JPH03216831A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve recording sensitivity and to enable overwriting by constituting the magnetic layer of a recording layer, first auxiliary layer and second auxiliary layer with each Curie temp. satisfying the specified relation. CONSTITUTION:On a substrate 1, a magnetic layer that consists of a recording layer 4, first auxiliary layer 5 and second auxiliary layer 6 is provided. The Curie temp. T1, T2, T3 of these layers, respectively, satisfy relations T1<T2, T2>=T3. By this method, magnetic bonds generate between the recording layer 4 and the first auxiliary layer 5, and between the first auxiliary layer 5 and second auxiliary layer 6, and moreover, the first and second auxiliary layers 5, 6 as are integrally magnetized and inverted at room temp., and this inverted magnetic field (coercive force) is made smaller than the coercive force of the recording layer 4. Thus, the recording sensitivity is improved and overwriting becomes possible.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a magneto-optical recording medium used in recording devices and the like.

[Prior Art] Magneto-optical recording is optical recording that allows information to be recorded, reproduced, and erased. In addition to these functions, new magneto-optical recording systems that allow overwriting have recently been proposed. Magneto-optical recording systems that allow overwriting can be broadly divided into two types: magnetic field modulation systems and optical intensity modulation systems. When comparing the two methods, the latter method is more advantageous because it is capable of high-speed modulation and high-speed recording, and can have a structure in which two magneto-optical recording media are bonded together. . In order to realize the light intensity modulation method, Japanese Patent Application Laid-Open No. 62-17
A magneto-optical recording medium such as that described in No. 5948 is used. That is, as the magnetic layer used in the recording medium, an exchange-coupled two-layer film with magnetic coupling is used. 2 to 5 are explanatory diagrams of a conventionally known light intensity modulation method using an exchange-coupled two-layer film. The magnetic film used for recording consists of two layers: an auxiliary layer and a recording layer. As shown in FIG. 2, at room temperature Tr, the coercive force 8 of the recording layer is larger than the coercive force 9 of the auxiliary layer, and the Curie temperature T of the auxiliary layer is higher than the Curie temperature T0 of the recording layer. Configure. In recording, first, as shown in FIG. 3, the magnetization 18 of the auxiliary layer 15 is aligned in the direction of the initializing magnetic field 13 by the initializing magnet 17. Here, the magnitude of the initialization magnetic field 13 is set to be larger than the coercive force 9 of the auxiliary layer 15 at room temperature and smaller than the coercive force 8 of the recording layer 4, as shown in FIG. Even if the magnetic field 13 is applied, the direction of the magnetization 19 of the recording layer 4 does not change. When recording information, the intensity of the laser beam is adjusted to a high laser power level (hereinafter referred to as P}l) 2 as shown in FIG. 6 under a bias magnetic field 14 of a constant strength shown in FIG.
3 and a low laser power level (hereinafter referred to as PL) 24. Figure 4(a) or Figure 5(a)
As shown in FIG. 2, the laser beam 20 is focused by a focusing lens 21 and irradiated onto the magnetic film. Laser light intensity is P
When I4, the laser beam 20 is emitted as shown in FIG. 4(a).
Since the temperature of the area irradiated by is close to the Curie temperature T of the auxiliary layer 15, the magnetization of the recording layer 4 disappears, and the magnetization of the auxiliary layer 15 moves in the direction of the bias magnetic field 14 applied by the permanent magnet 22. Turn. When the laser beam irradiation is finished and the magnetic film is cooled, magnetization of the recording layer 4 is also generated in the direction of the bias magnetic field 14, as shown in FIG. 4(b). On the other hand, when the laser beam intensity is P, as shown in FIG. 5(a), the temperature of the area irradiated with the laser beam 20 becomes close to the Curie temperature TIl of the recording layer 4. Therefore, as shown in FIG. 2, the coercive force 9 of the auxiliary layer 15 is larger than the bias magnetic field 14, so no reversal of magnetization occurs. When the laser beam irradiation ends and the magnetic film cools, the magnetization of the recording layer 4 has a larger exchange coupling force than the magnetization of the auxiliary layer 15 and the bias magnetic field 14, so the magnetization of the recording layer 4 also decreases. It faces in the opposite direction to the bias magnetic field 14.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional technology, in order to align the magnetization of the recording layer 4 with the magnetization of the auxiliary layer 15 using exchange coupling force during PL irradiation, the film thickness of the auxiliary layer 15 is It needs to be thicker than the film thickness of 4, and about 1000 people? A depth of 2,000 people was required. Therefore, the total thickness of the recording layer 4 is 15
00 to 3,000 people, so PL.
