JP3228964B2 - Magneto-optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium which is used for a magneto-optical memory, a magnetic recording, a display element and the like, and can be read out by using a magneto-optical effect such as a magnetic Kerr effect or a Faraday effect. More particularly, the present invention relates to a magneto-optical recording medium capable of overwriting by light modulation.

[0002]

2. Description of the Related Art A magneto-optical recording medium is known as an erasable optical memory medium. Compared to a conventional magnetic recording medium using a magnetic head, a magneto-optical recording medium has advantages such as high-density recording and non-contact recording / reproduction, but has an area to be recorded once before recording. Since the data has to be erased (it must be magnetized in one direction), the processing speed is low. To make up for this shortcoming,
A method in which a recording / reproducing head and an erasing head are separately provided, or a method in which a continuous laser beam is applied and a magnetic field is applied while modulating the magnetic field to perform recording is proposed.

[0003] However, these systems have the disadvantage that the device becomes large and the cost increases, or that high-speed modulation cannot be performed.

For this purpose, a method of performing overwriting (overwriting) by changing the power of a laser beam using an exchange-coupling laminated film has been proposed, and several methods and media suitable for the method have been proposed. ing.

[0005]

The method of modulating the laser power uses at least two layers of exchange-coupling laminated films having different Curie temperatures, and information written in a layer having a relatively higher Curie temperature is used. It consists of a process of transferring information to a layer having a lower Curie temperature, and erasing information written to a layer having a higher Curie temperature while transferring the information while retaining the information transferred to this layer. Therefore, the retention of information is left to the coercive force energy of the layer having a relatively lower Curie temperature, and the information must be read by reading the bit information held in this layer.

However, the storage stability of a bit generally decreases as the Curie temperature decreases, and the Kerr rotation angle, which is one of the factors that determine the quality of a reproduced signal, decreases as the Curie temperature decreases. For this reason, it is necessary to set the absolute Curie temperature of the layer having a relatively lower Curie temperature higher. On the other hand, to improve the recording sensitivity, the higher the Curie temperature is, the higher the Curie temperature is. The absolute Curie temperature of the layer needs to be set lower.

Therefore, it is extremely difficult to achieve both high recording sensitivity and high bit storage stability or high reproduction signal quality with the conventional medium configuration.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and it is possible to avoid the restriction on the relative relationship of the Curie temperatures in the conventional medium, and to provide a good medium. It is an object of the present invention to provide a magneto-optical recording medium capable of retaining information in a layer having an absolutely high Curie temperature while maintaining recording sensitivity or reading information from a layer having an absolutely high Curie temperature. And

The above object is achieved by a magneto-optical recording medium described below.

That is, n layers (n is an odd number of 7 or more) on the substrate
Is a magneto-optical recording medium in which a plurality of magnetic thin films are stacked by exchange coupling.
When the Curie temperature of the i-th magnetic layer is Tc _i , an appropriate constant external magnetic field (H
b) A magneto-optical recording medium characterized by satisfying the following conditions under application. (However, Tcn _{+ 1} is the ambient temperature, and m is an arbitrary natural number equal to or less than (n-1) / 2.) Tc ₁ ≧ Tc ₃ 2. 2. When m ≧ 2, Tc _2m ≧ Tc _{2 (m + 1)} Tc ₆ ≧ Tc ₂ ≧ Tc _{n + 1} 4. Tc _{2m + 1} ≧ Tc ₆ 5. At room temperature, the first magnetic layer is magnetized in an appropriate predetermined orientation state, and the first magnetization state in which the atomic spin of each magnetic layer is matched over the entire thickness direction, or
Except that the first magnetic layer is magnetized in the predetermined orientation state and there is an interface mismatch between the third magnetic layer and the fifth magnetic layer to form an interface domain wall, each magnetic layer has It must be in one of the second magnetization states where the atomic spins are matched.

[0011] 7. From the first and second magnetization states temperature of the sixth magnetic layer becomes temperatures above Tc6, until the temperature of the third magnetic layer is in a suitable first temperature state of not reaching the Tc ₃ The magnetizations of the fourth magnetic layer and the fifth magnetic layer are changed to the third so that the coupling state by the exchange interaction becomes stable when heated.
Atomic spin is aligned with respect to the magnetic layer to orient the magnetic layer, and the magnetization of the third magnetic layer is kept in the alignment state before heating.

8. When the temperature of the third magnetic layer is heated from the first and second magnetization states to an appropriate second temperature state at which the temperature of the third magnetic layer becomes Tc ₃ , the magnetization of the third magnetic layer becomes the same as before heating. State transition to an orientation state different from the orientation state.

9. In each cooling process after heating from the first and second magnetization states to the first and second temperature states, the temperature of the (2m) magnetic layer is Tc _2m
(2m) -th magnetic layer and (2m-th) magnetic layer so that the coupling state by exchange interaction becomes stable when the temperature drops to
+1) The magnetization of the magnetic layer is oriented with the atomic spin aligned with the (2m-1) -th magnetic layer, and the magnetization of the (2m-1) -th magnetic layer retains its previous alignment state.

[0014] 10. In the cooling process after heating from said first and second magnetization states until the second temperature state, the temperature of the second magnetic layer is lowered to a temperature of Tc _2, exchange interaction When the magnetizations of the second magnetic layer and the third magnetic layer are oriented with the atomic spins aligned with the first magnetic layer so that the coupling state by the action becomes stable, the magnetization of the fifth magnetic layer becomes To maintain the alignment state.

[0015] 11. In the first and each of the processes the second cooled after heating from the magnetization state until the first and second temperature state, always the predetermined alignment state magnetization of the first magnetic layer To hold.

[0016]

In the composite membrane having the above-mentioned layer structure,
The layer on which information is first written is the third magnetic layer, and the (2m + 1) -th magnetic layer (where m ≧ 2) transfers and holds this information. Reading is performed from the n-th magnetic layer side, and information held in a group of (2m + 1) -th magnetic layers is read. The first magnetic layer is a layer for erasing and initializing information written in the third magnetic layer after transfer.
The (2m) -th magnetic layer is a layer for controlling the presence or absence of magnetic coupling between the layers according to the medium temperature, and particularly the fourth magnetic layer is a layer for adjusting the magnitude of the coupling force between the layers. is there.

Next, by raising and lowering the temperature of the composite film to two kinds of temperature states having different magnetization states, two kinds of magnetization states corresponding to the respective temperature states are determined irrespective of the initial magnetization state. This will be described with reference to FIG.

First, the first magnetic layer is magnetized in a predetermined direction, the spins of each layer are all matched, and an initial state where no domain wall exists at the interface (hereinafter, this state is referred to as state A). Think about what happened.

From the initial state (state A; FIG. 1a), the surface of the magnetic layer is irradiated with a first kind of laser beam while applying an appropriate bias magnetic field described later, and the irradiated part is irradiated with a sixth laser beam.
The heating is performed until the temperature of the magnetic layer becomes equal to or higher than Tc ₆ and the temperature of the third magnetic layer reaches an appropriate first temperature state in which the temperature does not reach Tc ₃ . Assuming that there is no temperature gradient in the thickness direction of the magnetic layer, at this time, the (2
m) The magnetic layers are all above the Curie temperature, and the magnetic coupling of each layer is broken. The third magnetic layer maintains the initial magnetization state, and the magnetizations of the fourth magnetic layer and the fifth magnetic layer also have atomic spins matched to the third magnetic layer, and are caused by exchange interaction. An initial magnetization state in which the coupling state is stable is adopted (FIG. 1B). After the laser irradiation is stopped, when the medium temperature drops, the temperature gradually decreases to the Curie temperature or lower from the sixth magnetic layer, and the layers are sequentially coupled to each other in a state of magnetization such that stable coupling is achieved. That is, all the layers are in the initial magnetization state, and the magnetization state of the composite film remains in the state A (FIG. 1A).

Next, while applying the same bias magnetic field as above from the initial state (state A), the surface of the magnetic layer is irradiated with a second type of laser beam, and the irradiated portion is heated to the temperature of the third magnetic layer. There is heated to a suitable second temperature condition being a temperature of Tc ₃ neighborhood. At this time, by setting a bias magnetic field to be applied in an appropriate direction and magnitude so that the magnetization of the third magnetic layer is inverted at this temperature, the magnetization of the third magnetic layer in this portion is inverted ( FIG. 1c). At this time, the (2m) magnetic layers other than the fourth magnetic layer are all at the Curie temperature or higher, and the magnetic coupling of each layer is broken. For the Curie temperature Tc ₄ of the fourth magnetic layer, Tc
_Since the relationship with ₃ is not specified, the magnetic coupling between the third magnetic layer and the fifth magnetic layer may be disconnected at this time or may be coupled. Assuming that the fifth magnetic layer did not reverse magnetization at the same time as the third magnetic layer, it means that the spin orientation of the third magnetic layer and the fifth magnetic layer are not matched. Therefore, when the temperature of the fourth magnetic layer is equal to or lower than the Curie temperature, a spin transition region is formed between the third magnetic layer including the layer and the fifth magnetic layer, and the spin transition region is caused by the exchange interaction. Energy (interface domain wall energy) is accumulated. If the medium temperature drops from this temperature after the laser irradiation is stopped, the fourth magnetic layer becomes below the Curie temperature in any case, and this energy increases with the temperature drop. Attempts to match spin orientation. At this time, the fifth at this temperature
If the thickness and the like are adjusted and designed so that the coercive energy of the magnetic layer becomes smaller than the coercive energy of the third magnetic layer, the magnetization reversal of the fifth magnetic layer occurs preferentially, and
Matched to the spin of the magnetic layer (FIG. 1d). Thus, the magnetization state of the third magnetic layer, which is the magnetization state inverted from the initial state, is transferred to the fifth magnetic layer. (However, when the fifth magnetic layer reverses magnetization at the same time as the third magnetic layer, there is no limitation on the coercive force energy at this temperature. In addition, the fourth magnetic layer or the fifth magnetic layer reverses first. A process may be adopted in which this is transferred to the third magnetic layer later.) When the medium temperature further drops below the Curie temperature of the sixth magnetic layer, the seventh magnetic layer is magnetically coupled via this layer. In a similar process, the fifth
The magnetization state of the magnetic layer is transferred to the seventh magnetic layer (FIG. 1).
e). In this way, the magnetization state inverted from the initial state is sequentially transferred, and finally the medium temperature becomes Tc _n-1
When the following occurs, the image is transferred to the n-th magnetic layer, and the transfer ends.

On the other hand, when the temperature of the second magnetic layer becomes equal to or lower than the Curie temperature during the cooling process, the magnetization state (invariant from the initial state) of the first magnetic layer is transferred to the third magnetic layer, and the magnetization of the third magnetic layer is reduced. Invert again and return to the initial state. For this reason, the spin orientation of the third magnetic layer and the fifth magnetic layer is mismatched, and a spin transition region is formed between the two layers including the fourth magnetic layer, where the interface domain wall energy is accumulated. However, at this time, since the fifth magnetic layer is already bonded to the sixth and higher magnetic layers, the immediately preceding magnetization state can be maintained by the coercive force energy of these layers. As a result, the magnetization state of the magnetic composite film from the first magnetic layer to the third magnetic layer has the spin direction matched to the first magnetic layer magnetized in a predetermined direction, and the fifth magnetic layer From the magnetic layer to the n-th magnetic layer, the spin directions are aligned in a state opposite to that of the first magnetic layer, and there is a spin mismatch between the third magnetic layer and the fifth magnetic layer. It becomes a magnetized state in which the domain wall as the transition region exists (hereinafter, this state is referred to as state B; FIG. 1f).

