JPH0644630A - Method and device for forming bit and method for reproducing the same - Google Patents

Abstract

PURPOSE:To unnecessitate a recording magnetic field by heating a multilayered magneto-optical recording medium in which the Curie point of the 2nd layer is higher than that of the 1st layer to a temp. below the Curie point of the 2nd layer by irradiation with laser beams. CONSTITUTION:A multilayered magneto-optical recording medium in which the Curie point of the 2nd layer having vertical magnetic anisotropy as an auxiliary recording layer 2 is higher than that of the 1st layer having vertical magnetic anisotropy as a recording and reproducing layer 1 is heated to a temp. below the Curie point of the 2nd layer or a temp. close to the Curie point of the 1st layer by irradiation with laser beams. By this heating, bits having a direction of magnetization controlled by the 2nd layer can be formed in the 1st layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bit forming method useful for magneto-optical recording, a bit forming apparatus and a reproducing method thereof.

[0002]

2. Description of the Related Art Recently, an optical recording / reproducing method satisfying various requirements including high density, large capacity, high access speed, and high recording / reproducing speed, and a recording apparatus, reproducing apparatus and recording medium used therefor. Efforts are being made to develop. Among a wide range of optical recording / reproducing methods, the magneto-optical recording / reproducing method is the most attractive because of the unique advantage that information can be erased after it is used and new information can be recorded. Is full of.

A recording medium used in this magneto-optical recording / reproducing method has a single or multi-layered perpendicular magnetization film (p
erpendicular magnetic layer or layers). This magnetized film is, for example, amorphous GdFe, GdCo, GdFeC
o, TbFe, TbCo, TbFeCo, etc. The recording layer generally comprises concentric or spiral tracks, on which information is recorded. Here, in this specification, “upward” or “dow” with respect to the film surface.
nward) "is defined as" A direction "and the other is" reverse A direction ". The information to be recorded is binarized in advance, and this information has a bit (B
₁ ) and the bit (B ₀ ) having the magnetization in the “reverse A direction” are recorded. These bits B _{1 and} B ₀ correspond to either one or the other of digital signals 1 and 0, respectively. However, in general, the magnetization of the recorded track is
By applying a strong external magnetic field before recording, "reverse A
Orientation ". This process is called initialize. Then, the bit (B ₁ ) having the "A direction" magnetization is formed on the track. Information is this bit (B ₁ )
It is recorded depending on the presence or absence and / or the bit length. <Principle of bit formation> In the formation of bits, the characteristics of the laser, that is, the excellent coherence in space and time (coheren
ce) is advantageously used to focus the beam into a spot as small as the diffraction limit determined by the wavelength of the laser light. The narrowed light is applied to the track surface, and information is recorded by forming bits having a diameter of 1 μm or less in the recording / reproducing layer. In optical recording, theoretically recording densities up to about 10 ⁸ bits / cm ² can be achieved. This is because the laser beam can be concentrated into a spot with a diameter as small as about its wavelength.

As shown in FIG. 2, in magneto-optical recording, a laser beam (L) is focused on the recording / reproducing layer (1) and heated. Meanwhile, the recording magnetic field (Hb) in the opposite direction to the initialized direction is externally applied to the heated portion. Then, the coercive force Hc (coersivity) of the locally heated portion decreases and becomes smaller than the recording magnetic field (Hb). As a result, the magnetization of that portion is determined by the recording magnetic field (Hb).
Line up in the direction of. In this way, the oppositely magnetized bit is formed.

Ferromagnetic materials and ferrimagnetic materials have different temperature dependences of magnetization and Hc. Ferromagnetic materials have Hc that decreases near the Curie point, and recording is performed based on this phenomenon. Therefore, it is referred to as Tc writing (Curie point writing). Ferrimagnetic materials, on the other hand, have a compensation temperature below the Curie point, where the magnetization (M) is zero. On the contrary, Hc becomes very large near this temperature, and when it deviates from that temperature, Hc drops sharply. This lowered Hc is defeated by the relatively weak recording magnetic field (Hb). That is, recording becomes possible. This recording process is called T _comp. Writing (compensation point writing).

However, it is not necessary to stick to the Curie point or the vicinity thereof and the compensation temperature. In short, recording is possible by applying a recording magnetic field (Hb) that defeats the lowered Hc to the magnetic material having the lowered Hc at a predetermined temperature higher than room temperature. <Principle of Reproduction> FIG. 3 shows the principle of information reproduction based on the magneto-optical effect. Light is an electromagnetic wave having an electromagnetic field vector that is normally divergent in all directions on a plane perpendicular to the optical path. When the light is converted into linearly polarized light (L _p ) and applied to the recording / reproducing layer (1), the light is reflected on the surface of the recording / reproducing layer (1) or passes through the recording / reproducing layer (1). At this time, the polarization plane rotates according to the direction of the magnetization (M). This rotating phenomenon is due to the magnetic Kerr effect or magnetic Faraday.
y) Called the effect.

For example, if the plane of polarization of the reflected light is "A direction"
Rotation of θ k degrees with respect to magnetization causes rotation of −θ k degrees with respect to "reverse A direction" magnetization. Therefore, when the axis of the optical analyzer (polarizer) is set to be perpendicular to the plane inclined by -θk, the light reflected from the bit (B ₀ ) magnetized in the "reverse A direction" is transmitted through the analyzer. I can't. On the other hand, the bit (B ₁ ) magnetized in “A direction”
The light reflected from is multiplied by (sin2θk) ² and passes through the analyzer, where it is captured by a detector (photoelectric conversion means). As a result, the bit (B ₁ ) magnetized in the "A direction" appears brighter than the bit (B ₀ ) magnetized in the "reverse A direction" and produces a strong electrical signal at the detector. The electrical signal from this detector is modulated according to the recorded information, so that the information is reproduced.

The first developed magneto-optical recording medium has a recording / reproducing layer (1) of GdFe, GdFeCo, TbFe, TbFeCo, DyFe,
It consisted of an amorphous alloy thin film such as DyFeCo. After that, a medium was proposed in which the recording / reproducing layer (1) was divided into a recording (storing) layer and a reproducing layer in terms of function. JP-A-57-78652
That is the medium of the issue (corresponding USP 4,799,114). This medium has a two-layer film structure in which a recording layer and a reproducing layer are laminated. The recording layer is composed of an amorphous alloy thin film having a low Curie point and high coercive force, and the reproducing layer is composed of an amorphous alloy thin film having a high Curie point and high coercive force. As a material for the recording layer, TbFe or DyFe is proposed, and as a material for the reproducing layer,
GdFe or GdCo have been proposed. In this medium, the recording layer and the reproducing layer are exchange-coupled to each other. Therefore, the bits recorded on the recording layer are transferred to the reproducing layer by the exchange coupling force. As a result, bits are also formed in the reproduction layer.

[0009]

In the prior art, first of all,
By irradiating the recording layer with a laser beam, it is heated to a temperature higher than the Curie point of the recording layer. A recording magnetic field (Hb) is applied to this heated portion (area). As a result, bits are formed on the recording layer. Since the recording layer proposed by JP-A-57-78652 has a low Curie point, the intensity of the laser beam can be small. As such, the semiconductor laser as a light source has an advantage that a small and inexpensive one can be used.

However, a recording magnetic field (Hb) applying means such as a magnet is required (problem). This is a disadvantage as compared with a phase change type optical disk capable of repeating recording, reproduction and erasing similarly. The object of the present invention is to solve this problem.