There was a problem that the power of PH was extremely large. An object of the present invention is to provide a magneto-optical recording medium that has an exchange-coupled double layer film and has improved recording sensitivity. Another object of the present invention is to provide an overwritable magneto-optical recording medium with improved recording sensitivity. [Means for Solving the Problems] The above objects are (1) a magneto-optical recording medium having at least a substrate and a magnetic layer provided on the substrate, wherein the magnetic layer is a recording layer, a first auxiliary layer, It consists of a second auxiliary layer, and when the Curie temperatures of the recording layer, the first auxiliary layer, and the second auxiliary layer are T, T2, and T, respectively, the following relationship is satisfied: A magneto-optical recording medium characterized by (
2) Curie temperature T2 of the first auxiliary layer and second auxiliary layer,
(3) Curie temperatures T1, T2 of the recording layer, the first auxiliary layer, the second auxiliary layer; The magneto-optical recording medium according to 1 or 2 above, wherein T is in the range of 100°C≦T≦250°C, 150°C≦T2≦350°C, and 100°C≦T≦300°C, respectively; (4) The magnetization of the first auxiliary layer and the second auxiliary layer is reversed together at room temperature, and the coercive force of the first auxiliary layer and the second auxiliary layer at that time is smaller than the coercive force of the recording layer. (5) The optical recording medium according to item 4, wherein the composition of the second auxiliary layer changes continuously in the film thickness direction. (6) the magneto-optical recording medium according to (4) above, wherein the second auxiliary layer is composed of a plurality of layers having different compositions; (7) the coercive force of the second auxiliary layer is set to 1 Did you make the coercive force smaller than that of the auxiliary layer? (8) A magneto-optical recording medium having a substrate and at least a magnetic layer on the substrate, wherein the magnetic layer comprises a recording layer, a first auxiliary layer, and a second auxiliary layer. The recording layer,
When the Curie temperatures of the first auxiliary layer are T and T2, the following relationship is satisfied, and the Curie temperatures of the first auxiliary layer and the second auxiliary layer are substantially the same, A magneto-optical recording medium characterized in that the coercive force of the second auxiliary layer at a temperature near the Curie temperature is smaller than the coercive force of the first auxiliary layer, (9)
The magnetization of the first auxiliary layer and the second auxiliary layer is reversed together at room temperature, and the coercive force of the first auxiliary layer and the second auxiliary layer at that time is smaller than the coercive force of the recording layer. This is achieved by the magneto-optical recording medium as described in 8 above. In the present invention, the magnetic layer has three layers, for example, as shown in FIG. 7, from the side closest to the substrate, a recording layer 4, a first auxiliary layer 5, and a second auxiliary layer 6. Furthermore, the Curie temperature of each layer is configured to satisfy the above relationship. ? The Curie temperature T2 of the recording layer is preferably 100° C. or more and 250° C. or less in order to increase the rotation angle per force to some extent. The Curie temperature T2 of the first auxiliary layer is the Curie temperature T2 of the recording layer. Since the temperature must be set higher than 150° C. or more and 350° C. or less, it is desirable. The Curie temperature T of the second auxiliary layer is the Curie temperature T2 of the first auxiliary layer.
It must be lower than 100℃ or higher than 300℃.
Desirably below ℃. Furthermore, each Curie temperature is 1
50℃≦T1≦210℃, 200℃≦T2≦300℃,
More preferably, the range is 150°C≦T and ≦250°C. The thickness of the recording layer is preferably in the range of 100 to 800 layers, the thickness of the first auxiliary layer is preferably in the range of 400 to 1,500 layers, and the thickness of the second auxiliary layer is preferably in the range of 100 to 1,000 layers. Preferably within the human range. Furthermore, magnetic coupling forces act between the recording layer and the first auxiliary layer, and between the first auxiliary layer and the second auxiliary layer, and as shown in the magnetization vs. magnetic field curve in FIG. The magnetization of the second auxiliary layer is preferably reversed as a unit, and the coercive force 25 at this time is preferably smaller than the coercive force 26 of the recording layer. In the magnetic layer, R is a rare earth element and T is Fe. Co, Ni
When M is a transition metal, the general formula is (RXTI-x)x-YMY. It is preferable to use a material expressed by 0.1≦X≦0.4 and O≦Y≦0.2. For example, Tb-Fe, T
