JPH05325288A - Magneto-optical recording method - Google Patents

Abstract

PURPOSE:To provide the magneto-optical recording method which executes overwriting with a single beam and good reliability without the impression of a magnetic field or under a weak specified bias magnetic field. CONSTITUTION:The magneto-optical recording medium constituted by providing a recording layer consisting of a reproducing layer 3 and a memory layer 4 via a protective layer 2 on a substrate 1 and further, providing a protective layer 5 thereon is used. This memory layer 4 consists of an amorphous alloy of a rare earth-transition metal. The memory layer 4 has perpendicular magnetic anisotropy and the compensation temp. Tcomp thereof satisfies 70 deg.C<=Tcomp<=200 deg.C. This reproducing layer 3 consists of the amorphous alloy of the rare earth-transition metal and has the perpendicular magnetic anisotropy. The layer is smaller in coercive force Hc and is higher in Curie temp. To than the memory layer 4. Overwritable magneto-optical recording is executed by using such magneto-optical recording medium and changing only the irradiation conditions of the light with which the magneto-optical recording medium is irradiated without using the external magnetic field or under the weak specified external magnetic field of <=200Oe.

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 method capable of overwriting under an external magnetic field or under a weak constant external magnetic field.

[0002]

2. Description of the Related Art In recent years,
As a rewritable optical recording medium, a magneto-optical recording medium utilizing a magneto-optical effect has been vigorously researched and developed, and has already been put into practical use. This magneto-optical recording medium has the advantages of large-capacity and high-density recording, non-contact recording / playback, easy access, and overwriting (overwriting), so that it can be used for document information files, video / still image files, and computers. 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 in which the polarity of an applied magnetic field is reversed according to recording information to perform recording. 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 system is a system for recording by irradiating the irradiation laser beam on / off or by modulating the intensity according to the recording information. Of these methods, the multi-beam method is a pseudo-overwrite method in which the direction of the magnetic field is reversed for each rotation and recording / erasing is performed for each track by using two or three laser beams, but the device configuration is complicated. However, there is a drawback that the cost is increased. Further, the two-layer film system is one in which the recording layer of the magneto-optical recording medium is a two-layer film in order to achieve overwrite.
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 a memory layer made of TbFe and an auxiliary layer made of TbFeCo, for example. It is intended to realize overwriting by irradiating laser beams having different powers and applied powers. That is,
In this system, prior to recording, the magnetization of the auxiliary layer is aligned in one direction with an initializing magnetic field in advance, 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. Further, 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 requires an initialization magnet.
Since temperatures near c ₁ and Tc ₂ are used for recording and erasing, there is a problem that recording sensitivity is deteriorated.

A method of overwriting using a demagnetizing field has also been proposed (Han-Ping D. Shieh and
Mark H. Kryder; Appl. Phys. Lett. 49 (1986) 473, Han-
PingD. Shieh and Mark H. Kryder; IEEE Trans. Magn.
Vol.MAG-23 (1987) 171, MD Schultz, HP D. Shieh,
and MH Kryder; J. Appl. Phys. 63 (1988) 3844). However, this method has problems that it is difficult to control the laser pulse irradiation position because it is necessary to irradiate the laser pulse at the same place as the previously recorded bit, and only bit position recording is possible.

Therefore, the present applicant proposed a new magneto-optical recording method in Japanese Patent Application No. 2-64959 to solve these problems. This method is a magneto-optical recording method in which a perpendicular magnetic film of a magneto-optical recording medium is irradiated with light to form a magnetic recording pattern, and when recording is performed by irradiating light, the magnetization to be recorded is recorded. When switching the direction of from downward to upward or from upward to downward with respect to the medium surface, the irradiation method of light such as spot diameter of irradiation light, pulse width, irradiation power, single pulse or continuous pulse, etc. Is to record the signal by changing. According to this method, unlike the above-described method using the demagnetizing field, a new signal can be written regardless of the previously written signal, which is advantageous without complicating the device configuration.

However, when overwriting is performed by this method, the reliability of overwriting may deteriorate depending on the characteristics of the medium, and there is room for improvement in terms of the characteristics of the medium used.

The present invention has been made in view of the above circumstances, and it is possible to perform reliable overwriting with a single beam under a weak constant bias magnetic field or without applying a magnetic field, and a magneto-optical recording having a good reproducing characteristic. The purpose is to provide a method.