[0011]

According to the present invention, the first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, the second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie of the second layer is used. A multi-layered magneto-optical recording medium whose point is higher than that of the first layer is used. In the present invention, a laser beam is irradiated to heat the second layer to a temperature lower than the Curie point. This makes the first
The coercive force of the layer is reduced. Therefore, a bit having a magnetization direction controlled by the second layer is generated by a magnetic coupling (here, magnetic coupling means exchange coupling and / or magnetostatic coupling) force. Is formed.

Therefore, according to the present invention, firstly, "the first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, the second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the second layer is For a multilayer magneto-optical recording medium having a higher Curie point than that of the first layer,
A method of forming a bit in a first layer having a magnetization direction controlled by the second layer by irradiating a laser beam and heating the temperature to a temperature lower than the Curie point of the second layer "
I will provide a.

Secondly, according to the present invention, "the first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, the second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is" A multi-layered magneto-optical recording medium higher than that of the first layer is irradiated with a laser beam to heat it near the Curie point of the first layer, so that the bit having a magnetization direction controlled by the second layer is generated. A method of forming a first layer ".

Thirdly, in the present invention, "the first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, the second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is When there is a multi-layered magneto-optical recording medium in which is higher than that of the first layer, (a)
A laser beam light source; and (b) means for controlling the light source so that the temperature of the medium is increased to "a temperature lower than the Curie point of the second layer" when the medium is irradiated with the laser beam. A bit forming device for forming a bit having a magnetization direction controlled by the second layer in the first layer ".

Fourthly, in the present invention, "the first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, the second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is When there is a multi-layered magneto-optical recording medium in which is higher than that of the first layer, (a)
A laser beam light source; and (b) means for controlling the light source so that the temperature of the medium is increased to "the temperature near the Curie point of the first layer" when the medium is irradiated with the laser beam; And a bit forming device for forming a bit having a magnetization direction controlled by the second layer in the first layer.

Fifth, the present invention irradiates a laser beam on a "multilayer magneto-optical recording medium including at least a first layer having perpendicular magnetic anisotropy and a second layer having perpendicular magnetic anisotropy". Then, by heating at a temperature lower than the Curie point of the second layer or in the vicinity of the Curie point of the first layer,
A method of magneto-optically reproducing a bit having a magnetization direction controlled by a second layer, the bit being formed in the first layer.

[0017]

In the present invention, the second layer having a high Curie point is not heated above the Curie point when forming the bit. This is because the magnetization of the second layer is not lost. Therefore, the magnetization direction of the second layer does not change as compared with that before the beam irradiation. This point is also different from JP-A-57-78652.

Instead, the first layer is heated above or near its Curie point. Therefore, the coercive force of the first layer becomes zero or becomes extremely small. As a result, the force of the second layer extends through the magnetic coupling (exchange coupling and / or magnetostatic coupling) force to the first layer, and the bit having the magnetization direction controlled by the second layer is It is formed in one layer.

Thus, by irradiating the medium with the laser beam of the first level which is heated to a temperature lower than the Curie point of the second layer or in the vicinity of the Curie point of the first layer, the first layer is irradiated.
A "bit having a magnetization direction controlled by the second layer" is formed in the layer. The medium used in the present invention includes first and second layers having perpendicular magnetic anisotropy, and both layers are magnetically coupled.

The first layer is a recording / reproducing layer having a high coercive force and a low magnetization reversal temperature at room temperature. The second layer is a recording auxiliary layer having a lower coercive force and a higher magnetization reversal temperature at room temperature than the first layer. Both are made of perpendicularly magnetized films. Both the first layer and the second layer may themselves be composed of a multilayer film. In some cases, a third layer may be present between the first layer and the second layer. Further, there is no clear boundary between the first layer and the second layer, and one may gradually change to the other.

The medium is divided into a first embodiment and a second embodiment. In the first embodiment, the coercive force of the recording / reproducing layer (1) is H _C1 , that of the recording layer auxiliary layer (2) is H _C2 , the Curie point of the recording / reproducing layer (1) is T _C1 , and the recording auxiliary layer (2). ), T _C2 at room temperature, T _R at room temperature, T _{L at} the temperature of the recording medium when the first-level (low-level) laser beam is irradiated, and T _H at the time when a high-level laser beam is irradiated, when the coupling field recording layer (1) is subjected H _D1, the coupling field recording auxiliary layer (2) is subjected to the H _D2, satisfy equation 1 below, and satisfies equation 2-5 at room temperature .

[0022] _{T R <T C1 ≒ T L} <T C2 ≒ T H ······· formula _{1 H C1> H C2 + |} H D1 - (±) H D2 | ····· Formula 2 H _C1 ＞ H _D1・ ・ ・ Equation 3 H _C2 ＞ H _D2・ ・ ・ Equation 4 H _C2 + H _D2 < | Hini. | <H _C1 ± H _D1 ... Equation 5 In the above equation, the symbol “≈” indicates equality or almost equality. Further, in the above formula, the compound ± is the case of the medium of A (antiparallel) type described later in the upper stage,
The lower part shows the case of a P (parallel) type medium described later. The ferromagnetic material and the magnetostatically coupled medium belong to the P type.

Therefore, when an initial auxiliary magnetic field (Hini.) Is applied to this recording medium at room temperature, according to Equation 5, the magnetization direction of the recording / reproducing layer (1) is not reversed and the recording auxiliary layer (2) is not reversed. Only the magnetization is reversed. Therefore, when an initial auxiliary magnetic field (Hini.) Is applied to the medium before the laser beam irradiation, only the recording auxiliary layer (2) is "A direction" --- here, "A direction" is used for convenience. In the figure, the arrow pointing upward ↑ indicates that the "reverse A direction" can be turned to the arrow pointing downward ↓. This makes it possible to set the magnetization direction of the desired portion or region of the recording auxiliary layer (2) to the “A direction”.

[0024] The medium extends to the medium apart from Hini.
Even if i. becomes zero, the recording auxiliary layer (2)
The magnetization ↑ of is retained as it is without re-inversion. Then the first
The medium temperature is raised to T _L by irradiating a laser beam of level. Since T _L is lower than the Curie point of the second layer or near the Curie point T _C1 of the first layer, the magnetization of the recording / reproducing layer (1) disappears completely or almost, but at a temperature lower than the Curie point T _C2. Magnetization of the recording auxiliary layer (2) (coercive force)
Is quite large.

Since the medium is moving, the irradiated portion is immediately moved away from the laser beam and cooled by air. As the cooling progresses, the magnetization of the recording / reproducing layer (1) appears again or its coercive force increases. At this time, the magnetization direction of the first layer is set to the recording auxiliary layer (2) due to the magnetic coupling force.
Is affected by the direction of magnetization. As a result, depending on the type of medium, "A direction" ↑ (for P type) or "reverse A"
A bit of "direction" ↓ (for A type) is formed.

The second embodiment utilizes Hc lowered at a predetermined temperature above room temperature. The second embodiment uses a temperature T _S1 at which the recording / reproducing layer (1) is magnetically coupled to the recording auxiliary layer (2) instead of T _{C1 in} the first embodiment, and instead of T _C2 . The recording auxiliary layer (2) is Hb
Using a temperature T _S2 that inverts at the same way as in the first embodiment.

