JPH0562264A - Production of magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obviate the degradation in C/N and to enhance the reliability of repetitive reading out so as to allow overwriting even if the film thickness of a magnetic recording layer is thin by vibrating a substrate surface at the time of forming the recording layer on the substrate. CONSTITUTION:A high-frequency current is applied by front and rear electrodes to a piezoelectric vibrator 40 of a surface wave generating element 10 to generate surface acoustic waves on the vibrator 40. The magnetic recording film is formed by a sputtering film forming method while the substrate 20 is kept vibrated by transmitting the surface waves to the substrate 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a magneto-optical recording medium. More particularly, the present invention relates to a recording medium utilizing exchange coupling force, and more particularly to a method of manufacturing a highly reliable magneto-optical recording medium comprising an overwrite-capable exchange coupling multilayer film.

[0002]

2. Description of the Related Art In recent years, vigorous development of optical recording / reproducing methods and recording media used therefor satisfying various requirements such as high density, large capacity, large access speed, and large recording and reproducing speeds have been vigorously pursued. Has been. Magneto- optical recording medium : Among various optical recording / reproducing methods,
In particular, the magneto-optical recording / reproducing method has an excellent advantage and feature that information can be erased after being recorded and new information can be recorded again and again.
It has the greatest appeal as a recording medium that leads the advanced information society.

A recording medium used in this magneto-optical recording / reproducing system has a vertically magnetized film having a structure of one layer or multiple layers as a layer for recording, and the vertically magnetized film at that time is, for example, amorphous. GdFe and GdC
o, GdFeCo, TbFe, TbCo, TbFeCo
Are known. Generally, these perpendicular magnetic films are
It has a concentric or spiral track on which information is recorded.

The information to be recorded has been binarized in advance, and this information includes a bit (B ₁ ) having a magnetization "A direction" which is either upward or downward with respect to the film surface. It is recorded with two signals of the bit (B ₀ ) having the magnetization in the "reverse A direction". These bits B
₁ and B ₀ correspond to one or the other of the digital signals ₁ and ₀ , respectively. However, generally, the magnetization of the recorded track is aligned in the "reverse A direction" by applying a strong external magnetic field before recording. Then, the bit (B ₁ ) having the "A direction" magnetization is formed on the track. Therefore, the information includes the presence / absence of this bit (B ₁ ) and / or
Alternatively, it is expressed by the bit length. Principle of bit formation : In the formation of bits, the characteristic of laser as an optical means, that is, the coherence which is excellent in spatiotemporal time, is advantageously used, and the diffraction limit determined by the wavelength of laser light is used. The beam is narrowed down to almost the same small spot. The narrowed light is applied to the track surface, and the perpendicular magnetization film has a diameter of 1
Bits of μm or less are formed and information is recorded. In optical recording, theoretically recording densities up to about 10 ⁸ bits / cm ³ can be achieved. This is because the laser beam can be concentrated to a spot with a diameter as small as about its wavelength.

As shown in FIG. 1, in this magneto-optical recording, a laser beam (L) is focused on a perpendicular magnetization film (MO) and heated. Meanwhile, the recording magnetic field (Hb) in the opposite direction to the initialized direction is applied to the heated portion from the outside. Then, the coercive force Hc (coersivity) of the locally heated portion decreases and the recording magnetic field (H
It is smaller than b). As a result, the magnetization of that portion is aligned in the direction of the recording magnetic field (Hb). In this way, the oppositely magnetized bit is formed.

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

However, it is not necessary to stick to the Curie point or its vicinity and the compensation temperature. in short,
Recording can be performed at a predetermined temperature higher than room temperature by applying a recording magnetic field (Hb) that defeats the lowered Hc to the magnetic material having the lowered Hc. However, Hb that is too high to reverse the magnetization of the perpendicular magnetization film (MO) in the region (Hc of this region has the original high Hc) that has not reached the predetermined temperature higher than room temperature cannot be used. Reproduction principle : FIG. 2 shows the principle of information reproduction based on the magneto-optical effect. Light is usually an electromagnetic wave with electromagnetic field vectors diverging in all directions on a plane perpendicular to the optical path. This light is converted into linearly polarized light (L _p ),
Then, when the perpendicular magnetic film (MO) is irradiated, light is reflected on the surface thereof or transmitted through the perpendicular magnetic film (MO). At this time, the polarization plane rotates according to the direction of the magnetization M. This rotating phenomenon is called a magnetic Kerr effect or a magnetic Faraday effect.

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

By the way, in order to reuse the recorded medium, (1) the medium is initialized again by the initializing device, or (2) the recording device is provided with an erasing head similar to the recording head. Alternatively, (3) it is necessary to previously erase the recorded information by using a recording device or an erasing device as a pre-stage process. Therefore, in the magneto-optical recording system, it has been considered impossible to overwrite (write) new information on the spot regardless of the presence or absence of recorded information.

However, if the direction of the recording magnetic field Hb can be freely modulated between "A direction" and "reverse A direction" as required, overwriting becomes possible. However, it is impossible to modulate the direction of the recording magnetic field Hb at high speed. That is, for example, the recording magnetic field Hb
Is a permanent magnet, it is necessary to mechanically reverse the direction of the magnet. However, it is impossible to reverse the direction of the magnet at high speed. Even when the recording magnetic field Hb is an electromagnet, it is impossible to modulate the direction of a large-capacity current at such a high speed.

In fact, as a magneto-optical recording medium having a two-layer film structure, there is known a magneto-optical recording medium utilizing an exchange coupling force as disclosed in, for example, Japanese Patent Application Laid-Open No. 57-78652. However, the above-mentioned overwriting is impossible, and the portion already recorded before recording must be erased once. However, the technological progress is remarkable, and the intensity of the irradiation light beam is modulated according to the binary information to be recorded without modulating the intensity (including ON and OFF) of the recording magnetic field Hb or the direction of the recording magnetic field Hb. Then, an overwritable magneto-optical recording method, an overwritable magneto-optical recording medium used for the method, and an overwritable recording apparatus used for the same have been invented. These are a two-layer film medium utilizing the exchange coupling force (JP-A-62-17594), an exchange-coupling three-layer film medium (JP-A-64-50257, JP-A-1-273248),
It has already been proposed as an exchange coupling four-layer film medium (WO90 / 02400). Overwritable recording media : JP-A-62-1759 discloses these overwritable magneto-optical recording media.
In the case of this medium, for example, in the case of the medium described in Japanese Patent Laid-Open No. 48, "a recording / reproducing layer (referred to as a memory layer or an M layer) which basically consists of a magnetic thin film capable of perpendicular magnetization and a magnetic layer capable of perpendicular magnetization. A recording auxiliary layer (referred to as “recording layer” or W layer) made of a thin film, and both layers are exchange-coupled,
In addition, an overwritable multi-layered magneto-optical recording medium is used which is capable of keeping only the magnetization of the W layer in a predetermined direction without changing the magnetization direction of the M layer at room temperature.

Then, the information is represented and recorded by the bit having the "A direction" magnetization and the bit having the "reverse A direction" magnetization in the M layer (and also in the W layer in some cases). In this medium, the W layer can have its magnetization direction aligned with the “A direction” by an external means (for example, the initial auxiliary magnetic field Hini), and at that time, the M layer does not reverse the magnetization direction. Furthermore, the magnetization direction of the W layer once aligned in the “A direction” is not reversed even when subjected to the exchange coupling force from the M layer, and conversely, the magnetization direction of the M layer is changed to the “A direction”. It does not reverse even if it receives exchange coupling force from the aligned W layers.

The W layer has a lower coercive force Hc and a higher Curie point Tc than the M layer. According to this recording method, the magnetization direction of the W layer of the recording medium is aligned by the external means to the “A direction” before recording. This act can be referred to as "initialize". This initialization is unique to overwritable media. Then, the medium is irradiated with the laser beam pulse-modulated according to the binarized information. The intensity of the laser beam has a high level P _H and a low level P _L , which correspond to the high level and low level of the pulse. This low level is higher than the reproduction level P _R that illuminates the medium during reproduction. Then, as is already known, even when recording is not performed, a laser beam may be emitted at a <very low level> in order to access a predetermined recording location on the medium, for example. The irradiation at this <very low level> is also at a level that is the same as or close to the reproduction level P _R. Therefore, the output waveform of the laser beam is as shown in FIG. 3, for example.

Further, the recording beam is not a single beam but two adjacent beams, and is a low-level laser beam (for erasing) which does not modulate the preceding beam in principle.
It may be a high-level laser beam (for writing) that modulates the following beam according to information. In this case, the trailing beam is pulse-modulated between a high level and a base level (equal to or lower than the low level and may have zero output). The output waveform in this case is, for example, as shown in FIG.
Shown in.

A recording magnetic field Hb whose direction and intensity are not modulated acts on the medium irradiated with the beam. Hb is
The size cannot be narrowed down to the same size as the beam irradiated portion (spot region), and the region where Hb acts is much larger than the spot region. When illuminated by a low level beam, M is independent of the direction of magnetization of the previous bit.
One of the "A-oriented" bits (B ₁ ) or the "reverse A-oriented" bit (B ₀ ) is formed in the layer.

When the high level beam is irradiated, the other bit of the M layer is formed regardless of the magnetization direction of the previous bit. This completes the overwrite. The laser beam is pulse-modulated according to the information to be recorded. This fact itself is also performed in the conventional magneto-optical recording, and means for pulse-modulating the beam intensity according to the binary information to be recorded. Is a known means. For example, THE BELL SYSTEM TECHNICAL JOURNAL, Vol.62 (19
83), 1923-1936. Therefore, given the required high and low levels of beam intensity, it is readily available with only minor modifications to conventional modulation means.
For a person skilled in the art, such a modification would be easy given the high and low levels of beam intensity.

That is, the existing proposal having the above configuration
One of the characteristics of this method is to increase the beam intensity.
Level and low level. That is,
When the field intensity is at a high level, the recording magnetic field Hb is
Part means reverses the "A direction" magnetization of the W layer to the "reverse A direction".
And the "reverse A direction" magnetization of this W layer
Therefore, the "reverse A direction" magnetization in the M layer [or "A direction" magnetization]
Form a bit with. At low beam intensity
Indicates that the magnetization direction of the W layer is the same as in the initialized state.
Then, the action of the W layer (this action acts on the M layer through the exchange coupling force).
"A direction" magnetization to the M layer [or "reverse A"
Form a bit having a "direction" magnetization. Multi-layer structure : Also, this overwritable record / playback
The recording medium used in the method is in any of its embodiments.
However, the recording medium has a multi-layer structure including the M layer and the W layer.
There is.

The M layer is a magnetic layer having a high coercive force and a low magnetization reversal temperature at room temperature. The W layer is a magnetic layer having a lower coercive force and a higher magnetization reversal temperature at room temperature than the M layer. In addition,
Both the M layer and the W layer may themselves be composed of a multilayer film. In some cases, a third layer (for example, an exchange coupling σ _W adjustment layer) may be present between the M layer and the W layer.
Further, there is no clear boundary between the M layer and the W layer, and the one layer may gradually change to the other. (A) In one embodiment, the coercive force of the M layer is set to H _C1 , W
H _{C2 of} the layer, T _C1 of the Curie _{extension of} the M layer, T _C2 of the W layer, T _{R of} room temperature, and T _L of the temperature of the recording medium when a low-level P _L laser beam is irradiated. When the laser beam of level P _H is applied, it is T _H , and the coupling magnetic field received by the M layer is H _D1 (H _D1 is σ _W being the product of the M layer saturation magnetic moment M _S and the M layer thickness t. Calculated by dividing the quotient),
If the coupling field W layer is subjected to H _D2 and sigma _W a is calculated by the quotient by the product of the thickness t of the W layer saturated magnetic moment M _S and W layer), a recording medium, the following formula 1 and equations 2 to 5 at room temperature.

T _R <T _C1 ≈T _L <T _C2 ≈T _H …………………… Equation 1 H _C1 > H _C2 + | HD ₁ − (± HD ₂ ) | ………… … Formula 2 H _C1 > H _D1 ………………………………………………… Formula 3 H _C2 > H _D2 …………………………………… … Equation 4 H _C2 + H _D2 <| Hini. | <H _C1 ± H _D1 …………… Equation 5 In the above equation, the sign “≒” is equal or almost equal (± 20 ° C Place).

In the above formula, the composite ± is the case of the A (antiparallel) type medium described below in the upper stage, and the case of the P (parallel) type medium described below in the lower stage. The ferromagnetic medium belongs to the P type.
That is, the relationship between the coercive force and the temperature is generally represented by a graph as shown in FIG. The thin line represents that of the M layer, and the thick line represents that of the W layer.

Therefore, when an external means such as an initial auxiliary magnetic field (Hini.) Is applied to this recording medium at room temperature, according to the equation 5, the magnetization direction of the M layer is not inverted but only the magnetization of the W layer is inverted. .. Therefore, when an action is applied to the medium from an external means (for example, an initial auxiliary magnetic field Hini.) Before recording, only the W layer is "A direction" ---- here, "A direction" is upwardly directed on the paper for convenience. The arrow “↑” indicates that the “reverse A direction” can be magnetized to “−−−−−−” indicated by the arrow ↓.
Then, even if Hini. Becomes zero, according to the equation 4, the magnetization ↑ of the W layer is retained as it is without being re-inverted.

Conceptually, a state where only the W layer is magnetized in the "A direction" ↑ before recording by an external means is as follows:
It becomes FIG. In FIG. 6, the magnetization direction in the M layer represents the information recorded up to that point. In the following description, since there is no relation to the orientation, when this is indicated by X and is simplified, FIG. 6 can be shown as state 1 in FIG. 7. Here, the medium temperature is changed to T by irradiating a high level laser beam.
_Raise to _H. Then, since T _H is higher than the Curie point T _C1 , the magnetization of the M layer disappears. Furthermore, since T _H is near the Curie point T _C2 , the magnetization of the W layer disappears at all or almost disappears. Here, the recording magnetic field Hb of "A direction" or "reverse A direction" is applied according to the type of medium. Hb is
A stray magnetic field from the medium itself may be used. In order to simplify the explanation, it is assumed that the recording magnetic field Hb in the “reverse A direction” ↓ is applied.
Since the medium is moving, the irradiated portion is immediately moved away from the laser beam and cooled. When the temperature of the medium is lowered in the presence of Hb, the magnetization of the W layer is reversed according to Hb to become "inverse A direction" ↓ magnetization (state 2 in FIG. 7).

Then, the cooling is further advanced, and the medium temperature becomes T
_When it is slightly lower than _C1, the magnetization of the M layer appears again. In that case, due to the magnetic coupling (exchange coupling) force, the magnetization direction of the M layer is influenced by the W layer and becomes a predetermined direction. As a result, depending on the type of medium, “reverse A direction” ↓ bits (for P type media) or “A direction” ↑ bits (for A type media) are formed in the M layer. This state is the state 3 (P type) or the state 4 (A type) in FIG.

The change in state caused by this high level laser beam can be called a high temperature cycle. Next, the medium temperature is raised to T _L by irradiating the laser beam of low level P _L. Since T _L is near the Curie point T _C1, the magnetization of the M layer disappears completely or almost completely, but the Curie point T _C2
Since the temperature is lower than that, the magnetization of the W layer does not disappear. This state is shown as state 5 in FIG. Here, the recording magnetic field Hb
Is unnecessary, but Hb is turned ON and O at high speed (short time).
It is impossible to FF. Therefore, it is unavoidable and remains as it was during the high temperature cycle.

However, since H _C2 is still large, Hb does not reverse the magnetization ↑ of the W layer.
Since the medium is moving, the irradiated portion is immediately moved away from the laser beam and cooled. As cooling progresses, magnetization again appears in the M layer. The direction of the appearing magnetization has a predetermined direction due to the influence of the W layer due to the magnetic coupling force. As a result, “A direction” ↑ bit (for P type medium) or “reverse A direction” ↓ bit (for A type medium) is formed in the M layer depending on the type of medium. This magnetization does not change even at room temperature. This state is state 6 in FIG.
(P type) or state 7 (A type).

The change in state caused by the low level laser beam will be referred to as a low temperature cycle here. As described above, regardless of the magnetization direction of the M layer before recording, by selecting the high temperature cycle and the low temperature cycle, the bit in the "reverse A direction" ↓ and the bit in the "A direction" ↑ can be changed to M. Can be freely formed in layers. That is, overwriting is possible by modulating the laser beam in a pulse shape between a high level (high temperature cycle) and a low level (low temperature cycle) according to information. This will be further clarified with reference to FIG. The states of magnetization in FIG. 8 are all drawn as a result of room temperature or returning to room temperature.

The preceding description is, M layer, has been described magnetic composition has no compensation temperature T _{co mp.} Between room temperature and the Curie point W layer both. However, if the compensating temperature T _comp. Exists, the direction of the magnetization is reversed when the compensating temperature T _comp. Is exceeded. In reality, the directions of the sublattice magnetizations of RE and TM do not change, but the magnitude relation is large. Is reversed, the direction of magnetization as a whole (alloy) is reversed ---
The explanation becomes more complicated because the A and P types are reversed. In this case, the direction of the recording magnetic field Hb is also opposite to the direction ↓ in the explanation on the previous page when considering at room temperature. That is, Hb having the same direction as the magnetization direction ↑ of the initialized W layer is applied.

The recording medium is generally disc-shaped, and the medium is rotated during recording. Therefore, the recorded portion (bit) is again subjected to the action of the external means such as Hini. After the recording, and as a result, the magnetization of the W layer is aligned in the original “A direction” ↑. However, at room temperature, the magnetization of the W layer does not affect the M layer, so that the recorded information is retained.

Therefore, when the M layer is irradiated with linearly polarized light, the reflected light contains information, so that the information is reproduced as in the conventional magneto-optical recording medium. The perpendicularly magnetized films forming the M layer and the W layer have a ferromagnetic material and a ferrimagnetic material having no Curie point without a compensation temperature, and an amorphous ferrimagnetic material having both a compensation temperature and a Curie point. Selected from the group consisting of crystalline or crystalline. (B) In the above description, the Curie point is used as the magnetization reversal temperature, but in the second embodiment, Hc lowered at a temperature lower than the Curie point is used. .. This second embodiment is
Instead of T _{C1 in} the first embodiment, a temperature T _{S1 in} which the M layer is magnetically coupled to the W layer is used, and the W layer is replaced by Hb instead of T _C2.
Using a temperature T _S2 that inverts at the same way as in the first embodiment.

In the second embodiment, the coercive force of the M layer is set to H
_C1 , W of the W layer is H _C2 , the temperature at which the M layer is magnetically coupled to the W layer is T _S1 , the temperature at which the magnetization of the W layer is reversed at Hb is T _{S2, the} room temperature is T _R , and the low level P _L Temperature of the medium when irradiated with the laser beam of T _L , T _H when irradiated with the laser beam of high level P _H , and the coupling magnetic field received by the M layer is H _D1 (where H _D1 is σ _W is the M layer Saturation magnetic moment M _S and M
Calculated by the quotient divided by the product of the layer thickness t), the coupling magnetic field received by the W layer is H _D2 (where H _D2 is σ _W between the W layer saturation magnetic moment M _S and the W layer thickness t). (Calculated by the quotient divided by the product), the recording medium satisfies the following expression 6 and also satisfies the expressions 7 to 10 at room temperature.

T _R <T _C1 = T _L <T _C2 = T _H …………………… Equation 6 H _C1 > H _C2 + | H _D1 − (± H _D2 ) | …………… … Equation 7 H _C1 > H _D1 ………………………………………………… Equation 8 H _C2 > H _D2 …………………………………… ………… Formula 9 H _C2 + H _D2 <| Hini. │ <H _C1 ± H _D1 ……………… Formula 10 In the above formula, for the composite ±, the upper row is A (antiparalle
The case of the l) type medium, and the case of the lower stage is the case of the P (parallel) type medium.

In this embodiment, at high temperature T _H , the magnetization of the W layer has not disappeared, but is sufficiently weak, and the magnetization of the M layer has disappeared or is sufficiently weak. Since the recording magnetic field Hb ↓ is sufficiently large even if a sufficiently weak magnetization remains in both the M layer and the W layer, Hb ↓ can make the magnetization direction of the W layer and possibly the M layer follow Hb ↓. .. This state is state 2 in FIG. Immediately after this, or when the laser beam is no longer emitted and cooling is allowed to proceed, the medium temperature rises to T
_When falling below _H or moving away from Hb, the W layer influences the M layer via σ _W to make the magnetization direction of the M layer follow a stable direction. As a result, the state 3 (P type) or the state 4 (A type) in FIG. 9 is obtained.

On the other hand, at low temperature T _L , the W layer is of course M
The layers have not lost their magnetization. However, that of the M layer is relatively small. In this case, there are two types of bit states, state 5 and state 6 in FIG. 9 for the P type, and two types, state 7 and state 8 in FIG. 9 for the A type. In the states 6 and 8, the interface domain wall (indicated by a thick line −) between the M layer and the W layer.
Is occurring and is in a slightly unstable (metastable) state. State 1 indicates any of states 5 to 8. Just before the medium part in this state reaches the irradiation position of the laser beam,
Receives Hb ↓. Nevertheless, this state 6 or state 8 is retained. Because the W layer has sufficient magnetization at room temperature, the magnetization is not reversed by Hb ↓, and the memory layer in the state 8 whose direction is opposite to Hb ↓ is Under the influence of the exchange coupling force σ _W from the large W layer, the magnetization direction is maintained in the same direction as the W layer because of the P type.

Shortly thereafter, the state 6 or the state 8 is irradiated with a low level laser beam. Therefore, the medium temperature rises. Along with that, the coercive force of both layers decreases. However, since the W layer has a high Curie point, the decrease in coercive force H _C2 is small, Hb ↓ is not lost, and the magnetization direction “A direction” ↑ when initialized is maintained. On the other hand, although the M layer has a low Curie point, the medium temperature is still lower than the Curie point T _{C1 of the} M layer, so that the coercive force H _C1 remains. However, since H _C1 is small, the W layer is
Effect of Hb ↓ and effect via exchange coupling σ _W from W layer (in the case of P type, force to turn in the same direction)
Receive. In this case, the latter is stronger, and in the case of P type,

[0035] _{formula: H C1 + Hb <σ W} / 2M S1 t 1 _{formula: H C2> σ W / 2M} S2 t 2 ( Note: wherein the inequality respectively right σ _W 2M _S1 t ₁
(Or the fraction divided by 2M _S2 t ₂ )) are simultaneously satisfied. In the case of type A, _{Formula: H C1 -Hb <σ W /} 1M S1 t 1 _{formula: H S2> δ W / 2M} S2 t 2 ( Note: wherein the inequality respectively right sigma _W 2M _S1 t ₁
(Or the fraction divided by 2M _S2 t ₂ )) are simultaneously satisfied. The lowest temperature at which these equations are satisfied simultaneously is called T _LS . In other words, it is the minimum temperature T _LS at which the domain wall in state 6 or state 8 disappears.

As a result, the state 6 shifts to the state 9 and the state 8 shifts to the state 10. On the other hand, there is no domain wall 5
Is the same as the state 9, and similarly, the state 7 without the domain wall is the same as the state 10, so that in the end, the previous state (state 5 or 6 in the case of the P type, state 7 or 8 in the case of the A type).
Irrespective of whether), the state 9
A bit of (P type) or state 10 (A type) is formed.

This state does not change even when the medium temperature is lowered and then returned to room temperature due to the laser beam irradiation of the bit stopping or the bit moving away from the irradiation position. State 9 (P type) or state 1 in FIG. 9
0 (A type) is the same as state 6 (P type) or state 7 (A type) in FIG. 7. It will be appreciated that this allows a low temperature cycle to be achieved without raising the medium temperature to the Curie point T _C1 of the M layer.

Also in the case of the first embodiment in which the low temperature cycle is carried out at T _C1 or more, since the medium temperature passes through T _LS on the way from room temperature to T _C1 , at this time, in the case of the P type, the state If the transition from 6 to the state 9 is the type A, the transition from the state 8 to the state 10 occurs.
After that, T _C1 is reached, and the state 5 shown in FIG. 7 is established. The above description has explained the magnetic material composition in which there is no compensation temperature T _comp. Between the room temperature and the Curie point for both the M layer and the W layer. However, if the compensating temperature T _comp. Exists, the direction of the magnetization is reversed when the compensating temperature T _comp. Is exceeded, and the A and P types are reversed, and the explanation becomes complicated accordingly. Moreover, the direction of the recording magnetic field Hb is also opposite to the direction when considered at room temperature. Alloy amorphous ferrimagnetic material : In both the first and second embodiments, the M layer and the W layer are transition metals (for example, Fe and Co).
A recording medium which is an amorphous ferrimagnetic material selected from alloy compositions of heavy rare earth metals (eg Gd, Tb, Dy, etc.) is preferable.

In both the M layer and the W layer, the transition metal (transi)
tion metal) -heavyrare earth metal
) When selected from the alloy composition, the direction and magnitude of the magnetization appearing outside as each alloy is determined by the direction and magnitude of the sublattice magnetization of the transition metal atom (TM) inside the alloy and the heavy rare earth metal atom (RE). ) Is determined by the relationship with the direction and size of the sub-lattice magnetization. For example, as shown in FIGS. 10 and 11, the direction and magnitude of the sublattice magnetization of TM is represented by a vector indicated by a dotted arrow, and that of RE sublattice magnetization is represented by a vector indicated by a solid line arrow, The direction and magnitude of the entire magnetization can be represented by a vector indicated by an outlined arrow. At this time, the outline arrow (vector) is represented as the sum of the dotted arrow (vector) and the solid arrow (vector). However, in the alloy, due to the interaction between the TM sublattice magnetization and the RE sublattice magnetization, the dotted arrow (vector) and the solid arrow (vector) always have opposite directions.
Therefore, the dotted arrow (vector) and the solid arrow (vector)
The sum of and is such that when the strengths of both are equal, the vector of the alloy becomes zero (that is, the magnitude of the magnetization appearing outside is zero). The alloy composition when it becomes zero is the compensating composition (compen
sation composition). For any other composition, the alloy has an intensity equal to the intensity difference of both sublattice magnetizations and has a hollow arrow (vector) with an orientation equal to the orientation of the larger vector.

The sublattice magnetization states of RE and TM are roughly classified into four states, which are shown in (1A) to (4A) of FIG. The magnetization vector of the alloy (white arrow) in each state is shown in correspondence with (1B) to (4B) in FIG. For example, if the RE vector is larger than the TM vector, the sublattice magnetization state is shown in (1A) and the alloy magnetization vector is shown in (1B).

When the strength of either the TM vector or the RE vector of the composition of an alloy is larger, the alloy composition is called RE rich, for example, which has the larger strength, and is called the M layer. Both the W layer is divided into a TM rich composition and an RE rich composition. Therefore,
When the composition of the W layer is plotted on the ordinate and the composition of the W layer is plotted on the abscissa, the type of the entire medium can be classified into four quadrants shown in FIG. The P type described above belongs to the first and third quadrants, and the A type belongs to the second and fourth quadrants.

On the other hand, looking at the change of the coercive force with respect to the temperature change, there is an alloy composition having a characteristic that the coercive force temporarily increases to infinity and then drops before reaching the Curie point (temperature at which the coercive force is zero). .. It is called the compensation temperature (T _comp. ) Corresponding to this infinity. At a temperature lower than the compensation temperature, the RE vector (solid arrow) is larger than the TM vector (dotted arrow), so that it can be said to be TM rich, and vice versa at a temperature higher than the compensation temperature. Therefore,
The compensation temperature of the alloy of compensating composition can be said to be at room temperature.