[0009]

In order to achieve the above object, according to the present invention, a rare earth-transition metal amorphous alloy is provided, which has perpendicular magnetic anisotropy and a compensation temperature Tco.
a memory layer whose mp satisfies 70 ° C. ≦ Tcomp ≦ 200 ° C.,
The rare earth element is provided adjacent to the memory layer on the light incident side.
It consists of a transition metal amorphous alloy, has perpendicular magnetic anisotropy,
The coercive force Hc is smaller than that of the memory layer and the Curie temperature Tc
Of a magneto-optical recording medium having a recording layer composed of a reproducing layer having a large magnetic field and no irradiation of an external magnetic field or under a weak constant external magnetic field of 200 Oe or less. By providing a magneto-optical recording capable of overwriting, the magneto-optical recording method is provided.

Further, according to the present invention, in the above structure, a magneto-optical recording medium having a recording layer made of a rare earth-transition metal amorphous alloy represented by the following formula 1 is used as the magneto-optical recording medium. A featured magneto-optical recording method is provided.

[Chemical 1] (However, RE1 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er,
0.15 ≦ x ≦ 0.35 and 0 ≦ y ≦ 0.4. )

Further, according to the present invention, in the above structure, a magneto-optical recording medium having a recording layer made of a rare earth-transition metal amorphous alloy represented by the following formula 2 is used as the magneto-optical recording medium. A featured magneto-optical recording method is provided.

[Chemical 2] (However, RE1 is at least one heavy rare earth element selected from 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 ≦
0.35, 0 ≦ y ≦ 0.4, 0 ≦ z ≦ 0.5)

Further, according to the present invention, in the above structure, as the magneto-optical recording medium, Cr, N is contained in the recording layer.
There is provided a magneto-optical recording method characterized by using a magneto-optical recording medium containing at least one element selected from i, Cu, Bi, Sn, Pt, Au, Ag and Rh.

The present invention will be described in detail below with reference to the drawings. The method of the present invention is similar to the method previously proposed by the applicants,
Overwriting is performed by changing only the irradiation conditions of the light irradiating the magneto-optical recording medium, but the composition and physical properties have been specified to improve the reliability of overwriting. A magneto-optical recording medium is used.

First, a magneto-optical recording medium used in the method of the present invention will be described with reference to FIG. Magneto-optical recording medium of the configuration shown in Figure 1, glass, plastic, SiO _2, SiO on a transparent substrate 1 made of a ceramic, Si
Protective layer composed of ₃ N ₄ , AlN, etc. (film thickness 100 to 5
000Å) 2, a reproducing layer 3 and a memory layer 4 made of an amorphous magnetic film exhibiting perpendicular magnetic anisotropy are provided thereon, and SiO ₂ , SiO, Si ₃ N ₄ , AlN or the like is further formed thereon. A protective layer (film thickness 100 to 5000Å) 5 is provided. Each film can be formed by a sputtering method, a vapor deposition method, an ion plating method, or the like.

In the present recording medium, the recording layer has a two-layer structure of the reproducing layer 3 and the memory layer 4 as described above. The reproducing layer 3 is made of a rare earth-transition metal amorphous alloy and has a perpendicular magnetic property. Has a coercive force Hc smaller than that of the memory layer 4,
Curie temperature Tc is high. Curie temperature T of the reproduction layer 3
The value of c is preferably about 100 ° C to 300 ° C. Reproduction layer 3
It is preferable that the film thickness is less than 600Å.

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

[Chemical 1] (However, RE1 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er,
0.15 ≦ x ≦ 0.35 and 0 ≦ y ≦ 0.4)

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. that satisfy the above conditions are used.

In the constituent material of the reproduction layer 3, a part of the heavy rare earth metal element may be replaced with a light rare earth metal element in the above. That is, the amorphous alloy represented by the following formula 2 can also be preferably used.

[Chemical 2] (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) When a material having such a composition is used, reproduction characteristics are deteriorated when reproduction is performed using a light source in a short wavelength region. It has the advantage of being small.

