the above results, it was found that even when the light rare earth element was added to the first magnetic layer, the overwrite characteristic equivalent to that of the medium of Example 1 was obtained. It is advantageous to add a light rare earth element as in the present embodiment because the drop of the magneto-optical effect is small even when the wavelength of the laser light is shortened.

Example 4 Polycarbonate (PC) substrate with groove (diameter 13)
0 mm) and the following films were successively laminated in vacuum by an rf magnetron sputtering method to prepare a magneto-optical recording medium. Protective layer: Si ₃ N ₄ (800Å) reproducing _{layer:. (.. Gd 0 5} Tb 0 5) 0 22 (.. Fe 0 9 Co 0 1) 0.
₇₈ (300 Å) first magnetic _{layer:.. Tb 0 21 (.} . Fe 0 9 Co 0 1) 0 79 (500
Å) second magnetic layer:..... (Gd 0 8 Tb 0 2) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (500Å) the third magnetic _{layer:.. Dy 0 27 (.} . Fe 0 9 Co 0 1) 0 73 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

Reproduction layer, first magnetic layer, second magnetic layer and third layer
The magnetic characteristics of the magnetic layer are as follows.

[Table 7]

The overwrite characteristics of the medium of Example 4 were evaluated under the following conditions without applying an initializing magnetic field.
Regarding the bias magnetic field Hb, a magnetic field of 0.5 KOe was applied in the direction shown in FIG. 5 so as to satisfy the above-mentioned expression (5). Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s

Under the above conditions, 1M of the medium of Example 4 was used.
Table 8 shows the C / N when recording and reproducing the Hz signal and the C / N when the 2 MHz overwrite is performed on the C / N.

[Table 8]

From the above results, the reproduction C / N is further increased when the reproduction layer is provided as compared with the media of Examples 1 to 3.
It was found that the overwrite characteristics were also good.

Example 5 Polycarbonate (PC) substrate with groove (diameter 13)
0 mm) and the following films were successively laminated in vacuum by an rf magnetron sputtering method to produce a magneto-optical recording medium. Protective layer: Si ₃ N ₄ (800Å) reproducing layer:.. (... Nd 0 2 Gd 0 4 Tb 0 4) 0 23 (Fe 0 9 C
_{.. o 0 1) 0 77} (300Å) the first magnetic _{layer:.... Tb 0 21} (Fe 0 9 Co 0 1) 0 79 (500
Å) second magnetic layer:..... (Gd 0 8 Tb 0 2) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (500Å) the third magnetic _{layer:.. Dy 0 27 (.} . Fe 0 9 Co 0 1) 0 73 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

Reproducing layer, first magnetic layer, second magnetic layer and third layer
The magnetic characteristics of the magnetic layer are as follows.

[Table 9]

The overwrite characteristics of the medium of Example 5 were evaluated under the following conditions without applying an initializing magnetic field.
Regarding the bias magnetic field Hb, a magnetic field of 0.5 KOe was applied in the direction shown in FIG. 5 so as to satisfy the above-mentioned expression (5). Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s

Under the above conditions, 1M of the medium of Example 5 was used.
Table 10 shows the C / N when recording and reproducing the Hz signal and the C / N when the 2 MHz overwrite is performed on the C / N.

[Table 10]

From the above results, it was found that even when a light rare earth element was added to the reproducing layer, the C / N was higher than that of Example 1 in which the reproducing layer was not provided, and the overwrite characteristics were good. It is advantageous to add a light rare earth metal to the reproducing layer because the magneto-optical effect is less likely to drop even when the wavelength of laser light is shortened.

Example 6 Polycarbonate (PC) substrate with a groove (diameter 13)
The following films were continuously laminated in vacuum on the (0 mmφ) by the rf magnetron sputtering method to produce a magneto-optical recording medium. Protective layer: Si ₃ N ₄ (800Å) the first magnetic _{layer:.. Tb 0 21 (.} . Fe 0 9 Co 0 1) 0 79 (500
Å) second magnetic layer:..... (Gd 0 8 Tb 0 2) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (500Å) the third magnetic _{layer:.. Dy 0 27 (.} . Fe 0 9 Co 0 1) 0 73 (1000
Å) Thermal conduction layer: Al (1000 Å) Protective layer: Si ₃ N ₄ (500 Å)

The magnetic characteristics of the first magnetic layer, the second magnetic layer and the third magnetic layer were the same as in Example 1.

The overwrite characteristics of the medium of Example 6 were evaluated under the following conditions without applying an initializing magnetic field.
Regarding the bias magnetic field Hb, a magnetic field of 0.5 KOe was applied in the direction shown in FIG. 5 so as to satisfy the above-mentioned expression (5). Laser power during recording: 13 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s

1M for the medium of Example 6 under the above conditions
Table 11 shows the C / N when recording and reproducing the Hz signal and the C / N when the 2 MHz overwrite is performed on the C / N.

[Table 11]

From the above results, it was found that the C / N in the case where the heat conducting layer was provided was higher than that in the case of Example 1 in which the heat conducting layer was not provided, and the overwrite characteristic was good.

