KR930010474B1 - Manufacturing method of optical magnetic materials - Google Patents

Abstract

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Description

[Name of invention]

Magneto-optical recording medium and manufacturing method of magneto-optical recording medium

[Brief Description of Drawings]

Fig. 1A is a perspective view of the main part of the magneto-optical recording apparatus provided with the magneto-optical recording medium of the present invention.

1B is a partial sectional view showing an optical recording / reproducing state of the two-layer film of the magneto-optical recording medium of the present invention.

Fig. 1C is a characteristic diagram showing the change of laser beam power for recording in the area of the magneto-optical recording medium.

2 is a diagram showing a relationship between a temperature and an inverted magnetic field in the first magnetic layer of the magneto-optical recording medium of the two-layer film according to the present invention.

3 is a detailed block diagram of a two-layer film magneto-optical recording medium according to the present invention.

4 is a state diagram of each layer in the recording state of the two-layer film magneto-optical recording medium according to the present invention.

5 is a state diagram of magnetization having a compensation temperature at room temperature in a rare earth metal and a transition metal alloy.

FIG. 6A is a partial sectional view showing the optical recording / reproducing state of the three-layer film of the magneto-optical recording medium of the present invention. FIG.

Fig. 6B is a characteristic diagram showing the change of the laser beam wave source for recording in the area of the magneto-optical recording medium.

7 is a state diagram of each layer in the recording state of the three-layer film magneto-optical recording medium of the present invention.

8 is an explanatory diagram showing that overwriting is possible at room temperature.

9 is a detailed block diagram of a four-layer film magneto-optical recording medium of the present invention.

10 is a state diagram of each layer in the recording state of the four-layer film magneto-optical recording medium of the present invention.

11 to 91 are explanatory views for explaining the conditions when the composition of each layer of the four-layer film magneto-optical recording medium of the present invention is changed.

92A is a specific block diagram of another three-layer film magneto-optical recording medium of the present invention.

FIG. 92B is an explanatory diagram showing the relationship between the temperature of each magnetic layer and the saturation magnetization; FIG.

93 is a state diagram of each layer in the recording state of another three-layer film magneto-optical recording medium of the present invention.

94 is a detailed block diagram of the four-layer film magneto-optical recording medium of the present invention before initialization.

FIG. 95A is an explanatory diagram showing a method for initialization. FIG.

95B is a configuration diagram when the initialized objects are put together.

96 is a block diagram showing another method for initialization.

FIG. 97 is an explanatory diagram showing yet another method for initialization. FIG.

FIG. 98 is a detailed block diagram of the magneto-optical disk medium initialized in FIG. 97. FIG.

99A is a perspective view of major parts of a conventional optical recording and reproducing apparatus

99B is a sectional view showing an optical recording reproduction state of a magneto-optical recording medium.

99C and 100 are characteristic diagrams showing changes in laser power for recording.

Detailed description of the invention

[Technical Field]

The present invention relates to a magneto-optical recording medium having an optical modulation overwrite function capable of directly writing new information on old information and a production method for producing the magneto-optical recording medium.

[Background]

99a and c are, respectively, a perspective view of the main parts of a conventional optical recording and reproducing apparatus disclosed in, for example, a publication (Preliminary Proceedings of the 34th Association for Applied Physics Relations, 28P-ZL-3, 1987), and optical recording of a recording medium. Fig. 1 is a sectional view showing the main part of the reproduction state, and a characteristic diagram showing the variation of laser power for recording in the area of the recording medium. In the figure, reference numeral 1 denotes a magneto-optical recording medium, numeral 2 is a substrate made of glass or plastic, numeral 3 is a first magnetic layer, numeral 4 is a second magnetic layer, and recording medium 1 is a substrate 2. ), The first magnetic layer 3 and the second magnetic layer 4, and an exchange coupling force acts between the first magnetic layer 3 and the second magnetic layer 4, and the exchange coupling force is a quantum layer ( 3) It acts to make each magnetization direction of (4) equal. (5) denotes an objective lens for irradiating a laser beam to the information carrier (1), (6) a condensing spot condensed by the objective lens (5), and (7) among the information recorded in the first magnetic layer (3). The magnetization direction of the single magnetic layer 3 represents an upward portion in FIG. 99b, which means "1" of binarization data. (9) is an initialization magnet for generating a magnetic field of about 5000Oe for the initial magnetization of the second magnetic layer (4), (8) is provided at a position facing the objective lens (5) with the information carrier (1) in between A bias magnet that generates a magnetic field of -600Oe. In Fig. 99c, R ₁ is laser power for recording information 1, R ₀ is laser power for recording information 0, and the vertical axis in Fig. 99c represents laser power, and the abscissa represents area. In Fig. 99A, the left-hand side shows the new data DN and the right-hand side shows the old data D0 with respect to the dashed-dotted line.