b-Fe-Co. Tb-Dy-Fe-Co. Gd-
Tb-Fe and a small amount of Cu. W. T1,
V. Cr. Sn. Pb, MO, Nb. Pt.
Pd. A material containing at least one type of Rh or the like is used. Since the recording layer is a layer responsible for recording and reproducing information, it is preferable to determine the material composition so that the rotation angle per force is large. For this purpose, for example, Tb-Fe-Co,
Gd-Tb-Fe. Compositions such as Tb-Dy-FeCo are preferred. Furthermore, since the direction of magnetization of the first auxiliary layer must be easily reversed by the initializing magnetic field, it is preferable to determine the material composition so that the first auxiliary layer has a relatively small coercive force at room temperature. For this purpose, for example, Tb-Dy-Fe-
Co, Gd-Dy-Fe-Co, Gd-Tb-Fe, and materials to which a small amount of 31, pb, etc. are added are used. The second auxiliary layer is Tb-Fe-Co. Gd-Tb-Fe
．． Gd-Fe-Co. Tb-Dy-Fe-Co.
A composition such as Gd-Dy-Fe-Co is used. The elements constituting the second auxiliary layer are preferably the same as the elements constituting the first auxiliary layer. For example, Tb-D in the first auxiliary layer
If y-Fe-Co is used, the second auxiliary layer is Tb-Dy-Fe-Co, which has a lower Curie temperature than the first auxiliary layer.
Use. However, even if the constituent elements are different, the first auxiliary layer and the second auxiliary layer can have a property of reversing their magnetization together at room temperature. For example, the first auxiliary layer can be made of Tb-Fe and the second auxiliary layer can be made of Dy-Fe. Further, the second auxiliary layer may be constructed so that its composition changes continuously. Furthermore, the second auxiliary layer may be further composed of several laminated films. In either case, it is necessary that the Curie temperature of the second auxiliary layer be substantially the same as or lower than the Curie temperature of the first auxiliary layer. As the substrate, glass, polycarbonate, polymethyl methacrylate, etc. are used. Further, it is preferable to provide a dielectric layer on one or both sides of the three magnetic layers. As the dielectric layer, silicon nitride, aluminum nitride, silicon oxide, aluminum oxide, etc. are used.

[Effect 1] When the laser beam enters from the recording layer side, the magnetic layer is heated as shown in Figure 9, creating a temperature distribution 27 where the temperature is high on the recording layer side and low on the second auxiliary layer side. . P
When irradiated with H-level laser light, this temperature distribution is higher than the Curie temperature T1 of the magnetic layer in the recording layer part, and higher than the Curie temperature T1 of the magnetic layer in the first auxiliary layer part.
2, and furthermore, the second auxiliary layer portion is formed to have a Curie temperature T3 higher than the Curie temperature T3 of the magnetic layer. Therefore, even if the absolute value of the temperature of the second auxiliary layer is not so high, as shown in FIG. 3
0 disappears, the laser beam irradiation ends, and each layer cools down, as shown in FIG. 11(b)? The respective magnetizations are oriented in the direction of the bias magnetic field 14 so as to be reversed from their initial states. T, the vertical relationship between T2 and T3 is not limited to the case shown in Figure 9 (T3<T, <T2), but <T1<T
．． Of course, the same effect can be obtained even if <72. The above is a description of recording during PH irradiation, but the initialization of the magnetic layer and the recording (to be precise, erasing) operation during PL irradiation are also the same in principle as in the prior art. That is, as shown in FIG. 10, before recording, the magnetizations 29 and 30 of the first and second auxiliary layers 5 and 6 are aligned in the direction of the initializing magnetic field l3 by the initializing magnet 17. Here, as shown in FIG. 8, the magnitude of the initializing magnetic field 13 is determined by
It is set to be larger than the coercive force 25 of the auxiliary layer and smaller than the coercive force 26 of the recording layer. Therefore, as shown in FIG. 10, even if the initialization magnetic field 13 is applied, the direction of the magnetization 19 of the recording layer does not change. When the laser light intensity is PL, as shown in FIG. 12(a), the temperature of the area irradiated by the laser light 20 is . The Curie temperature of the recording layer approaches T■. At this time, the first
The coercive force of the second auxiliary layer is set to be larger than the bias magnetic field 14, similar to the coercive force 9 of the auxiliary layer in a conventional magneto-optical recording medium, so that reversal of magnetization does not occur. When the laser beam irradiation is finished and the magnetic film is cooled, the magnetization 19 of the recording layer has a larger exchange coupling force with the magnetization 29 of the first auxiliary layer than the bias magnetic field 14, so that as shown in FIG. (b
), the magnetization 19 of the recording layer 4 is also affected by the bias magnetic field 1.