Next, a change in the magnetization state when the initial state is the state B will be considered.

From this state (state B; FIG. 1f), while applying the same bias magnetic field as above, the surface of the magnetic layer is irradiated with the first kind of laser beam, and the irradiated part is irradiated with the sixth laser beam.
The temperature of the magnetic layer becomes Tc ₆ or more and the temperature of the third magnetic layer becomes Tc.
heating to up to an appropriate first temperature state of not reaching the c _3. In this case, the spin orientation of the third magnetic layer and the fifth magnetic layer is not matched, and a spin transition region is formed between the two layers including the fourth magnetic layer, and the interface domain wall energy is accumulated. ing. The fifth magnetic layer was maintained in this magnetized state by being supported by the coercive force energy of these layers by bonding with the sixth magnetic layer and higher layers. The magnetization state cannot be maintained only by the coercive force energy, and the magnetization is reversed so that the spin direction matches the third magnetic layer (FIG. 1g). When the medium temperature drops after stopping the laser irradiation, the respective layers are sequentially coupled while the spin directions are matched so that the coupling due to the exchange interaction becomes a stable state when the medium temperature gradually decreases from the sixth magnetic layer. . That is, each of the layers has a magnetization state in which the spin direction matches the first magnetic layer magnetized in a predetermined direction, and eventually, the magnetization state of the composite film becomes state A (FIG. 1A).

Finally, from the state B (FIG. 1f), the surface of the magnetic layer is irradiated with the above-mentioned second kind of laser beam while applying the same bias magnetic field as described above, and the temperature of the third magnetic layer is set to Tc _3. Consider a case in which heating is performed to a suitable second temperature state which is a temperature close to the temperature. In this case, the magnetization of the third magnetic layer in this portion is reversed (FIG. 1h), and in the subsequent cooling process, the same process as in the case where the initial state is the state A (FIG. 1i, e) is finally completed. The magnetization state of the film becomes state B (FIG. 1f).

As described above, regardless of the initial magnetization state of the medium, a magnetization state of state A can be formed in the irradiation area by the first type of laser beam, and a magnetization state of state B can be formed by the second type of laser beam. Therefore, it is possible to record information while overwriting by moving the irradiation unit while switching and modulating these two types of laser beams according to the information. Here, the two types of laser beams may be any type as long as they induce the first temperature state and the second temperature state in the irradiated portion of the medium, respectively. And a combination of two types of laser beams having different pulse widths.

Further, the object of solving the above-mentioned conventional problems can also be achieved by the following magneto-optical recording medium.

That is, the (n-2) layer (n is an odd number of 7 or more) on the substrate
Is a magneto-optical recording medium in which the magnetic thin films of (n) are stacked by exchange coupling and
Magnetic layer, a fourth magnetic layer, ..., the n-th magnetic layer, when the Curie temperature of the i-th magnetic layer was Tc _i, a magneto-optical recording medium, characterized in that the following conditions are met. (However,
Tc _{n + 1} is an ambient temperature, and m is an arbitrary natural number of 2 or more and (n-1) / 2 or less. 1. Tc _2m ≧ Tc _{2 (m + 1)} 2. Tc _{2m + 1} ≧ Tc ₆ , Tc ₃ ≧ Tc ₆ 3.Tc _{2m + 1} ≧ Tc ₃ 4. Appropriate first external magnetic field (Hini) When applied, the third magnetic layer is oriented so as to be in a stable state with respect to the external magnetic field, and the magnetization of the fifth magnetic layer maintains the oriented state before the external magnetic field is applied.

The following conditions correspond to the first external magnetic field (Hi
ni), after applying a suitable constant second external magnetic field (H
b) To be valid under applied voltage.

5. At room temperature, the third magnetic layer and the fifth
The magnetic layer holds the magnetization state immediately after the application of the first external magnetic field (Hini). Or the second magnetization state in which the atomic spins of the respective magnetic layers are matched except that there is an interface magnetic wall mismatch between the third magnetic layer and the fifth magnetic layer. The magnetized state is taken.

6. From the above-mentioned first and second magnetization states, the temperature of the sixth magnetic layer becomes equal to or higher than the temperature of Tc ₆ , and the temperature of the third magnetic layer becomes an appropriate first temperature state which does not reach Tc _3. The magnetizations of the fourth magnetic layer and the fifth magnetic layer are aligned with their atomic spins with respect to the third magnetic layer so that the coupling state by the exchange interaction becomes stable when heated to a minimum. The magnetization of the magnetic layer must maintain the orientation state before heating.

[0031] 7. Magnetization of the third magnetic layer when the temperature of said first and second third magnetic layer from the magnetization state of was heated to a suitable second temperature condition being a temperature of Tc ₃ is preheated State transition to an orientation state different from the orientation state.

8. In each cooling process after heating from the first and second magnetized states to the first and second temperature states, the temperature of the (2m) magnetic layer becomes Tc.
The so coupled state by exchange interaction becomes stable state when the drops to a temperature of _2m (2m) magnetic layer and the (2
The magnetization of the (m + 1) -th magnetic layer is aligned with the atomic spin with respect to the (2m-1) -th magnetic layer, and the magnetization of the (2m-1) -th magnetic layer keeps its previous alignment state.

[0033]

Since the magnetic layer for initializing the third magnetic layer is omitted in the composite film having the above-described layer structure, a magnetic field Hini is applied by external auxiliary means, It is necessary to initialize the third magnetic layer by a magnetic field. Other operations are the same as those of the above-described magneto-optical recording medium.

Regardless of which magneto-optical recording medium is used, reading of recorded information from the recording medium on which information has been recorded is performed by irradiating a linearly polarized low-power laser beam to the n-th magnetic layer side. To improve recording sensitivity,
Although it is necessary to set the Curie temperature of the third magnetic layer low, the magnetic layer on the reading side can be set to a high Curie temperature independently of this, so that the incident laser beam is reflected by a group of high Curie temperature magnetic layers. Thus, a high magneto-optical effect can be obtained. Further, since the recorded information is held by the magnetic layer having a high Curie temperature, the recorded information can be stably stored even when the temperature of the medium is increased by the reading laser.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 2 is a schematic sectional view showing a schematic structure of a magneto-optical recording medium according to the first embodiment of the present invention, wherein 1 in the figure denotes a transparent substrate made of glass or plastic. On this substrate, for example, Si ₃ N ₄ , AlN, SiO ₂ , Si
O, ZnS, undercoat layer made of a dielectric material such as MgF ₂ 2
Is provided. On the undercoat layer 2, seven magnetic composite films 3 satisfying the above conditions are sequentially formed from the seventh magnetic layer 37 to the first magnetic layer 31. In order to further prevent corrosion of the magnetic film thereon, for example, Si ₃ N ₄ protective layer 4 made of a dielectric material, such as are formed. These layers are formed by, for example, continuous sputtering using a magnetron sputtering apparatus or continuous evaporation. In particular, the magnetic layers are exchange-coupled to each other by being continuously formed without breaking the vacuum.

In the above-mentioned medium, each magnetic layer may be made of various magnetic materials.
One or more rare earth metal elements such as Pr, Nd, Sm, Gd, Tb, Dy, and Ho are 10 to 40 atomic% and one or more iron group elements such as Fe, Co, and Ni are one or more. It can be constituted by a rare earth-iron group amorphous alloy composed of 90 to 60 atomic%. In addition, Cr, Mn, Cu, Ti, A
Elements such as 1, Si, Pt, and In may be added in small amounts.

In the rare earth-iron group amorphous alloy, when the rare earth element is a heavy rare earth element such as Gd, Tb, Dy, Ho, etc., the magnetic moment of the rare earth element and the magnetic moment of the iron group element are antiparallel. And exhibit so-called ferrimagnetism. In this case, since the net magnetization appears as a difference between the respective sublattice magnetizations, the saturation magnetization can be freely controlled by adjusting the composition ratio of the two. When the rare earth element is a light rare earth element such as Pr, Nd, or Sm, the magnetic moment of the rare earth element and the magnetic moment of the iron group element are connected in parallel, and exhibit ferromagnetism. In this case, it is difficult to control the saturation magnetization, but some adjustment can be made by adding a heavy rare earth element.

The Curie temperature can also be controlled by the composition ratio between the rare earth element and the iron group element. However, in order to control independently of the saturation magnetization, the iron group element contains Fe as a main component, A method of controlling the amount of substitution using Co in which the part is substituted can more preferably be used. That is, the Curie temperature can be raised by about 6 ° C. by substituting 1 atomic% of Fe with Co, and the amount of Co to be added is adjusted by using this relationship so as to obtain a desired Curie temperature. The Curie temperature can also be lowered by adding a small amount of a nonmagnetic element such as Cr or Ti. Alternatively, the Curie temperature can be controlled by using two or more kinds of rare earth elements and adjusting their composition ratio. Since the Curie temperature can be freely controlled by these methods, it is easy to realize the conditions related to the Curie temperature required for carrying out the present invention. However, considering the operating environment temperature, recording sensitivity and recording power margin, the Curie temperature of the third magnetic layer is in the range of 150 to 250 ° C., the Curie temperature of the sixth magnetic layer is in the range of 120 to 180 ° C. The Curie temperature of the first magnetic layer is suitably 250 ° C. or more, and the Curie temperature of the n-th magnetic layer is suitably 180 ° C. or more.

The mechanism of the temperature dependence of various physical properties of the magnetic material is complicated and its control is also very difficult. For this reason, in the implementation of the present invention, the conditions defining the transition process of the magnetization orientation state accompanying the temperature change of the medium have no temperature dependence, and an experiment is performed using "film thickness" as an important parameter which is easy to control. The film thickness that satisfies the condition will be determined. However, from the viewpoint of recording sensitivity, the total thickness of the magnetic layer is about 250 nm.
It is desirable that: The first magnetic layer and the third magnetic layer have a thickness of 10 to 50 nm, and the other (2m +
1) 1 to 20 nm for the magnetic layer, 5 to 25 nm for the fourth magnetic layer, and 0.5 to 10 nm for the other (2m) magnetic layers, and the (2m + 1) ) The total thickness of the magnetic layer is desirably 20 nm or more. Example 1 A track groove and a format signal having a diameter of 8 in which a format signal was previously formed were placed in a sputtering apparatus provided with a 5-element target source.
Set a 6mm disc-shaped polycarbonate substrate,
Evacuated to vacuum.

First, sputtering is performed using a Si ₃ N ₄ target in an Ar gas atmosphere of 0.3 Pa,
An underlayer of silicon nitride of about 60 nm thickness was deposited on the substrate.

Next, sputtering is performed using three targets of Tb, Fe, and Co to form a Tb ₂₀ layer having a thickness of about 20 nm.
A (Fe ₈₅ Co ₁₅ ) ₈₀ seventh magnetic layer was deposited on the undercoat layer. The composition was controlled by adjusting the power applied to each target, and the film thickness was controlled by adjusting the sputtering time. Subsequently, a sixth magnetic layer of Tb ₂₀ (Fe _96.7 Co _3.3 ) ₈₀ was deposited to a thickness of about 5 nm by changing the distribution of the applied power. Subsequently, the distribution of the power to be applied is changed again, and Tb ₂₀ (Fe ₈₅ Co ₁₅ )
_Eighty fifth magnetic layers were deposited to a thickness of about 10 nm. After standing for several hours in this state, sputtering is performed using four targets of Gd, Tb, Fe, and Co, and the third target of (Tb ₇₀ Gd ₃₀ ) ₂₀ (Fe ₉₀ Co ₁₀ ) ₈₀ having a thickness of about 150 nm A magnetic layer was deposited on the fifth magnetic layer.