Next, the operation will be described. The recording medium 1 is rotationally driven in the direction of the arrow a in Figs. 99A and B by a holding drive mechanism (not shown). The first magnetic layer 3 has the same properties as the recording layer of the information carrier used for a general magneto-optical disk made of, for example, Tb ₂₁ and Fe ₇₉ , and also functions as a recording layer and a lead layer here. The second magnetic layer 4 is called an auxiliary layer made of, for example, Gd ₂₄ Tb ₃ Fe ₇₃ , and is provided to exhibit the performance of overwriting, that is, the ability to overwrite new data in real time on old data. have. Here, the characteristics of the first magnetic layer 3 and the second magnetic layer 4 are the curie temperatures of Tc ₁ and Tc ₂ , respectively, and the coercive force near room temperature, Hc ₁ and Hc ₂ , respectively. When Hw ₁ and Hw ₂ are set, the following relationship is established.

Tc ₁ <Tc ₂

Hc ₁ -Hw ₁ > Hc ₂ + Hw ₂

Here, a case of reproducing information recorded in the recording layer, that is, the first magnetic layer 3, will be described first. As shown in FIG. 99B, the first magnetic layer 3 is magnetized upward or downward in the figure in the direction corresponding to the binary code, i.e., "1" and "0" in the film thickness direction. At the time of reproduction, the condensing spot 6 is irradiated to the first magnetic layer 3, and the magnetization direction of the first magnetic layer 3 of the irradiating portion of the condensing spot 6 is converted into optical information by conventionally known light force effects. The information is detected by the information carrier 1. At this time, the laser intensity irradiated onto the recording medium 1 is the intensity A corresponding to the intensity A shown in the characteristic diagram showing the change in the temperature of the magnetic film in the spot caused by the laser beam power of FIG. 100, and at this intensity, the focusing spot 6 The maximum rise temperatures of the first magnetic layer 3 and the second magnetic layer 4 of the irradiation unit do not reach the Curie temperatures Tc1 and Tc ₂ of the first magnetic layer 3 and the second magnetic layer 4. Therefore, the magnetization direction, that is, the recording information, is not lost by the condensed spot irradiation.

Next, the operation of the overwrite will be described. The initialization magnet 9 in FIG. 99 generates a magnetic field of size Hini in the direction (upward) of arrow b shown in the drawing. This magnetic field Hini has a relationship of Hc ₁ -Hw ₁ >Hini> Hc ₂ + Hw ₂ with respect to the coercive force and the exchange coupling force of the first magnetic layer 3 and the second magnetic layer 4. As a result, as shown in FIG. 99B, when the information carrier 1 is rotated in the direction of the arrow a., The magnetization direction of the second magnetic layer 4 passing through the vicinity of the initialization magnet 9 is the first magnetic layer 3. Regardless of the direction of magnetization, all magnetize in musk. At this time, the magnetization direction of the first magnetic layer (3) is not affected by the magnetic field of the initial magnet or the exchange coupling force acting from the second magnetic layer (4) in the vicinity of room temperature and remains as it is.

When recording the information # 1 ', that is, when the magnetization direction of the first magnetic layer 3 is upward, the laser beam intensity corresponds to the intensity B in FIG. At this time, the portion in the condensing spot 6 rises in temperature and exceeds the Curie temperature Tc ₁ of the first magnetic layer 3, but does not reach the Curie temperature Tc ₂ of the second magnetic layer 4. As a result, the magnetization of the first magnetic layer 3 is lost, but the magnetization direction of the second magnetic layer 4 remains upward magnetized by the initialization magnet 8. Then, the disc is rotated so that the light collecting spot 6 is not irradiated so that the temperature of the first magnetic layer 3 falls below the Curie temperature Tc ₁ , and the magnetization direction of the second magnetic layer 4 becomes the first magnetic layer 3. Is transferred to the first magnetic layer 3, and the magnetization direction of the first magnetic layer 3 is upward, that is, in a direction corresponding to the information # 1 '.

When recording the information # 0, that is, when the magnetization direction of the first magnetic layer 3 is downward, the laser beam intensity corresponds to the intensity C in FIG. At this time, the portion in the condensing spot 6 rises in temperature and exceeds not only the Curie temperature Tc ₁ of the first magnetic layer 3 but also the Curie temperature Tc ₂ of the second magnetic layer 4. As a result, the magnetization in the condensing spot 6 is lost in both the first magnetic layer 3 and the second magnetic layer 4. The direction of the arrow C in FIG. 99 by the bias magnet 9 at the stage where the disk rotates and is not irradiated to the condensing spot 6 so that the temperature of the second magnetic layer 4 falls below its Curie temperature Tc ₂ ( Due to the weak magnetic field applied downward, the magnetization direction of the second magnetic layer 4 becomes downward. In addition, the magnetization direction of the second magnetic layer 4 is transferred to the first magnetic layer 3 when the temperature of the first magnetic layer 3 falls below the Curie temperature Tc ₁ , and the magnetization direction of the first magnetic layer 3 is reduced. Is in a downward direction, that is, in a direction corresponding to the information # 0 '.

By the operation described above, when overwriting, the laser beam intensity is modulated by the intensity B and the intensity C in FIG. 100 according to the binary codes X0 and X1 of the information, thereby realizing on the old data. Overwrite is possible with time. Since a conventional magneto-optical recording medium is constructed as described above, an initializing magnet having a large magnetic field must be used, so that the entire structure of the optical disc recording and reproducing apparatus is dressed, which causes the apparatus to be enlarged.

