JPH08194976A - Magnetooptic recording medium and magnetooptic recording method - Google Patents

Abstract

PURPOSE: To realize highly reliable overwriting with low initial field by providing respective magnetic layers constituting a magnetooptic recording medium while satisfying specified properties and conditions. CONSTITUTION: A recording layer comprises a laminated structure of first magnetic layer 3, a second magnetic layer 4 and a third magnetic layer 5 having properties and conditions satisfying following expressions; Tcomp3 <Troom< Tc≈Tcomp2 < Tc2 Hc1 >Hc2 >Hc3 Hc1 >δw1 /2Ms1 t1 δw1 /2Ms2 t2 <Hc2 <δw2 /2Ms2 t2 , where Ms1 , Ms2 represents saturation magnetization of first and second magnetic layer, Hc1 -Hc3 and Tc1 -Tc3 represents coersive force and Curie point of first to third magnetic layers 3, 4, 5. t1 , t2 represents the thickness of first and second magnetic layer 3, 4, Tcomp2 , Tcomp3 represents the compensation temperature of second and third magnetic layers 4, 5, Tr represents the room temperature and δw1 , δw2 represents the interface domain wall energy between first and second magnetic layers and second and third magnetic layers, respectively.

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 with a low 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 having a large magnetic field is required.

The present invention has been made in view of the above-mentioned state of the art, and provides a magneto-optical recording medium and a magneto-optical recording method which can be overwritten with high reliability in a low initializing magnetic field and have good reproduction characteristics. With the goal.

[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 Tc ₃ , the room temperature is Troom, and the interface wall energy between the first magnetic layer and the second magnetic layer is σw. ₁ , the interfacial domain wall energy between the second magnetic layer and the third magnetic layer is σw ₂
There is provided a magneto-optical recording medium characterized by satisfying the following conditions. _{Tcomp 3 <Troom <Tc 3 <} Tc 1 ≒ Tcomp 2 <Tc 2 Hc 1> Hc 2> Hc 3 Hc 1> σw 1 / 2Ms 1 t 1 σw 1 / 2Ms 2 t 2 <Hc 2 <σw 2 / 2Ms 2 t ₂

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.

Embedded image (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 ≦
0.4, 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.

Embedded image (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 ≦
0.4, 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 third magnetic layer opposite to the light incident side. To be done.

Further, according to the present invention, using any of the magneto-optical recording medium described above, performs initialization by applying a low initializing magnetic field, it erases by Tc ₁ near MadeNoboru temperature, Tc ₂ There is provided a magneto-optical recording method, which is characterized in that recording is performed by raising the temperature to the vicinity.

Further, according to the present invention, there is provided a magneto-optical recording method having the above-mentioned structure, wherein the initialization of the second magnetic layer is performed by using an initialization magnetic field Hini satisfying the following condition. . Hc ₁ ± σw ₁ / 2Ms ₁ t ₁ >Hini> Hc ₃ + σw ₂ / 2Ms ₃ t
₃ (where Ms ₃ is the saturation magnetization of the third magnetic layer, t ₃ is the thickness of the third magnetic layer)

The present invention will be described below in detail with reference to the drawings. FIG.
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 (having a thickness of 100 to 5000Å) 2 made of N or the like is provided, and a first magnetic layer 3, a second magnetic layer 4, and a third magnetic layer 5 each made of an amorphous magnetic film exhibiting perpendicular magnetic anisotropy are provided thereon. Are provided in that order, and SiO ₂ and
Protective layer made of SiO, Si ₃ N ₄ , AlN, etc. (film thickness 1
00 to 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.

Embedded image (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 ≦
0.4, 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.

Embedded image (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 ≦
0.4, 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.

Embedded image (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 ≦
0.4, 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 , the Curie temperature is Tc ₂ , the film thickness is t ₂ , the coercive force of the third magnetic layer 5 is Hc ₃ , the compensation temperature is Tcomp ₃ , and the Curie temperature is Tc ₃ .
c _3, Troom to room temperature, the interface wall energy between the first magnetic layer 3 and the second magnetic layer 4 .sigma.w _1, the interface wall energy between the second magnetic layer 4 and the third magnetic layer 5 is taken as .sigma.w ₂ The following conditions must be met. _{Tcomp 3 <Troom <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) σw 1 / 2Ms _{2 t 2 <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. In addition, the magnetization of the second magnetic layer 4 is surely set to the first
In order to transfer the magnetization to the magnetic layer 3, Tcomp ₂ and Tc ₁ must be substantially equal (| Tcomp ₂ −Tc ₁ | <30 ° C.), and Tcomp ₂ must be smaller than Tc ₂ . Further, in order to eliminate the influence of the magnetization of the third magnetic layer 5 at the time of erasing and recording operations, initialization is performed in a magnetic field as low as possible, so that Tcomp ₃ <Troom <Tc ₃
<It must be Tc ₁ . Tc ₁ is suitably 140 to 220 ° C., Tc ₂ is suitably 220 to 300 ° C.
70 to 140 ° C. is suitable for c ₃ .

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 . In addition, the second magnetic layer 4
Since the magnetization of the third magnetic layer 5 is used to ensure the initialization of the above, 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 is used to ensure 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, and to ensure the initialization using the magnetization of the third magnetic layer 5 ( 4) must be satisfied. Hc ₁ is suitably 5 KOe or more, Hc ₂ is suitably 0.5 to ₃ KOe, and Hc ₃ is suitably 0.5 KOe or less. Ms ₁ is 0 to 150 em
u / cc is suitable and Ms ₂ is 100 to 300 emu /
cc is suitable. Those satisfying the above conditions (1) to (4) change the magnetization direction of the second magnetic layer 4 by applying a low initialization magnetic field of about 0.5 to 2.5 KOe for initialization. Since it can be changed by the laser irradiation temperature and the magnetization can be transferred to the first magnetic layer 3 by the exchange coupling force, overwriting can be performed.

Although the recording layer has a three-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]

Embedded image (where RE3 is at least one heavy rare earth metal element selected from Tb, Gd, Dy, Ho and Er, R 3
E4 is a light rare earth metal element of at least one of Ce, Pr, Nd, Pm, Sm and Eu, and is 0.15
≦ a ≦ 0.4, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.5)

[0028] Specifically, Tb-Fe, Gd-Fe, Gd-Tb-F
e, Tb-Dy-Fe, Gd-Dy-Fe, Tb-Fe
-Co, Gd-Fe-Co, Dy-Fe-Co, Tb-
Dy-Fe-Co, Gd-Tb-Fe-Co, Gd-D
y-Fe-Co, Tb-Ho-Fe-Co, Tb-Er
-Fe-Co, etc., and Ce, Pr, Nd, P
A material to which at least one kind of light rare earth element of m, Sm and Eu is added is used. The thickness of the reproducing layer needs to be thin enough to transmit light.
The optimum value is 0Å or less. 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 preferably 0.1 to 2 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. Therefore, the Curie temperature Tcr of the reproducing layer 9 must satisfy the condition of Tcr> Tc _1. should not. Tcr is 120 to 3
It is preferably 00 ° C. The magnetization information transferred to the reproducing layer 9 is read out by utilizing the magneto-optical effect using the reproducing 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 third magnetic layer 5 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. The method of the present invention performs recording and erasing by changing the power of irradiation light using a low initialization magnetic field Hini. This initialization magnetic field needs to satisfy the following conditions. Hi
The specific value of ni is 0.5 to 2.5 KOe, preferably 1 to 2.5 KOe. Also, the bias magnetic field Hb
As 200 to 800 Oe, preferably 300 to 60
A magnetic field of 0 Oe is used. Hc ₁ ± σw ₁ / 2Ms ₁ t ₁ >Hini> 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. When erasing in the present invention, after passing through the bottom of the initializing magnetic field, by irradiating a lower laser power (PL), near Tc ₁ membrane temperature T (Tc ₁ -30 ≦
Increase to T ≦ Tc ₁ +30 [° 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 direction opposite to the energy-stable magnetization of the second magnetic layer 4 due to the exchange coupling force of the magnetization of the second magnetic layer 4. When the initialization magnetic field Hini is applied thereto, Hc ₃ is small first, so that the magnetization of the third magnetic layer 5 is reversed in the magnetic field direction of the initialization magnetic field Hini, and then the third magnetic layer 5 and the second magnetic layer 4 are exchanged. By the binding force,
The magnetization of the second magnetic layer 4 is oriented in the direction opposite to the third magnetic layer 5 (the direction opposite to Hini). This completes the initialization.
When laser irradiation is performed after this initialization, the film temperature of the irradiated portion rises to near the Curie temperature Tc _{1 of} the first magnetic layer 3, so that the magnetization of the first magnetic layer 3 gradually decreases,
At Tc ₁ , it becomes zero, and the initialized magnetization of the second magnetic layer 4 is frozen as it is because Hc ₂ becomes very large near 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 (facing the opposite direction to the magnetization of the second magnetic layer 4), and the room temperature Tro is reached.
When returning to om, Hc ₁ is so large that it is frozen as it is. The magnetization of the third magnetic layer 5 is oriented in the opposite direction to the magnetization of the second magnetic layer 4 due to the exchange coupling force with the second magnetic layer 4 during the temperature decrease process. 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 -30 ≦ 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 near Tc 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 third magnetic layer 5 is oriented in the opposite direction to 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,
Since recording and erasing are performed by using the third magnetic layer 5 having a small coercive force Hc _3, the initializing magnetic field is low, the device can be downsized, and the stability of the recording magnetic domain is excellent. ing.

[0035]

Hereinafter, embodiments of the present invention will be described.
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 (} 900Å) 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 (} 900Å) the first magnetic _{layer: Tb 0 21 (Fe 0 9} Co 0 . _{1) 0.79} (500
Å) second magnetic layer:..... (Gd 0 6 Tb 0 4) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (600Å) the third magnetic _{layer:. Tb 0 17 Fe 0 83} (1000Å) protective _{layer:. Si 3 N 4 (500Å} )

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]

Regarding σw, the medium of the comparative example is 2.2 erg / cm ² , and the medium of Example 1 is σw ₁ = 1.
9 erg / cm ² , σw ₂ = 3.2 erg / cm ² ,
The value of σw / 2Mst is σw / 2 in the medium of the comparative example.
Ms ₁ t ₁ = 6.5 KOe, σw / ₂ Ms ₂ t ₂ = 0.4 KOe
And in the medium of Example 1, σw ₁ / 2Ms ₂ t ₂ = 1.0
_{KOe, σw 2 / 2Ms 2 t} 2 = 1.6KOe, σw 1 / 2Ms 1
t ₁ = 5.6 KOe and σw ₂ / 2Ms ₃ t ₃ = 1.0 KOe.

With respect to the mediums of Comparative Example and Example 1 produced as described above, the overwrite characteristics were measured and compared under the following conditions. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Initializing magnetic field (Comparative Example medium): 3 KOe (Example 1 medium): 1.5 KOe Bias magnetic field: 0.4KOe

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, even when the initializing magnetic field was lowered, could obtain the overwrite characteristic equivalent to that when the conventional high initializing magnetic field was 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 (900Å) 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 6 Tb 0 4) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (600Å) Intermediate _{layer:.. Gd 0 35 (.} . Fe 0 85 Co 0 15) 0 65 (40
Å) third magnetic _{layer:. Tb 0 17 Fe 0 83} (1000Å) protective _{layer:. Si 3 N 4 (500Å} )

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. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Initializing magnetic field: 1.5 KOe Bias magnetic field: 0.4 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, 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). 1)
It was found that the overwrite characteristic was further improved.

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 (900Å) 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 6} Tb 0 4) 0 28 (.. Fe 0 85 Co 0 15)
. _{0 72} (600Å) the third magnetic _{layer:. Tb 0 17 Fe 0 83} (1000Å) protective _{layer:. Si 3 N 4 (500Å} )

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. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Initializing magnetic field: 1.5 KOe Bias magnetic field: 0.4 KOe

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 (900Å) 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 6 Tb 0 4) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (600Å) the third magnetic _{layer:. Tb 0 17 Fe 0 83} (1000Å) protective _{layer:. Si 3 N 4 (500Å} )

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. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Initializing magnetic field: 1.5 KOe Bias magnetic field: 0.4 KOe

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 (900Å) 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 6 Tb 0 4) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (600Å) the third magnetic _{layer:. Tb 0 17 Fe 0 83} (1000Å) protective _{layer:. Si 3 N 4 (500Å} )

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. Laser power during recording: 12 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Initializing magnetic field: 1.5 KOe Bias magnetic field: 0.4 KOe

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 (900Å) the first magnetic _{layer:.. Tb 0 21 (.} . Fe 0 9 Co 0 1) 0 79 (500
Å) second magnetic layer:..... (Gd 0 6 Tb 0 4) 0 28 (Fe 0 85 Co 0 15)
. _{0 72} (600Å) the third magnetic _{layer:. Tb 0 17 Fe 0 83} (1000Å) thermally conductive layer:. Al (1000Å) protective layer: Si ₃ N ₄ (500Å)

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. Laser power during recording: 13 mW Laser power during erasing: 6 mW Laser power during reproducing: 1 mW Linear velocity: 7 m / s Initializing magnetic field: 1.5 KOe Bias magnetic field: 0.4 KOe

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 invention of claim 1, by stacking the first magnetic layer, the second magnetic layer and the third magnetic layer satisfying the above conditions, overwriting is possible with a low initialization magnetic field. Media 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 invention of claim 6, by using the medium as described above, the temperature is raised to around Tc ₁ to perform erasing, and the temperature is raised to around Tc ₂ to perform recording, whereby a low initialization magnetic field is obtained. Overwriting is possible with. (7) According to the invention of claim 7, by limiting the initialization magnetic field Hini to a value within a predetermined range, overwriting can be performed with higher reliability.

[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 Tc _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. _{Tcomp 3 <Troom <Tc 3 <} Tc 1 ≒ Tcomp 2 <Tc 2 Hc 1> Hc 2> Hc 3 Hc 1> σw 1 / 2Ms 1 t 1 σw 1 / 2Ms 2 t 2 <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. Embedded image (However, RE1 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er, and RE2 is C.
e, Pr, Nd, Pm, Sm, and at least one kind of light rare earth metal element of Eu, and 0.15 ≦ x ≦ 0.4, 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: Embedded image (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 Eu, which are at least one kind of light rare earth metal element, and 0.15 ≦ a ≦ 0.4, 0 ≦ b ≦ 0.4, 0 ≦ c ≦ 0.
5) 5. A heat conducting layer is provided adjacent to the surface of the third 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 a low initializing magnetic field Hini is applied for initialization, and the temperature is raised to around Tc ₁ for erasing. , Tc ₂ , the magneto-optical recording method is characterized in that the recording is carried out by raising the temperature. 7. The magneto-optical recording method according to claim 6, wherein the initialization of the second magnetic layer is performed by using an initialization magnetic field Hini satisfying the following condition. Hc ₁ ± σw ₁ / 2Ms ₁ t ₁ >Hini> Hc ₃ + σw ₂ / 2Ms ₃ t
₃ (where Ms ₃ is the saturation magnetization of the third magnetic layer, t ₃ is the thickness of the third magnetic layer)