The second embodiment is the coercive force of the recording / reproducing layer (1).
Power H_C1, H of the recording auxiliary layer (2)_C2, Recording / playback layer
The temperature at which (1) is magnetically coupled to the recording auxiliary layer (2)
To T _s1And the magnetization of the recording auxiliary layer (2) is reversed at Hb.
Temperature to T_S2, Room temperature T_R, The first level (low level)
The temperature of the medium when irradiated with the laser beam is T_LHigh level
T when irradiating the laser beam_H, Record again
The coupling magnetic field received by the raw layer (1) is H_D1, Recording auxiliary layer (2)
H is the coupling magnetic field_D2If, the following formula 6 is satisfied
And satisfies Equations 7-10 at room temperature.

[0028] _{T R <T s1 ≒ T L} <T s2 ≒ T H ······· formula _{6 H C1> H C2 + |} H D1 - (±) H D2 | ····· Formula 7 H _C1 > _HD1 ... Equation 8 H _C2 > _HD2 ... Equation 9 H _C2 + _HD2 < │Hini. │ <H _C1 ± H _D1・ ・ ・ Equation 10 In the above equation, for the composite ±, A (anti
This is a case of a parallel type medium, and the lower part is a case of a P (parallel) type medium described later.

In both the first and second embodiments, both the recording / reproducing layer (1) and the recording auxiliary layer (2) are transition metals (for example, F
A recording medium which is an amorphous ferrimagnetic material selected from the alloy composition of (e, Co) -heavy rare earth metal (eg, Gd, Tb, Dy, etc.) is preferable. Both the recording / reproducing layer (1) and the recording auxiliary layer (2) have a transition metal-heavy rare earth metal (h)
eavy rare earth metal) When selected from the alloy composition, the direction and magnitude of the magnetization that appears outside each alloy is the transition metal atom (hereinafter abbreviated as TM) inside the alloy.
Of the heavy rare earth metal atom (hereinafter abbreviated as RE). For example, the spin direction and magnitude of TM are represented by a dotted vector, that of RE spin is represented by a solid line vector, and the magnetization direction and magnitude of the entire alloy is represented by a double solid line vector. The vector of the entire alloy is expressed as the sum of the TM vector and the RE vector. However, in the alloy, the TM vector and the RE vector always have opposite directions due to the interaction between the TM spin and the RE spin (see FIG. 4). Therefore, the sum of the TM vector and the RE vector becomes zero when the intensities of both are equal. That is, the alloy vector becomes and the magnitude of the magnetization appearing outside becomes zero. The alloy composition when it reaches zero is called the compensation composition. For other compositions, the alloy vector has an intensity equal to the intensity difference between both spins and has an orientation equal to the direction of the larger vector. This vector appears outside as magnetization. TM vector (dotted arrow) and RE
The relationship between the size and direction of the vector (solid arrow) is shown in Fig. 4.
There will be four (1A) to (4A). At this time, the alloy vector (double solid arrow) becomes four (1B) to (4B) corresponding to (1A) to (4A) in FIG.

When the strength of each of the TM spin and RE spin vectors of a certain alloy composition is large, the alloy composition takes the spin name of the larger strength and is XX rich, for example, RE rich. be called. For example, in FIG.
The alloy composition of (1A) is RE rich because the RE vector (solid arrow) is larger than the TM vector (dotted arrow).

Both the recording / reproducing layer (1) and the recording auxiliary layer (2) are classified into a TM-rich composition and an RE-rich composition. Therefore, if the composition of the recording / reproducing layer (1) is plotted on the ordinate and the composition of the recording auxiliary layer (2) on the abscissa, the type of the entire medium can be classified into four quadrants shown in FIG. . The P type described above belongs to the first and third quadrants, and the A type belongs to the second and fourth quadrants. The intersection of the ordinate and the abscissa represents the compensation composition of both layers.

On the other hand, looking at the change in coercive force with respect to temperature change, there is an alloy composition having a characteristic that the coercive force temporarily increases to infinity and then drops before reaching the Curie point (temperature at which coercive force is zero). . The temperature corresponding to this infinity is called the compensation temperature (T _comp. ). Compensation temperature is TM
It does not exist between room temperature and the Curie point in rich alloy compositions. Since the compensation temperature below room temperature is meaningless in magneto-optical recording, the compensation temperature in this specification means that it exists between room temperature and the Curie point.

When the presence or absence of the compensation temperature of the first layer and the second layer is classified, the medium is classified into four types. The first quadrant medium includes all four types. When a "graph showing the relationship between coercive force and temperature" is written for the four types, there are four types shown in FIGS. 6 and 7. The thin line is that of the recording / reproducing layer (1), and the thick line is that of the recording auxiliary layer (2).

Table 1 shows the recording medium when the recording / reproducing layer (1) and the recording auxiliary layer (2) are classified as RE-rich or TM-rich and whether they have a compensation temperature or not. It is classified into the 9 classes shown below.

[0035]

[Table 1]

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0037]

EXAMPLE 1 The overwrite process will be described in detail by taking a specific medium No. 1 belonging to the recording medium of class 1 (P type, 1 quadrant, type 1) shown in Table 1 as an example. This medium No. 1 has the following formula 11: T _R <T _comp.1 <T _C1 ≈
T _{L ≈T comp.2} <T _{c2 ≈T H.} A graphical representation of this relationship is as shown in FIG. The thin line is the first
The graph of the layer is shown, and the thick line shows the graph of the second layer.

The room temperature T _R with the magnetization initial field Hini of the recording and reproducing layer (1). Recording auxiliary layer without reversing only by (2) is inverted condition is an expression 12. This medium No. 1 satisfies Equation 12 at room temperature.

[0039]

[Equation 1]

However, H _C1 is the coercive force of the recording / reproducing layer (1),
H _C2 is the coercive force of the recording auxiliary layer (2), M _S1 is the saturation magnetization of the layer (1), M
_S2 is the saturation magnetic moment of the layer (2), t ₁ is the thickness of the layer (1), t ₂ is the thickness of the layer (2), and σ _w is the interface wall energy. At this time, Hi
The conditional expression of ni. is shown in Expression 15. When the Hini. Disappears, the inverted magnetization of the recording auxiliary layer (2) is affected by the magnetization of the recording / reproducing layer (1) due to the exchange coupling force. Even so, the condition that the magnetization of the layer (2) is maintained without being reversed again is expressed by the formula 13
Indicated by ~ 14. This medium No. 1 satisfies the expressions 13 to 14.

[0041]

[Equation 2]

[0042]

[Equation 3]

[0043]

[Equation 4]

The magnetization of the recording auxiliary layer (2) of the recording medium satisfying the conditions of formulas 12 to 14 at room temperature is, for example, "A direction" by Hini. Four
1A / 1B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is "reverse A direction" ↓. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. In this state, H _C2 is sufficiently large.

In this state, when the laser beam moves out of the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The influence of the TM spin (1A in FIG. 4) affects each spin of the recording / reproducing layer (1) by the exchange coupling force. That is, the force of aligning the RE spins (solid arrows) and the TM spins (dotted arrows) works. As a result, the magnetization ↓ shown in 2A / 2B of FIG. 4 appears in the layer (1). Since the temperature in this state is T _comp.1 or higher, the TM spin is larger.

When the medium temperature further cools below T _comp.1 ,
The magnitude relation between the RE spin and the TM spin of the layer (1) is reversed (2A → 1A in FIG. 4). As a result, the magnetization of the layer (1) becomes “A direction” ↑ (1B in FIG. 4). This state is maintained even if the medium temperature drops to room temperature. Thus, the layer (1)
A bit of “A direction” ↑ is formed at. The magnetization of the layer (1) in the non-irradiated portion is "inverse A direction" ↓.

[0047]

[Embodiment 2] The overwrite process will be described in detail by taking a specific medium No. 2 belonging to the recording medium of class 2 (P type, 1 quadrant, type 2) shown in Table 1 as an example. This medium No. 2 has the following equation 16: T _R <T _C1 ≈ _TL ≈
T _comp.2 <T _{c2 ≈T H.} A graphical representation of this relationship is as shown in FIG.

The conditions under which only the magnetization is reversed in the auxiliary recording layer without reversing magnetization by the initial auxiliary magnetic field Hini. Of recording layer at room temperature T _R (1) (2) is an expression 17. This medium No. 2 satisfies Expression 17.

[0049]

[Equation 5]

At this time, the conditional expression of Hini. Is expressed by Expression 20. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is retained without being re-inverted again are shown in Equations 18 to 19. This medium No.2
Satisfies Eqs. 18-19.

[0051]

[Equation 6]

[0052]

[Equation 7]

[0053]

[Equation 8]

The magnetization of the recording auxiliary layer (2) of the recording medium satisfying the conditions of formulas 17 to 19 at room temperature is Hini. Which satisfies the condition of formula 20 until just before irradiation: For example, "A direction" ↑ ( (See 1A in Fig. 4). At this time, the recording / reproducing layer (1) remains in the previous state. The previous state is "reverse A direction" ↓. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, since T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), the layer
The magnetization of (1) disappears. In this state, H _C2 is sufficiently large.

In this state, when the laser beam moves out of the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The influence of the TM spin (1A in FIG. 4) affects each spin of the recording / reproducing layer (1) by the exchange coupling force. That is, the force of aligning the RE spins and the TM spins works. As a result, the magnetization of “A direction” ↑ shown in 1A / 1B of FIG. 4 appears in the layer (1). This state does not change even if the medium temperature further decreases. Thus, the bit “A direction” ↑ is formed in the layer (1). The magnetization of the layer (1) in the unirradiated part is
“Reverse A direction” ↓.

[0056]

[Third Embodiment] The overwrite process will be described in detail by taking a specific medium No. 3 belonging to the recording medium of class 3 (P type, 1 quadrant, type 3) shown in Table 1 as an example. This medium No. 3 has the following formula 21: T _R <T _comp.1 <T
Have a relationship of _{C1 ≒ T L <T c2 ≒} T H. A graphical representation of this relationship is as shown in FIG.

The condition where the magnetization of the recording / reproducing layer (1) is not reversed by the initial auxiliary magnetic field Hini. At room temperature T _R but only the recording auxiliary layer (2) is reversed is equation 22. This medium No. 3 satisfies Expression 22.

[0058]

[Equation 9]

At this time, the conditional expression of Hini. Is expressed by Expression 25. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is maintained without being re-inverted again are shown in Equations 23 to 24. This medium No.3
Satisfies Equations 23-24.

[0060]

[Equation 10]

[0061]

[Equation 11]

[0062]

[Equation 12]

The magnetization of the recording auxiliary layer (2) of the recording medium satisfying the conditions of formulas 22 to 24 at room temperature is, for example, "A direction" by Hini. Four
1A / 1B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is "reverse A direction" ↓. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. In this state, H _C2 is sufficiently large.

In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The influence of the TM spin (1A in FIG. 4) extends to each spin of the recording / reproducing layer (1) by the exchange coupling force. That is, the force of aligning the RE spins and the TM spins works. In this case, since the temperature is T _comp.1 or higher, the TM spin is larger (see FIG. 4).
2A). As a result, the "reverse A direction" ↓ magnetization shown in 2A / 2B of FIG. 4 appears in the layer (1).

When the medium temperature is further cooled to T _comp.1 or less, the magnitude relation between the RE spin and the TM spin of the layer (1) is reversed (2A → 1A in FIG. 4) as in the high temperature cycle. as a result,
The magnetization of the layer (1) is “↑” shown in 1B of FIG.
This state is maintained even if the medium temperature drops to room temperature.
Thus, the bit “A direction” ↑ is formed in the layer (1). The magnetization of the layer (1) that was not irradiated was
The direction is ↓.

[0066]

Fourth Embodiment The overwrite process will be described in detail by taking a specific medium No. 4 belonging to the recording medium of class 4 (P type, 1 quadrant, type 4) shown in Table 1 as an example. This medium No. 4 has the following formula 26: T _R <T _C1 ≈T _L <T
have a relationship of _c2 ≒ T _H. A graphical representation of this relationship is as shown in FIG.

The condition where the magnetization of the recording / reproducing layer (1) is not reversed by the initial auxiliary magnetic field Hini. At room temperature T _R but only the recording auxiliary layer (2) is reversed is equation 27. This medium No. 4 satisfies Expression 27.

[0068]

[Equation 13]

At this time, the conditional expression of Hini. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is still retained without being re-inverted are shown by Equations 28 to 29. This medium No.4
Satisfies Eqs. 28-29.

[0070]

[Equation 14]

[0071]

[Equation 15]

[0072]

[Equation 16]

The magnetization of the recording auxiliary layer (2) of the recording medium satisfying the conditions of formulas 27 to 29 at room temperature is, for example, "A direction" by Hini. Four
1A / 1B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is "reverse A direction" ↓. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, since T _L exceeds the Curie point T _C1 of the recording / reproducing layer (1), the magnetization of the layer (1) disappears. In this state, H _C2 is still large enough.

In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The influence of the TM spin (1A in FIG. 4) affects each spin of the recording / reproducing layer (1) by the exchange coupling force. That is, the exchange coupling force is R
It works to align E spins and TM spins. As a result, the layer (1) has “A direction” shown in 1A / 1B of FIG.
↑ Magnetization appears. This state is maintained even if the medium temperature drops to room temperature. In this way, the layer (1) is "A direction" ↑
Bits are formed. The magnetization of the layer (1) in the non-irradiated portion is "inverse A direction" ↓.

[0075]

[Embodiment 5] The overwrite process will be described in detail by taking a specific medium No. 5 belonging to the recording medium of Class 5 (A type, 2 quadrants, type 3) shown in Table 1 as an example. This medium No. 5 has the following formula 31: T _R <T _comp.1 <T _C1 ≈
It has a relationship of T _L <T _c2 ≈T _H. A graphical representation of this relationship is as shown in FIG.

[0076] room temperature T _R with the magnetization initial field Hini of the recording and reproducing layer (1). Recording auxiliary layer without reversing only by (2) is inverted condition is an expression 32. This medium No. 5 satisfies the expression 32.

[0077]

[Equation 17]

At this time, the conditional expression of Hini. Is expressed by Expression 35. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is retained without being re-inverted again are shown in Equations 33 to 34. This medium No.5
Satisfies Equations 33-34.

[0079]

[Equation 18]

[0080]

[Formula 19]

[0081]

[Equation 20]

The magnetization of the recording auxiliary layer (2) of the recording medium satisfying the conditions of formulas 32 to 34 at room temperature is, for example, "A direction" by Hini. Four
4A / 4B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is “A direction” ↑.

The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. However, at this temperature the H _c2 of layer (2) is sufficiently high. When the irradiation of the beam ends in this state, the medium temperature starts to drop. Medium temperature is T _C1
When it goes down a little, the influence of RE and TM spins (4A in FIG. 4) of the recording auxiliary layer (2) affects each spin of the recording / reproducing layer (1) by the exchange coupling force. In other words, RE spins, TM
The power to align the spins works. At this time, the temperature is T
_{Since it is comp.1} or higher, TM spin is larger. as a result,
In the layer (1), the "A direction" ↑ magnetization shown in 4A / 4B in FIG. 4 appears.