The present invention has been made to solve the above problems, and an object thereof is to obtain an optical magnetic recording medium which can be easily overwritten without requiring an initial magnet. Furthermore, it aims at obtaining the manufacturing method of such a magneto-optical recording medium.

[Initiation of invention]

The present invention of claim 1 includes a first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer by exchange force.

Tc ₁ <Tc ₂

However, Tc ₁ : Curie temperature of the first magnetic layer

Tc ₂ : Curie temperature of the second magnetic layer

And also at room temperature

Hc ₁ ＞ Hw ₁ , Hc ₂ ＞ Hw ₂

However, Hc ₁ : coercive force of the first magnetic layer

Hc ₂ : coercive force of the second magnetic layer

Hw ₁ : Amount of inverse magnetic field due to exchange force of first magnetic layer

Hw ₂ : Swift amount of inverted magnetic field due to exchange force of second magnetic layer

Satisfies the above, and the second magnetic layer is a magneto-optical recording medium characterized in that the magnetization is not reversed during recording and reproduction.

The present invention of claim 2 has a first magnetic layer having vertical fraud anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in an exchange force, the second magnetic layer provided in the second magnetic layer and exchanged with the second magnetic layer in an exchange force. A third magnetic layer,

Tc ₁ <Tc ₂ <Tc ₃

However, Tc ₁ : Curie temperature of the first magnetic layer

Tc ₂ : Curie temperature of the second magnetic layer

Tc ₃ : Curie temperature of the third magnetic layer

And also at room temperature

Hc ₁ > Hw _{1 (2)} , Hc ₃ > Hw _{3 (2)}

, And between Tc ₁ at room temperature

Hc ₂ <Hw _{2 (3)} -Hw _{2 (1)}

However, Hc ₁ : coercive force of the first magnetic layer

Hc ₂ : coercive force of the second magnetic layer

Hc ₃ : Coercive force of the third magnetic layer

Hwi (j): A magneto-optical recording medium characterized by the presence of a temperature that satisfies the shift amount of the inversion magnetic field of the i-th layer due to the exchange coupling force acting between the j-th layer and the i-th layer.

The present invention of claim 3, further comprising: a first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in an exchange force, and provided in the second magnetic layer to exchange with the second magnetic layer in an exchange force. A third magnetic layer, provided in the third magnetic layer, and having a fourth magnetic layer coupled to the third magnetic layer by exchange force;

Tc ₁ <Tc ₂ , Tc ₃ <Tc2, Tc ₁ <Tc ₄ , Tc ₃ <Tc ₄

However, Tc ₁ : Curie temperature of the first magnetic layer

Tc ₂ : Curie temperature of the second magnetic layer

Tc ₃ : Curie temperature of the third magnetic layer

Tc ₄ : Curie temperature of the fourth magnetic layer

And also at room temperature

Hc ₁ > Hw _{1 (2)} , Hc ₄ > Hw _{4 (3)}

And at room temperature to the lower temperature of Tc ₁ and Tc ₃

Hc ₂ <Hw _{2 (3)} -Hw _{2 (1)} , Hc ₃ <Hw _{3 (4)} -Hw _{3 (2)}

However, Hc ₁ : coercive force of the first magnetic layer

Hc ₂ : coercive force of the second magnetic layer

Hc ₃ : Coercive force of the third magnetic layer

Hc ₄ : Coercive force of the fourth magnetic layer

Hwi (j): A magneto-optical recording medium characterized by the presence of a temperature that satisfies the shift amount of the inversion magnetic field of the i-th layer due to the exchange coupling force acting between the j-th layer and the i-th layer.

The invention of claim ₄ is a magneto-optical recording medium according to claim 3, wherein Tc ₂ ≤ Tc ₄ .

The present invention according to claim 5 includes a first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in an exchange force, and provided in the second magnetic layer to exchange the exchange force with the second magnetic layer. A third magnetic layer, the third magnetic layer,

Tc ₁ <Tc ₂ , T ₃ <Tc ₂

However, Tc ₁ : Curie temperature of the first magnetic layer

Tc ₂ : Curie temperature of the second magnetic layer

Tc ₃ : Curie temperature of the third magnetic layer

And also at room temperature

Hc ₁ > Hw _{1 (2)} , Hc ₃ > Hw _{3 (2)}

, And also between Tc ₃ at room temperature

Hc ₂ <Hw _{2 (3)} -Hw _{2 (1)}

However, Hc ₁ : coercive force of the first magnetic layer

Hc ₂ : coercive force of the second magnetic layer

Hc ₃ : Coercive force of the third magnetic layer

Hwi (j): A magneto-optical recording medium characterized by the presence of a temperature that satisfies the shift amount of the inversion magnetic field of the i-th layer due to the exchange coupling force acting between the j-th layer and the i-th layer.

The present invention of claim 6 is a magneto-optical recording medium, characterized in that Tc ₃ ≤Tc ₂ according to claim 5.

The present invention of claim 7 includes a fourth magnetic layer provided between the second magnetic layer and the third magnetic layer, and having a fourth magnetic layer coupled to the second magnetic layer and the third magnetic layer in an exchange force, respectively, Tc ₄ <Tc ₃ <Tc ₂ , Tc ₁ <Tc ₂ , Tc ₄ : satisfies the Curie temperature of the fourth magnetic layer, satisfies Hc ₁ > Hw _{1 (2)} and Hc ₃ > Hw _{3 (4)} at room temperature, and further at Tc ₄ at room temperature. Claim _5, wherein a temperature satisfying Hc ₂ <Hw _{2 (4)} -Hw _{2 (1)} and Hc ₄ <Hw _{4 (3)} -Hw _{4 (2)} exists A magneto-optical recording medium according to the above description.

A magneto-optical recording medium according to any one of claims 1 to 7, wherein an interface control layer for controlling exchange force is provided at an interface between the magnetic layers.

The invention of claim 9 has an initialization layer which does not magnetize inversion during recording and reproducing, and has an initialization layer in an atmosphere in which a magnetic field is applied in one direction by a magnetic field applying means in a method of manufacturing an overwriteable magneto-optical recording medium. The substrate is arranged so that the direction of application of the substrate and the surface of the substrate is substantially perpendicular, and the initialization layer is initialized in advance.

10. A method of manufacturing an optical magnetic recording medium having an initialization layer which does not invert magnetization during recording and reproducing, wherein the substrate has the initialization layer in an atmosphere in which magnetic fields are applied in one direction by a magnetic field applying means. Is arranged so that the direction of application of the household and the surface of the substrate are substantially perpendicular to each other, and the initializing layers are initialized in advance, and then bonded to each other.

The invention of claim 11 is a manufacturing method of an overwriteable magneto-optical recording medium having an initialization layer which does not invert magnetization during recording and reproduction, wherein the magnetic field is applied in one direction after the substrates having the initialization layer are bonded to each other. A bonded magnet substrate is arranged so that the application direction and the substrate surface are substantially perpendicular to each other.

12. The invention of claim 12 is a method of manufacturing an overwriteable magneto-optical recording medium having an initialization layer that does not invert magnetization during recording and reproducing, wherein the two substrates each having an initialization layer having different coercive force are bonded to each other after being initialized. A magnetic field larger than the coercive force of the layer is applied substantially perpendicular to the substrate, and then a magnetic field in a direction opposite to the magnetic field is substantially perpendicular to the substrate, which is smaller than the coercive force of the one initialization layer and greater than the coercive force of the other initialization layer. It is a method of manufacturing a magneto-optical recording medium, characterized in that the application.

The above-described configuration of the present invention of claim 1 to 8, that is, to enable optical modulation overwrite by using a magneto-optical recording medium having a first magnetic layer and an initialization layer as an information recording layer, and to provide an auxiliary layer. This allows the transfer from the initialization layer to the recording layer to be performed more efficiently.

The present invention also relates to a method of applying a magnetic field larger than the coercive force of the initialization layer in order to make the magnetization direction of the initialization layer of the magneto-optical recording medium in a predetermined direction in advance.

Best Mode for Carrying Out the Invention

An overwriteable magneto-optical recording medium which does not require an initialization magnet will be described in detail below. 1A and 1B are a perspective view of the principal parts of a magneto-optical recording apparatus provided with the magneto-optical recording medium of the present invention, respectively. Partial cross-sectional view showing the magneto-optical reproduction state of the two-layer film of the magneto-optical recording medium of the present invention, and for example, laser beam power variation for recording in the area of the magneto-optical recording medium of one embodiment of the present invention. It is a characteristic diagram which shows. In the figure, reference numeral 11 denotes a magneto-optical recording medium according to one embodiment of the present invention, numeral 20 denotes a laser beam of a beam-emitting device that irradiates the magneto-optical recording medium 11, and records and reproduces information. The beam spot irradiated onto the magneto-optical recording medium 11 by concentrating the laser beam 20 by the objective lens 5, and the beam spot 18 irradiating by the beam emitting element of the magneto-optical recording medium 11 The magnetic field applied to the portion is a magnetic field generating device of a certain direction. The magneto-optical recording medium 11 is rotationally driven in the direction of arrow a in the figure. As described above, the information carrier 11 is composed of two layers of magnetic layers 13 and 14, and is sequentially formed of the first magnetic layer 13 and the second magnetic layer 14 from the side to which the laser beam is irradiated. have. Here, the first magnetic layer 13 is a recording layer for maintaining the magnetization directions indicating the information # 0 'and # 1', and is a lead layer, and the second magnetic layer 14 is provided so as to exhibit an override performance. This second magnetic layer 14 is called an initialization layer and has a function that combines an auxiliary layer and an initialization magnet in the conventional example.

Here, the properties of the first magnetic layer 13 and the second magnetic layer 14 has the Curie when the temperature that each Tc _1, Tc _2, Tc ₁ <Tc _2, which is related, and Hc _1, Hc for the respective coercive force Suppose that ₂ , and the exchange coupling force of both layers is Hw ₁ (i = 1,2), there is the following relationship.

Equation (a) holds at any temperature T ₀ , lower than Tc ₁ at room temperature. That is, in the temperature range of room temperature-T ₀ , the coercive force Hc ₁ of the first magnetic layer 13 is greater than the sum of the influence Hw ₁ of the exchange coupling force and the applied magnetic field Hb in the magnetic field generating device 18 during recording, and the second This means that the magnetization direction indicated by the recording information can be maintained without being influenced by the magnetization direction of the magnetic layer 14.

Equation (b) holds throughout the operating conditions. That is, within the operating condition range, the coercive force Hc ₂ of the second magnetic layer 14 is greater than the sum of the influence Hq _w2 of the exchange coupling force and the applied magnetic field Hb of the magnetic field generating device 18 during recording. Initializing upward as shown in FIG. 1b does not cause magnetization reversal and maintains the upward magnetization state.

2 shows a characteristic diagram of the temperature change of the inverting magnetic field of the first magnetic layer 13. The inverse magnetic field is the minimum necessary magnetic field for inverting magnetization, and is added as Hc ₁ -Hw ₁ .

In FIG. 1C, the state of temperature change of the inverted magnetic field when the laser intensity is R ₁ is indicated by a solid line in FIG. 2, and the dotted line when the laser intensity is R ₀ .

Next, the operation at the time of recording will be described. First, the recording operation when recording the information # 0 ', that is, when the magnetization direction of the first magnetic layer 13 is made downward, will be described.

When light of laser intensity R ₁ is irradiated, the temperature in condensing spot 16 rises to Tr ₁ in FIG. 2. When the disk is rotated so that the light collecting spot 16 is not irradiated, the temperature of the first magnetic layer 13 decreases. As can be seen from the solid line in FIG. 2, in all the temperature regions of Tc ₁ -room temperature, since | Hb |> Hw ₁ -Hc ₁ , the magnetization direction of the first magnetic layer 13 is the direction of the bias magnetic field Hb, that is, downward. It is done.

Next, the recording operation when recording the information 1, i.e., when the magnetization direction of the first magnetic layer 13 is upward, will be described.

When light of laser intensity R ₀ is irradiated, the temperature in condensing spot 16 rises to Tr ₀ in FIG. 2. Then, when the disk is rotated so as not to irradiate the light collecting spot 16, the temperature of the first magnetic layer 13 is lowered. As can be seen from the dotted line in FIG. 2, for example, | Hb |> Hw ₁ -Hc _{1 in the} vicinity of the temperature Tp, the magnetization direction of the first magnetic layer 13 is the direction in which the exchange force acts, that is, the second magnetic layer. The magnetization direction (14) is upward.

By the operation as described above, the laser beam intensity is set to the binary code of the information at time of overwriting. By modulating the intensity R ₁ and the intensity R ₀ corresponding to each point in FIG. 4 in accordance with # ₁ , it is possible to overwrite in real time on the old data without an initializing magnet.

Next, in the case where the laser intensity is R ₀ and R ₀ , the reason why the temperature change of the inverting magnetic field of the first magnetic layer 13 differs as in the solid line as shown in FIG. 2 is explained.

The temperature of both quantum layers is increased by laser irradiation, but the heating rate thereafter is greater in the first magnetic layer 13 than in the second magnetic layer 14.

This is based on the following reasons.

(Iii) Since the laser is irradiated from the first magnetic layer 13 side, the highest attainment temperature of the second magnetic layer 14 is higher than the highest attainment temperature of the second magnetic layer 14, and therefore, the heat radiation rate is also large.

(Ii) The first magnetic layer is in contact with the substrate and radiates heat through the substrate.

(Iii) The film thickness of the first magnetic layer is extremely thin, and the heat dissipation is large.

Thus, the heat radiation rate of the first magnetic layer 13 is greater. The second magnetic layer 14 when the temperature of the first magnetic layer 13 rises to Tr ₀ in FIG. 2 by the laser of intensity R ₀ , and then the temperature of the first magnetic layer 13 decreases to near Tp in FIG. 2. ) Is called T ₂ r ₀ . In addition, after the temperature of the first magnetic layer 13 rises to Tr ₁ in FIG. 2 by the laser of intensity R ₁ , the second magnetic layer (when the temperature of the first magnetic layer 13 decreases to the vicinity of Tp in FIG. 2) If the temperature of 14) is T ₂ r ₁ , T ₂ r ₀ &lt; T ₂ r ₀ is obtained from the above difference in the heat release rate. That is, in the case of when irradiated with a large laser intensity is R ₁ a second temperature of the magnetic layer 14 in the vicinity of Tp is high. Considering that the exchange coupling force tends to decrease when the magnetic layer becomes high temperature, the exchange coupling force when the large laser intensity R ₁ is irradiated becomes small. Therefore, the difference between the solid line and the dotted line is caused by the temperature change of the inverting magnetic field of the first magnetic layer 13 in FIG. And this causes the hysteresis of magnetization with respect to temperature, and enables overwriting. The operation at the time of reproduction is the same as before.

Next, an embodiment in which the first layer and the second layer of the present invention are made of an alloy of rare earth-transition metal will be described.

When both the first layer and the second layer are selected from the alloy composition of the rare earth-transition metal, the direction and size of the magnetization appearing outside as each alloy is the sublattice magnetization of the transition metal atom (hereinafter referred to as TM) inside the alloy. It is determined from the relationship between the direction and the magnitude of the magnetic moment per unit volume and the direction and the magnitude of the sublattice magnetization of the rare earth metal (hereinafter referred to as RE).

For example, the direction and magnitude of the sublattice magnetization of TM are indicated by a dotted vector ↑, the direction and magnitude of the sublattice magnetization of RE is indicated by a solid vector ↑, and the direction and size of the magnetization of the entire alloy is doubled. Solid vector To be displayed.

Vector Vector It is expressed as the sum of and ↑. However, among alloys, vector for interaction between TM sublattice magnetization and RE sublattice magnetization And vector ↑ are in opposite directions. therefore, Sum of ↑ and ↑ or ↓ The sum of and becomes the vector of the alloy when the strength of both are the same (i.e. the magnitude of the external magnetization is zero).

The alloy composition at the time of zero is called a compensation composition. When the composition is other than this, the alloy has the same strength as that of the bipolar lattice magnetization, and the same direction as the direction of the larger vector ( or Has The magnetization of this vector is external. For example ↑ Is ↑ Is It becomes

When either one of the TM sublattice magnetization and the RE sublattice magnetization of a certain alloy composition has a large intensity, the alloy composition is named after the sublattice magnetization of the larger strength, for example, called RE rich. Shall be. It is divided into TM richin composition and RE richin composition for both the first magnetic layer and the second magnetic layer.

3 is a cross-sectional view of the magneto-optical recording medium composed of this rare earth-transition metal alloy, in which (2) is a substrate and (21) is MFeCo (where M is one or more of Tb or Dy). The magnetic alloy layer 22 is a second amorphous magnetic alloy layer of GdTbFe. As the substrate 2, a nonmagnetic material such as glass or plastic is used as the material. The MFeCo ternary first amorphous magnetic alloy layer (hereinafter referred to as the first magnetic alloy layer) 21 has a range of 0.15 &lt; x &lt; 0.3 when Mx (Fe _1-y Co _y ) _1-x . , y is in the range of 0 <y≤0.5. The second amorphous magnetic alloy layer (hereinafter referred to as a second magnetic alloy layer) 22 has (Gd _1-y Tb _y ) _x Co _1-x where x is in the range of 0.15 <x <0.35, and y is It is the range of 0.3 <= y <= 1.

In addition, in order to form the magnetic layer of the above structure, a film is formed by the sputtering method, the vacuum deposition method, etc., for example.

Hereinafter, it demonstrates in detail according to an Example.

Example 1

Sputtering method on substrate

First Magnetic Alloy Layer: Tb ₂₃ Fe ₇₂ Co ₅ 500Å

2nd magnetic alloy layer: Gd ₁₄ Tb ₁₄ Co ₇₂ 1500Å

It is obtained by forming ferrimagnetic materials in order, and the magnetic layers are bonded by exchange force. Curie temperature of the first magnetic alloy layer 21 is about 180 ℃, the second magnetic alloy layer 22 has a magnetizing inversion magnetic field of 1 k Oe or more from room temperature to 250 ℃, the second magnetic alloy layer 22 is operated Does not cause magnetization reversal in the temperature range. In the first magnetic alloy layer 21, the exchange force becomes larger than the coercive force at about 150 ° C., and the difference is about 1 k Oe as a magnetic field where the difference between the exchange force and the coercive force is greatest. The external magnet 18 of the magnetic field generating device generates a magnetic field of about 1 k Oe upward. The second magnetic layer 22 is magnetized uniformly upward. At this time, the magnetic field direction of the external magnet 18 is set upward as opposed to the above-described example.

Recording to the magneto-optical recording medium 23 having such a configuration will be described with reference to FIG. As shown in ① or ⑤ of FIG. 4, the first magnetic alloy layer Tb ₂₃ Fe ₇₂ Co ₅ has a compensation composition at room temperature, and the magnetization of the entire alloy is zero. On the other hand, the second magnetic alloy layer Gd ₁₄ Tb ₁₄ Co ₇₂ is RE rich and the magnetization of the whole alloy is directed upward. In the case of this embodiment, the recording of the information '0' or '1' is determined by whether the TM sublattice magnetization of the first magnetic alloy layer 21 faces downward (0) or upwards (1). . The recording of the information # 1 is shown in ①-④ of FIG. First, when the light of the laser intensity r ₁ (see also the _first c) is irradiated, the temperature in the condensing spot rises to Tr ₁ and exceeds the Curie point of the first magnetic alloy layer 21, so that the first magnetic alloy layer 21 The magnetization of is lost (figure 4 ②). When the light collecting spot is not irradiated by the rotation of the disk, the temperature of the first magnetic alloy layer is lowered. Hw ₁ -Hc ₁ is maximized in the vicinity of Tp of FIG. 2, but the magnetization direction of the first magnetic alloy layer is increased by the bias magnetic field Hb (| Hb |> Hw ₁ -Hc ₁ ) larger than this. It becomes the direction (upward) of Hb. At this temperature, the first magnetic alloy layer is TM rich. This is because the compensation point is near room temperature in FIG.

Thus, the TM sublattice magnetization is upward (Fig. 4 ③). When the temperature is lowered to room temperature, the first magnetic alloy layer becomes a compensation composition (FIG. 4 ④). The recording of the information '0' is shown in ⑤-⑧ of FIG. When light of laser intensity R ₀ is irradiated, the temperature in the condensing spot rises to Tr ₀ (Fig. 4 (⑥)). When the disk is rotated so that the light collecting spot is not irradiated, the temperature of the first magnetic alloy layer is lowered.

As described above, in the vicinity of Tp (about 150 ° C.) in FIG. 2, the magnetization direction of the second magnetic alloy layer is transferred by the exchange force (Hb <Hw ₁ -Hc ₁ ). In this case, the TM sublattice magnetization of the first magnetic alloy layer becomes downward (FIG. 4 ⑦). When the temperature is lowered to room temperature, the first magnetic alloy layer is compensated for adjustment (Fig. 4 (8)). By modulating only the laser light intensity in such an operation, light modulation can be directly overwritten, and a signal having a pit length of 0.8-5 μm at a line speed of 6 m / sec is generated by the magnetic field of the external magnet 18. The laser power was modulated with a peak power of 161 mW, a bottom power of 5 mW and light modulation to obtain a characteristic with an erase ratio of 25 dB or more. Laser power at the time of regeneration was performed at 1.5 mW.

EXAMPLES 2-8

The coercive force of the second magnetic layer 14 should be large enough near the Curie temperature of the ground magnetic layer 13, and the magneto-optical recording of another embodiment of the present invention shown in Table 1 as in Example 1 on a class substrate by sputtering the magnetic layer Obtained an information carrier.

TABLE 1

In the magneto-optical recording apparatus of another embodiment of the present invention using the magneto-optical recording information carriers shown in Table 1, respectively, at a line speed of 6 m / sec, as shown in Table 2, at an erase ratio of 20 dB or more and an optimum power of 23, respectively. The characteristic of about -35 dB was obtained, and the light modulation direct overwrite similar to Example 1 was possible.

TABLE 2

Another magneto-optical recording medium of another embodiment is as follows.

Example 9

First magnetic alloy layer: Tb ₂₃ Fe ₆₇ Co ₁₀ (film thickness 500 kPa)

2nd magnetic alloy layer: Gd ₁₂ Tb ₁₂ Co ₇₆ (film thickness 1500Å)

A good overwrite can be achieved in the same manner as in Example 1 by the combination of the composition and the film thickness.

Example 10

Substrate: 1.2mm thick plastic substrate

TbFeCo Ternary 1st amorphous magnetic alloy layer: Tb _23.6 (Fe ₉₀ Co ₁₀ ) _76.4

Thickness: 500Å

Coercivity at room temperature: about 10KOe

Curie Temperature: 180 ℃

GdTbCo Ternary 2nd Amorphous Magnetic Alloy Layer: Gd ₅₀ (Tb ₅₀ ) ₂₄ Co ₇₆

Thickness: 1800Å

Coercive force at room temperature: about 1KOe

Curie Temperature: 300 ℃

After the initialization of the magneto-optical recording medium of Example 10 was performed only once with 10 KOe, the disk speed 6 m / sec and the recording magnetic field were fixed at 1 KOe, and only the light power by the light beam was modulated at 15 mW and 5 mW. The signal at 1.5 MHz could be overwritten 1000 times without an initialization magnet.

Example 11-15

Except for using the first magnetic layer and the second magnetic layer of the composition shown in Table 3, the magneto-optical recording information carrier of the other embodiment of the present invention was obtained in the same manner as in the tenth embodiment, and was subjected to the same single light beam as that of the tenth embodiment. Was examined for the overwrite.

[Comparative Examples 1,2]

Except for using the first magnetic layer and the second magnetic layer of the composition shown in Table 3, the magneto-optical recording information carrier of Comparative Example was obtained in the same manner as in Example 10, and the overwrite with a single light beam as in Example 10 was investigated. It was.

TABLE 3

Next, a description will be given of a three-layer film structure as an magneto-optical recording medium capable of overwriting without the need for an initialization magnet.

6A and 6B, the same code | symbol as FIG. 1 is attached | subjected to FIG. Denoted at 24 is the first magnetic layer, 25 at the second magnetic layer, and 26 at the third magnetic layer. The first magnetic layer 24, the second magnetic layer 25 and the third magnetic layer 26 are all transition metal-rare earth alloys in this embodiment, and all the layers are TM rich. The first magnetic layer 24 and the second magnetic layer 25 are coupled by an exchange coupling force, and the exchange coupling force acts to equalize the directions of the TM sublattice magnetization on both sides. The second magnetic layer 25 and the third magnetic layer 26 are likewise coupled by exchange coupling force.

The magnetization of the third magnetic layer 26 is initialized upward in the figure by an electromagnet or the like in advance.

The first magnetic layer 24 is a recording layer for holding the sublattice magnetization (here, TM sublattice magnetization) indicating the information # 0 'and # 1'. The second magnetic layer 25 and the third magnetic layer 26 are provided to exhibit overwrite performance. In particular, the second magnetic layer 25 is called an auxiliary layer, and the sublattice magnetization direction of the second magnetic layer 25 is transferred to the first magnetic layer 24 (that is, the sublattice magnetization direction of the first magnetic layer 24). This second magnetic layer coincides in the sublattice magnetization direction, making it possible to direct the magnetization direction of the first magnetic layer 24 to the desired direction.