[0069]

【The invention's effect】

(1) According to the first aspect of the invention, by stacking the first magnetic layer, the second magnetic layer and the third magnetic layer satisfying the above conditions, it becomes possible to overwrite without using an initializing magnetic field. A magnetic recording medium is provided. (2) According to the invention of claim 2, by providing an intermediate layer between the first magnetic layer and the second magnetic layer and / or between the second magnetic layer and the third magnetic layer, the overwrite characteristic Is further improved. (3) According to the invention of claim 3, a better overwrite characteristic can be obtained by using an amorphous magnetic film having a specific composition for each of the first magnetic layer, the second magnetic layer and the third magnetic layer. . Further, by adding a light rare earth element to the first magnetic layer, the second magnetic layer or the third magnetic layer,
It is possible to improve the overwrite characteristic when the wavelength of the irradiation light is shortened. (4) According to the invention of claim 4, the reproduction C / N and overwrite characteristics can be further improved by stacking the reproduction layers. Further, by adding a light rare earth element to the reproducing layer, it is possible to improve the overwrite characteristic when the irradiation light has a short wavelength. (5) According to the invention of claim 5, by providing the heat conducting layer, the reproduction C / N and overwrite characteristics can be further improved. (6) According to the sixth aspect of the invention, by using the above medium, the temperature is raised to around Tc ₁ to perform erasing, and the temperature is raised to around Tc ₂ to perform recording, thereby setting the initialization magnetic field. Overwriting is possible without applying voltage. (7) According to the invention of claim 7, by limiting the bias magnetic field Hb to a value within a predetermined range, overwriting can be performed more reliably without using the initialization magnetic field.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a magneto-optical recording medium according to the present invention.

FIG. 2 is a cross-sectional view showing a configuration example in which an intermediate layer is provided between a first magnetic layer and a second magnetic layer in the medium of FIG.

FIG. 3 is a cross-sectional view showing a configuration example in which a reproducing layer is provided adjacent to a light incident side surface of a first magnetic layer in the medium of FIG.

FIG. 4 is a cross-sectional view showing a configuration example in which a heat conduction layer is provided adjacent to the surface of the medium of FIG. 1 opposite to the light incident side of the second magnetic layer.

5A is an explanatory diagram of a recording method according to the present invention, and FIG. 5B is an explanatory diagram of an erasing method.

[Explanation of symbols]

 1 Substrate 2, 6 Protective Layer 3 First Magnetic Layer 4 Second Magnetic Layer 5 Third Magnetic Layer 7, 8 Intermediate Layer 9 Reproducing Layer 10 Thermal Conduction Layer

Claims (7)

[Claims] 1. A first magnetic layer and a second magnetic layer exhibiting perpendicular magnetic anisotropy.
The magnetic layer and the third magnetic layer are laminated, the saturation magnetization of the first magnetic layer is Ms ₁ , the coercive force is Hc ₁ , the Curie temperature is Tc ₁ , the film thickness is t ₁ , and the saturation magnetization of the second magnetic layer is Ms ₂ , H coercive force
c ₂ , compensation temperature is Tcomp ₂ , Curie temperature is Tc ₂ , film thickness is T ₂ , coercive force of the third magnetic layer is Hc ₃ , compensation temperature is Tcomp ₃ ,
The Curie temperature T _3, Troom to room temperature, .sigma.w ₁ the interface wall energy of the first magnetic layer and the second magnetic layer, the following conditions when the interface wall energy of the second magnetic layer and the third magnetic layer and .sigma.w ₂ A magneto-optical recording medium satisfying the following. _{Troom <Tcomp 3 ≒ Tc 3 <} Tc 1 <Tcomp 2 <Tc 2 Hc 1> Hc 2> Hc 3 Hc 1> σw 1 / 2Ms 1 t 1 Hc 2 <σw 2 / 2Ms 2 t 2 2. An intermediate layer for adjusting the exchange coupling force between both layers is provided between the first magnetic layer and the second magnetic layer and / or between the second magnetic layer and the third magnetic layer. The magneto-optical recording medium according to claim 1. 3. The magneto-optical recording according to claim 1, wherein each of the first magnetic layer, the second magnetic layer and the third magnetic layer comprises an amorphous magnetic film represented by the following general formula 1. Medium. [Chemical 1] (However, RE1 is at least one heavy rare earth metal element of Tb, Gd, Dy, Ho and Er, and RE2 is C
e, Pr, Nd, Pm, Sm, and at least one light rare earth metal element of Eu, and 0.15 ≦ x ≦
0.35, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.5) 4. An amorphous magnetic film represented by the following general formula 2 which exhibits perpendicular magnetic anisotropy adjacent to the light-incident side of the first magnetic layer and having a smaller coercive force and a higher Curie temperature than the first magnetic layer. 4. The magneto-optical recording medium according to claim 1, further comprising a reproducing layer made of: [Chemical 2] (However, RE3 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er, and RE4 is C
e, Pr, Nd, Pm, Sm, and at least one kind of light rare earth metal element of Eu, and 0.15 ≦ a ≦
0.35, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.5) 5. A heat conducting layer is provided adjacent to the surface of the second magnetic layer opposite to the light incident side.
4. The magneto-optical recording medium according to any one of 4 above. 6. The magneto-optical recording medium according to claim ₁ , wherein the temperature is raised to near Tc ₁ for erasing without applying an initializing magnetic field, and the data is erased up to around Tc _2. A magneto-optical recording method, wherein recording is performed at an elevated temperature. 7. A recording bias magnetic field H satisfying the following condition in the process of heating the initialization of the second magnetic layer to near Tc _1.
7. The magneto-optical recording method according to claim 6, wherein b is used. Hc ₁ ± σw ₁ / 2Ms ₁ t ₁ >Hb> Hc ₃ + σw ₂ / 2Ms ₃ t ₃ (where Ms ₃ is the saturation magnetization of the third magnetic layer and t ₃ is the thickness of the third magnetic layer)