When the medium temperature further cools below T _comp.1 ,
The magnitude relationship between the RE spin and the TM spin of layer (1) is reversed (4A → 3A in FIG. 4). As a result, the magnetization of layer (1) is
It becomes "inverse A direction" ↓ shown in 3B of FIG. This state is maintained even if the medium temperature drops to room temperature. In this way, the bit of "the direction of reverse A" ↓ is formed in the layer (1). The magnetization of the layer (1) in the unirradiated portion is “A direction” ↑.

[0085]

[Embodiment 6] The overwrite process will be described in detail by taking a specific medium No. 6 belonging to the recording medium of class 6 (A type, 2 quadrants, type 4) shown in Table 1 as an example. This medium No. 6 has formula 36: T _R <T _C1 ≈T _L <T _c2
≒ have a relationship of T _H. A graphical representation of this relationship is as shown in FIG.

The condition that the magnetization of the recording / reproducing layer (1) is not reversed by the initial auxiliary magnetic field Hini. At room temperature T _R but only the recording auxiliary layer (2) is reversed is equation 37. This medium No. 6 satisfies Expression 37.

[0087]

[Equation 21]

At this time, the conditional expression of Hini. Is shown by the expression 40. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is maintained without being re-inverted again are shown in Equations 38 to 39. This medium No.6
Satisfies Equations 38-39.

[0089]

[Equation 22]

[0090]

[Equation 23]

[0091]

[Equation 24]

The magnetization of the recording auxiliary layer (2) of the recording medium satisfying the conditions of formulas 37 to 39 at room temperature is, for example, "A direction" by Hini. Four
4A / 4B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is “A direction” ↑. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. In this state, H _C2 is sufficiently large.

In this state, when the laser beam deviates from the spot region, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The effect of the TM spin (4A in FIG. 4) extends to each spin of the recording / reproducing layer (1) by the exchange coupling force. The exchange coupling force works to align RE spins and TM spins. As a result, in the layer (1), “inverse A direction” shown in 3A / 3B of FIG. 4 ↓
Appears. This is maintained even when the medium temperature drops to room temperature. In this way, in the layer (1) "For reverse A" ↓
Bits are formed. The magnetization of the layer (1) in the unirradiated portion is “A direction” ↑.

[0094]

[Embodiment 7] The overwrite process will be described in detail by taking a specific medium No. 7 belonging to the recording medium of class 7 (P type, 3 quadrants, type 4) shown in Table 1 as an example. This medium No. 7 has the formula 41: T _R <T _C1 ≈T _L <T _c2
≒ have a relationship of T _H. A graphical representation of this relationship is as shown in FIG.

[0095] room temperature T _R with the magnetization initial field Hini of the recording and reproducing layer (1). Recording auxiliary layer without reversing only by (2) is inverted condition is an expression 42. This medium No. 7 satisfies the expression 42.

[0096]

[Equation 25]

At this time, the conditional expression of Hini. Is expressed by Expression 45. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is still retained without being re-inverted are shown by equations 43 to 44. This medium No.7
Satisfies Equations 43-44.

[0098]

[Equation 26]

[0099]

[Equation 27]

[0100]

[Equation 28]

The magnetization of the recording auxiliary layer (2) of the recording medium which satisfies the conditions of formulas 42 to 44 at room temperature is, for example, "A direction" by Hini. Four
4A / 4B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is “reverse A direction” ↓. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. In this state, H _C2 is sufficiently large.

In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The effect of the TM spin (4A in FIG. 4) extends to each spin of the recording / reproducing layer (1) by the exchange coupling force. The exchange coupling force works to align RE spins and TM spins. As a result, the magnetization of “A direction” ↑ shown in 4A / 4B of FIG. 4 appears in the layer (1). This state is maintained even if the medium temperature drops to room temperature. Thus, the bit “A direction” ↑ is formed in the layer (1). Layer of unirradiated part (1)
The magnetization is "in the opposite A direction" ↓.

[0103]

[Embodiment 8] The overwrite process will be described in detail by taking a specific medium No. 8 belonging to the recording medium of class 8 (A type, 4 quadrants, type 2) shown in Table 1 as an example. This medium No. 8 has the following formula 46: T _R <T _C1 ≈T _L ≈T
_It has a relationship of _comp.2 <T _{c2 ≈T H.} A graphical representation of this relationship is as shown in FIG.

The condition where the magnetization of the recording / reproducing layer (1) is not reversed by the initial auxiliary magnetic field Hini. At room temperature T _R but only the recording auxiliary layer (2) is reversed is equation 47. This medium No. 8 satisfies Equation 47 at room temperature.

[0105]

[Equation 29]

At this time, the conditional expression of Hini. Is expressed by Expression 50. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The conditions under which the magnetization of the layer (2) is retained without being re-inverted again are shown by the equations 48 to 49. This medium No.8
Satisfies Equations 48-49.

[0107]

[Equation 30]

[0108]

[Equation 31]

[0109]

[Equation 32]

The magnetization of the recording auxiliary layer (2) of the recording medium which satisfies the conditions of formulas 47 to 49 at room temperature is, for example, "A direction" by Hini. Four
1A / 1B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is “A direction” ↑. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. However, at this temperature the H _c2 of layer (2)
Is big enough.

In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The influence of the TM spin (1A in FIG. 4) extends to each spin of the recording / reproducing layer (1) by the exchange coupling force. That is, the force of aligning the RE spins and the TM spins works. As a result, the magnetization in the "reverse A direction" ↓ shown in 2A / 2B of FIG. 4 appears in the layer (1). This state is maintained even if the medium temperature drops to room temperature. In this way, the bit of "the direction of reverse A" ↓ is formed in the layer (1). Layer of unirradiated part (1)
Magnetization is “A direction” ↑.

[0112]

[Embodiment 9] A specific medium No. 9 belonging to the recording medium of Class 9 (A type, 4 quadrants, type 4) shown in Table 1 will be described in detail as an example. This medium No. 9 has the formula 51: T _R <T _C1 ≈T _L <T
have a relationship of _c2 ≒ T _H. A graphical representation of this relationship is as shown in FIG.

The condition under which the magnetization of the recording / reproducing layer (1) is not reversed by the initial auxiliary magnetic field Hini. At room temperature T _R but only the recording auxiliary layer (2) is reversed is equation 52. This medium No. 9 satisfies the expression 52.

[0114]

[Expression 33]

At this time, the conditional expression of Hini. Is shown by the expression 55. When Hini. Disappears, the recording auxiliary layer is reversed (2)
Is influenced by the magnetization of the recording / reproducing layer (1) by the exchange coupling force. The condition that the magnetization of the layer (2) is retained without being re-inverted again is expressed by the equations 53 to 54. This medium No.9
Satisfies Equations 53-54.

[0116]

[Equation 34]

[0117]

[Equation 35]

[0118]

[Equation 36]

The magnetization of the recording auxiliary layer (2) of the recording medium which satisfies the conditions of formulas 52 to 54 at room temperature is, for example, "A direction" by Hini. Four
1A / 1B). At this time, the recording / reproducing layer (1)
Remains as it was before. The previous state is “A direction” ↑. The medium temperature is raised to T _L by irradiating the first level laser beam. Then, T _L is almost equal to the Curie point T _C1 of the recording / reproducing layer (1), so that the magnetization of the layer (1) disappears. In this state, H _C2 is sufficiently large.

In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. When the medium temperature falls slightly below T _C1 , RE of the recording auxiliary layer (2),
The influence of the TM spin (1A in FIG. 4) extends to each spin of the recording / reproducing layer (1) by the exchange coupling force. The exchange coupling force works to align RE spins and TM spins. As a result, in the layer (1), “inverse A direction” shown in 2A / 2B of FIG. 4 ↓
Appears. This state is maintained even if the medium temperature drops to room temperature. In this way, the layer (1) is "inverse A direction"
The ↓ bit is formed. The magnetization of the layer (1) in the unirradiated portion is “A direction” ↑.

Reference Example 1 Medium No. 1 A two-source electron beam heating vacuum vapor deposition apparatus was used, and two evaporation sources shown in Table 2 below were placed. A glass substrate having a thickness of 1.2 mm and a diameter of 200 mm is set in the chamber of the apparatus. The inside of the chamber of the apparatus is once evacuated to a vacuum degree of 1 × 10 ⁻⁶ Torr. Or less. afterwards,
Deposition is performed at a deposition rate of about 3Å / sec while maintaining the degree of vacuum at 1 to 2 × 10 ^-6 Torr. This allows Gd ₁₄ Dy ₁₂ Fe ₇₄ with a thickness of 1000Å to be formed on the substrate.
The first layer (recording / reproducing layer) is formed. Then, the evaporation source is replaced while maintaining the vacuum state. Then, vapor deposition is performed again to form a second layer (recording auxiliary layer) of Gd ₂₄ Tb ₃ Fe ₇₃ having a thickness of 2000Å on the first layer. Both the first and second layers are perpendicular magnetization films.

Thus, the two-layer magneto-optical recording medium No. 1 belonging to class 1 (P type / first quadrant / type 1) was manufactured. The manufacturing conditions and characteristics of this medium are shown in Table 2 below.

[0123]

[Table 2]

This medium has T _L = 170 ° C. and T _H = 230 ° C.
Then, Equation 11 is satisfied, and from Table 2, H _C1 = 5600 Oe,
The right side of the equation 12 is calculated to be 868 Oe, which satisfies the equation 12. Further, in the expression 15, H _C2 + (σ _w / 2M _S2 t
₂ ) = 468 Oe, H _C1 − (σ _w / 2M _S1 t ₁ ) = 51
Since it is 00 Oe, if Hini.
To be satisfied. Then, the magnetization of layer (1) will be Hin at room temperature.
Only the magnetization of the recording auxiliary layer (2) is reversed without being reversed by i.

Further, H _C1 = 5600 Oe, (σ _w / 2M _S1
Since t ₁ ) = 400 Oe, Equation 13 is satisfied, and H _C2 = 35
0 Oe, (σ _w / 2M _S2 t ₂ ) = 118 Oe, so
Since 14 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, if the initial auxiliary magnetic field of Hini. = 600 Oe is applied in the “A direction” ↑, and the recording magnetic field of Hb = 600 Oe is applied in the “A direction” ↑, overwriting becomes possible.
Since Hb and Hini. Have the same size and direction, in this case, it is possible to use a recording device that also serves as one applying means for each.

It is assumed that this medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on this medium. At this time, using the apparatus of Example 10 or 11,
The intensity of the beam is set to the first level = 6.6 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 170 ° C. at the first low-level irradiation.

Reference Example 2 / Medium No. 2 As in Reference Example 1, the first layer (recording / reproducing layer) of Tb ₂₇ Fe ₇₃ having a thickness of 500 Å and the Gd ₂₄ having a thickness of 2000 Å thereon were formed on the substrate. A second layer (recording auxiliary layer) of Tb ₃ Fe ₇₃ is formed. As a result, class 2 (P
Media No. 2 belonging to type 1st quadrant type 2) was manufactured.

The manufacturing conditions and characteristics of this medium are shown in Table 3 below.

[0129]

[Table 3]

This medium has T _L = 150 ° C. and T _H = 230 ° C.
Then, Equation 16 is satisfied, and from Table 3, H _C1 = 7000 Oe,
When the right side of Expression 17 is calculated to be 1330 Oe, Expression 17 is satisfied. Further, in the equation 20, H _C2 + (σ _w / 2M _S2 t
₂ ) = 497 Oe, H _C1 − (σ _w / 2M _S1 t ₁ ) = 6167
Since it is Oe, if Hini. Is set to 600 Oe, Equation 20 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 5600 Oe, (σ _w / 2M _S1
Since t ₁ ) = 833 Oe, Equation 18 is satisfied, and H _C2 = 35
0 Oe, (σ _w / 2M _S2 t ₂ ) = 147 Oe, so
Since 19 is satisfied, even if Hini. Is removed, the magnetizations of layer (1) and layer (2) are respectively retained. Therefore, an initial auxiliary magnetic field of Hini. = 600 Oe is applied to, for example, “A direction” ↑, and a recording magnetic field of Hb = 600 Oe is “A direction”.
Applying to ↓ enables overwriting. Incidentally, H
Since b and Hini. have the same size and direction, in this case,
It is possible to use a recording device that also serves as one of the respective application means.

It is assumed that this medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on this medium. At this time, using the apparatus of Example 10 or 11,
The beam intensity is the first level = 5.7 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 150 ° C. at the first low-level irradiation.

Reference Example 3 / Medium No. 3 As in Reference Example 1, the first layer (recording / reproducing layer) of Gd ₂₃ Tb ₃ Fe ₇₄ having a thickness of 500 Å and the Tb having a thickness of 1000 Å thereon were formed on the substrate. ₂₈ Fe ₆₅ Co ₇ 2nd layer (
A recording auxiliary layer). As a result, the medium No. 3 belonging to the class 3 (P type, first quadrant, type 3) was manufactured.

The manufacturing conditions and characteristics of this medium are shown in Table 4 below.

[0135]

[Table 4]

This medium has T _L = 170 ° C. and T _H = 220 ° C.
Then, Equation 21 is satisfied, and from Table 4, H _C1 = 8000 Oe,
The right side of the equation 22 is calculated to be 4389 Oe, which satisfies the equation 22. Further, in the equation 25, H _C2 + (σ _w / 2M _S2 t
₂ ) = 3278 Oe, H _C1 − (σ _w / 2M _S1 t ₁ ) = 6889
Since it is Oe, if Hini. Is 4000 Oe, then Equation 25 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the recording auxiliary layer (2) is reversed.

Further, H _C1 = 8000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 1111 Oe, Equation 23 is satisfied, and H _C2 = 30
00 Oe, (σ _w / 2M _S2 t ₂ ) = 278 Oe, so the formula
Since 24 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, by applying an initial auxiliary magnetic field of Hini.

It is assumed that this medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on this medium. At this time, using the apparatus of Example 10 or 11,
The intensity of the beam is set to the first level = 6.6 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 170 ° C. at the first low-level irradiation.

[Reference Example 4 / Medium No. 4] Similar to Reference Example 1, the first layer (recording / reproducing layer) of Tb ₁₃ Dy ₁₃ Fe ₇₄ having a thickness of 1000 Å was formed on the substrate, and the same was formed thereon. 1000 Å thick Gd ₁₄ Dy ₁₄ Fe
The second layer of ₇₂ (recording auxiliary layer) is formed. As a result, media belonging to class 4 (P type, first quadrant, type 4)
No. 4 was manufactured.

Table 5 shows the manufacturing conditions and characteristics of this medium.