Facing in the opposite direction from 4. Note that the magnitude of the exchange coupling force is determined by using the saturation magnetization and film thickness of each magnetic layer as MS, h1, Ms2, h2, . Ms. ,,h3, and when the domain wall energies of the recording layer, the first auxiliary layer interface, and the first and second auxiliary layer interfaces are σ and σ−, the exchange coupling force acting on the recording layer as a magnetic field Hexc... Hexc, = a w. /2Ms. h. ,
Exchange coupling force acting on the first auxiliary layer...Hexc2,
= a w1/2 Mszhz (for recording layer)
Hexc23=: a W, / 2 Mszhz (
Exchange coupling force acting on the second auxiliary layer (relative to the second auxiliary layer)...
・・・・Hexc,=a w. / 2 M S, h
It is expressed as l. Therefore, in order to control the magnitude of the exchange coupling force, the domain wall energy σW, the recording layer, the first
, Ms and h of the second auxiliary layer may be controlled. In order to control the domain wall energy, for example, (1) after forming each layer, maintain it in an argon gas atmosphere containing nitrogen gas to reduce the domain wall energy, (2) sputter-etch the surface of each layer to reduce the domain wall energy. Techniques such as increasing the In addition, in order to control saturation magnetization, V.
Cr. Mn, Cu. Sn. Techniques such as adding trace elements such as Sb are used. Even if the first auxiliary layer and the second auxiliary layer are made of materials with the same Curie temperature, the coercive force near the Curie temperature is higher in the second auxiliary layer than in the first auxiliary layer. If configured to be small, the same effect as described above can be obtained. [Example] Hereinafter, an example of the present invention will be described with reference to FIG. Example 1 On a circular glass substrate 1, an ultraviolet curable resin layer 2 having groups formed at a pitch of 1.6 μm has a thickness of 30 μm.
Only m are provided. The following film was formed thereon by sputtering. First, a silicon nitride film 3 was laminated by 850 people. Sputtering was carried out at a pressure of 1.times.10@-2 Torr using silicon as a target and a mixed gas of argon and nitrogen as sputtering gas. By changing the mixing ratio of nitrogen gas, it is possible to control the refractive index of silicon nitride. Here, the refractive index is 2.
The nitrogen gas mixing ratio was set to 10% so that the temperature was 0. Next, as a recording layer, Tb2 and F having a Curie temperature T of 170°C are used.
e, 2Co, 400 people, TbxtDyxcFesoCOit film with T2 of 250°C as the first auxiliary layer 5, 10
00 people, T as the second auxiliary layer 6, TELx at 200℃
sDyzoFessCOto membranes were laminated by 500 people. As a target, Tb. D
y. A composite target on which Co or other chips were arranged was used. Of course, an alloy target may also be used. Finally, in order to prevent the magnetic layers 4, 5, and 6 from being oxidized and corroded, a silicon nitride film 7 was formed by only 1000 people. When the thus completed magneto-optical recording medium 25 was irradiated with laser light and recorded, the characteristics shown in Table 1 were obtained. As a comparative example, Tc was used as an auxiliary layer on the recording layer.
A magneto-optical recording medium is shown in which a Tt)xtDytiFesocOxt film having a temperature of 250° C. is provided with a thickness of 1500 mm. The thickness of the magnetic layer of both magneto-optical recording media is 1900 mm, but when the linear velocity is 11 m/see, the IMHz signal (duty 5
0%) and the minimum recording power required to record 13n
The carrier wave-to-noise ratio C/N during signal reproduction when recorded with +W laser light is 8 for each of the magneto-optical recording media of the present invention.