In order to prevent corrosion of the magnetic film, a target of about 60 nm was again formed thereon using a Si ₃ N ₄ target.
A protective layer of silicon nitride having a thickness of

After the substrate was taken out of the sputtering apparatus, a UV curable resin was spin-coated on the film surface side to improve the mechanical strength, and then cured to form a protective coat layer having a thickness of about 8 μm. A single-plate magneto-optical disk was manufactured.

The composition, thickness and Curie temperature of each magnetic layer selected in the magneto-optical disk of the first embodiment were set to the first values.
Fry on the table. This example shows the simplest configuration in which the process of the present invention can be performed. In particular, the fourth magnetic layer is regarded as having the same material and composition as the third magnetic layer, and has a thickness of 0%.
nm and is substantially omitted. However, in order to adjust the interface domain wall energy between the third magnetic layer and the fifth magnetic layer, the surface is intentionally contaminated by leaving it in a chamber for several hours after the formation of the fifth magnetic layer. The exchange interaction between the layers is appropriately weakened by the lamination. FIGS. 3 and 4 show the temperature dependence of the saturation magnetization, coercive force, and interface domain wall energy density of each layer.

The process of transition of the magnetization orientation state due to the medium temperature change, which is a feature of the present invention, will be described with reference to FIG. In the following description, the saturation magnetization of the i-th magnetic layer is Ms _i , the coercive force is Hc _i , the film thickness is h _i , the Curie temperature is Tc _i, and the interface domain wall between the i-th magnetic layer and the j-th magnetic layer. Let the energy density be σw _ij .

In the medium immediately after the film formation, the atomic spins in the film thickness direction are all matched, but in a maze state in the film surface direction, the TM spin of each layer (spin of iron group element atom)
There are a portion aligned "up" and a portion aligned "down" perpendicular to the film surface.

An external magnetic field Hini of, for example, about 4 kOe is applied to the medium in a downward direction.

In the portion where the TM spins of each layer are all aligned upward, in the case of this medium, since each layer is dominated by the iron group element sublattice magnetization at room temperature, the magnetization is also all expressed upward (FIG. 5A). . Therefore, for a sufficiently small downwardly directed external magnetic field H, 2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ H-σw ₃₅ (110) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms _{3 h 3 + Ms 5 h 5)} H-σw 57 (111) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (Ms 3 h 3 + Ms 5 h 5 + Ms 7 _{h 7) H (112) 2Ms} 5 Hc 5 h 5> 2Ms 5 h 5 H-σw 35 -σw 57 (113) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (Ms 5 h 5 + Ms _{7 h 7) H-σw 35} (114) 2Ms 7 Hc 7 h 7> 2Ms 7 h 7 H-σw 57 (115) is established. Now, when the external magnetic field H is continuously increased to Hini, the relation of the other equations is maintained (11
Since the relationship of the expression (0) is reversed, the magnetization of the third magnetic layer can be inverted downward without causing the magnetization of the fifth magnetic layer to be inverted, so that the third magnetic layer can be oriented in a state stable to the external magnetic field Hini. Thereafter, an external magnetic field H of, for example, 300 Oe is directed upward.
When b is applied, the following equation holds at room temperature, and the state where the domain wall exists at the interface between the third magnetic layer and the fifth magnetic layer (referred to as state B1) is maintained (FIG. 5B).

2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ Hb + σw ₃₅ (120) 2Ms ₅ Hc ₅ h ₅ > -2Ms ₅ h ₅ Hb + σw ₃₅ -σw ₅₇ (121) 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ > -2 (Ms ₅ h ₅ + Ms ₇ h ₇ ) Hb + σw ₃₅ (122) 2Ms ₇ Hc ₇ h ₇ > -2 Ms ₇ h ₇ Hb-σw ₅₇ (123) In the part where the spins are all aligned downward (FIG. 5c), the magnetization is also all expressed downward, so that
Even if a downward external magnetic field Hini is applied, the magnetization state does not change. Thereafter, even if an external magnetic field Hb of 300 Oe is applied upward, the magnetization state does not change because the coercive force of each layer is larger than Hb, and the TM spin of each layer is all downward, and the atomic spin is It is consistent throughout the thickness direction. The magnetization state at this time is referred to as state A1 (see FIG. 5).
d).

When the medium is heated from the state B1 and the medium temperature rises, σw ₅₇ decreases as the medium approaches Tc ₆ , and the relationship of the equation (121) is reversed. Invert. That is, the spin of the fifth magnetic layer matches the spin of the third magnetic layer.

In the state after the inversion of the fifth magnetic layer, the following expression holds, and the domain wall has moved to the interface between the fifth magnetic layer and the seventh magnetic layer (FIG. 5E).

2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ Hb-σw ₃₅ (130) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₃ h ₃ + Ms ₅ h ₅ ) Hb + σw _{57 (131) 2Ms 5 Hc 5 h} 5> 2Ms 5 h 5 Hb- σw 35 + σw 57 (132) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb + σw 57 (133) temperature of the medium in this state is lowered Then, σw ₅₇ sharply increases, and the relationship of Expression (133) is reversed, so that the seventh magnetic layer is inverted downward. That is, the spin of the seventh magnetic layer matches the spin of the fifth magnetic layer (FIG. 5f). Then, the temperature drops to room temperature while maintaining this state. After all, every layer is T
The state where the M spin is directed downward, that is, state A1 (FIG. 5)
c, d).

On the other hand, when the medium temperature is further increased from Tc ₆ and heated to near Tc ₃ , the relationship of the expression (131) is reversed, so that the third magnetic layer and the fifth magnetic layer are simultaneously inverted upward. As a result, the spin direction of each layer is aligned upward (FIG. 5g). When the temperature drops from this state, Tc
_{When the} magnetic layer becomes ₆ or less, the fifth magnetic layer and the seventh magnetic layer are magnetically coupled. However, since the spin directions are matched, the temperature returns to room temperature while maintaining this state (FIG. 5A). When a downward external magnetic field Hini is applied again from this state, the state B
1 (FIG. 5b).

Next, the medium is heated while applying an external magnetic field Hb upward from the state A1 (FIG. 5d). In this case, even if heating is performed up to Tc ₆ , no change in state occurs at all in this temperature range because the coercive force of each layer is greater than Hb (FIG. 5H). Even if the temperature drops from this state, the spins are all matched, the orientation does not change, and remains in the state A1 (FIGS. 5c and 5d).

[0056] On the other hand, when further heated to Tc ₃ near the Tc _6, in the case of this medium Tc _3, Tc ₅ and Tc ₇
Are equal, the coercive force of each layer decreases, and the third magnetic layer, the fifth magnetic layer, and the seventh magnetic layer reverse magnetization upward almost simultaneously at a temperature at which the coercive force of each layer becomes Hb or less (FIG. 5).
g).

When the temperature drops from this state, the fifth magnetic layer and the seventh magnetic layer are magnetically coupled at Tc ₆ or less.
Since the directions of the spins are already aligned in the upward direction, they reach room temperature as they are (FIG. 5a). Then, when a downward external magnetic field Hini is applied again from this state, the state becomes state B1 (FIG. 5B).

From the above description, it is apparent that this medium satisfies the conditions characteristic of the present invention.
In the above description, it is necessary to accurately consider the coercive force energy and the Zeeman energy of the sixth magnetic layer. However, the description is extremely complicated, and the film thickness is relatively small. Since the contribution is small, especially at a temperature near Tc ₆ , the magnitude is negligible, and is omitted here.

The magneto-optical disk according to the first embodiment was set on a magneto-optical disk drive having an optical head having a wavelength of about 780 nm and NA = 0.53, and was rotated at 3600 rpm to measure at a position having a radius of 24 mm. A permanent magnet was fixed at a position different from the optical head, and the recording film was set so that a magnetic field for initialization of 4 kOe was applied to the recording film in a direction perpendicular to the film surface.

300 Oe opposite to the magnetic field for initialization
The recording laser beam is applied with the bottom bias (Pb) and the peak power (Pp) while applying the recording bias magnetic field.
The recording was performed by performing pulse modulation to the two values, and reading was performed with a reproduction power of 1.0 mW. The pulse width was fixed at 57 nsec, (2.7) modulation recording was performed at a channel rate of 17.4 MHz, and the bit error rate at this time was measured. When the above-described recording is performed by varying the bottom power and the peak power after the entire recording state of the disk, the area of the recording power at which the bit error rate is 5 × 10 ⁻⁵ or less is shown by hatching in FIG. . Good overwrite characteristics are obtained in this region. FIG. 7 shows the relationship between C / N and recording power when a 3T pattern is recorded after the entire surface of the disk has been erased.

[0061] Then waving reproducing power, compares the degradation of the recorded one of the reproduced signal after repeated regeneration 10 ⁴ times over the track, a signal reproduced by the reproducing power 1.0mW before and after the repeated reproduction I checked by doing. As a result, reproduction deterioration did not occur up to 3.1 mW. Comparative Example 1 Example 1 was repeated except that the configuration of the magnetic layer was as follows.
A magneto-optical disk was manufactured by the same configuration and manufacturing method as described above.

After the formation of the undercoat layer, the readout magnetic layer having the same material and composition as the sixth magnetic layer in Example 1 was formed to a thickness of 35 nm.
It was formed in thickness. Curie temperature of this layer is about 150 ℃
It is. After being left for several hours in this state, a write magnetic layer having the same material and composition as the third magnetic layer in Example 1 was formed to a thickness of 150 nm. The Curie temperature of this layer is about 220 ° C. The configuration of the magnetic layer is the above-described two-layer configuration, and the interface is intentionally contaminated and the exchange interaction between the layers is appropriately weakened in order to adjust the interface domain wall energy as in the first embodiment.

The magneto-optical disk according to Comparative Example 1 was evaluated exactly as in Example 1. The region of the recording power at which the bit error rate at this time is 5 × 10 ⁻⁵ or less is shown by hatching in FIG. FIG. 9 shows the relationship between C / N and recording power. Compared with the case of the first embodiment, the C / N is lower by about 2 to 3 dB as a whole, and accordingly, the margin of power for performing good recording is narrowed. The maximum reproduction power that did not cause deterioration due to repeated reproduction was 2.1 mW, which was lower than that in Example 1. Comparative Example 2 Example 1 except that the configuration of the magnetic layer was as follows.
A magneto-optical disk was manufactured by the same configuration and manufacturing method as described above.

After the formation of the undercoat layer, sputtering is performed using three targets of Tb, Fe and Co, and the readout magnetic layer of Tb ₂₀ (Fe _91.7 Co _8.3 ) _{80 having} a thickness of 35 nm is used as the undercoat layer. Deposited on top. The Curie temperature of this layer is about 180 ° C. After leaving this state for several hours, a write magnetic layer having the same material and composition as the third magnetic layer in Example 1 was formed to a thickness of 150 nm. The Curie temperature of this layer is about 220 ° C. The configuration of the magnetic layer was the above two-layer configuration. As in the first embodiment, in order to adjust the interface domain wall energy, the interface is intentionally contaminated and the exchange interaction between the layers is appropriately weakened.

The magneto-optical disk according to Comparative Example 2 was evaluated exactly as in Example 1. In FIG. 10, the area of the recording power where the bit error rate is 5 × 10 ⁻⁵ or less is shown by hatching in FIG. The power margin of the bottom power is smaller than that of the first embodiment. The maximum reproduction power that did not cause deterioration due to repeated reproduction was 2.6 mW, which was lower than that in Example 1. Comparative Example 3 Example 1 was repeated except that the configuration of the magnetic layer was as follows.
A magneto-optical disk was manufactured by the same configuration and manufacturing method as described above.