[0141]

[Table 5]

This medium has T _L = 120 ° C. and T _H = 160 ° C.
Then, Equation 26 is satisfied, and from Table 5, H _C1 = 8000 Oe,
The right side of Expression 27 is calculated to be 3750 Oe, so Expression 27 is satisfied. Further, in Equation 30, H _C2 + (σ _w / 2M _S2 t
₂ ) = 3250 Oe, H _C1 − (σ _w / 2M _S1 t ₁ ) = 7500
Since it is Oe, if Hini. Is 4000 Oe, the formula 30 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 8000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 500 Oe, Equation 28 is satisfied, and H _C2 = 30
00Oe, (σ _w / 2M _S2 t ₂ ) = 250 Oe, so the formula
Since 29 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, by applying an initial auxiliary magnetic field of Hini.

It is assumed that the medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on the medium. At this time, using the apparatus of Example 10 or 11,
The beam intensity is the first level = 4.3 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 120 ° C. at the first low-level irradiation.

[Reference Example 5 / Medium No. 5] As in Reference Example 1, a first layer (recording / reproducing layer) of Gd ₁₃ Dy ₁₃ Fe ₇₄ having a thickness of 500Å and a thickness of 600Å thereon were formed on the substrate. Second of Tb ₁₈ Fe ₇₄ Co ₈
A layer (recording auxiliary layer) is formed. This allows for class 5
Medium No. 5 belonging to (A type, second quadrant, type 3) was manufactured.

The manufacturing conditions and characteristics of this medium are shown in Table 6 below.

[0147]

[Table 6]

This medium has T _L = 165 ° C. and T _H = 210 ° C.
Then, Equation 31 is satisfied, and from Table 6, H _C1 = 6000 Oe,
The right side of Expression 32 is calculated to be 3445 Oe, which satisfies Expression 32. Also, in Equation 35, H _C2 + (σ _w / 2M _S2 t
₂ ) = 3444 Oe, H _C1 + (σ _w / 2M _S1 t ₁ ) = 6889
Since it is Oe, if Hini. Is 4000 Oe, Equation 35 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 6000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 889 Oe, Equation 33 is satisfied, and H _C2 = 30
00 Oe, (σ _w / 2M _S2 t ₂ ) = 444 Oe, so
Since 34 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, by applying an initial auxiliary magnetic field of Hini.

It is assumed that the medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on the medium. At this time, using the apparatus of Example 10 or 11,
The beam intensity is the first level = 6.4 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 165 ° C. at the first low-level irradiation.

Reference Example 6 Medium No. 6 Using a ternary RF magnetron sputtering apparatus, three targets of Tb, Fe and FeCo alloy shown in Table 7 below are placed. First, two targets of Tb and Fe (binary) are used, and then two targets of Tb and FeCo alloy (binary) are used. Thickness 1.2mm, diameter 200mm
The glass substrate of 1 is set in the chamber of the apparatus.

The inside of the chamber of the device was once set at 7 × 10 ⁻⁷ Tor.
r. After evacuating to a vacuum degree below, Ar gas was added at 5 × 10 ^-3 Torr.
Introduce. Then, sputtering is performed at a deposition rate of about 2Å / sec. Thus, the first layer (recording / reproducing layer) of Tb ₂₇ Fe ₇₃ having a thickness of 500 Å is formed on the substrate. Then, the target is changed while maintaining the vacuum state. Then, sputtering is performed again, and the second layer (recording auxiliary layer) of Tb ₁₈ Fe ₇₄ Co ₈ having a thickness of 1000 Å is formed on the first layer.
To form. Both the first and second layers are perpendicular magnetization films.

Thus, the two-layer magneto-optical recording medium No. 6 belonging to class 6 (A type, second quadrant, type 4) was manufactured. The manufacturing conditions and characteristics of this medium are shown in Table 7 below.

[0154]

[Table 7]

This medium has T _L = 155 ° C. and T _H = 220 ° C.
Then, Equation 36 is satisfied, and from Table 7, H _C1 = 7000 Oe,
The right side of the equation 37 is calculated to be 3750 Oe, so the equation 37 is satisfied. Further, in the equation 40, H _C2 + (σ _w / 2M _S2 t
₂ ) = 3500 Oe, H _C1 + (σ _w / 2M _S1 t ₁ ) = 8250
Since it is Oe, if Hini. Is 4000 Oe, the expression 40 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 7000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 1250 Oe, Expression 38 is satisfied, and H _C2 = 30
00 Oe, (σ _w / 2M _S2 t ₂ ) = 500 Oe, so the formula
Since 39 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, by applying an initial auxiliary magnetic field of Hini.

It is assumed that this medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on this medium. At this time, using the apparatus of Example 10 or 11,
The beam intensity is the first level = 5.9 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 155 ° C. at the first low-level irradiation.

[Reference Example 7 / Medium No. 7] As in Reference Example 6, the first layer (recording / reproducing layer) of Tb ₂₁ Fe ₇₉ having a thickness of 1000 Å and the Tb ₁₈ having a thickness of 1000 Å were formed on the substrate. A second layer (recording auxiliary layer) of Fe ₇₄ Co ₈ is formed. As a result, class 7 (P
Media No. 7 belonging to Type 3rd quadrant Type 4) was manufactured.

The manufacturing conditions and characteristics of this medium are shown in Table 8 below.

[0160]

[Table 8]

This medium has T _L = 155 ° C. and T _H = 220 ° C.
Then, Equation 41 is satisfied, and from Table 8, H _C1 = 7000 Oe,
The right side of the equation 42 is calculated to be 4571 Oe, which satisfies the equation 42. Also, in Equation 45, H _C2 + (σ _w / 2M _S2 t
₂ ) = 3500 Oe, H _C1 − (σ _w / 2M _S1 t ₁ ) = 5929
Since it is Oe, if Hini. Is 4000 Oe, then Equation 45 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 7000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 1071 Oe, Equation 43 is satisfied, and H _C2 = 30
00 Oe, (σ _w / 2M _S2 t ₂ ) = 500 Oe, so the formula
Since 44 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, overwriting becomes possible by applying the initial auxiliary magnetic field of Hini.

It is assumed that the medium is moved at a constant linear velocity of 8.5 m / sec by the rotating means and a laser beam is irradiated on the medium. At this time, using the apparatus of Example 10 or 11,
The beam intensity is the first level = 5.9 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 155 ° C. at the first low-level irradiation.

Reference Example 8 / Medium No. 8 As in Reference Example 6, the first layer (recording / reproducing layer) of Tb ₂₁ Fe ₇₉ having a thickness of 500Å and the Gd ₂₄ having a thickness of 2000Å were formed on the substrate. A second layer (recording auxiliary layer) of Tb ₃ Fe ₇₃ is formed. As a result, class 8 (A
Media No. 8 belonging to type, 4th quadrant, type 2) was manufactured.

The manufacturing conditions and characteristics of this medium are shown in Table 9 below.

[0166]

[Table 9]

This medium has T _L = 155 ° C. and T _H = 230 ° C.
Then, Equation 46 is satisfied, and from Table 9, H _C1 = 7000 Oe,
When the right side of Expression 47 is calculated to be 2273 Oe, Expression 47 is satisfied. Also, in Equation 50, H _C2 + (σ _w / 2M _S2 t
₂ ) = 570 Oe, H _C1 + (σ _w / 2M _S1 t ₁ ) = 9143
Since it is Oe, if Hini. Is set to 800 Oe, Equation 50 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 7000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 2143 Oe, expression 48 is satisfied, and H _C2 = 35
0 Oe, (σ _w / 2M _S2 t ₂ ) = 220 Oe, so the formula
Since 49 is satisfied, the magnetizations of layer (1) and layer (2) are retained even if Hini. Is removed. Therefore, if the initial auxiliary magnetic field of Hini. = 800 Oe is applied in the “A direction” ↑, and the recording magnetic field of Hb = 800 Oe is applied in the “A direction” ↑, overwriting becomes possible.
Since Hb and Hini. Have the same size and direction, in this case, it is possible to use a recording device that also serves as one applying means for each.