mW. It was 55 dB. In contrast, in the magneto-optical recording medium of the comparative example, the output power remained at 10 mW and 50 dB, respectively. In this magneto-optical recording medium, the recording power is 2I
The sensitivity is as high as oW, and therefore, when recording with the same recording power (13n+W), a larger recording magnetic domain (mark) is formed, and the C/N is also improved. (Leaving space below) Table 1 Examples 2 to 6 A magneto-optical recording medium was prepared in the same manner as in Example 1, except that the materials for the recording layer, first and second auxiliary layers were as shown in Table 2. did. For example, in Example 2, the recording layer is Tb,
, FeGICo, film (T, = 200°C, h1 =
Gd24FeG.500) as the first auxiliary layer. co
．． The membrane (T2 = 300°C, h, : 500 people) was
Gd as an auxiliary layer. rbl2Fe7. co. Membrane (chi=170℃, h3=50
0 people) are used. In this Example 2, the recording layer, the first
Since the Curie temperatures of both the auxiliary layers are set high, stable overwrite characteristics can be obtained even under fluctuations in ambient temperature. In addition, in Example 3, the recording layer? Gd with large car rotation angle. Since Fe, B, and ■ are used, the reproduction performance can be improved. In Example 4, since Nb is added to the recording layer, high corrosion resistance of the magnetic layer can be achieved. Cr can also be used instead of Nb. As an example of other media configurations. For example, the first auxiliary layer and the second auxiliary layer may be composed of one magnetic layer whose composition changes continuously. In Example 5, the recording layer was made of Tb1, Fe. Co
, Cr film (T, = 190°C, h, = 300 people) was used, and on top of that, TbzJeG4 was used on the side near the recording layer.
co1■ (T2= 220℃), Tb2 z on the far side
D)'z Fe6s Cot o (Tz =200
A composition gradient is provided in the first and second auxiliary layers so as to have a composition of (°C). The total thickness of the first and second auxiliary layers is 11
There are 00 people. Furthermore, in Example 6, TbxoD was added to the recording layer.
YsFe7@Co6 film (T. = 210℃, h. =
200 people) to the first auxiliary layer.
After forming the Cu* film (T2=260°C, h2=soo), the second auxiliary layer was formed using Tb, Fe, Co,
, membrane (T, = 250℃, l13 = 300 people) and Tb
1. FesaCoi, membrane (T4 = 230°C. h. =
In Example 5, which was composed of two layers (300 people), the Dy concentration gradually increased from the substrate toward the atmosphere, and the CO concentration decreased on the contrary. By providing a composition gradient in this manner, the effect of reducing the initialization magnetic field was observed. Furthermore, in Example 6, the effect of further reducing the laser power required for recording was observed. (Left below) Table 2? Example 7 An example is shown in which the magnitude of the initialization magnetic field is reduced by laminating a second auxiliary layer having a smaller coercive force than the first auxiliary layer. The recording layer is a Tb, Fe, 4Co film (T1=190℃,
h = 400 people, coercive force He = 15KOe in a single layer
). TbxsDY17Fes7COz* film (T, = 290°C, h, = 400 people, Ha = 4KOe in single layer) for the first auxiliary layer, TI for the second auxiliary layer) zoD! /tt
Fe43Co2. Membrane (T, = 250℃, h, =
When a laminated film was constructed using 600 He = 2 KOe in a single layer, the He of the first and second auxiliary layers was I KO
It became e. When only 1000 first auxiliary layers were stacked on the recording layer, the coercive force of the first auxiliary layer was 3 KOe, so the initialization magnetic field could be significantly reduced. Effects of the Invention According to the present invention, three magnetic layers are provided, a recording layer, a first auxiliary layer, and a second auxiliary layer, and the Curie temperatures of each layer are T1 and T2.
, T3, the configuration satisfies the following relationships: T1<T, T2≧T, so that recording and erasing can be performed with a laser power lower in intensity than conventional ones. Therefore, conventionally, recording at a linear velocity of 20 m/sec was the limit due to the maximum output of the semiconductor laser, but the present invention has made it possible to record at a linear velocity of 44 m/sec. This linear velocity is 360O
This is the linear velocity near the outermost circumference when rotating at rpm. By realizing such a large-diameter magneto-optical recording medium, it has become possible to store a large amount of information such as moving images at high speed on the magneto-optical recording medium of the present invention. Further, according to the present invention, magnetic coupling forces act between the recording layer and the first auxiliary layer and between the first auxiliary layer and the second auxiliary layer, and furthermore, the first and second auxiliary layers act at room temperature. The two auxiliary layers together undergo magnetization reversal, and the reversal magnetic field (coercive force) at that time
By making the coercive force smaller than the coercive force of the recording layer, overwriting by light intensity modulation was made possible. In addition, when using a second auxiliary layer whose coercive force is smaller than that of the first auxiliary layer and whose saturation magnetization is conversely larger, the coercive force of the first and second auxiliary layers is the same as when each magnetic layer is in a single layer state. Since the coercive force is smaller than the coercive force of , the initializing magnetic field can be reduced. Even if the first auxiliary layer and the second auxiliary layer are made of materials having substantially the same Curie temperature, the coercivity of the second auxiliary layer near the Curie temperature may be higher than that of the first auxiliary layer. By arranging the structure so that . However, in order to achieve sufficient sensitivity improvement, the temperature difference between the Curie temperature T2 of the first auxiliary layer and the Curie temperature T of the second auxiliary layer must be 3°C.