Further, in order to improve the magneto-optical effect, overwrite characteristics and corrosion resistance, the constituent material of the reproducing layer 3 is
At least one element selected from the group consisting of Cr, Ni, Cu, Bi, Sn, Pt, Au, Ag and Rh may be added. In this case, the addition amount is 0.1 at% to 10a.
t% is suitable.

Next, the memory layer 4 will be described. The memory layer 4 is made of a rare earth-transition metal amorphous alloy, has perpendicular magnetic anisotropy, and has a compensation temperature Tcomp of 70 ° C. ≦ Tcomp.
Satisfies ≤200 ° C. Curie temperature Tc ≧
It shall satisfy Tc> Tcomp at 100 ° C. The coercive force Hc of the memory layer 4 is preferably about 1 to 10 KOe. The film thickness of the memory layer 4 is preferably 500 to 5000Å.

The constituent material of the memory layer 4 is Tb-F.
e, Gd-Fe, Gd-Tb-Fe, Tb-Dy-F
e, Gd-Dy-Fe, Tb-Fe-Co, Gd-Fe
-Co, Dy-Fe-Co, Tb-Dy-Fe-Co,
Gd-Tb-Fe-Co, Gd-Dy-Fe-Co, T
b-Ho-Fe-Co, Tb-Er-Fe-Co, Tb
-Nd-Fe-Co, Tb-Sm-Fe-Co, Tb-
Eu-Fe-Co or the like can be used.

In this configuration example, the recording layer has a two-layer structure,
In order to control the magnetic interaction between the reproducing layer 3 and the memory layer 4, an intermediate layer may be provided between the two layers. The material of the intermediate layer is SiN, SiO, SiO, Fe, C
o, Fe-Co, Ni, Cr, Tb, Gd, Dy, Tb
-Fe, Gd-Fe, Dy-Fe, Tb-Fe-Co,
Gd-Fe-Co, Dy-Fe-Co, Nd-Fe-C
o, Nd-Co, etc. can be used, and the film thickness is several Å to 5000 Å
Is appropriate.

On the other hand, the substrate 1 is made of glass, plastic,
Although a transparent material such as ceramics is used, it is particularly preferable to use a glass substrate because it is necessary to create a difference in temperature distribution depending on irradiation conditions in order to perform overwriting.

The layer structure of the magneto-optical recording medium used in the present invention is not limited to that shown in FIG. 1, and various modifications and changes can be made. For example, a reflective film is provided on the protective layer 5. Alternatively, the protective layers 2 and 5 may be appropriately removed.

Next, the magneto-optical recording method of the present invention will be described. The magneto-optical recording method of the present invention realizes overwriting by changing only the irradiation condition of irradiation light using the above-mentioned magneto-optical recording medium. As the external magnetic field, a small bias magnetic field of several Oe to 200 Oe may be applied during recording or erasing, or may not be applied in some cases. The irradiation conditions to be changed include the spot diameter of the irradiation light, the pulse width, the irradiation power, single pulse or continuous pulse, and the like. These may be changed alone, or two or more kinds may be changed.

A specific example of the method of changing the irradiation condition will be described here, but the present invention is not limited to the example shown here. First, as a first example, the direction of the magnetic domain of the portion to be recorded is changed from upward to downward, or
When switching from downward to upward, there is a method of changing the pulse width of irradiation light from other times. The recording and erasing operations using this method will be described below.

FIG. 2 shows the experimental results by the present inventors. The pulse width was changed to the rare earth-transition metal type amorphous magnetic film satisfying the above conditions (the laser power was also adjusted so that the irradiation energy was constant). It represents the change of the radius of the reversed magnetic domain (when returning to room temperature) and the radius of the area heated to the Curie temperature Tc or higher when laser irradiation is performed. Thus, it can be seen that the size of the written magnetic domain differs by changing the laser irradiation conditions. Further, it can be seen that there are irradiation conditions that cannot be written. Therefore, in this example, the magneto-optical recording medium having the above configuration is used, and a small bias magnetic field Hex (0 to 200 Oe) is applied in the saturation direction of the magnetization of the recording layer.
Recording and erasing are performed by combining the irradiation condition A (condition that the reversed magnetic domain becomes large) and the condition B (condition that the reversed magnetic domain becomes small). The principle is shown in FIG.
In FIG. 3, the case where a domain wall is formed is represented as “1”, and the case where a new domain wall is not formed by extending the previous magnetic domain is represented as “0”. First, as shown in (a), laser light is first irradiated under the A irradiation condition to form a large inverted magnetic domain, and "1" is recorded. After that, when recording "0", (b),
As shown in (c), laser light is irradiated under the B irradiation condition such that a part of the previous magnetic domain overlaps the irradiation spot. At that time, a small reversal magnetic domain with respect to the previous one is formed in the central portion, and the previous magnetic domain extends to the portion of the small reversal magnetic domain so that "0" recording can be performed. When this is repeated and laser light is continuously irradiated under the B irradiation condition, the previous magnetic domain is expanded more and more. And want to cut the magnetic domain,
That is, when it is desired to create a new magnetic domain wall and perform "1" recording, irradiation is performed under the A irradiation condition so that a part of the previous magnetic domain overlaps as in (d). Then, a large inverted magnetic domain is formed with respect to the previous magnetic domain, so that the previous magnetic domain cannot be extended and stops there, and "1" recording can be performed.

Other recording and erasing methods are shown in FIGS.
There is something like. In FIG. 4, in addition to the irradiation conditions of A and B in the above example, recording is performed under the irradiation conditions of A and B by using the condition A ′ of the irradiation condition for completely erasing the reversed magnetic domain.
Erasing is performed under the irradiation conditions of A'and B.

FIG. 5 shows the conditions A and A'in the method of FIG.
That is, the irradiation condition A for forming the reversed magnetic domain and the irradiation condition A'for erasing the reversed magnetic domain are used, and recording is performed under the A irradiation condition.
Erase under irradiation conditions.

In the method of the present invention, overwriting can also be realized by changing the pulse width and irradiation power, combining a single pulse and a continuous pulse, or combining DC and a pulse.

Up to now, in the case of these methods, in order to improve the erasing property at the time of overwriting, it is necessary to make the thickness of the magnetic film thicker than 750Å, and the magneto-optical effect utilizing the Faraday effect is enhanced. However, it was not possible to improve the reproduction characteristics. However, in the present invention, it is possible to improve the reproduction characteristics by providing the reproduction layer 3 adjacent to the memory layer 4 having a large film thickness and having a thin film thickness so that light can be transmitted to the light incident side. .. In this case, the magnetization of the reproducing layer 3 must be in a state in which the magnetization information of the memory layer 4 is transferred, and therefore the coercive force of the reproducing layer 3 must be smaller than that of the memory layer 4.
Further, if the magnetization information of the reproducing layer 3 is lost before the magnetization information of the memory layer 4 is lost, a read error occurs, so that the reproducing layer 3
The Curie temperature must be higher than that of the memory layer 4. The magnetization transfer between the reproducing layer 3 and the memory layer 4 may use the exchange coupling force between both layers or the magnetostatic coupling force. The magnetization information transferred to the reproducing layer 3 is read out by utilizing the magneto-optical effect using the reproducing laser light. At this time, the thickness of the reproducing layer 3 is thin enough to transmit light (600 Å or less),
Since not only the Kerr effect but also the Faraday effect can be used, the magneto-optical effect can be enhanced and the reproduction characteristics can be improved.

[0032]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to the examples 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 obtain a recording medium. Layer structure protective layer of Comparative Example: Si ₃ N ₄ (800Å) recording _{layer:. Tb 0 26 (..} Fe 0 9 Co 0 1) 0 74 (1000Å) protective _{layer:. Si 3 N 4 (500Å} ) Example 1 of the layer structure protective layer: Si ₃ N ₄ (800Å) reproducing _{layer:. (.. Gd 0 5} Tb 0 5) 0 2 (.. Fe 0 9 Co 0 1) 0.
₈ (300 Å) Memory _{layer:.. Tb 0 26 (.} . Fe 0 9 Co 0 1) 0 74 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

The coercive force of the recording layer of the medium of the comparative example is 5 KO.
e, the Curie temperature was 200 ° C., the coercive force of the reproducing layer of the medium of Example 1 was 2 KOe, the Curie temperature was 240 ° C., the coercive force of the memory layer was 5 KOe, the Curie temperature was 200 ° C., and the compensation temperature was 120 ° C. It was

The overwrite characteristics of the medium of Comparative Example 1 (conventional type) not provided with the above reproducing layer and the medium of Example 1 of the present invention were measured and compared under the following conditions. Laser power during recording: 8 mW Pulse width: 200 ns Laser power during erasing: 15 mW Pulse width: 50 ns Laser power during reproducing: 1 mW Linear velocity: 7 m / s External magnetic field: 80 Oe

Table 1 shows the C / N when a 1 MHz signal was recorded and reproduced on the mediums of Example 1 and the comparative example, and the C / N when a 2 MHz overwrite was performed thereon.

[0037]

[Table 1] From the above results, the reproduction C / N of Example 1 provided with the reproduction layer having specific magnetic characteristics was higher than that of Comparative Example,
It was found that the overwrite characteristics were also good.

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 recording medium. Protective layer: Si ₃ N ₄ (800Å) reproducing _{layer:. (.. Nd 0 25} Tb 0 75) 0 2 (.. Fe 0 9 Co 0 1) 0.
₈ (300 Å) Memory _{layer:.. Tb 0 26 (.} . Fe 0 9 Co 0 1) 0 74 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

The reproducing layer of the medium of Example 2 has a coercive force of 1 KO.
e, Curie temperature is 220 ° C, coercive force of memory layer is 5K
Oe, Curie temperature was 200 ° C., and compensation temperature was 120 ° C.

The overwrite characteristics of this medium were measured and evaluated under the following conditions. Laser power during recording: 8 mW Pulse width: 200 ns Laser power during erasing: 15 mW Pulse width: 50 ns Laser power during reproducing: 1 mW Linear velocity: 7 m / s External magnetic field: 80 Oe

Recording a signal of 1 MHz on the medium of Example 2,
Table 2 shows the C / N at the time of reproduction and the C / N at the time of performing overwriting at 2 MHz on this.

[0042]

[Table 2]

From the above results, it was found that the medium of Example 2 had better reproduction C / N and overwrite characteristics than the medium of Comparative Example. When a light rare earth element is added,
Even if the wavelength of the laser light is shortened, the magneto-optical effect hardly drops, which is advantageous.

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 prepare a recording medium. Protective layer: Si ₃ N ₄ (800Å) reproducing _{layer:. Tb 0 2 {..} (.. Fe 0 9 Co 0 1) 0 95 Cr 0 05} 0.
₈ (300 Å) Memory _{layer:.. Tb 0 26 (.} . Fe 0 9 Co 0 1) 0 74 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

The reproducing layer of the medium of Example 3 has a coercive force of 1.5.
KOe, Curie temperature 220 ° C., coercive force of memory layer 5 KOe, Curie temperature 200 ° C., compensation temperature 120
It was ℃.

The overwrite characteristics of this medium were measured and evaluated under the following conditions. Laser power during recording: 8 mW Pulse width: 200 ns Laser power during erasing: 15 mW Pulse width: 50 ns Laser power during reproducing: 1 mW Linear velocity: 7 m / s External magnetic field: 80 Oe

A signal of 1 MHz was recorded on the medium of Example 2,
Table 3 shows the C / N at the time of reproducing and the C / N at the time of overwriting at 2 MHz on this.

[0048]

[Table 3]

From the above results, it was found that the medium of Example 3 had better reproduction C / N and overwrite characteristics than the medium of Comparative Example. Further, since Cr of the reproducing layer is added, the magneto-optical effect and the corrosion resistance can be improved.

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 recording medium. Protective layer: Si ₃ N ₄ (800Å) reproducing _{layer:.. (.. Gd 0} 5 Tb 0 5) 0 2 (.. Fe 0 9 Co 0 1) 0 8
(300 Å) Intermediate layer: Si ₃ N ₄ (50Å) Memory _{layer:.. Tb 0 26 (.} . Fe 0 9 Co 0 1) 0 74 (1000
Å) Protective layer: Si ₃ N ₄ (500 Å)

The reproducing layer of the medium of Example 4 has a coercive force of 2 KO.
e, Curie temperature is 240 ° C, coercive force of memory layer is 5K
Oe, Curie temperature was 200 ° C., and compensation temperature was 120 ° C.

The overwrite characteristics of this medium were measured and evaluated under the following conditions. Laser power during recording: 8 mW Pulse width: 200 ns Laser power during erasing: 15 mW Pulse width: 50 ns Laser power during reproducing: 1 mW Linear velocity: 7 m / s External magnetic field: 80 Oe

A signal of 1 MHz was recorded on the medium of Example 4,
Table 4 shows the C / N at the time of reproduction and the C / N at the time of performing an overwrite of 2 MHz on this.

[0054]

[Table 4]

From the above results, it was found that the medium of Example 4 had better reproduction C / N and overwrite characteristics than the medium of Comparative Example. Further, since the intermediate layer is provided between the reproducing layer and the memory layer, the exchange magnetic interaction between the two layers can be controlled, so that the overwrite characteristic and the reproducing C / N can be optimized.

[0056]

According to the first aspect of the present invention, since the medium having the reproducing layer adjacent to the memory layer and having the smaller coercive force Hc and the higher Curie temperature Tc on the light incident side is used, Overwriting can be reliably performed only by changing the irradiation conditions of the irradiation light without using an external magnetic field or under a weak constant external magnetic field, and the reproduction C / N can also be improved.

According to the second aspect of the invention, since a material having a specific composition is used as the constituent material of the memory layer of the medium, overwriting can be performed more reliably only by changing the irradiation conditions of the irradiation light. The reproduction C / N is also improved.

According to the invention of claim 3, since a light rare earth metal is partially used as the rare earth metal, in addition to the above effects,
The wavelength of recording can be shortened.

According to the invention of claim 4, C is contained in the recording film.
r, Ni, Cu, Bi, Sn, Pt, Au, Ag, Rh
Since at least one of these elements is added, the magneto-optical effect, overwrite characteristics and corrosion resistance are further improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of the layer structure of a magneto-optical recording medium used in the method of the present invention.

FIG. 2 is a diagram showing a change in radius of an inverted magnetic domain and a radius of an area heated to a Curie temperature Tc or higher when laser irradiation is performed with a pulse width changed on a magnetic film having specific magnetic characteristics. ..

FIG. 3 is a diagram illustrating the principle of recording and erasing in an example recording method according to the present invention.

FIG. 4 is an explanatory diagram of another example in which irradiation conditions of irradiation light are changed.

FIG. 5 is an explanatory diagram of still another example in which the irradiation condition of irradiation light is changed.

[Explanation of symbols]

 1 substrate 2, 5 protective layer 3 reproduction layer 4 memory layer

Front page continuation (72) Inventor Masaetsu Takahashi 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Inventor Koji Deshi 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh, Inc. (72) Inventor Saiaki Saiki 1-3-6 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd. (72) Inventor Miko Kurosawa 1-3-3 Nakamagome, Ota-ku, Tokyo In Ricoh Co., Ltd.

Claims (4)

[Claims] 1. A rare earth-transition metal amorphous alloy,
It has perpendicular magnetic anisotropy and the compensation temperature Tcomp is 70 ° C. ≦
A memory layer satisfying Tcomp ≦ 200 ° C., a rare earth-transition metal amorphous alloy which is provided adjacent to the memory layer on the light incident side and has perpendicular magnetic anisotropy; Using a magneto-optical recording medium having a recording layer composed of a reproducing layer having a small coercive force Hc and a high Curie temperature Tc, the magneto-optical recording is performed without using an external magnetic field or under a weak constant external magnetic field of 200 Oe or less. A magneto-optical recording method, wherein overwritable magneto-optical recording is performed by changing only an irradiation condition of light applied to a medium. 2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is a magneto-optical recording medium whose reproducing layer is composed of a rare earth-transition metal amorphous alloy represented by the following formula (1). Recording method. [Chemical 1] (However, RE1 is a heavy rare earth metal element of at least one of Tb, Gd, Dy, Ho and Er,
0.15 ≦ x ≦ 0.35 and 0 ≦ y ≦ 0.4) 3. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is a magneto-optical recording medium whose reproducing layer is composed of a rare earth-transition metal amorphous alloy represented by the following formula (2). Recording method. [Chemical 2] (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) 4. A magneto-optical recording medium in which at least one element of Cr, Ni, Cu, Bi, Sn, Pt, Au, Ag and Rh is added to the reproducing layer as the magneto-optical recording medium. The magneto-optical recording method according to any one of claims 1 to 3, wherein