After the formation of the undercoat layer, sputtering is performed using three targets of Tb, Fe and Co, and the readout magnetic layer of Tb ₂₀ (Fe _91.7 Co _8.3 ) ₈₀ having a thickness of about 35 nm is undercoated. Deposited on top of the layer. The Curie temperature of this layer is about 180 ° C. After standing for several hours in this state, sputtering is performed using four targets of Gd, Tb, Fe, and Co to have a thickness of about 150 nm (Tb ₇₀ Gd ₃₀ ) ₂₀ (Fe _83.3 Co _16.7 ) _80. A magnetic layer for writing was formed. The Curie temperature of this layer is about 26
0 ° C. The configuration of the magnetic layer was the above two-layer configuration.
As in the first embodiment, the interface is intentionally contaminated to adjust the interface domain wall energy, and the exchange interaction between the layers is appropriately weakened.

The magneto-optical disk according to Comparative Example 1 was evaluated exactly as in Example 1. In FIG. 11, the area of the recording power where the bit error rate is 5 × 10 ⁻⁵ or less is shown by hatching in FIG. Compared with the case of the first embodiment, the recording sensitivity is poor, and a large laser power is required to perform good recording. The maximum playback power that does not cause deterioration due to repeated playback is 2.6 mW
Which was lower than that of Example 1. Reference Example 2 A magneto-optical disk was manufactured by the same configuration and manufacturing method as in Example 1 except that the configuration of the magnetic layer was as shown in Table 2. Also in this example, the fourth magnetic layer is substantially omitted,
A Cr of about 0.5 to 1 nm is provided between the third magnetic layer and the fifth magnetic layer.
The interface domain wall energy is adjusted by interposing a layer. Temperature dependences of the saturation magnetization, coercive force and interface domain wall energy density of each layer are shown in FIGS.

The following describes, with reference to FIG. 15, how the medium having this configuration realizes the process of transition of the magnetization orientation state with the medium temperature change. The compensation temperature of the i-th magnetic layer and Tcomp _i below.

An external magnetic field Hini of, for example, about 6 kOe is applied to the medium in an upward direction. In the case of this medium, the third
The magnetic layer has a rare earth element sublattice magnetization dominance at room temperature, and the other magnetic layers have an iron group element sublattice magnetization dominant at room temperature, so that the TM spin of each layer is aligned in the upward direction perpendicular to the film surface. The magnetization of the three magnetic layers develops downward, and the other magnetic layers develop the same upward magnetization as the TM spin (FIG. 15a). Therefore, for a sufficiently small external magnetic field H upward, 2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ H-σw ₃₅ (210) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms _{3 h 3 -Ms 5 h 5) H} -σw 57 (211) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (Ms 3 h 3 -Ms 5 h 5 -Ms 7 h
_{7) H- σw 79 (212)} 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> 2 (Ms 3 h 3 -Ms
_{5 h 5 -Ms 7 h 7 -Ms} 9 h 9) H (213) 2Ms 5 Hc 5 h 5> -2Ms 5 h 5 H- σw 35 -σw 57 (214) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc ₇ h ₇ > -2 (Ms ₅ h ₅ + Ms ₇ h ₇ ) H- σw ₃₅ -σw
_{79 (215) 2Ms 5 Hc 5} h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> -2 (Ms 5 h 5 + Ms 7 h 7 + Ms 9
h ₉ ) H (216) 2Ms ₇ Hc ₇ h ₇ > -2Ms ₇ h ₇ H- σw ₅₇ -σ w ₇₉ (217) 2Ms ₇ Hc ₇ h ₇ + 2Ms ₉ Hc ₉ h ₉ > -2 (Ms ₇ h ₇ + Ms ₉ h ₉ ) H- σw ₅₇ (21
8) 2Ms ₉ Hc ₉ h ₉ > -2Ms ₉ h ₉ H-σw ₇₉ (219) holds. When the external magnetic field H is continuously increased to Hini, (21) while maintaining the relationship of the other equations
Since the relationship of the expression (0) is reversed, the magnetization of the third magnetic layer can be inverted upward without inverting the magnetization of the fifth magnetic layer, so that the third magnetic layer can be oriented in a stable state with respect to the external magnetic field Hini. Thereafter, when an external magnetic field Hb of, for example, 200 Oe is applied upward, the following equation is established at room temperature.
The state where the domain wall exists at the interface between the third magnetic layer and the fifth magnetic layer is maintained. At this time, the magnetization state of the magnetic composite film in this portion is set to state B2 (FIG. 15B).

2Ms ₃ Hc ₃ h ₃ > -2Ms ₃ h ₃ Hb + σw ₃₅ (220) 2Ms ₅ Hc ₅ h ₅ > -2Ms ₅ h ₅ Hb + σw ₃₅ -σw ₅₇ (221) 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ > -2 (Ms ₅ h ₅ + Ms ₇ h ₇ ) Hb + σw ₃₅ -σw
_{79 (222) 2Ms 5 Hc 5} h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> -2 (Ms 5 h 5 + Ms 7 h 7 + Ms 9
_{h 9) Hb + σw 35 (} 223) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb-σw 57 -σw 79 (224) 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> -2 (Ms ₇ h ₇ + Ms ₉ h ₉ ) Hb-σw ₅₇ (22
5) 2Ms ₉ Hc ₉ h ₉ > -2Ms ₉ h ₉ Hb-σw ₇₉ (226) The part where the TM spin of each layer is aligned downward (Fig. 15).
In c), the magnetization of the third magnetic layer is directed upward, and
The coercive force of the 7 magnetic layers is 6 kOe or more. Therefore, in this case, no state change occurs even if an external magnetic field Hini of about 6 kOe is applied upward. After that, even if an external magnetic field Hb of 200 Oe is applied upward, the cause of the state change is only the Zeeman energy due to the external magnetic field and the coercive force of each layer is larger than Hb, so that the magnetization state does not change. In this state, all the TM spins of each layer face downward, and the atomic spins are matched over the entire thickness direction. The magnetization state at this time is referred to as state A2 (FIG. 15D).

When the medium is heated from the state B2 to increase the medium temperature, σw ₅₇ decreases as the medium approaches Tc ₆ ,
Since the relationship of the expression (221) is reversed, the fifth magnetic layer is reversed. That is, the TM spin of the fifth magnetic layer matches the third magnetic layer and is directed downward.

In the state after the inversion of the fifth magnetic layer, the following expression holds, and the domain wall has moved to the interface between the fifth magnetic layer and the seventh magnetic layer (FIG. 15E).

2Ms ₃ Hc ₃ h ₃ > -2 Ms ₃ h ₃ Hb-σw ₃₅ (230) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (-Ms ₃ h ₃ + Ms ₅ h ₅ ) Hb _{+ σw 57 (231) 2Ms 5} Hc 5 h 5> 2Ms 5 h 5 Hb- σw 35+ σw 57 (232) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb + σw 57 -σw 79 (233) 2Ms _{7 Hc 7 h 7 + 2Ms 9} Hc 9 h 9> -2 (Ms 7 h 7 + Ms 9 h 9) Hb + σw 57 (234) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 ( 235) When the medium temperature drops from this state, σw ₅₇ sharply increases, and the relationship of Expression (233) is reversed, so that the seventh magnetic layer is inverted. That is, the TM spin of the seventh magnetic layer matches the fifth magnetic layer and is directed downward.

In the state after the inversion of the seventh magnetic layer, the following expression holds, and the domain wall has moved to the interface between the seventh magnetic layer and the ninth magnetic layer (FIG. 15F).

2Ms ₃ Hc ₃ h ₃ > -2 Ms ₃ h ₃ Hb-σw ₃₅ (240) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (-Ms ₃ h ₃ + Ms ₅ h ₅ ) Hb _{-σw 57 (241) 2Ms 3 Hc} 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (-Ms 3 h 3 + Ms 5 h 5 + Ms 7 h 7) Hb + σw 79 (242 _{) 2Ms 5 Hc 5 h 5>} 2Ms 5 h 5 Hb- σw 35 -σw 57 (243) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (Ms 5 h 5 + Ms 7 h 7) Hb- _{σw 35 + σw 79 (244)} 2Ms 7 Hc 7 h 7> 2Ms 7 h 7 Hb- σw 57 + σw 79 (244) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb + σw 79 (245) this state When the temperature further decreases, σw ₇₉ sharply increases, and the relationship of Expression (245) is reversed, so that the ninth magnetic layer is inverted. That is, the TM spin of the ninth magnetic layer is aligned with the seventh magnetic layer and directed downward (FIG. 15g). Then, the temperature drops to room temperature in this state. Finally, the TM of each layer
The state is a state in which all the spins are aligned downward, that is, state A2 (FIGS. 15C and 15D).

The medium temperature is further raised from Tc ₆ to
When heated to more than omp ₃ , the third magnetic layer becomes dominant in the iron-group element sublattice magnetization, and the polarity is reversed (the direction of the spin is not changed). (FIG. 15h).

2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ Hb-σw ₃₅ (250) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₃ h ₃ + Ms ₅ h ₅ ) Hb + σw _{57 (251) 2Ms 5 Hc 5 h} 5> 2Ms 5 h 5 Hb- σw 35 + σw 57 (252) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb + σw 57 -σw 79 (253) 2Ms 7 Hc 7 _{h 7 + 2Ms 9 Hc 9 h} 9> -2 (Ms 7 h 7 + Ms 9 h 9) Hb + σw 57 (254) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 (255) medium since the temperature is further raised to Tc of about ₅ (to Tc ₃₎ (251) relationship equation is reversed, the third magnetic layer and a fifth magnetic layer is inverted simultaneously, TM spin is upward (FIG. 15i). When the temperature drops from this state, Tco
Although the polarity of the third magnetic layer is reversed again when the voltage becomes mp ₃ or less, 2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ Hb-σw ₃₅ (260) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₃ h ₃ -Ms ₅ h ₅ ) Hb- σw ₅₇ (261) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ > 2 (Ms ₃ h ₃ -Ms ₅ h _{5 -Ms 7 h 7) Hb- σw} 79 (262) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 7 h 9> 2 (Ms 3 h 3 -Ms ₅ h ₅ -Ms ₇ h ₇ -Ms ₉ h ₉ ) Hb (263) 2Ms ₅ Hc ₅ h ₅ > -2Ms ₅ h ₅ Hb-σw ₃₅ -σ w ₅₇ (264) 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc _{7 h 7> -2 (Ms 5} h 5 + Ms 7 h 7) Hb-σw 35 -σw 79 (265) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> -2 _{(Ms 5 h 5 + Ms 7} h 7 + Ms 9 h 9) Hb-σw 35 (266) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb-σw 57 -σw 79 (267) 2Ms 7 Hc 7 h ₇ + 2Ms ₉ Hc ₉ h ₉ > -2 (Ms ₇ h ₇ + Ms ₉ h ₉ ) Hb-σw ₅₇ (268) 2Ms ₉ Hc ₉ h ₉ > -2Ms ₉ h ₉ Hb-σw ₇₉ (269) The magnetization state does not change (FIG. 15
j). Then, a fifth magnetic layer and the seventh magnetic layer becomes Tc ₆ or less, The seventh magnetic layer becomes Tc ₈ or less and the ninth
The magnetic layers are magnetically coupled to each other. But T of each layer
Since the direction of M spin is aligned upward, the temperature returns to room temperature while maintaining this state (FIG. 15A). However, when an upward external magnetic field Hini is applied again from this state, the state becomes B2 (FIG. 15B). .

Next, the medium is heated while applying an external magnetic field Hb directed upward from the state A2 (FIG. 15D). In this case, even if the material is heated up to Tc ₆ , the cause of the state change is only the Zeeman energy due to the external magnetic field, and since the coercive force of each layer in this temperature range is larger than Hb, no state change occurs ( (FIG. 15k). Even if the temperature drops from this state, the spins are all matched, and the direction of the spins does not change. That is, the state A2 remains (see FIG. 15).
d).

On the other hand, when heating from Tc ₆ to over Tcomp ₃ (FIG. 15L) to near Tc ₅ (〜Tc ₃ ), the third magnetic layer and the fifth magnetic layer are simultaneously magnetized in the same manner as described above. , The TM spin is directed upward. But the seventh
The magnetic layer and the ninth magnetic layer have a high Curie temperature and still have a sufficient coercive force at this point, so that the downward magnetization (downward TM spin) is maintained (FIG. 15m). .

The temperature drops from this state, and Tcomp
_When it becomes ₃ or less (FIG. 15n), and further reaches about Tc ₆ , the fifth magnetic layer and the seventh magnetic layer start to be magnetically coupled. When the temperature further falls to about Tc ₈ , the magnetic layers 7 and 9 also start to be coupled. The relational expression relating to the magnetization reversal before and after this is as follows.

2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ Hb-σw ₃₅ (270) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₃ h ₃ -Ms ₅ h ₅ ) Hb + σw ₅₇ (271) 2Ms ₅ Hc ₅ h ₅ > -2Ms ₅ h ₅ Hb-σw ₃₅ + σw ₅₇ (272) 2Ms ₇ Hc ₇ h ₇ > 2Ms ₇ h ₇ Hb + σw ₅₇ -σw ₇₉ (273) 2Ms ₇ Hc ₇ h _{7 + 2Ms 9 Hc 9 h 9} > 2 (Ms 7 h 7 + Ms 9 h 9) Hb + σw 57 (274) 2Ms 9 Hc 9 h 9> 2Ms 9 h 9 Hb- σw 79 (275) temperature of the medium in this state Falls, σw ₅₇ sharply increases, and the relationship of the expression (273) is reversed, so that the seventh magnetic layer is reversed. That is, the TM spin of the seventh magnetic layer matches the fifth magnetic layer and faces upward.

In the state after the inversion of the seventh magnetic layer, the following expression holds, and a domain wall is formed at the interface between the seventh magnetic layer and the ninth magnetic layer (FIG. 15O).

2Ms ₃ Hc ₃ h ₃ > 2Ms ₃ h ₃ Hb-σw ₃₅ (280) 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₃ h ₃ -Ms ₅ h ₅ ) Hb + σ w _{57 (281) 2Ms 3 Hc 3 h} 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (Ms 3 h 3 -Ms 5 h 5 -Ms 7 h 7) Hb + σw 79 (282) 2Ms 5 Hc ₅ h ₅ > -2Ms ₅ h ₅ Hb-σw ₃₅ -σw ₅₇ (283) 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ > -2 (Ms ₅ h ₅ + Ms ₇ h ₇ ) Hb-σw ₃₅ + σw ₇₉ (284) 2Ms ₇ Hc ₇ h ₇ > -2Ms ₇ h ₇ Hb-σw ₅₇ + σw ₇₉ (285) 2Ms ₉ Hc ₉ h ₉ > 2Ms ₉ h ₉ Hb + σw ₇₉ (286) Falls, σw ₇₉ sharply increases, and the relationship of Expression (286) is reversed, so that the ninth magnetic layer is inverted. That is, the TM spin of the ninth magnetic layer matches the seventh magnetic layer and faces upward (FIG. 15p). Then, the temperature drops to room temperature in this state (FIG. 15c). Eventually, the TM spins of the respective layers are aligned in the upward direction and aligned, but from this state, the upward external magnetic field Hini is again raised.
Is applied, the state becomes state B2 (FIG. 15d).

As described above, this medium is different from the first embodiment in detail.
Nevertheless, they have similar configurations and characteristics .

The magneto-optical disk according to Reference Example 1 was evaluated exactly as in Example 1. However, in this case, the bias magnetic field for recording was in the same direction as the magnetic field for initialization. As a result, good recording characteristics and reproduction durability were obtained.

The magneto-optical disk according to the second embodiment also satisfies the conditions characteristic of the present invention, and the magneto-optical disk according to the second embodiment is the same as the first embodiment.
Although the details are different, similar configurations and characteristics can be similarly described. Example 2 A magneto-optical disk was manufactured by the same configuration and manufacturing method as in Example 1 except that the configuration of the magnetic layer was as shown in Table 3. In this example, a GdFeCo layer having a saturation magnetization of 400 emu / cm ³ at room temperature was provided as the fourth magnetic layer. The other materials and compositions of the magnetic layer are exactly the same as in the first embodiment. Since σw ₃₅ can be effectively reduced by the interposition of the fourth magnetic layer,
In a system in which the thickness of each magnetic layer is thinner than in the first embodiment, the same process as in the first embodiment is realized.

The magneto-optical disk according to the second embodiment was evaluated exactly as in the first embodiment. As a result,
Good magnetic properties and reproduction durability were obtained. REFERENCE EXAMPLE 2 A magneto-optical disk was manufactured in exactly the same manner as in Example 2 except that the magnetic layers were configured as shown in Table 4 and two magnetic layers were added as described below. .

After the magnetic layers exactly the same as in Reference Example 1 were sequentially laminated from the seventh magnetic layer to the third magnetic layer, sputtering was performed using two targets of Tb and Fe, and 5 nm
A second additional magnetic layer made of a TbFe amorphous alloy having a thickness of 3 mm was laminated on the third magnetic layer. Subsequently, sputtering is performed using two targets of Tb and Co, and a first additional magnetic layer made of a 30 nm thick TbCo amorphous alloy is laminated on the second additional magnetic layer. The entire additional magnetic layer was magnetized in one direction after the film formation. _Assuming that the interface domain wall energy between the additional magnetic layer 1 and the third magnetic layer is _{σw 1′3} , σw _1′3 at room temperature was 5.0 erg / cm ³ .

As described below, in this medium, the minimum value of the external magnetic field Hini required for orienting the third magnetic layer in a predetermined direction before recording is set to _{σw 1'3} / 2 compared to the case of Reference Example 1.
Ms ₃ h ₃ can be reduced.

That is, in the first embodiment, in order to satisfy the relational expression relating to the initialization of the third magnetic layer, 2Ms ₃ Hc ₃ h ₃ <2Ms ₃ h ₃ Hini−σw ₃₅ (410), Hini> Hc ₃ + σw ₃₅ / 2Ms ₃ h ₃ = 5.2 kOe (411), but in Reference Example 2 , 2Ms ₃ Hc ₃ h ₃ <2Ms ₃ h ₃ Hini- σw ₃₅ + _{σw 1'3} (412) since it is _{satisfied, Hini> Hc 3 + σw 35} / 2Ms 3 h 3 - σw 1'3 / 2Ms 3 h 3 = 1.6kOe (41
3) Example 3 A magneto-optical disk was manufactured in exactly the same manner as in Example 1, except that the configuration of the magnetic layer was as shown in Table 5. FIG. 16, FIG. 17, and FIG. 18 show the temperature dependence of the saturation magnetization, coercive force, and interface domain wall energy density of each layer. The following describes, with reference to FIG. 19, how the medium having such a configuration realizes the process of transition of the magnetization orientation state due to the medium temperature change, which is a feature of the present invention.

The medium immediately after film formation is in a maze state, and the orientation state of the first magnetic layer varies depending on the location. However, a sufficient magnitude of an external magnetic field may be applied in an appropriate direction, or an appropriate bias may be applied. By heating the medium to around Tc ₁ under a magnetic field, it can be magnetized to a desired orientation state.

For example, at room temperature, 7 kOe
Consider the case where an external magnetic field H _{0 of a} degree is applied. In a portion where the TM spins of the respective layers in the medium are aligned upward in the direction perpendicular to the film surface (FIG. 19A), the following formula holds for a sufficiently small downward external magnetic field H. 2Ms ₁ Hc ₁ h ₁ > 2Ms ₁ h ₁ H-σw ₁₃ (510) 2Ms ₁ Hc ₁ h ₁ + 2Ms ₃ Hc ₃ h ₃ > (2Ms ₁ h ₁ -2Ms ₃ h ₃ -Ms ₄ h ₄ ) H- _{σw 35 (511) 2Ms 1 Hc} 1 h 1 + 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5> (2Ms 1 h 1 -2Ms 3 h 3 -Ms 4 h 4 + 2Ms 5 h 5) H-σw _{57 (512) 2Ms 1 Hc 1} h 1 + 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> (2Ms 1 h 1 -2Ms 3 h 3 -Ms 4 h 4 + 2Ms 5 _{h 5 + 2Ms 7 h 7)} H- σw 79 (513) 2Ms 1 Hc 1 h 1 + 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> (2Ms ₁ h ₁ -2Ms ₃ h ₃ -Ms ₄ h ₄ + 2Ms ₅ h ₅ + 2Ms ₇ h ₇ + 2Ms ₉ h ₉ ) H (514) 2Ms ₃ Hc ₃ h ₃ > (-2Ms ₃ h ₃ -Ms _{4 h 4) H- σw 13 -σw} 35 (515) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5> (-2Ms 3 h 3 -Ms 4 h 4 + 2Ms 5 h 5) H-σw 13 - _{σw 57 (516) 2Ms 3 Hc} 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> (-2Ms 3 h 3 -Ms 4 h 4 + 2Ms 5 h 5 + 2Ms 7 h 7) H- _{σw 13 - σw 79 (517)} 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> (-2Ms 3 h 3 -Ms 4 h 4 + 2Ms 5 _{h 5 + 2Ms 7 h 7 +} 2Ms 9 h 9) H-σw 13 (518) 2Ms 5 Hc 5 h 5> (-Ms 4 h 4 + 2Ms 5 h 5) H- σw 35 -σw 57 (519) 2M _{s 5 Hc 5 h 5 + 2Ms} 7 Hc 7 h 7> (-Ms 4 h 4 + 2Ms 5 h 5 + 2Ms 7 h 7) H-σw 35 -σw 79 (51A) 2Ms 5 Hc 5 h 5 + 2Ms 7 _{Hc 7 h 7 + 2Ms 9 Hc} 9 h 9> (-Ms 4 h 4 -2Ms 5 h 5 + 2Ms 7 h 7 + 2Ms 9 h 9) H- σw 35 (51B) 2Ms 7 Hc 7 h 7> 2Ms 7 _{h 7 H-σw 57 -σw 79} (51C) 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> 2 (Ms 7 h 7 + Ms 9 h 9) H-σw 57 (51D) 2Ms 9 Hc 9 h _9> When 2Ms ₉ h ₉ the H-.sigma.w ₇₉ (51E) external magnetic field H is continuously increased to H _0, the relationship previously (510) below is reversed than other formulas. Therefore,
The magnetization of the first magnetic layer is reversed, and an interface domain wall is formed between the first magnetic layer and the third magnetic layer. In this state, the third magnetic layer is not magnetized by the external magnetic field H ₀ , but when the application of H ₀ is stopped, 2Ms ₃ Hc ₃ h ₃ > (− 2Ms ₃ h ₃ -Ms ₄ h ₄ ) Since the relationship of H + σw ₁₃ -σw ₃₅ is reversed as the external magnetic field H decreases, the magnetization of the third magnetic layer is reversed. As a result, in the magnetization state of the magnetic composite film, TM spins from the first magnetic layer to the third magnetic layer are aligned downward, and TM spins from the fifth magnetic layer to the ninth magnetic layer are aligned upward. Is consistent and the third
The magnetization state is such that a spin mismatch exists between the magnetic layer and the fifth magnetic layer. The magnetization state is state B5 ₀ (Figure 19b).

When the TM spin of each layer is aligned downward in the direction perpendicular to the film surface (FIG. 19c), the same consideration is given.
In this case, even if an external magnetic field of about 7 kOe is applied downward, the relation of each equation does not reverse, so that the magnetization state does not change. At this time, the magnetization state of the magnetic composite film matches from the first magnetic layer to the ninth magnetic layer such that the spins are aligned downward. This state is a state A5 ₀ (Figure 19d).

Therefore, the first magnetic layer (and the third magnetic layer) can be magnetized in a predetermined direction by this operation. In this case, the first magnetic layer is magnetized so that the TM spin is directed downward.

[0095] upward for example 200Oe from state B5 ₀
When the external magnetic field Hb is applied, at room temperature, the following equation holds, and the state where the domain wall exists at the interface between the third magnetic layer and the fifth magnetic layer is maintained. The magnetization state of the magnetic composite film at this time is set to state B5 (FIG. 19B).

2Ms ₁ Hc ₁ h ₁ > 2Ms ₁ h ₁ Hb- σw ₁₃ (520) 2Ms ₁ Hc ₁ h ₁ + 2Ms ₃ Hc ₃ h ₃ > (2Ms ₁ h ₁ -2Ms ₃ h ₃ -Ms ₄ h _{4 ) Hb + σw 35 (521)} 2Ms 3 Hc 3 h 3> (-2Ms 3 h 3 -Ms 4 h 4) Hb-σw 13 + σw 35 (522) 2Ms 5 Hc 5 h 5> (Ms 4 h 4 - _{2Ms 5 h 5) Hb + σw} 35 -σw 57 (523) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> (Ms 4 h 4 -2Ms 5 h 5 -2Ms 7 h 7) Hb + σw 35 -σw ₇₉ (524) 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ + 2Ms ₉ Hc ₉ h ₉ > (Ms ₄ h ₄ -2Ms ₅ h ₅ -2Ms ₇ h ₇ -2Ms ₉ h ₉ ) Hb + σw ₃₅ ( _{525) 2Ms 7 Hc 7 h 7} > -2Ms 7 h 7 Hb-σw 57 -σw 79 (525) 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> -2 (Ms 7 h 7 + Ms 9 h 9 _{) Hb-σw 57 (526)} 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 the (527), each layer of the spin in the case of applying an external magnetic field upwards 200Oe from state A5 ₀ all Since there is a match and no domain wall exists at any interface, the only factor that causes a state change is the Zeeman energy due to the external magnetic field. However, since the coercive force of each layer at room temperature is larger than Hb, no state change occurs. The magnetization state of the magnetic composite film at this time is set to state 5A (FIG. 19c).

When the medium is heated from the state B5 to increase the medium temperature, the σw ₅₇ decreases as the temperature approaches Tc ₆ , and the relation of the equation (523) is reversed before the other equations. The five magnetic layers are inverted. That is, the spin of the fifth magnetic layer matches the spin of the third magnetic layer.

In the state after the inversion of the fifth magnetic layer, the following equation holds, and the domain wall has moved to the interface between the fifth magnetic layer and the seventh magnetic layer (FIG. 19E).

2Ms ₁ Hc ₁ h ₁ > 2Ms ₁ h ₁ Hb-σw ₁₃ (530) 2Ms ₁ Hc ₁ h ₁ + 2Ms ₃ Hc ₃ h ₃ > (2Ms ₁ h ₁ -2Ms ₃ h ₃ -Ms ₄ h ₄ ) Hb-σw ₃₅ (531) 2Ms ₁ Hc ₁ h ₁ + 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₁ h ₁ -Ms ₃ h ₃ -Ms ₄ h ₄ + Ms ₅ h _{5 ) Hb + σw 57 (532)} 2Ms 3 Hc 3 h 3> (-2Ms 3 h 3 -Ms 4 h 4) Hb-σw 13 -σw 35 (533) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5> _{2 (-Ms 3 h 3 -Ms 4} h 4 + Ms 5 h 5) Hb-σw 13 + σw 57 (534) 2Ms 5 Hc 5 h 5> (2Ms 5 h 5 -Ms 4 h 4) Hb- σw 35 + σw ₅₇ (535) 2Ms ₇ Hc ₇ h ₇ > -2Ms ₇ h ₇ Hb + σw ₅₇ -σ w ₇₉ (536) 2Ms ₇ Hc ₇ h ₇ + 2Ms ₉ Hc ₉ h ₉ > -2 (Ms ₇ h ₇ + When _{ms 9 h 9) Hb + σw} 57 (537) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 (538) temperature of the medium in this state is lowered, .sigma.w ₅₇ increases rapidly, (536 Since the relationship of the expression (3) is reversed, the seventh magnetic layer is reversed. That is, the TM spin of the seventh magnetic layer matches with the fifth magnetic layer.

In the state after the inversion of the seventh magnetic layer, the following expression holds, and the domain wall has moved to the interface between the seventh magnetic layer and the ninth magnetic layer (FIG. 19f).

2Ms ₁ Hc ₁ h ₁ > 2Ms ₁ h ₁ Hb- σw ₁₃ (540) 2Ms ₁ Hc ₁ h ₁ + 2Ms ₃ Hc ₃ h ₃ > (2Ms ₁ h ₁ -2Ms ₃ h ₃ -Ms ₄ h _{4 ) Hb-σw 35 (541)} 2Ms 1 Hc 1 h 1 + 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5> 2 (Ms 1 h 1 -Ms 3 h 3 -Ms 4 h 4 + Ms 5 h 5 _{) Hb- σw 57 (542) 2Ms} 1 Hc 1 h 1 + 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> 2 (Ms 1 h 1 -Ms 3 h 3 -Ms 4 _{h 4 + Ms 5 h 5 +} Ms 7 h 7) Hb + σw 79 (543) 2Ms 3 Hc 3 h 3> (-2Ms 3 h 3 -Ms 4 h 4) Hb-σw 13 -σw 35 (544) 2Ms 3 _{Hc 3 h 3 + 2Ms 5 Hc} 5 h 5> 2 (-Ms 3 h 3 -Ms 4 h 4 + Ms 5 h 5) Hb-σw 13 -σw 57 (545) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ > 2 (-Ms ₃ h ₃ -Ms ₄ h ₄ + Ms ₅ h ₅ + Ms ₇ h ₇ ) Hb-σw ₁₃ + σw ₇₉ (546) 2Ms ₅ Hc ₅ h _{5 > (-Ms 4 h 4 + 2Ms} 5 h 5) Hb-σw 35 -σw 57 (547) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> (-Ms 4 h 4 + 2Ms 5 h 5 + 2Ms _{7 h 7) Hb- σw 35 +} σw 79 (548) 2Ms 7 Hc 7 h 7> 2Ms 7 h 7 Hb- σw 57 + σw 79 (549) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb + σw When ₇₉ (54A) further temperature from this state is lowered, .sigma.w ₇₉ increases sharply, ( Because 4A) equation relationship is reversed, the ninth magnetic layer is reversed. That is, the TM spin of the ninth magnetic layer matches the seventh magnetic layer (FIG. 19g). Then, the temperature drops to room temperature in this state. As a result, the TM spins of each magnetic layer are all aligned downward. Accordingly, the magnetization state of the magnetic composite film at this time is state A5 (FIG. 19D).

On the other hand, when the medium temperature is further increased from Tc ₆ and heated to Tcomp ₃ or more, the third magnetic layer becomes dominant in the iron-group element sublattice magnetization and the polarity is inverted. , (FIG. 19h).

[0103] _{2Ms 1 Hc 1 h 1> 2Ms} 1 h 1 Hb- σw 13 (550) 2Ms 1 Hc 1 h 1 + 2Ms 3 Hc 3 h 3> (2Ms 1 h 1 + 2Ms 3 h 3 -Ms 4 h 4 ) Hb-σw ₃₅ (551) 2Ms ₁ Hc ₁ h ₁ + 2Ms ₃ Hc ₃ h ₃ + 2Ms ₅ Hc ₅ h ₅ > 2 (Ms ₁ h ₁ + Ms ₃ h ₃ -Ms ₄ h ₄ + Ms ₅ h _{5 ) Hb + σw 57 (552)} 2Ms 3 Hc 3 h 3> (2Ms 3 h 3 -Ms 4 h 4) Hb- σw 13 -σw 35 (553) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5> 2 (Ms ₃ h ₃ -Ms ₄ h ₄ + Ms ₅ h ₅ ) Hb- σw ₁₃ + σw ₅₇ (554) 2Ms ₅ Hc ₅ h ₅ > (2Ms ₅ h ₅ -Ms ₄ h ₄ ) Hb- σw ₃₅ + σw _{57 (555) 2Ms 7 Hc 7} h 7> -2Ms 7 h 7 Hb + σw 57 -σw 79 (556) 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> -2 (Ms 7 h 7 + Ms 9 _{h 9) Hb + σw 57 (} 557) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 (558) when the medium temperature is increased to be about Tc ₃ further, (55
Since the relationship of the expression (3) is reversed, the third magnetic layer is reversed.
In the state after the reversal, there is a spin mismatch between the first magnetic layer and the third magnetic layer, between the third magnetic layer and the fifth magnetic layer, and between the fifth magnetic layer and the seventh magnetic layer. 19
i). (However, in this temperature state, since the temperature of the magnetic layer interposed between the respective layers exceeds each Curie temperature, no interface domain wall energy is accumulated at any of the interfaces.) 2Ms ₁ Hc ₁ h ₁ > _{2Ms 1 h 1 Hb + σw 13} (560) 2Ms 3 Hc 3 h 3> (-2Ms 3 h 3 + Ms 4 h 4) Hb + σw 13 + σw 35 (561) 2Ms 5 Hc 5 h 5> (2Ms 5 h ₅ -Ms ₄ h ₄ ) Hb + σw ₃₅ + σw ₅₇ (562) 2Ms ₇ Hc ₇ h ₇ > -2Ms ₇ h ₇ Hb + σw ₅₇ -σw ₇₉ (563) 2Ms ₇ Hc ₇ h ₇ + 2Ms ₉ Hc ₉ h _{9> -2 (Ms 7 h 7} + Ms 9 h 9) Hb + σw 57 (564) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 (565) when the medium temperature in this state is lowered, With the increase in σw ₃₅ , the relationship of the expression (562) is reversed, the magnetization of the fifth magnetic layer is reversed, and the spin is matched with the third magnetic layer. As a result, the spin mismatch exists only between the first magnetic layer and the third magnetic layer, and the following equation holds (FIG. 19j).

2Ms ₁ Hc ₁ h ₁ > 2Ms ₁ h ₁ Hb + σw ₁₃ (570) 2Ms ₃ Hc ₃ h ₃ > (-2Ms ₃ h ₃ + Ms ₄ h ₄ ) Hb + σw ₁₃ -σw ₃₅ (571) 2Ms _{3 Hc 3 h 3 + 2Ms 5} Hc 5 h 5> 2 (-Ms 3 h 3 + Ms 4 h 4 -Ms 5 h 5) Hb + σw 13 -σw 57 (572) 2Ms 3 Hc 3 h 3 + 2Ms 5 _{Hc 5 h 5 + 2Ms 7 Hc} 7 h 7> 2 (-Ms 3 h 3 + Ms 4 h 4 -Ms 5 h 5 -Ms 7 h 7) Hb + σw 13 - σw 79 (573) 2Ms 3 Hc 3 h _{3 + 2Ms 5 Hc 5 h 5} + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> 2 (-Ms 3 h 3 + Ms 4 h 4 -Ms 5 h 5 -Ms 7 h 7 - Ms 9 h 9 _{) Hb + σw 13 (574)} 2Ms 5 Hc 5 h 5> (Ms 4 h 4 -2Ms 5 h 5) Hb- σw 35 -σw 57 (575) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7> ( _{Ms 4 h 4 -2Ms 5 h 5} -2Ms 7 h 7) Hb-σw 35 -σw 79 (576) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> (Ms 4 h _{4 -2Ms 5 h 5 -2Ms 7 h} 7) Hb-σw 35 (577) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb-σw 57 -σw 79 (578) 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc ₉ h ₉ > -2 (Ms ₇ h ₇ -Ms ₉ h ₉ ) Hb-σw ₅₇ (579) 2Ms ₉ Hc ₉ h ₉ > -2Ms ₉ h ₉ Hb-σw ₇₉ (57A) When the temperature further decreases, Tcomp ₃ or less,
The magnetism of the magnetic layer is reversed again, but since the following equation holds, the magnetization state does not change (FIG. 19k). _{2Ms 1 Hc 1 h 1> 2Ms} 1 h 1 Hb + σw 13 (580) 2Ms 3 Hc 3 h 3> (2Ms 3 h 3 + Ms 4 h 4) Hb + σw 13 -σw 35 (581) 2Ms 3 Hc 3 h 3 _{+ 2Ms 5 Hc 5 h 5>} 2 (Ms 3 h 3 + Ms 4 h 4 -Ms 5 h 5) Hb + σw 13 -σw 57 (582) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + 2Ms 7 _{Hc 7 h 7> 2 (Ms} 3 h 3 + Ms 4 h 4 -Ms 5 h 5 -Ms 7 h 7) Hb + σw 13 - σw 79 (583) 2Ms 3 Hc 3 h 3 + 2Ms 5 Hc 5 h 5 + _{2Ms 7 Hc 7 h 7 + 2Ms} 9 Hc 9 h 9> 2 (Ms 3 h 3 + Ms 4 h 4 -Ms 5 h 5 -Ms 7 h 7 - Ms 9 h 9) Hb + σw 13 (584) 2Ms 5 Hc ₅ h ₅ > (-2Ms ₅ h ₅ + Ms ₄ h ₄ ) Hb-σw ₃₅ -σw ₅₇ (585) 2Ms ₅ Hc ₅ h ₅ + 2Ms ₇ Hc ₇ h ₇ > (-2Ms ₅ h ₅ + Ms ₄ h _{4 -2Ms 7 h 7) Hb- σw} 35 -σw 79 (586) 2Ms 5 Hc 5 h 5 + 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 h 9> (-2Ms 5 h 5 + Ms 4 h 4 - _{2Ms 7 h 7 -2Ms 9 h 9} ) Hb-σw 35 (587) 2Ms 7 Hc 7 h 7> -2Ms 7 h 7 Hb-σw 57 -σw 79 (588) 2Ms 7 Hc 7 h 7 + 2Ms 9 Hc 9 _{h 9> -2 (Ms 7 h} 7 + Ms 9 h 9) Hb-σw 57 (589) 2Ms 9 Hc 9 h 9> -2Ms 9 h 9 Hb-σw 79 (58A) fifth become Tc ₆ or less and a magnetic layer and a seventh magnetic layer, the seventh magnetic become Tc ₈ or less If it a ninth magnetic layer is magnetically coupled respectively but .sigma.w ₅₇ and .sigma.w ₇₉ is increased, since the spins are aligned, still maintains this state. When the temperature further decreases to Tc ₂ or less, the first magnetic layer and the third magnetic layer start to be magnetically coupled. However, since the spin directions of these two layers are not matched, a domain wall is formed at the interface. Is done. Then, σw ₁₃ increases while the medium temperature falls to room temperature, and the relationship of the expression (581) is reversed while maintaining the relationship of the other expression, whereby the third magnetic layer is inverted. That is, the spin of the third magnetic layer matches the spin of the first magnetic layer, and the layers above the fifth magnetic layer maintain their previous magnetization state (FIG. 19l). Eventually, the magnetization state of the magnetic composite film at this time becomes state B5 (FIG. 19B).

Next, the medium is heated while applying an external magnetic field Hb upward from the state A5 (FIG. 19d). Be heated to Tc ₆ in this case, since the factors that cause a state change each layer of coercive force at this temperature range on only Zeeman energy produced by the external magnetic field is greater than Hb,
No state change occurs (FIG. 19m). Even if the temperature drops from this state, all the spins are aligned and their directions do not change. Accordingly, the magnetization state of the magnetic composite film at this time is state A5 (FIG. 19D).

On the other hand, further heating from Tc _6
When it exceeds ₃ (FIG. 19n) and reaches near Tc ₃ , the magnetization of the third magnetic layer is reversed as in the case described above (FIG. 19o),
In the subsequent cooling process, the fifth, seventh, and ninth magnetic layers are sequentially magnetically coupled and oriented so that the spins match the third magnetic layer (FIGS. 19p to 19s). Finally, the third magnetic layer is combined with the first magnetic layer, and as a result, the magnetization is reversed so that the spin is matched with the first magnetic layer (FIG. 19t). B5 (FIG. 19b) can be similarly explained.

As described above, this medium satisfies the characteristics characteristic of the present invention. In the above description, the coercive force energy and Zeeman energy of the second, sixth, and eighth magnetic layers were ignored. Although the coercive force energy of the fourth magnetic layer was neglected, the Zeeman energy was not negligible, and was considered based on the following assumption. That is, when there is a spin mismatch between the third magnetic layer and the fifth magnetic layer, it is considered that a spin transition region is formed over the entire thickness direction of the fourth magnetic layer. Assumed that the magnetizations of the fourth magnetic layer do not contribute to Zeeman energy because they cancel each other out in the layer.

The magneto-optical disk according to the third embodiment has a wavelength
780 nm, applied to a magneto-optical disk drive with an optical head of NA = 0.53, rotated at 3600 rpm, radius 24 m
The measurement was performed at the position of m.

An external magnetic field of about 7 kOe was applied in advance to magnetize the first magnetic layer in one direction over the entire surface of the disk. Using this disk, 200
While applying a recording bias magnetic field of Oe, the recording laser beam was pulse-modulated into two values, a bottom power (Pb) and a peak power (Pp), and recording was performed, and read was performed at a reproduction power of 1.0 mW. Pulse width 57 ns
c at a channel rate of 17.4 MHz (2.
7) Modulation recording was performed, and the bit error rate at this time was measured. After recording the entire surface of the disk and performing the above recording while varying the bottom power and the peak power, the recording power region where the bit error rate is 5 × 10 ⁻⁵ or less is shown by hatching in FIG. . Good overwrite characteristics are obtained in this region. FIG. 2 shows the relationship between C / N and recording power when a 3T pattern was recorded after the entire surface of the disk was erased.
It is shown in FIG.

[0110] Next, compare waving reproducing power, a signal reproduced by the reproducing power 1.0mW before and after recorded one over the track repeatedly degradation of the reproduced signal after repeatedly reproduced ¹⁰⁴ times played We examined by doing. As a result, reproduction deterioration did not occur up to 3.2 mW.

Hereinafter, it can be explained that the magneto-optical disks of Examples 4 to 7 also satisfy the conditions characteristic of the present invention. Reference example
Although the details are different for the magneto-optical disk of No. 3,
Having similar configuration and characteristics can be similarly explained. Example 4 A magneto-optical disk was manufactured in exactly the same manner as in Example 1 except that the configuration of the magnetic layer was as shown in Table 6. In the configuration of the magnetic layer of this disk, the (2m)
The magnetic layer is a ferromagnetic in-plane magnetized film.
Since the perpendicular magnetic anisotropy of the (2m + 1) magnetic layer is large, it is possible to form and maintain good magnetic domains. Further, since the light rare earth element was used for the magnetic layer on the read side, the magneto-optical effect at a short wavelength was improved. Furthermore, in this disk, m is 3
At this time, the Curie temperature of the (2m) th magnetic layer and the second (m)
+1) The Curie temperature of the magnetic layer is equal. However, even in such a case, a slight temperature gradient occurs in the thickness direction of the magnetic layer at the time of laser irradiation, so that the recording process of the present invention is established. Example 5 A magneto-optical disk was manufactured in exactly the same manner as in Example 1, except that the configuration of the magnetic layer was as shown in Table 7. In the configuration of the magnetic layer of this disk, the (2m) -th magnetic layer is an in-plane magnetic film as in the fourth embodiment. Further, on the seventh magnetic layer, another magnetic layer for the purpose of improving the magneto-optical effect at a short wavelength was exchange-coupled and laminated. Further, the fourth magnetic layer is substantially omitted, and the third magnetic layer is omitted.
The portion of about 10 nm near the interface between the magnetic layer and the fifth magnetic layer,
The sputtering Ar gas pressure during film formation is increased from the normal 0.3 Pa to 3.0
The interface domain wall energy was adjusted by raising to Pa. Example 6 A magneto-optical disk was manufactured in exactly the same manner as in Example 1, except that the configuration of the magnetic layer was as shown in Table 8. In the configuration of the magnetic layer of this disk, the fourth magnetic layer itself has a three-layer composite film configuration composed of the 41st, 42nd, and 43rd magnetic layers in that order. This medium is heated to Tc ₃ vicinity, the magnetization of each layer of the third when the magnetization of the magnetic layer and the fifth magnetic layer is lost at the same time the fourth magnetic layer is inverted, which transferred to the third magnetic layer and the fifth magnetic layer Take the process of being done. Each layer of the fourth magnetic layer at a temperature Tc ₃ neighborhood has a sufficiently large magnetization, and to have configured a small material coercive force, magnetization and the fourth magnetic layer by demagnetizing field itself Can be inverted. This eliminates the need for a bias magnetic field during recording.

As in this example, another magnetic layer is laminated before and after the magnetic composite film of the present invention, or one of the magnetic composite films of the present invention formed into a composite film is also included in the present invention. Example 7 A magneto-optical disk was produced in exactly the same manner as in Example 1, except that the configuration of the magnetic layer was as shown in Table 9. In the configuration of the magnetic layer of this disk, the (2m
+1) A periodic structure film in which Pt 2 nm and Co 0.5 nm are alternately laminated on the magnetic layer is disposed, and TbFeCo is disposed on the (2m) magnetic layer to hold it. 4 each as the ninth magnetic layer
A Pt / Co periodic structure for two periods is formed as the seventh and fifth magnetic layers for each period. Reference Example 3 The structure of the magnetic layer was as shown in Table 10, and after the ninth magnetic layer was sequentially laminated from the first magnetic layer, the thickness was increased by 60 nm through a 30 nm silicon nitride layer for the purpose of improving thermal characteristics. Al thermal diffusion layer was formed. Except for this, a magneto-optical disk was manufactured in exactly the same configuration and manufacturing method as in Example 1.

[0113]

As described above in detail, the magneto-optical recording medium of the present invention has an overwrite function by optical modulation, and has higher sensitivity and higher reproduction signal quality than a conventional medium having the same function. Information preservation,
In particular, there is an effect of improving the reproduction durability, and the laser power margin at the time of recording / reproduction is expanded.

The present invention can be applied in various ways besides the above-described embodiment. The present invention is not limited to a structure in which the interface between the magnetic layers is steep and has a clear structure.
A configuration in which the composition gradually changes in the film thickness direction is also possible. Further, the magneto-optical recording medium of the present invention does not necessarily require an external magnetic field for recording. For example, recording can be performed using demagnetizing field energy, Bloch domain wall energy, or the like. The invention is intended to cover all such applications without departing from the scope of the claims.

[0115]

[Table 1]

[0116]

[Table 2]

[0117]

[Table 3]

[0118]

[Table 4]

[0119]

[Table 5]

[0120]

[Table 6]

[0121]

[Table 7]

[0122]

[Table 8]

[0123]

[Table 9]

[0124]

[Table 10]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a recording process of a magneto-optical recording medium according to an embodiment of the present invention, and illustrates a transition process of a magnetization orientation state of a magnetic layer with a change in a medium temperature. 1 to 7 in the figure correspond to the first to seventh magnetic layers, respectively. Arrows indicate the directions of atomic spins at which the energy state becomes stable when coordinated in parallel with each other. The hatched portion indicates that there is a mismatch of atomic spins, thereby forming an interface domain wall.

FIG. 2 is a schematic sectional view showing a schematic configuration of a magneto-optical recording medium according to one embodiment of the present invention.

FIG. 3 is a diagram showing the temperature dependence of the saturation magnetization and the coercive force of each magnetic layer of the magneto-optical recording medium according to the first embodiment of the present invention.

FIG. 4 is a diagram showing the temperature dependence of the interface domain wall energy density between magnetic layers.

FIG. 5 is a diagram illustrating a recording process of the magneto-optical recording medium according to the first embodiment of the present invention, and illustrates a transition process of the magnetization orientation state of the magnetic layer with a change in the medium temperature. 3 to 7 in the figure correspond to the third to seventh magnetic layers, respectively. Arrows indicate the direction of the atomic spin of the iron group element, and white arrows indicate the direction of the magnetization. The hatched portion indicates that there is an atomic spin mismatch.

FIG. 6 is a diagram showing an area of a recording power where a bit error rate is 5 × 10 ⁻⁵ or less in the magneto-optical recording medium according to the first embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between C / N and recording power in the magneto-optical recording medium according to the first embodiment of the present invention.

FIG. 8 is a diagram showing an area of a recording power where a bit error rate is 5 × 10 ⁻⁵ or less in the magneto-optical recording medium of Comparative Example 1.

FIG. 9 is a diagram showing the relationship between C / N and recording power in the magneto-optical recording medium of Comparative Example 1.

FIG. 10 is a diagram showing a region of a recording power where a bit error rate is 5 × 10 ⁻⁵ or less in the magneto-optical recording medium of Comparative Example 2.

FIG. 11 is a diagram showing an area of a recording power where a bit error rate is 5 × 10 ⁻⁵ or less in a magneto-optical recording medium of Comparative Example 3.

FIG. 12 is a diagram showing the temperature dependence of the saturation magnetization of each magnetic layer of the magneto-optical recording medium in Reference Example 1 .

FIG. 13 is a diagram showing the temperature dependence of the coercive force of each magnetic layer in Reference Example 1 .

FIG. 14 is a diagram showing the temperature dependence of the interface domain wall energy density between magnetic layers in Reference Example 1 .

FIG. 15 is a diagram illustrating a recording process of the magneto-optical recording medium in Reference Example 1 , and illustrates a process of transition of a magnetization orientation state of the magnetic layer with a change in medium temperature. 3 to 9 in the figure correspond to the third to ninth magnetic layers, respectively. Arrows indicate the direction of the atomic spin of the iron group element, and white arrows indicate the direction of the magnetization. The hatched portion indicates that there is an atomic spin mismatch.

FIG. 16 is a diagram showing the temperature dependence of the saturation magnetization of each magnetic layer of the magneto-optical recording medium according to the third embodiment of the present invention.

FIG. 17 is a diagram showing the temperature dependence of the coercive force of each magnetic layer.

FIG. 18 is a diagram showing the temperature dependence of the interface domain wall energy density between magnetic layers.

FIG. 19 is a diagram illustrating a recording process of a magneto-optical recording medium according to a third embodiment of the present invention, and illustrates a transition process of a magnetization orientation state of a magnetic layer with a change in medium temperature.
In the drawing, 1 to 9 correspond to the first to ninth magnetic layers, respectively. Arrows indicate the direction of the atomic spin of the iron group element, and white arrows indicate the direction of the magnetization. The hatched portion indicates that there is an atomic spin mismatch.

FIG. 20 is a diagram showing an area of a recording power where a bit error rate is 5 × 10 ⁻⁵ or less in a magneto-optical recording medium according to a third embodiment of the present invention.

FIG. 21 is a diagram showing a relationship between C / N and recording power in a magneto-optical recording medium according to a third embodiment of the present invention.

Claims (7)

(57) [Claims] 1. A magneto-optical recording medium in which an n-layer (n is an odd number of 7 or more) magnetic thin film is laminated by exchange coupling on a substrate. , A second magnetic layer,
.., The Curie temperature of the i-th magnetic layer is T
a magneto-optical recording medium characterized by satisfying the following conditions under the application of an appropriate constant external magnetic field (Hb), where c _i , where Tc _{n + 1} is the ambient temperature, and m is (n− 1) An arbitrary natural number of not more than / 2). _{1. When} Tc ₁ ≧ Tc ₃ 2.m ≧ 2, Tc _2m ≧ Tc _{2 (m + 1)} 3.Tc ₆ ≧ Tc ₂ ≧ Tc _{n + 1} 4.Tc _{2m + 1} ≧ Tc ₆ 5.Tc _{2m + 1} ≧ Tc ₃ 6. At room temperature, the first magnetic layer is magnetized in an appropriate predetermined orientation state, and the first magnetization in which the atomic spin of each magnetic layer is matched over the entire film thickness direction. State or
The first magnetic layer is magnetized in the predetermined orientation state,
A second magnetization state in which the atomic spins of each magnetic layer are matched except that there is an interface spin between the magnetic layer and the fifth magnetic layer and an interface domain wall is formed. That you are taking. 7. Temperature of the sixth magnetic layer becomes equal to or higher than the temperature of Tc ₆ from the first and second magnetization states of the temperature of the third magnetic layer is Tc ₃
The magnetizations of the fourth magnetic layer and the fifth magnetic layer are adjusted with respect to the third magnetic layer so that the coupling state by the exchange interaction becomes stable when heated to an appropriate first temperature state that does not reach the first temperature state. The alignment is performed by aligning the atomic spins, and the magnetization of the third magnetic layer maintains the alignment state before heating. Orientation state before magnetization heating of the third magnetic layer when 8. heated from the first and second magnetization states of the up suitable second temperature state where the temperature is the temperature of Tc ₃ of the third magnetic layer State transition to a different orientation state. 9. The temperature of the (2m) magnetic layer in the course of cooling each after heating from the first and second magnetization states of the until the first and second temperature state of the can drops to a temperature of Tc _2m The magnetizations of the (2m) -th magnetic layer and the (2m + 1) -th magnetic layer are adjusted to match the atomic spin with the (2m-1) -th magnetic layer so that the coupling state by the exchange interaction becomes stable when It is oriented, and the magnetization of the (2m-1) -th magnetic layer keeps its previous orientation state. 10. From the first and second magnetization states, the second
In the course of cooling after heating to a temperature state the temperature of the second magnetic layer is lowered to a temperature of Tc _2, the second magnetic layer as bonded state by exchange interaction becomes a stable state, and a third When the magnetization of the magnetic layer is oriented with the atomic spins aligned with respect to the first magnetic layer, the magnetization of the fifth magnetic layer retains its previous alignment state. 11. From the first and second magnetization states, the first
And in each of the steps of heating and cooling until reaching the second temperature state, the magnetization of the first magnetic layer always maintains the predetermined orientation state. 2. A magneto-optical recording medium in which a (n-2) layer (n is an odd number of 7 or more) magnetic thin films are laminated on a substrate by exchange coupling. A magnetic thin film in order of a third magnetic layer,
The fourth magnetic layer, ..., the n-th magnetic layer, the i when the Curie temperature of the magnetic layer was changed to Tc _i, the following magneto-optical recording medium, characterized in that the condition is satisfied (but Tc _{n + 1} is an ambient temperature, and m is an arbitrary natural number of 2 or more and (n-1) / 2 or less. 1. Tc _2m ≧ Tc _{2 (m + 1)} 2. Tc _{2m + 1} ≧ Tc ₆ , Tc ₃ ≧ Tc ₆ 3. Tc _{2m + 1} ≧ Tc ₃ 4. Apply an appropriate first external magnetic field (Hini) Then, the magnetization of the third magnetic layer is oriented so as to be in a stable state with respect to the external magnetic field, and the magnetization of the fifth magnetic layer maintains the orientation state before the application of the external magnetic field. The following conditions must be satisfied under the application of a suitable constant second external magnetic field (Hb) after the application of the first external magnetic field (Hini). 5. At room temperature, the third magnetic layer and the fifth magnetic layer maintain the magnetization state immediately after the application of the first external magnetic field (Hini), and the atomic spin of each magnetic layer extends over the entire thickness direction. In the first magnetization state where the magnetic spins are aligned, or the atomic spins of each magnetic layer are aligned except that there is an interface magnetic wall between the third magnetic layer and the fifth magnetic layer and an interface domain wall is formed. The second magnetization state or any one of the magnetization states. 6. Temperature of the sixth magnetic layer becomes equal to or higher than the temperature of Tc ₆ from the first and second magnetization states of the temperature of the third magnetic layer is Tc ₃
The magnetizations of the fourth magnetic layer and the fifth magnetic layer are adjusted with respect to the third magnetic layer so that the coupling state by the exchange interaction becomes stable when heated to an appropriate first temperature state that does not reach the first temperature state. The alignment is performed by aligning the atomic spins, and the magnetization of the third magnetic layer maintains the alignment state before heating. Orientation state before magnetization heating of the third magnetic layer when 7. heated from the first and second magnetization states of the up suitable second temperature state where the temperature is the temperature of Tc ₃ of the third magnetic layer State transition to a different orientation state. 8. Temperature of the (2m) magnetic layer in the first and each of the cooling process after heating the second magnetization state until the first and second temperature state of the said is lowered to a temperature of Tc _2m The magnetizations of the (2m) -th magnetic layer and the (2m + 1) -th magnetic layer are aligned with the atomic spin with respect to the (2m-1) -th magnetic layer so that the coupling state by the exchange interaction becomes stable when It is oriented, and the magnetization of the (2m-1) -th magnetic layer keeps its previous orientation state. 3. The magneto-optical recording medium according to claim 1, wherein each magnetic layer is a rare earth element.
A magneto-optical recording medium comprising an iron group amorphous alloy. 4. The magneto-optical recording medium according to claim 1, wherein the fourth magnetic layer is made of a material and a composition having a domain wall energy density smaller than that of the other magnetic layers. A magneto-optical recording medium characterized by the following. 5. The magneto-optical recording medium according to claim 4, wherein the fourth magnetic layer is made of an amorphous alloy of a rare earth element containing Gd as a main component and an iron group element. Magneto-optical recording medium. 6. The magneto-optical recording medium according to claim 4, wherein the fourth magnetic layer is made of a rare earth-iron group amorphous alloy having a rare earth sublattice magnetization dominant. recoding media. 7. The magneto-optical recording medium according to claim 1, wherein a thickness of the (2m) magnetic layer excluding the fourth magnetic layer is 0.5 nm or more and 10 nm or less. Magneto-optical recording medium.