From the above, it is more preferable that the temperature is 5°C or higher.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional structure diagram of a magneto-optical recording medium according to an embodiment of the present invention, and FIGS. 2, 3, 4, and 5 explain the principle of conventional optical intensity modulation recording. A schematic diagram, FIG. 6 is a diagram for explaining the temporal change in laser power, FIG. 7 is a schematic diagram for explaining the principle of the magneto-optical recording medium of the present invention, and FIGS. 8 and 9 are diagrams for explaining the temporal change in laser power. , a diagram showing its characteristics, Figure 1O,
FIGS. 11 and 12 are schematic diagrams illustrating the principle of optical intensity modulation recording using the magneto-optical recording medium of the present invention. 1... Substrate 2... Ultraviolet curing resin layer 4...
...Recording layer 6...Second auxiliary layer 9...Auxiliary layer coercive force T1,...Curie temperature 13...Initialization magnetic field 15...Auxiliary layer 18, 19, 29, 30... ... Magnetization 20 ... Laser light 21 ... Stop lens 23 ... High laser power level 24 ... Low laser power level 25 ... Coercive force of first and second auxiliary layers 26 ... Recording Coercive force of layer 27... Temperature distribution 5... First auxiliary layer 8... Coercive force Tr of recording layer... Room temperature l4... Bias magnetic field 17... Initialization magnet

Claims (1)

[Claims] 1. A magneto-optical recording medium having at least a substrate and a magnetic layer provided on the substrate, wherein the magnetic layer is a recording layer,
It consists of a first auxiliary layer and a second auxiliary layer, and the Curie temperatures of the recording layer, first auxiliary layer, and second auxiliary layer are T_1 and T_, respectively.
2. When T_3, T_1<T_2, T_2≧T_
3. A magneto-optical recording medium characterized by satisfying the following relationship. 2. Curie temperature T_2 of the first auxiliary layer and second auxiliary layer
, T_3 satisfy the relationship T_2>T_3. 3. The Curie temperatures T_1, T_2, and T_3 of the recording layer, first auxiliary layer, and second auxiliary layer are 100°C≦T_1, respectively.
The magneto-optical recording medium according to claim 1 or 2, characterized in that the temperature is in the following ranges: ≦250°C, 150°C≦T_2≦350°C, 100°C≦T_3≦300°C. 4. The magnetization of the first auxiliary layer and the second auxiliary layer is reversed together at room temperature, and the coercive force of the first auxiliary layer and the second auxiliary layer at that time is smaller than the coercive force of the recording layer. The magneto-optical recording medium according to claim 1, 2 or 3, characterized in that: 5. The magneto-optical recording medium according to claim 4, wherein the composition of the second auxiliary layer changes continuously in the thickness direction. 6. The magneto-optical recording medium according to claim 4, wherein the second auxiliary layer is composed of a plurality of layers having different compositions. 7. The magneto-optical recording medium according to claim 4, wherein the coercive force of the second auxiliary layer is smaller than the coercive force of the first auxiliary layer. 8. A magneto-optical recording medium having a substrate and at least a magnetic layer on the substrate, the magnetic layer comprising a recording layer, a first auxiliary layer,
It consists of a second auxiliary layer, and when the Curie temperatures of the recording layer and the first auxiliary layer are T_1 and T_2, respectively, the relationship T_1<T_2 is satisfied, and the Curie temperatures of the first auxiliary layer and the second auxiliary layer are are substantially the same, and the coercive force of the second auxiliary layer is smaller than the coercive force of the first auxiliary layer at a temperature near the Curie temperature. 9. The magnetization of the first auxiliary layer and the second auxiliary layer is reversed together at room temperature, and the coercive force of the first auxiliary layer and the second auxiliary layer at that time is smaller than the coercive force of the recording layer. The magneto-optical recording medium according to claim 8, characterized in that: