JPH05120746A - Cartridge for overwritable magneto-optical recording medium - Google Patents

Abstract

(57) [Abstract] [Purpose] A sufficient initial auxiliary magnetic field (Hini.) Application strength is applied to an overwritable magneto-optical recording disk, and the mechanical strength of the cartridge body incorporating this means is reduced. prevent. [Configuration] At least two of a memory layer and a writing layer
A magneto-optical recording disk (3) and Hini. Magnets (5) and (6) which can be overwritten by a light modulation method composed of layers are housed in a cartridge body. Then, the whole cartridge body (1) or a part thereof is made of a magnetic material,
Hini. Form a magnetic circuit with the magnet. [Effect] Sufficient Hini. Applied strength can be obtained, and the magnetic material has high mechanical strength, so that the mechanical strength of the cartridge can be prevented from lowering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cartridge containing an overwritable magneto-optical recording disk (medium).

[0002]

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

The recording medium used in this magneto-optical recording / reproducing method has a perpendicular magnetic layer (perpendicular magnetic layer or layers) consisting of one layer or multiple layers as a layer for recording. This magnetic film is made of, for example, amorphous GdFe or Gd
It consists of Co, GdFeCo, TbFe, TbCo, TbFeCo, and the like. The perpendicular magnetic film generally has concentric or spiral tracks, and information is recorded on the tracks. There are two types of tracks, explicit and implicit. [Explicit Track] The magneto-optical recording medium has a disk shape. In a disc having explicit tracks, information recording tracks are formed in a spiral or concentric shape when viewed in a direction perpendicular to the disc plane. There is a groove for tracking and separation between two adjacent tracks. Conversely, the space between the grooves is called a land. In reality, the land and groove are reversed on the front and back of the disc. Therefore, looking at the disk in the same way as the beam enters, the front side is called a groove and the back side is called a land. Since the perpendicularly magnetized film is formed on the groove and the land over the entire surface, the groove portion may be the track or the land portion may be the track. There is no particular relationship between the width of the groove and the width of the land.

In order to form such a land and groove,
The substrate has a land formed in a spiral or concentric shape on the surface and a groove sandwiched between two adjacent lands.
A perpendicular magnetization film is formed on such a substrate. [Mark] In the present specification, “upwar (upwar
d) ”or“ downward ”,
Orientation "and the other is defined as" reverse A orientation ". The information to be recorded is binarized in advance, and this information has two signals: a mark (B ₁ ) having a magnetization in the “A direction” and a mark (B ₀ ) having a magnetization in the “reverse A direction”. Recorded in. These marks B ₁ and B ₀ correspond to either 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. In the old sense, the act of aligning the directions of magnetization is "initialization ^* (initia
lize ^* ) ”. Then, "A direction" on the truck
A mark (B ₁ ) having a magnetization of ₁ is formed. Information is represented by the presence or absence of this mark (B ₁ ) and / or the mark length. The mark has been called a pit or a bit in the past, but is recently called a mark. [Principle of mark formation] In the formation of marks, the characteristic of the laser, that is, the excellent coherence in space and time (coheren
ce) is preferably used to focus the beam into a spot that is almost as small as the diffraction limit determined by the wavelength of the laser light. The narrowed light is applied to the track surface, and information is recorded by forming marks with a diameter of 1 μm or less on the perpendicular magnetization film. In optical recording, recording densities up to about 10 ⁸ marks / cm ² can theoretically be achieved. This is because the laser beam can be concentrated into a spot with a diameter as small as about its wavelength.

As shown in FIG. 3, in magneto-optical recording, a laser beam (L) is focused on a perpendicular magnetization film (MO) and heated. Meanwhile, a recording magnetic field (Hb) in the opposite direction to the initialized ^* direction is externally applied to the heated portion. Then, the coercive force Hc (coersivity) of the locally heated portion decreases and becomes smaller than the recording magnetic field (Hb). As a result, the magnetization of that portion is aligned in the direction of the recording magnetic field (Hb). In this way, the oppositely magnetized mark is formed.

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

However, it is not necessary to stick to the Curie point or its vicinity and the compensation temperature. In short, recording is possible by applying a recording magnetic field (Hb) for compensating the lowered Hc to the magnetic material having the lowered Hc at a predetermined temperature higher than room temperature. However, the perpendicular magnetization film (Mc in the region where Hc in this region has the original high Hc) that has not reached a predetermined temperature higher than room temperature (M
Too high Hb that reverses the magnetization of (O) is not possible. [Reproduction Principle] FIG. 4 shows the principle of information reproduction based on the magneto-optical effect. Light is an electromagnetic wave that has an electromagnetic field vector that is normally divergent in all directions on a plane perpendicular to the optical path. When the light is converted to linearly polarized light (L _p ) and is applied to the perpendicular magnetic film (MO), the light is reflected on its surface 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 caused by the magnetic Kerr effect or the magnetic Faraday.
y) Called the effect.

For example, if the plane of polarization of the reflected light is "A direction"
Rotation of θ k degrees with respect to magnetization causes rotation of −θ k degrees with respect to "reverse A direction" magnetization. Therefore, when the axis of the optical analyzer (polarizer) is set perpendicular to the plane inclined by -θk, the light reflected from the mark (B ₀ ) magnetized in the "reverse A direction" passes through the analyzer. I can't. On the other hand, the mark (B ₁ ) magnetized in “A direction”
The light reflected from is transmitted by the analyzer by the amount multiplied by (sin2θk) ^2, and is captured by the detector (photoelectric conversion means). As a result, the mark (B
₁ ) appears brighter than the mark (B ₀ ) magnetized in the "reverse A direction", and generates a strong electric signal in the detector. The electrical 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) initialize the medium again ^* initialize it with the device ^* , or
Alternatively, (2) it is necessary to add an erasing head similar to the recording head to the recording device, or (3) it is necessary to erase the recorded information in advance by using the recording device or the erasing device as a pre-stage process. Therefore, in the magneto-optical recording method, it has hitherto been impossible to perform overwriting capable of recording 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. For example, when 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.

However, the technological progress is remarkable, and the intensity of the irradiation light beam should be recorded without modulating the intensity of the recording magnetic field Hb (including ON and OFF) or without modulating the direction of the recording magnetic field Hb. A magneto-optical recording method capable of overwriting, a magneto-optical recording medium capable of being overwritten, and an overwritable recording device also employed therein have been invented simply by modulating in accordance with binary information. A patent application has been filed (JP-A-62-175948 = DE3,619,61)
8A1 = US patent pending Ser. No. 453,255). Hereinafter, this invention is referred to as a "basic invention". [Explanation of Basic Invention] In the basic invention, "a recording / reproducing layer basically consisting of a magnetic thin film capable of perpendicular magnetization is used.
(In this specification, this recording / reproducing layer is referred to as a memory layer memory
layer or M layer) and a recording auxiliary layer reference layer composed of a magnetic thin film capable of perpendicular magnetization (in this specification, this recording auxiliary layer is a writing layer writing layer or W).
Layers) and both layers are exchange-coupled, and
An overwritable multi-layered magneto-optical recording medium in which only the magnetization of the W layer can be oriented in a predetermined direction without changing the magnetization direction of the M layer at room temperature is used.

Then, the information is represented and recorded by the mark having the "A direction" magnetization and the mark 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 has an external means (for example, an initial auxiliary magnetic field Hin.
By i.), the direction of the magnetization can be aligned in the “A direction”. Moreover, at that time, the magnetization direction of the M layer is not reversed, and further, the magnetization direction of the W layer once aligned in the “A direction” is not reversed even when the exchange coupling force from the M layer is received. On the contrary, the magnetization direction of the M layer is not reversed even when receiving the exchange coupling force from the W layer aligned in the “A direction”.

The W layer has a lower coercive force H _C and a higher Curie point T _C than the M layer. According to the recording method of the basic invention, the recording medium has the magnetization direction of the W layer aligned in the “A direction” by external means before recording. This act is specifically referred to herein 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. As is already known, even when recording is not performed, the laser beam may be turned on at <very low level>, for example, to access a predetermined recording location on the medium. This <very low level> is also the same as or close to the reproduction level P _R. Therefore, for example, the output waveform of the laser beam in the basic invention is as shown in FIG.

Although not specified in the specification of the basic invention, in the basic invention, the recording beam is not a single beam but two beams which are close to each other, and in principle, does not modulate the preceding beam. It is also possible to use a level laser beam (for erasing) and a high level laser beam (for writing) that modulates the trailing 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
It cannot be narrowed down to the same size as the irradiated portion of the beam (spot area), and the area on which Hb acts is much larger than the spot area. When illuminated by a low level beam, M is independent of the direction of magnetization of the previous mark.
One of the "A-oriented" mark (B ₁ ) and the "reverse A-oriented" mark (B ₀ ) is formed on the layer.

When a high level beam is irradiated, the other mark is formed on the M layer regardless of the magnetization direction of the previous mark. This completes the overwrite. In the basic invention, the laser beam is pulse-modulated according to the information to be recorded. However, this is also done in the conventional magneto-optical recording, and it should be recorded.
The means for pulse-modulating the beam intensity in accordance with the digitized information is a known means. For example, THE BELL SYSTEM TECHN
ICAL JOURNAL, Vol. 62 (1983), 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.

One of the features of the basic invention is that
There are high and low levels of beam intensity. That is, when the beam intensity is at a high level, the "A direction" magnetization of the W layer is reversed to "reverse A direction" by the recording magnetic field Hb or other external means (re
verse), and the "reverse A direction" magnetization of the W layer forms a mark having the "reverse A direction" magnetization (or "A direction" magnetization) in the M layer. When the beam intensity is low, the magnetization direction of the W layer is the same as in the "initialized" state, and
By the action of the layer (this action is transmitted to the M layer through the exchange coupling force), the M layer is magnetized “A direction” [or “reverse A direction”].
Magnetization] is formed.

In the present specification, ○○○ [or △△△]
With the expression, when XX outside [] is read first, XX outside [] will be read also in the following XX [or ΔΔ △ ]. On the contrary, ○○○
If you select and read the △△△ one in [] without reading, read the following △ ○ △ [or △△△ ] without reading ○○○. Should be read.

The medium used in the basic invention is roughly classified into a first embodiment and a second embodiment. In any of the embodiments, the recording medium has a multilayer structure including an M layer and a W layer. 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. 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 adjustment layer for the exchange coupling force σ _W : see JP-A-64-50257 and JP-A-1-273248) may be present between the M layer and the W layer. Furthermore, there is no clear boundary between the M layer and the W layer, and it is possible to gradually change from one to the other.

In the first embodiment, the coercive force of the M layer is H _C1 ,
The W layer has H _C2 , the M layer has a Curie point T _C1 , the W layer has T _C2 , the room temperature is T _R , and the temperature of the recording medium when irradiated with a low-level P _L laser beam is T _L , When a high-level P _H laser beam is irradiated, it is T _H , and the coupling magnetic field received by the M layer is H _D1 (H _D1 is σ _W multiplied by the saturation magnetic moment M _S of the M layer and the film thickness t of the M layer. Is calculated by dividing the coupling magnetic field received by the W layer by H _D2 (where H _D2 is σ _W divided by the product of the W layer saturation magnetic moment M _S and the W layer thickness t). The recording medium is defined by the following formula 1
And satisfying formulas 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 ) | ………… Equation 2 H _C1 > HD ₁ ……………………………………… Formula 3 H _C2 > H _D2 ………………………………… Formula 4 H _C2 + H _D2 <| Hini. | <H _C1 ± H _D1 ──Equation 5 In the above equation, the symbols “≈” are equal or almost equal (±
20 ° C). Further, in the above formula, regarding the composite ±, the upper row is for an A (antiparallel) type medium described later, and the lower row is for a P (parallel) type medium described later. 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 Equation 5, the magnetization direction of the M layer is not reversed and W
Only the magnetization of the layer is reversed. Therefore, when an action (for example, an initial auxiliary magnetic field Hini.) Is applied to the medium before recording, only the magnetization of the W layer is "A direction" --- here, "A direction" is used for convenience. In the specification sheet, it is indicated by an upward arrow ↑, and "reverse A direction" is indicated by a downward arrow ↓.
Aligned to −. And even if Hini.
As a result, the magnetization ↑ of the W layer is retained as it is without being re-inverted.

When the magnetization of only the W layer is aligned to "A direction" ↑ by the external means by the external means, the state "initialized" --- is shown conceptually. It will be 8. In FIG. 8, 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 shown by X and is simplified, FIG. 8 can be shown as state 1 in FIG. 9.

Here, the medium temperature is raised to T _H by irradiating a high level laser beam. Then, 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 completely or almost. Here, the recording magnetic field Hb of "A direction" or "reverse A direction" is applied according to the type of medium. Hb may be a stray magnetic field from the medium itself. 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. 9).

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, a "reverse A direction" ↓ mark (P type medium) or an "A direction" ↑ mark (A type medium) is formed in the M layer depending on the type of medium. This state is shown in Figure 9.
State 3 (P type) or state 4 (A type).

The change in state caused by this high level laser beam will be referred to as a high temperature cycle here. 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 at all or almost disappears. However, since the temperature is lower than the Curie point T _C2 , 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 it is impossible to turn the Hb on and off at a high speed (short time). Therefore, it is unavoidable and remains as it was during the high temperature cycle.

However, since H _C2 is still large, H
The magnetization ↑ of the W layer is not reversed by b. 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, depending on the type of medium, a mark “A direction” ↑ (for P type medium) or a mark “reverse A direction” ↓ (for A type medium) is formed in the M layer. This magnetization does not change even at room temperature. This state is the state 6 (P type) or the state 7 (A type) in FIG.

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 mark of “reverse A direction” ↓ and the mark of “A direction” ↑ can be obtained. It can be freely formed on the M layer. 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. See FIG. 10. The states of magnetization in FIG. 10 are all drawn as a result of room temperature or returning to room temperature.

In the above description, 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 has been described. 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 the 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 description 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 (mark) is again subjected to the action of external means such as Hini. After recording, and as a result, the magnetization of the W layer is aligned in the original “A direction” ↑. That is, the W layer is “initialized”. But,
At room temperature, the influence of the magnetization of the W layer does not affect the M layer,
Therefore, 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.

The above description is for the first embodiment using the Curie point as the magnetization reversal temperature. On the other hand, the second embodiment utilizes Hc lowered at a temperature lower than the Curie point. The second embodiment is the first
If the temperature T _S1 at which the M layer is magnetically coupled to the W layer is used instead of T _{C1 and} the temperature T _S2 at which the W layer is inverted at Hb is used instead of T _{C2 in} the embodiment, the first embodiment It is described similarly to the embodiment.

In the second embodiment, the coercive force of the M layer is H _C1 ,
Let W _C2 be that of the W layer, T _s1 be the temperature at which the M layer is magnetically coupled to the W layer, T _{S2 be} the temperature at which the magnetization of the W layer is reversed at Hb, T _{R be} the room temperature, and _{L be} the low level P _L. the temperature of the medium when irradiated with a laser beam T _L, it T _H when irradiated with a laser beam of high level P _H, the coupling magnetic field M layer receives H _D1 (H _D1 is the sigma _W of the M layer Saturation magnetic moment M _S
Calculated by the quotient divided by the product of M and the film thickness t of the M layer), and the coupling magnetic field received by the W layer is H _D2 (where H _D2 is σ _W is the W layer saturation magnetic moment M _S and the W layer thickness t). (Calculated by the quotient divided by the product of and), the recording medium satisfies the following expression 6 and satisfies the expressions 7 to 10 at room temperature.

T _R <T _s1 ≈T _L <T _s2 ≈T _H ………… Equation 6 H _C1 > H _C2 + | HD ₁ − (± HD ₂ ) | …… Equation 7 H _C1 > HD ₁ ……………………………………… Formula 8 H _C2 > H _D2 ─ …………………………………… Formula 9 H _C2 + H _D2 <| Hini. | <H _C1 ± H _D1 ──Equation 10 In the above equation, for composite ±, the upper row is A (antiparalle
In the case of the l) type medium, the lower row shows the case of the P (parallel) type medium.

In the second 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. The recording magnetic field Hb ↓ is sufficiently large even if a sufficiently weak magnetization remains in both the M layer and the W layer, so that the Hb ↓ can cause the magnetization direction of the W layer and, in some cases, the M layer to follow the Hb ↓. . This state is state 2 in FIG. Immediately thereafter, or when the laser beam is no longer emitted and cooling is allowed to proceed and the medium temperature falls below T _H or moves away from _H b, the W layer is σ _W.
To influence the M layer through the magnetic field to make the magnetization direction of the M layer follow a stable direction. As a result, the state becomes the state 3 (P type) or the state 4 (A type) in FIG.

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 mark states, that is, state 5 and state 6 in FIG. 11 for the P type, and state 7 and state 8 in FIG. 11 for the A type. In the states 6 and 8, the interface domain wall (indicated by a thick line ━) is formed between the M layer and the W layer, and the state is slightly unstable (metastable). 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,
Hb ↓ is applied. 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 ↓. In addition, the memory layer in the state 8 whose direction is opposite to Hb ↓ has a larger exchange coupling force σ from the W layer than the influence of Hb ↓.
_Under the influence of W, the magnetization direction is maintained in the same direction as the W layer due to 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 coercive force H
The decrease in _C2 is small, it does not lose to Hb ↓, and the magnetization direction "A direction" ↑ when "initialized" is maintained. On the other hand, although the M layer has a low Curie point, since the medium temperature is still lower than the Curie point T _{c1 of the} M layer, the coercive force H _C1 remains. However, since H _C1 is small, the effect of Hb ↓ on the W layer and the effect via the exchange coupling force σ _w from the W layer (in the case of the P type, the force to turn the same direction)
Receive. In this case, the latter is stronger, and two equations of 2: H _c1 + Hb <(σ _w / 2M _S1 t ₁ ) 3 of Equation 10: H _c2 + Hb> (σ _w / 2M _S2 t ₂ ) are obtained. At the same time satisfied. The lowest temperature at which these equations are satisfied simultaneously is called T _LS . In other words, the minimum temperature at which the domain wall in state 6 or state 8 disappears is T _LS .

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 mark of (P type) or state 10 (A type) is formed.

This state does not change even when the medium temperature is lowered by returning the irradiation of the laser beam to the mark or deviating from the irradiation position, and then returning to room temperature. This FIG. 11 state 9 (P type) or state 10
(A type) is state 6 (P type) or state 7 in FIG.
It is the same as (A type). 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.

In fact, 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 during the rise from room temperature to T _C1 , at this time, in the case of the P type, the state 6 The transition from state 8 to state 9 occurs in the case of type A, and the transition from state 8 to state 10 respectively. After that, T _C1 is reached, and the state 5 in FIG. 9 is reached. 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. Further, the direction of the recording magnetic field Hb is also opposite to the direction when considered at room temperature.

In both the first and second embodiments, the M layer and the W layer are made of a transition metal (eg Fe, Co) -heavy rare earth metal (eg G).
d, Tb, Dy, etc.) A recording medium which is an amorphous ferrimagnetic material selected from alloy compositions is preferable. Both the M layer and the W layer are a transition metal and a heavy rare earth metal (heavy metal).
When selected from the alloy composition, the direction and magnitude of the magnetization appearing externally as each alloy is the direction and magnitude of the sublattice magnetization of the transition metal atom (TM) inside the alloy and the heavy rare earth metal. It is determined by the relationship with the direction and size of the sublattice magnetization of the atom (RE). For example, 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, and the direction and magnitude of magnetization of the entire alloy are outlined. It is represented by the vector indicated by the arrow. At this time, the white arrow (vector) is a dotted arrow (vector) and the solid arrow (vector)
Expressed as the sum of and. 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 sum of the dotted arrows (vectors) and the solid arrows (vectors) makes the alloy vector zero (that is, the magnitude of the magnetization appearing outside) when the strengths of the two are equal. The alloy composition when it reaches zero is called the compensation 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.

Therefore, the magnetization vector of the alloy is written adjacent to the vector of the dotted line and the vector of the solid line, for example, as shown in FIG. The sublattice magnetization states of RE and TM are roughly classified into four states, which are shown in (1A) to (4A) of FIG. And the magnetization vector (open arrow) of the alloy in each state is shown corresponding to (1B) to (4B) of FIG. For example, if the RE vector is larger than the TM vector,
The state of sublattice magnetization is shown in (1A), and the magnetization vector of the alloy is shown in (1B).

When the strength of the TM vector or RE vector of a certain alloy composition is larger, the alloy composition is named as the one having the larger strength and is XX rich, for example, RE.
Called to be rich. For both M and W layers,
It is divided into TM-rich composition and RE-rich composition.
Therefore, when the composition of the M layer is plotted on the ordinate and the composition of the W layer is plotted on the abscissa, the types of the medium of the basic invention are shown in FIG.
It can be classified into the four quadrants shown in. 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). .. The temperature corresponding to this infinity is called the compensation temperature (T _comp. ). At a temperature lower than the compensation temperature, the RE vector (solid arrow) is larger than the TM vector (dotted arrow), so it can be said to be TM rich, and vice versa at a temperature higher than the compensation temperature. Therefore, it can be said that the compensation temperature of the alloy having the compensation composition is 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 means that it 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
Are classified into four types. 1 quadrant medium is 4
All types are included. Therefore, if both the M layer and the W layer are classified into RE-rich or TM-rich and whether or not they have a compensation temperature, the recording medium is classified into 9 classes shown in FIG. [Explanation of Class 1-1] Class 1 shown in FIG. 15 here
The overwrite principle will be described in detail by taking as an example the medium No. 1-1 belonging to the recording medium (P type, 1 quadrant, type 1).

[0047] The medium No.1-1, the following equation _{11: T R <T comp.1 <} T L <T H ≦ T C1 ≦ T c2 and 2 of Formula _11: T comp.2 <relation T _C1 Have. In the present specification, “=” in “≦” means that they are equal or almost equal (± 20 ° C. or so). Similarly, “≒” means that they are almost equal (± 20 ° C). For the purpose of simplifying the explanation, the following explanation is T _H <T _C1 <T
Those having the relationship of _c2 will be described. T _comp.2 is
It may be higher than, equal to, or lower than T _L , but for the purpose of simplifying the description, in the following description, T _L <T
_{It will be comp.2} . FIG. 16 is a graph showing the above relationship. The thin line shows the graph of the M layer, and the thick line shows W.
A layer graph is shown.

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.

[0049]

[Equation 1]

Equation 12 is expressed as This medium No.1-1
Satisfies Equation 12. However, H _C1 : Coercive force of M layer H _C2 : Coercive force of W layer M _S1 : Saturation magnet moment of M layer (saturation magnet)
ization) 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 (interface wa
ll energy) At this time, the conditional expression of Hini. is expressed by Expression 15 shown in Expression 4. When the Hini. Disappears, the magnetizations of the M layer and the W layer are affected by the exchange coupling force. Nevertheless, the conditions under which the magnetizations of the M layer and W layer are maintained without being inverted are expressed by equations 13-14. This medium No. 1-1 satisfies equations 13-14.

[0051]

[Equation 2]

[0052]

[Equation 3]

The magnetization of the W layer of the recording medium which satisfies the conditions of equations 12 to 14 at room temperature should be measured by the time immediately before recording.

[0054]

[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 state 1 or state 2 in FIG.
Indicated by either. The states 1 and 2 are held until just before recording. The recording magnetic field Hb is "A direction" ↑
Will be applied to.

Note that it is difficult to narrow the recording magnetic field Hb to the same range as the irradiation area (spot area) of the laser beam, as is the case with general magnetic fields. When the medium is a disc, once the recorded information (mark) is rotated once, it is in the state 1 or 2 again under the influence of Hini. After that, the mark passes near a laser beam irradiation region (spot region). At this time, the marks in state 1 and state 2 are affected by the approach to the recording magnetic field Hb applying means. In this case, if the magnetization direction of the M layer of the mark in the state 2 having the magnetization opposite to Hb is reversed by Hb, the information just recorded one rotation before disappears. The conditions that should not be so are

[0057]

[Equation 5]

It is represented by 2 of the equation 15 shown in The disk-shaped medium No. 1-1 must satisfy the condition (2) of conditional expression 15 at room temperature. Conversely, one condition that determines Hb is
It is shown by 2 in Expression 15. The marks 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 ---- When a low level laser beam is irradiated, the medium temperature rises above T _comp.1 . Then, from P type to A
Move to type. Then, although the directions of the RE and TM spins of the M layer do not change, the magnitude relationship between the strengths is (3A) in FIG.
To reverse (4A). Therefore, the magnetization of the M layer is as shown in FIG.
Invert from (3B) to (4B). As a result, the mark in state 1 shifts to state 3, and the mark in state 2 shifts to state 4.

Following the irradiation of the laser beam, the medium temperature eventually becomes T _LS . Then, the two in Equation 10 and the one in Equation 10
3 are satisfied at the same time. As a result, even if Hb ↑ exists, the mark in state 4 transits to state 5. On the other hand, state 3
The mark of 10 is 2 even in the presence of Hb ↑ and 3 of 10
Is satisfied at the same time, so it remains as it is.
That is, the state 3 is changed to the same state as the state 5.

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. for that reason,
The magnetization of the M layer is reversed from (2B) to (1B) in FIG. As a result, the mark 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, M layer "A direction" ↑
Mark is formed.

[0062] ----- When the laser beam of the high-temperature cycle ----- high level is irradiated, the medium temperature is increased to the 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. Then, although the directions of the RE and TM spins of the W layer are not changed, the magnitude relationship of the strength is reversed from (1A) to (2A) in FIG. Therefore, the magnetization of the W layer changes from (1B) to (2
Invert to B). 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. The temperature rises further,
At T _H , the temperatures of the M layer and the W layer are close to the Curie point, so that the coercive force becomes small. As a result, the medium is

[0063]

[Equation 6]

(1) or

[0065]

[Equation 7]

(2) or

[0067]

[Equation 8]

The two expressions shown in either of (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. In state 10, the medium is

[0069]

[Equation 9]

4 of Expression 15 shown in is satisfied. Therefore, W
Even if Hb ↑ acts on the layer, it does not reverse. When the temperature of the medium further decreases from the temperature in the state 10,
_When it becomes _comp.1 or less, it returns from the A type to the original P type. Then, the magnitude relation 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 is reversed from (4B) to (3B) in FIG.
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 shown in Formula 11), the magnetization ↓ of the M layer is ↑
State 11 is maintained without being inverted by Hb.

[0072]

[Equation 10]

In this way, the mark of "inverse A direction" ↓ is formed on the M layer. By the way, in order to protect the magneto-optical recording medium from dust, damage or scratches, it is necessary to store the medium in a cartridge.

However, when the overwritable medium is housed in the cartridge, it is far from the initial auxiliary magnetic field (Hini.) Applying means provided in the magneto-optical recording device,
Since the magnetic field with the strength required for “initialization” cannot be obtained,
The first problem arises in that the Hini. Applying means (for example, a permanent magnet or an electromagnet) must be upsized.
When a magneto-optical recording device that can use both a non-overwritable magneto-optical recording medium and an over-writable magneto-optical recording medium is set, the Hini. Means must be set up.

In this case, the Hini. Applying means is moved away from the medium when the medium that cannot be overwritten is used, and the Hini.
It is necessary to bring the applying means close to the medium. As a result, Hi
ni. A second problem is that a driving device for moving the applying means is required, which complicates the structure of the magneto-optical recording device.

In order to solve the first and second problems, Hi
ni. A cartridge incorporating an applying means was invented (see JP-A-64-46247). This cartridge can also be recorded by a conventional overwritable magneto-optical recording device.

[0077]

When used in a magneto-optical recording device that cannot be overwritten, the outer dimensions of the cartridge must be the same as before. Generally, the size of Hini. Is 2000 to 4000 Oe, and the permanent magnet that generates such a strong magnetic field is considerably large. Therefore, when a large permanent magnet is built in the cartridge main body made of resin or other non-magnetic material, it is necessary to reduce the thickness of the main body at that portion or to make the magnet itself thin.

However, if the wall thickness is made thin, the strength of the cartridge is lowered, and if the magnet is made thin, a sufficient Hini. Cannot be obtained. It is an object of the present invention to provide a cartridge containing Hini. Application means for providing sufficient magnetic field strength without compromising the strength of the cartridge.

[0079]

According to the present invention, "a magneto-optical recording disk which can be overwritten by an optical modulation method comprising at least two layers of a memory layer and a writing layer is housed and an initial auxiliary magnetic field applying means is incorporated. In a cartridge for magneto-optical recording medium, the whole or a part of the main body of the cartridge is made of a magnetic material, and a magnetic circuit is formed by the magnetic material and the applying means.

[0080]

[Function] The magnetic body that constitutes the whole body or a part of the cartridge has strength that is almost equal to or higher than that of the body, so that the strength of the cartridge does not decrease, and it also functions as a yoke of the magnetic circuit. Strength increases, and it is enough to use a small magnet as Hini.
Hini. Is obtained.

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

[0082]

1 is a schematic vertical sectional view of a cartridge according to a first embodiment of the present invention. In FIG. 1, a disc-shaped overwritable magneto-optical recording medium (3) is rotatably supported by a cartridge body (1) having a predetermined size. The rotating shaft that supports the shaft is directly or indirectly connected to a coupler (not shown) exposed to the outside of the cartridge body (1). By connecting this coupler to the coupler on the side of the magneto-optical recording device, the rotational force from the spindle motor (rotating means) on the side of the device can be transmitted to the rotary shaft. This rotation causes the medium (3) to rotate.

Hini. Permanent magnet (5) as an applying means,
(6) are installed to face each other so as to sandwich the magneto-optical recording medium (3). The entire cartridge body (1) is made of a magnetic material, and the permanent magnets (5) and (6) form a magnetic circuit. This magnetic circuit faces upward or downward with respect to the magnetic film of the medium (3).
Give Hini. Here, the magnetic circuit is formed over the entire recording area of the medium (3) in the radial direction.

Further, an opening (4) for irradiating the medium (3) with a laser beam is provided in a part of the cartridge body (1). The opening (4) is provided with a shutter (2) and a shutter rail (2a) so that the shutter (2) can be opened and closed as needed by means not shown.

The arrangement positions of the permanent magnets (5) and (6) are not limited to the positions shown in FIG. 1, and similar effects can be obtained even if they are installed at arbitrary positions on the medium. FIG. 2 is a schematic vertical sectional view of the second embodiment of the present invention. In the second embodiment, only a part of the cartridge body (1a) made of a non-magnetic material such as resin is made of a magnetic material, and this magnetic material constitutes the yoke (5a). The yoke (5a) and the permanent magnets (5) and (6) form a magnetic circuit.

The width of the yoke (5a) is preferably at least the same as that of the permanent magnets (5) and (6) in order to increase the magnetic flux density. In this case, it goes without saying that the same effect can be obtained even if the magnetic circuit is not formed at the position shown in FIG. 2 but is formed at an arbitrary position on the magneto-optical medium.

[0087]

As described above, according to the present invention, the entire main body or a part of the main body of the cartridge is formed of a magnetic material, and the
ni. Form a magnetic circuit with the applying means. Therefore, Hini. With high magnetic flux density can be given to the medium.
Therefore, sufficient Hini. Can be given without lowering the mechanical strength of the cartridge.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a cartridge according to a first embodiment of the present invention.

FIG. 2 is a schematic vertical sectional view of a cartridge according to a second embodiment of the present invention.

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

FIG. 4 is a conceptual diagram illustrating a reproducing principle of a magneto-optical recording method.

FIG. 5 is a waveform diagram of a laser beam when overwriting according to the basic invention.

FIG. 6 is a waveform diagram of a laser beam when overwriting with two beams according to the basic invention.

FIG. 7 shows M of an overwritable magneto-optical recording medium.
It is a graph which shows the relationship between coercive force and temperature about a layer and a W layer.

FIG. 8 is a conceptual diagram showing the magnetization directions of the M layer and the W layer.

FIG. 9 is an explanatory diagram showing changes in the magnetization directions of the M layer and the W layer.

FIG. 10 shows a P-type medium and an A-type medium,
It is explanatory drawing which shows how the direction of magnetization of M layer and W layer changes as a result of a low temperature cycle and a high temperature cycle. Both show the state at room temperature.

FIG. 11 is an explanatory diagram showing changes in the magnetization directions of the M layer and the W layer.

FIG. 12 is an explanatory diagram for comparing a vector indicating a sublattice magnetization of a rare earth (RE) atom (solid arrow) with a vector indicating a sublattice magnetization of a transition metal (TM) atom (dotted arrow). Is.

FIG. 13 is an explanatory diagram showing the relationship between the vector of sublattice magnetization and the vector (open arrow) indicating the direction of magnetization of the alloy.

FIG. 14 is an explanatory diagram illustrating that, when the M layer and the W layer are divided into RE-rich and TM-rich, the overwritable medium is divided into four classifications (quadrants 1 to 4). is there.

FIG. 15 is an explanatory diagram illustrating that when the medium of the basic invention is classified from various viewpoints, the medium is eventually classified into nine classes of class 1 to class 9.

FIG. 16 is an overwritable magneto-optical recording medium N.
10 is a graph showing the relationship between coercive force and temperature for the M layer and W layer of 1-1.

FIG. 17 is a conceptual diagram showing how the directions of magnetization of the M layer and the W layer change as a result of a low temperature cycle and a high temperature cycle for the medium of medium No. 1-1.

[Explanation of symbols]

1 ... Cartridge body (whole body is made of magnetic material) 1a ... Cartridge body (whole body is made of resin etc.) 2 ... Shutter 2a ... Shutter rail 3 ... Magneto-optical recording Disk (medium) 4 ... Aperture 5 ... Permanent magnet (an example of initial auxiliary magnetic field applying means) 5a ... Yoke 6 ... Permanent magnet (an example of initial auxiliary magnetic field applying means) L ... Laser beam Lp ··· Linearly polarized light B ₁ ··· Mark (or mark) with “A direction” magnetization B ₀ ··· Mark (or mark) with “reverse A direction” magnetization S ・ ・ ・ Substrate SS ・ ・ ・ 2P Substrate G: Glass substrate PP: Cured groove material resin MO: Perpendicular magnetization film (magneto-optical recording layer) M: Memory layer W: Writing layer

Claims (1)

[Claims] 1. A cartridge for a magneto-optical recording medium, which accommodates a magneto-optical recording disk which is composed of at least two layers of a memory layer and a writing layer and which can be overwritten by an optical modulation method, and which has a built-in initial auxiliary magnetic field applying means. A cartridge characterized in that the whole or a part of the main body of the cartridge is made of a magnetic material, and the magnetic material and the applying means form a magnetic circuit.