On the contrary, the compensation temperature does not exist between room temperature and the Curie point in the TM-rich alloy composition. Since the compensation temperature below room temperature is meaningless in magneto-optical recording, the compensation temperature in this specification refers to that which exists between room temperature and the Curie point. Classifying the presence or absence of the compensation temperature of the M layer and the W layer, the medium is type 1
~ It is classified into four types of type 4. The first quadrant medium includes all four types. So, M layer and W
If both layers are classified as RE-rich or TM-rich and whether they have a compensation temperature or not, the recording medium is classified into 9 classes as shown in FIG. <Class 1-1> Here, the medium No. belonging to the recording medium of Class 1 (P type / I quadrant / Type 1) shown in FIG.
Taking 1-1 as an example, the overwrite principle will be described in detail.

[0044] The medium No. 1-1 has the formula _{11: T R <T comp <} 2 of _{T L <T H ≦ T C1} ≦ T C2 and the formula 11:.. T _comp has a relation <T _C1 .. For the purpose of simplifying the description, the following description will describe those having a relationship of T _H <T _C1 <T _C2 . _Whether T _comp.2 is higher than or equal to T _L ,
It may be low, but for the purpose of simplifying the explanation, in the following explanation, T _L <T _comp.2 . FIG. 14 is a graph showing the above relationship. The thin line shows the graph of the M layer, and the thick line shows the graph of the W layer.

At room temperature T _R , the magnetic field of the M layer is the initial auxiliary magnetic field Hin.
The condition that only W layer is inverted without being inverted by i.

[0046]

[Equation 1]

Equation 12 is expressed as This medium No. 1
−1 satisfies Expression 12. However, H _C1 : Coercive force of M layer H _C2 : Coercive force of W layer M _S2 : Saturation magneti of M layer (saturation magneti
zation) M _S2 : saturation magnetic moment of W layer t ₁ : thickness of M layer t ₂ : thickness of W layer σ _W : domain wall energy = exchange coupling force (interfacewal)
l cnergy) At this time, the conditional expression of Hini. is shown by the following Expression 15. When the Hini. Disappears, the magnetizations of the M layer and the W layer are affected by the exchange coupling force. However, the conditions under which the magnetizations of the M layer and the W layer are maintained without being inverted are represented by Expressions 13 to 14. This medium No. 1-1 satisfies the expressions 13 to 14.

[0048]

[Equation 2]

[0049]

[Equation 3]

The magnetization of the W layer of the recording medium satisfying the conditions of equations 12 to 14 at room temperature is as high as before the recording.

[0051]

[Equation 4]

Hini. That satisfies the expression 15 shown in FIG. At this time, the M layer remains in the previous recording state. This state is shown as either state 1 or state 2 in FIG. The states 1 and 2 are held until just before recording. Then, the recording magnetic field Hb is applied in the “A direction” ↑. The recording magnetic field Hb is
As is the case with general magnetic fields, it is difficult to narrow the area to the same area as the laser beam irradiation area (spot area). When the medium is a disc, once the information (bit) once recorded is rotated once, it is in the state 1 or the state 2 again under the influence of Hini. After that, the bit passes near the irradiation area (spot area) of the laser beam. At this time, the bits in state 1 and state 2 are affected by the fact that the recording magnetic field Hb approaches the applying means. In this case, if the magnetization direction of the M layer of the bit in the state 2 having the opposite magnetization direction to Hb is reversed by Hb, the information just recorded one rotation before will be lost. The conditions that should not be so are

[0053]

[Equation 5]

It is expressed by 2 in the formula 15 shown in The disk medium No. 1-1 needs to satisfy the condition (2) of conditional expression 15 at room temperature. Conversely, one condition that determines Hb is represented by 2 in Equation 15. Now, the bits in states 1 and 2 finally reach the spot area of the laser beam. There are two types of laser beam intensities, low level and high level, as in the basic invention.

-Low Temperature Cycle-The medium temperature is increased to T by being irradiated with a low level laser beam.
_rises above _comp.1 . Then, the P type is changed to the A type. Although the directions of the RE and TM spins of the M layer do not change, the magnitude relationship of the intensity is shown in (3) of FIG.
Reverse from A) to (4A). Therefore, the magnetization of the M layer is reversed from (3B) to (4B) in FIG. As a result, the bit in state 1 goes to state 3, and the bit in state 2 goes to state 4.

Following the irradiation of the laser beam, the medium temperature eventually becomes T ₁ . Then,

[0057]

[Equation 6]

The condition (3) of the condition (15) is satisfied. As a result, even if Hb is ↑, the bit in state 4 transits to state 5. On the other hand, the bit in the state 3 maintains the same state even if Hb ↑ exists, because 3 in Expression 15 is satisfied. That is, the state 3 is changed to the state 5 which is the same state. In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. Medium temperature is T
_When it cools down below _comp.1, it will return to the original P type from A type. Then, the magnitude relationship between the RE spin and the TM spin of the M layer is reversed from (2A) to (1A) in FIG. Therefore, the magnetization of the M layer is reversed from (2B) in FIG. 11 to (1B). As a result, the bit in the state 5 shifts to the state 6 (the magnetization of the M layer is “A direction” ↑). This state 6 is maintained even when the medium temperature drops to room temperature. In this way, the bit “A direction” ↑ is formed in the M layer.

_-High Temperature Cycle-When irradiated with a high level laser beam, the medium temperature rises to a low temperature T _L via T _comp.1 . As a result, the state 7 is the same as the state 5. Irradiation with a high level laser beam further raises the medium temperature. When the medium temperature exceeds T _comp.2 of the W layer, the A type shifts to the P type. Although the directions of the RE and TM spins of the W layer do not change, the magnitude relationship between the strengths varies from (1A) to (2) in FIG.
Reverse to A). Therefore, the magnetization of the W layer is reversed from (1B) to (2B) in FIG. As a result, the magnetization of the W layer becomes “inverse A direction” ↓. This state is state 8.

However, since H _C2 is still large at this temperature, the magnetization of the W layer is not reversed by ↑ Hb. When the temperature further rises to T _H , the coercive force of the M layer and the W layer becomes small because the temperature is close to the Curie point. As a result, the medium is

[0061]

[Equation 7]

(1) shown in, or

[0063]

[Equation 8]

(2) shown in, or

[0065]

[Equation 9]

The two expressions (3) shown in (3) are simultaneously satisfied. Therefore, the magnetizations of both layers are reversed almost at the same time and follow the direction of Hb ↑. This state is state 9. In this state, when the laser beam deviates from the spot area, the medium temperature starts to drop. When the medium temperature becomes T _{comp. 2} or less, the P type shifts to the A type. Then, the directions of the spins of RE and TM do not change, but the magnitude relationship of the strength is reversed from (4A) to (3A) in FIG. Therefore, the magnetization of the W layer is reversed from (4B) to (3B) in FIG. As a result, the magnetization of the W layer becomes “inverse A direction” ↓. This state is state 10. State 1
At 0, the medium is

[0067]

[Equation 10]

4 of Expression 15 shown in is satisfied. for that reason,
Even if Hb ↑ acts on the W layer, it does not reverse. The temperature of the medium further decreases from the temperature in the state 10,
When it becomes T _comp.1 or less, it returns from the A type to the original P type. Then, the magnitude relationship between the intensity of the RE spin and the intensity of the TM spin of the M layer is reversed from (4A) to (3A) in FIG. Therefore, the magnetization of the M layer changes from (4B) to (3
Invert to B). As a result, the magnetization of the M layer becomes “inverse A direction” ↓. This state is state 11.

Eventually, the temperature of the medium drops from the temperature in state 11 to room temperature. Since H _c1 at room temperature is sufficiently large (see 5 in Equation 15), the magnetization ↓ of the M layer is not inverted by ↑ Hb, and the state 11 is maintained.

[0070]

[Equation 11]

In this way, the bits of "inverse A direction" ↓ are formed in the M layer. Although the above description has been given for the two-layer film of the M layer and the W layer, if such a two-layer film is provided, overwriting is possible even in a medium including a multilayer film of three or more layers. Especially in the above description, the initial auxiliary magnetic field is used as an external means.
Although it has been described using Hini., The basic invention may be any specific example of such external means. That is, the magnetization of the W layer should be oriented in a predetermined direction before recording.

Therefore, a utilization invention has been proposed in which the exchange coupling force from the initialization layer is used instead of Hini. This utilization invention is described in claim 3 of the specification published in International Patent Publication No. WO90 / 02400 as described above. This International Patent Publication was published on March 8, 1990. This invention is also used in the Japanese journal "OPTRONICS" 1990.
It is also introduced on pages 227 to 231 of No. 4 of the year. Next, this invention of use will be described. Use invention : The state of FIG. 16 shows the structure of the medium of this use invention.

This medium is composed of a substrate and a magnetic film having a four-layer structure formed on the substrate. This magnetic film is
In order, an M layer made of a vertically magnetizable magnetic thin film, a W layer made of a vertically magnetizable magnetic thin film, a switch layer made of a vertically magnetizable magnetic thin film (hereinafter referred to as an S layer), and a vertically magnetizable In principle, it has a four-layer structure (which may not include the S layer) with an initialization layer (hereinafter referred to as one layer) formed of a magnetic thin film.

In the International Patent Publication, the M layer is the first magnetic layer, the W layer is the second magnetic layer, the S layer is the third magnetic layer (see claim 3), and the one layer is It is called the fourth magnetic layer (see claim 3). In the parts other than the third item, the names of the third magnetic layer and the fourth magnetic layer are opposite to each other, which seems to be a mistake. In addition, the magazine "OPTRON
In ICS ", the S layer is called a control layer. Recently, in Japanese academic societies, the S layer is often referred to as a memory layer, a" recording layer ", a switch layer and an initialization layer. I will follow this.

In this four-layer structure medium, the M layer and the W layer are exchange-coupled, and it is possible to direct only the magnetization of the W layer to a predetermined direction without changing the magnetization direction of the M layer at room temperature. You can
Moreover, the W layer and the I layer are S at a temperature below the Curie point of the S layer.
Exchange coupled through the layers. The I layer has the highest Curie point and does not lose its magnetization even when irradiated with a high level laser beam. The I layer always holds the magnetization in a predetermined direction, and this serves as a means for repeatedly initializing the W layer in preparation for the next recording each time recording is performed. Therefore, the I layer is called the initialization layer.

However, the process of high temperature cycle (eg
If T_H(In the vicinity), the magnetization reversal of the W layer must occur.
In that case, the influence from the I layer can be ignored.
Must be small. When the temperature rises, the W layer
Exchange coupling force between layer I and layer I _W24Is smaller, so
It is convenient. But T_HIs sufficient for_W24But
If left, an S layer is required between the W and I layers
Become. If the S layer is a non-magnetic material, σ_W24Is zero or emergency
Becomes smaller. But T_HSomewhere lower to room temperature
At the temperature of σ due to the initialization of the W layer_W24Must be big
I have to. At that time, the S layer is seen between the W layer and the I layer.
It is necessary to give a sufficiently large exchange coupling force.
Yes. For that purpose, the S layer needs to be magnetic. Therefore,
At a relatively low temperature, the S layer becomes a magnetic material and becomes a W layer.
Apparently sufficiently large exchange coupling force σ with the I layer_W24To
At relatively high temperature, it becomes a non-magnetic material and becomes a W layer.
Apparently zero or very small exchange coupling force with the I layer
σ_W24Is to give. Therefore, the S layer is the switch layer
Called.

Using FIG. 16 described above, the four-layer film overlay
Ito's principle will be described with reference to its typical example. In addition, each layer
Any of the layers of T is between room temperature and Curie point._comp.Have
The explanation becomes more complicated. Also, in FIG. 16, the white outline
Arrows indicate the direction of magnetization of each layer. State before recording
Is either state 1 or state 2. Focus on the M layer
Then, the state 1 is the bit (B direction) for "A".₁) And the state
State 2 is a bit for "inverse A direction" (B ₀), M layer and W
There is an interface domain wall (indicated by the bold line ━) between the layers, which makes it somewhat uneasy.
It is in a stable state (metastable).

-Low Temperature Cycle-When the bits in state 1 and state 2 are irradiated with a laser beam to raise the temperature, the magnetization of the S layer is first erased. Therefore, the state 1 shifts to the state 3, and the state 2 shifts to the state 4. When the temperature further rises to reach T _LS , the magnetization of the M layer becomes weak and the action via the exchange coupling force from the W layer becomes strong. As a result, the magnetization of the M layer in state 4 is reversed, and at the same time, the domain wall between layers disappears. This is state 5. Since the bit in the state 3 originally has no domain wall between layers, the state 5 directly shifts to the state 5.

Here, when the irradiation of the laser beam stops or moves away from the irradiation position, the temperature of the bit in the state 5 starts to decrease, and finally the state goes to the state 1 via the state 3. This is the low temperature cycle. When the temperature further rises from the state 5 and exceeds the Curie point of the M layer, the magnetization disappears and the state 6 is established. Here, when the irradiation of the laser beam stops or moves away from the irradiation position, the temperature of the bit in the state 6 starts to decrease, and eventually the Curie point of the M layer reaches a slightly lower temperature.
Then, magnetization appears in the M layer. The direction of this magnetization is
Due to the action via the exchange coupling force from the W layer, the orientation becomes stable with respect to the magnetization direction of the W layer (direction in which no domain wall is generated between layers). Since the type is P type here, the state 5 is reproduced. The temperature drops further, and accordingly state 3 occurs, followed by state 1 bits. This process is another example of a low temperature cycle.

-High Temperature Cycle-When the laser beam is irradiated to the bits in the states 1 and 2 to raise the temperature, the state 6 is passed through the state 5 as described above.
Leading to. When the temperature rises further, the coercive force of the W layer drops significantly. Therefore, the magnetization is inverted by the recording magnetic field Hb ↓. This is state 8.

Here, when the irradiation of the laser beam stops or moves away from the irradiation position, the medium temperature starts to decrease. Eventually, the medium temperature falls slightly below the Curie point of the M layer. Then, magnetization appears in the M layer. This magnetization direction is affected by the exchange coupling force from the W layer and becomes stable with respect to the magnetization direction of the W layer (direction in which no domain wall is formed between layers). Here, since it is the P type, the state 9 appears.

When the temperature is further lowered, magnetization appears in the S layer, and as a result, the W layer and the I layer are magnetically coupled (by an exchange coupling force). As a result, the magnetization direction of the W layer is stable with respect to the magnetization direction of the I layer (direction in which no domain wall is formed between layers). Since it is of P type here, the magnetization of the W layer is inverted in the “A direction”, and as a result, an interface domain wall is generated between the M layer and the W layer. This state is maintained even at room temperature, and the bit of state 2 is generated.

This is the high temperature cycle. When the temperature further rises after the state 8 appears due to the recording magnetic field Hb ↓, the temperature eventually exceeds the Curie point of the W layer. Then, the state 7 appears. Here, when the irradiation of the laser beam stops or moves away from the irradiation position, the medium temperature starts to decrease. Eventually, the medium temperature falls slightly below the Curie point of the W layer. Then, magnetization appears in the W layer.
The direction of this magnetization follows the direction of the recording magnetic field Hb ↓. As a result, the state 8 appears.

When the temperature is further lowered, the bit of the state 2 is formed through the state 9. This process is another example of a high temperature cycle. —Overwrite— As described above, the bit (B ₁ ) of the state 1 is formed in the M layer in the low temperature cycle and the 2 bits (B ₀ ) of the state in the M layer are formed in the high temperature cycle regardless of the previous recording state. It is formed. Therefore, overwriting becomes possible.

[0085]

Although the overwritable recording medium having the principle and configuration as described in detail above has been improved and devised, in actuality, the above-mentioned overwriting is actually performed. In the case of a writable exchange-coupling multilayer magneto-optical recording medium, the required conditions are satisfied with respect to the magnetic characteristics of each layer (for example, saturation magnetization Ms, coercive force Hc, etc.), film thickness, interlayer exchange-coupling force σ _w, etc. Control is required.

This also applies to the general conversion coupling multilayer film magneto-optical recording medium. For example, in a magneto-optical recording medium composed of an overwritable exchange-coupling two-layer film, in order to prevent the information of the first layer serving as a memory layer from being erased by the magnetization of the initialized second layer (auxiliary layer). , As described above, the following equation 13

[0087]

[Equation 12]

It is necessary to satisfy the above condition, and the initialized magnetization of the second layer is not reversed by the magnetization of the first layer.

[0089]

[Equation 13]

It is necessary to satisfy the following. Further, in order to enable overwriting, it is necessary to satisfy the conditions for transferring the magnetization of the recording auxiliary layer to the recording layer in the low temperature process and the laser power irradiation temperature T _L. In addition, in the multi-layered magneto-optical recording medium other than overwriting, the unevenness of the exchange coupling force σ _w causes the reduction of the CN ratio, and also in the single-layered magneto-optical recording medium, the film thickness of the recording film is also increased. Mura, magnetic characteristics (for example, coercive force _Hc )
Since the CN ratio decreases due to the unevenness, the uniform thin film is required not only in the overwritable magneto-optical recording medium but also in general magneto-optical recording media.

However, in general, when a recording medium is formed by a vapor phase film forming method such as sputtering which is an ordinary means, the surface of the formed thin film often has fine irregularities. Also, the magnetic characteristics may not always be uniform over the entire surface of the substrate in a minute area. The existence of such a non-uniform thin film region on the substrate surface naturally means the existence of a minute area that cannot satisfy the above-mentioned conditions. Therefore, in terms of the characteristics of the magneto-optical recording medium, it causes a problem such as a decrease in C / N, particularly a decrease in read reliability during repetition. Then, there is a problem that such inconveniences and drawbacks become remarkable when the film thickness of each layer of the recording medium is thinned particularly for higher sensitivity.

Therefore, the present invention solves the above-mentioned drawbacks of the conventional exchange-coupling multilayered magneto-optical recording medium, and causes a drawback such as a decrease in C / N even when the thickness of each layer is reduced. It is an object of the present invention to provide a method for manufacturing a new magneto-optical recording medium, which has high reliability in repeated reading. Still another object of the present invention is to provide a new method for manufacturing an exchange-coupling multi-layered magneto-optical recording medium which can be overwritten as the recording medium.

[0093]

In order to solve the above problems, the present invention provides a magneto-optical recording medium characterized by vibrating the surface of a substrate when forming a magnetic recording layer on the substrate. Provide a manufacturing method.

[0094]

According to the present invention, when the magnetic recording layer is formed on the substrate by various means such as sputtering, the surface of the substrate is vibrated and the surface acoustic wave is generated, so that the magnetic characteristics of each layer ( Nonuniformity of various characteristics such as saturation magnetization Ms, coercive force Hc), surface shape (unevenness, minute unevenness of film thickness), exchange coupling force σ _w is eliminated, and a uniform thin film is realized.

As described above, by forming the magnetic recording layer while applying vibration, the required conditions as described above can be satisfied satisfactorily over the entire recording surface, and in order to achieve high sensitivity. Even if the thickness of each layer is reduced, the magneto-optical recording medium (multilayer film in which the magnetic recording layers are exchange-coupled with each other has high reliability, in particular, does not cause inconveniences and defects such as decrease in C / N and has high reliability in repeated reading. , And a highly reliable overwritable recording medium (same as above).

The present invention will be described in more detail with reference to the following examples.

[0097]

EXAMPLE FIG. 17 of the accompanying drawings is a sectional view showing a state in which a magneto-optical recording medium is formed into a film by a sputtering method. Of course, the present invention is not limited to sputtering, and other appropriate means may be adopted. For example, as shown in FIG. 17, in the case of sputtering, first, the substrate (20) is It is fixed to the mounting jig (31) together with the inner mask (32) and the outer mask (33), and the surface wave generating element (10) as vibration applying means is brought into contact with the substrate (20).

At this time, the surface wave generating element (10)
It is preferable that the vibration is transmitted to the entire substrate (20), for example, as shown in FIG. Below the mounting jig (31) and the substrate (20),
Arrange a target (34) for sputtering,
Film-forming components are scattered from the target (34) under reduced pressure in vacuum, and a thin film of a magnetic recording layer having a required thickness and component materials is attached to the surface of the substrate (20).

FIG. 19 exemplifies the positional relationship between the substrate (20) and the surface wave generating element (10) and the generation of vibration. In this example, the surface wave generating element (10) is composed of a piezoelectric vibrator (40), an elastic body (41) and an electrode (42). In this configuration,
A high frequency current is applied by the front and back electrodes (42) made of aluminum, for example, to generate a surface acoustic wave in the piezoelectric vibrator (40). This surface acoustic wave is elastic body (41)
Is transmitted to the substrate (20) via the and the whole surface of the substrate (20) is vibrated.

Of course, the vibration applying means is not limited to the use of such a surface wave generating element (10). FIG. 19 shows what is known as a so-called wedge type transducer.
Excitation by various surface acoustic waves such as excitation of Rayleigh waves by a comb-shaped transducer or the like and other various physical vibration means can be adopted. As the constituent material of these means, various materials including those known so far are appropriately adopted.

For example, an exchange-coupling multilayer magneto-optical recording medium capable of overwriting was produced by the sputtering film forming method as described above. <Manufacturing Example> A 1.2 mm thick disk-shaped glass substrate with pregrooves is fixed to a mounting jig in a vacuum chamber of a sputtering apparatus equipped with a ternary target source, as shown in FIGS. The surface wave vibration was generated by the surface wave generating element illustrated in FIG.

After the inside of the vacuum chuck bar was evacuated to 5 × 10 ^-5 Pa, the disk glass substrate was rotated and argon gas was introduced. And the argon gas pressure is 1 mTorr
set to r. Nitrogen gas was added to this argon gas and introduced into the vacuum chamber. First, Al was used as the first target and reactive sputtering was performed to form AlN.
Was formed into a thin film having a thickness of 700Å. This AlN was used as a protective layer.

Then, the introduction of N ₂ gas was stopped, and sputtering was carried out in argon gas using a TbFeCo alloy as a second target. A first layer made of a perpendicular magnetization film having a thickness of 150 Å was formed. Furthermore, as a third target, TbDyFeCo and Al are simultaneously sputtered to form a second layer which is an exchange coupling force adjusting layer (intermediate layer) having a film thickness of 100 Å, and only Al sputtering is performed in the sputtered state. Stop and TbDy
A third layer made of Co was formed.

Further, again using the first target and performing sputtering with argon gas and nitrogen gas in the same manner as described above, an Al layer having a thickness of 1000 Å as a protective layer is formed.
An N layer was formed. As described above, the glass 2p substrate (20) and the AlN protective layer (2) as shown in FIG.
1), TbFeCo first layer (22), TbDyFeCo
/ Al second layer (23), TbDyFeCo third layer (2
4), an overwritable exchange-coupled magneto-optical recording medium comprising the AlN protective layer (25) was prepared.

For comparison, a recording medium was also prepared as a comparative sample by forming a film without applying the vibration by the same procedure as above. <Evaluation of Characteristics> The recording medium of the present invention and the recording medium as a comparative example produced as described above were set in a recording / reproducing apparatus, and the characteristics of the recording medium were evaluated.

Recording was performed by passing an external magnetic field generating portion of 4 KOe at a linear velocity of 11 m / sec, and at first, 30% duty was applied.
This was done by recording the signal modulated at 4.0 MHz. Next, the recorded portion is 30% duty, 7.
The signal modulated at 5 MHz was overwritten (overwritten), and then the overwrite signal was continuously and repeatedly reproduced by a 1.7 mW laser beam.

The modulated binary recording laser powers are 8.0 mW and 4.0 mW, respectively. This record
The number of times the recording medium was repeatedly read and the C / N were evaluated according to the reproduction specifications. FIG. 21 shows the result. In the figure, A shows a recording medium formed by applying a vibration by the method of the present invention, and B shows
It shows a recording medium formed as a film without vibration as a comparative example.

As is clear from the result of FIG. 21, in the case of the recording medium of the comparative example formed without vibration (B).
Then, C / N decreases with the number of repetitions,
In the case of the recording medium formed by applying the vibration of the present invention (A)
As described above, although the thickness of the first layer made of the TbFeCo perpendicularly magnetized film is extremely thin as 150 Å,
It is possible to obtain a highly reliable recording medium with almost no decrease in C / N.

Of course, the manufacturing method of the present invention is not limited to the above examples. The composition of the recording medium having a multi-layer structure may be various ones including conventionally known ones, and the film thickness, vibration applying means and the like may be appropriately selected. In any case, various modes are possible.

[0110]

As described above in detail, in the case of the present invention, by vibrating the substrate surface to form the magnetic recording layer, the C / N is reduced even when the film thickness is thin. Therefore, it is possible to obtain a magneto-optical recording medium having a multi-layered structure, which has high reliability of repeated reading and utilizes exchange coupling force, in particular, an overwritable recording medium.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the principle of bit formation.

FIG. 2 is a schematic cross-sectional view showing the principle of information reproduction based on the magneto-optical effect.

FIG. 3 is an output waveform diagram of a laser beam for an overwritable magneto-optical recording medium.

FIG. 4 is an output waveform diagram of two laser beams that are close to each other.

FIG. 5 is a correlation diagram between coercive force and temperature.

FIG. 6 is a conceptual diagram showing a “A direction” magnetization state of a W layer by an external action.

FIG. 7 is a conceptual diagram showing magnetization states in a high temperature cycle and a low temperature cycle.

8A and 8B are conceptual diagrams showing, by type, a magnetization state of overwrite by pulse-shaped modulation of a laser beam.

FIG. 9: Hc lowered at temperatures below the Curie point
FIG. 3 is a conceptual diagram showing a magnetized state of an overwritable magneto-optical recording medium that utilizes

FIG. 10 is a conceptual diagram showing sublattice magnetization of a transition metal and a rare metal.

FIG. 11 is a conceptual diagram showing the magnetization direction of the entire alloy corresponding to FIG.

FIG. 12 is a classification diagram of vector strength of alloy composition.

FIG. 13 is a classification diagram in which presence / absence of compensation temperature and vector intensity are classified.

FIG. 14 is a correlation diagram of coercive force and temperature for class 1-1 in FIG.

FIG. 15 is a conceptual diagram showing a configuration and a magnetized state of a utilization invention using an exchange coupling force from an initialization layer.

FIG. 16 is a conceptual diagram showing a magnetization state of the invention of use.

FIG. 17 is a cross-sectional view showing the structure of a sputtering film formation example of the present invention.

FIG. 18 is a plan view illustrating the arrangement of surface acoustic wave elements.

FIG. 19 is a cross-sectional view exemplifying the positional relationship between the surface acoustic wave generation element and the substrate and the configuration of this element.

FIG. 20 is a cross-sectional view illustrating the configuration of a recording medium manufactured by the method of the present invention.

FIG. 21 is a correlation diagram of the C / N ratio and the number of repeated readings of the recording medium manufactured by the method of the present invention and the comparative medium.

[Explanation of symbols]

 10 Surface Wave Generating Element 20 Substrate 31 Mounting Tool 32 Inner Mask 33 Outer Mask 34 Target 40 Piezoelectric Vibrator 41 Elastic Body 42 Electrode 21 AlN Protective Layer 22 TbFeCo First Layer 23 TbDyFeCo / Al Second Layer 24 TbDyFeCo Third Layer 25 AlN protective layer

Claims (1)

[Claims] 1. A method of manufacturing a magneto-optical recording medium, which comprises vibrating a surface of a substrate when forming a magnetic recording layer on the substrate.