It is assumed that this medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on this medium. At this time, using the apparatus of Example 10 or 11,
The beam intensity is the first level = 5.9 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 155 ° C. at the first low-level irradiation.

Reference Example 9 / Medium No. 9 As in Reference Example 1, the first layer (recording / reproducing layer) of Gd ₄ Tb ₁₉ Fe ₇₇ having a thickness of 1000 Å and the thickness of 500 Å thereon were formed on the substrate. Second of Tb ₂₉ Fe ₆₁ Co ₁₀ of
A layer (recording auxiliary layer) is formed. This allows for class 9
Medium No. 9 belonging to (A type, 4th quadrant, type 4) was manufactured.

The manufacturing conditions and characteristics of this medium are shown in Table 10 below.

[0172]

[Table 10]

This medium has T _L = 170 ° C. and T _H = 220 ° C.
Then, Equation 51 is satisfied, and from Table 10, H _C1 = 7000 Oe,
The right side of Expression 52 is calculated to be 4167 Oe, so Expression 47 is satisfied. Further, in the equation 55, H _C2 + (σ _w / 2M _S2 t
₂ ) = 3500 Oe, H _C1 + (σ _w / 2M _S1 t ₁ ) = 8667
Since it is Oe, if Hini. Is 4000 Oe, the equation 55 is satisfied. Then, the magnetization of the layer (1) is not reversed by Hini. At room temperature, but only the magnetization of the recording auxiliary layer (2) is reversed.

Further, H _C1 = 7000 Oe, (σ _w / 2M _S1
Since t ₁ ) = 1667 Oe, Equation 53 is satisfied, and H _C2 = 30
00 Oe, (σ _w / 2M _S2 t ₂ ) = 500 Oe, so the formula
Since 54 is satisfied, even if Hini. Is removed, the magnetizations of the layer (1) and the layer (2) are respectively retained. Therefore, by applying an initial auxiliary magnetic field of Hini.

It is assumed that the medium is moved by a rotating means at a constant linear velocity of 8.5 m / sec and a laser beam is irradiated on the medium. At this time, using the apparatus of Example 10 or 11,
The intensity of the beam is set to the first level = 6.6 mW (on disk).
The beam is pulse modulated by the control means between a first level and a second level (zero). Then, the temperature of the medium reaches T _L = 170 ° C. at the first low-level irradiation.

[0176]

[Embodiment 10] This apparatus is dedicated to bit formation. Basically speaking, (a) a laser beam light source; and (b)
From the control means for controlling the light source to an intensity (first level) at which the temperature of the medium is increased to "a temperature lower than the Curie point of the second layer" when the medium is irradiated with the laser beam. Become. The device is capable of forming a bit in the first layer having a magnetization orientation controlled by the second layer. The first level depends on the medium.

[0177]

[Embodiment 11] This device is dedicated to bit formation. As far as the basic structure is concerned, (a) a laser beam light source; and (b)
When the medium is irradiated with the laser beam, the temperature of the medium is “the temperature near the Curie point of the first layer”.
Control means for controlling the light source at an increasing intensity (first level). The device is capable of forming a bit in the first layer having a magnetization orientation controlled by the second layer. The first level depends on the medium.

[0178]

As described above, according to the present invention, in magneto-optical recording, the force of the second layer is borrowed, and this force is transferred to the first layer (recording layer) through the exchange coupling force or other magnetic coupling force. The recording magnetic field Hb is unnecessary because it affects the reproduction layer) and thereby forms a bit in the first layer.

[Brief description of drawings]

FIG. 1 is a conceptual diagram showing a vertical cross section of a magneto-optical recording medium having a two-layer film structure used in the present invention.

FIG. 2 is a conceptual diagram illustrating a recording principle of a magneto-optical recording method.

FIG. 3 is a conceptual diagram illustrating a reproducing principle of a magneto-optical recording method.

FIG. 4 is a vector diagram explaining that there are four kinds of relationships between the magnitude relationship between RE and TM spins and the magnetization direction of the alloy in the RE-TM alloy.

FIG. 5 shows RE rich or T for the first layer and the second layer.
FIG. 6 is an explanatory diagram illustrating that there are four types of media as a whole when divided by M rich.

FIG. 6 is a graph showing the relationship between coercive force and temperature for the first layer (thin line) and the second layer (thick line) of media of types 1 and 2, respectively.

FIG. 7 is a graph showing the relationship between coercive force and temperature for the first layer (thin line) and the second layer (thick line) of media of types 3 and 4, respectively.

FIG. 8 is a graph showing the relationship between coercive force and temperature for the first layer (thin line) and the second layer (thick line) of a class 1 medium.

FIG. 9 is a graph showing the relationship between coercive force and temperature for the first layer (thin line) and the second layer (thick line) of Class 2 and 8 media.

FIG. 10 is a graph showing the relationship between coercive force and temperature for the first layer (thin line) and the second layer (thick line) of Class 3 and 5 media.

FIG. 11 is a graph showing the relationship between coercive force and temperature for the first layer (thin line) and the second layer (thick line) of the media of Classes 4, 6 and 7 and 9, respectively. L ... Laser beam Lp ... Linearly polarized light B ₁ ... Bit having "A-direction" magnetization B ₀ ... Bit having "reverse A-direction" magnetization 1 ... Recording / reproducing layer (first layer) 2. ..Recording auxiliary layer (second layer) S ... substrate or more

Claims (5)

[Claims] 1. A first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, a second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is higher than that of the first layer. By irradiating a laser beam on a high multi-layered magneto-optical recording medium and heating it to a temperature lower than the Curie point of the second layer, a bit having a magnetization direction controlled by the second layer is formed on the first layer. How to form. 2. A first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, a second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is higher than that of the first layer. Method for forming a bit having a magnetization direction controlled by the second layer on the first layer by irradiating a high multilayer magneto-optical recording medium with a laser beam to heat it near the Curie point of the first layer . 3. A first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, a second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is higher than that of the first layer. When there is a high multilayer magneto-optical recording medium, (a) a laser beam light source; and (b) when the laser beam is applied to the medium,
The magnetization direction controlled by the second layer, comprising means for controlling the light source so as to increase the temperature of the medium to “a temperature lower than the Curie point of the second layer”. A bit forming device for forming a bit included in a first layer. 4. The first layer having perpendicular magnetic anisotropy is a recording / reproducing layer, the second layer having perpendicular magnetic anisotropy is a recording auxiliary layer, and the Curie point of the second layer is higher than that of the first layer. When there is a high multilayer magneto-optical recording medium, (a) a laser beam light source; and (b) when the laser beam is applied to the medium,
A magnetization direction controlled by the second layer, characterized in that it comprises means for controlling the light source so that the temperature of the medium is increased to "the temperature near the Curie point of the first layer". A bit forming device for forming a bit on a first layer. 5. A laser beam is applied to a “multilayer magneto-optical recording medium including at least a first layer having perpendicular magnetic anisotropy and a second layer having perpendicular magnetic anisotropy” to form the second layer. A bit having a magnetization direction controlled by the second layer is formed in the first layer by heating at a temperature lower than the Curie point of the layer or in the vicinity of the Curie point of the first layer, and then the bit is magneto-optical. How to play.