The third magnetic layer 26 is an initialization layer. The sublattice magnetization direction of the third magnetic layer 26 is transferred to the second magnetic layer 25 so that the sublattice magnetization direction of the second magnetic layer 26 at room temperature can be matched in a predetermined direction. have.

Next, specific characteristics of the first magnetic layer 24, the second magnetic layer 25, and the third magnetic layer 26 will be described.

If the curie temperatures of each layer are Tc ₁ , Tc ₂ , and Tc ₃ , respectively, Tc ₁ <Tc ₂ <Tc ₃ . In addition, since all three layers are TM rich in this Example, it is necessary to satisfy the following conditions at room temperature.

At room temperature,

There exists a temperature which satisfies the following zone condition between room temperature and Tc ?.

Where Hci is the coercive force of the i-th magnetic layer

Hwi (j): Shift amount of inverting magnetic field of layer i by exchange coupling force acting between layer j and layer i

Hb: The magnetic field applied at the time of recording by the bias magnet 18 will be described next. Since reproduction is the same as in the conventional example, the following overwrite recording is performed.

The recording medium is subjected to environmental changes shown in Table 4 while passing through the light collecting spot.

TABLE 4

Environment III is about 1 μm in size of the condensing spot 16, and Environments II and IV are about 1 mm before and after the condensation spot, and in Environment III, the maximum according to the laser intensity is caused by the heating effect of the condensing spot 16. The temperature of the magnetic film in the condensing spot 16 rises to the temperature. Then, when passing through the condensing spot 16, it cools and returns to room temperature in progress of several 10 micrometers.

This is made possible by binaryly modulating the laser intensity described above in overwrite recording. The recording made by the stronger laser intensity R ₁ is called &quot; HIGH recording &quot;, and the maximum attainable temperature of the magnetic film at that time is called Thigh. On the other hand, the recording by the weaker laser intensity R ₀ is called "LOW recording", and the maximum achieved temperature of the magnetic film at that time is called Tlow.

Here, the detailed procedure of "LOW recording" and "HIGH recording" will be described using magnetization change against environmental change.

LOW record

Environment I: The first magnetic layer 24 has a characteristic of satisfying the above formula (1). That is, since the coercive force Hc ₁ is larger than the exchange coupling force Hw _{1 (2} ) from the second magnetic layer 25, the magnetization state can be maintained before that.

Thus, the sublattice magnetization remains up or down in accordance with previously recorded information. As can be seen from Equation (3), the third magnetic layer 26 has a sufficiently large coercive force Hc ₃ and continues to take the direction of magnetization of the TM sublattice magnetized upward. The second magnetic layer 25 has a large exchange coupling force from the third magnetic layer 26 in equation (2), and the TM sublattice magnetization is directed toward the TM sublattice magnetization of the third magnetic layer 26, that is, upward. . Therefore, in the environment I, there are two kinds of states, in which the information of "1" is written in the first magnetic material 24 serving as the recording layer and in the case where the information of "0" is written. This is the case where the information of "1" is written to the first magnetic layer 24 and the case where the information of "0" is written. When the TM sublattice magnetization of the first magnetic layer 24 is upward, the state of "1" and the downward direction of the TM magnetic lattice are named "0".

In the drawings, Denotes the TM sublattice magnetization, and ↑ denotes the RE sublattice magnetization. The length is proportional to the size of each sublattice magnetization. Therefore, in all layers Is longer than ↑ because all magnetic layers are TM rich in this embodiment. In addition, in the state of "1", since the sublattice magnetization is reversed in the first magnetic layer 24 and the second magnetic layer 25, they are in a state in which they exchange with each other. Thus, the interface between the two layers is? W ₁₂ . Energy stays in an unstable state. This instability in the drawing Expressed as

The reason why the first magnetic layer 24 and the second magnetic layer 25 can maintain such an unstable state is that both layers satisfy the conditions shown in the formulas (1) and (2), as described above.

Environment II: The difference from Environment I is that the external magnetic field Hb downward of the bias magnet 18 is applied. In Fig. 7 ①, only the first magnetic layer 24 in the state of "0" is in a slightly unstable state. However, in this case, since Hb is downward, it acts in the direction which keeps the magnetization state of the 1st magnetic layer 24 in the state of "0". Since the other layers are in a sufficiently stable state and the size of the magnetic field Hb is only small at a number of 100Oe, the magnetization is not reversed by the external magnetic field Hb. Therefore, the state of FIG. 7 ① is maintained in environment II.

Environment III: The magnetic film in the condensing spot 16 irradiated with the laser intensity R ₁ is heated to the maximum temperature Tlow. This Tlow Satisfies. In this Tlow, since the first magnetic layer 24 is equal to or higher than the Curie temperature Tc ₁ , the magnetization is lost. On the other hand, in the second magnetic layer 25 and the third magnetic layer 26, the Curie temperatures Tc ₂ and Tc ₃ are sufficiently high, and the magnetization state in the environment II. Part Contents: Keep. Therefore, the magnetization state at the highest temperature Tlow &quot;

When the light exits from the condensing spot 16, the magnetic layer cools rapidly. During the cooling process, the first magnetic layer 24 begins to appear spontaneously where the temperature of the first magnetic layer 24 is slightly lower than Tc ₁ .

At this temperature, the coercive force of the first magnetic layer 24 is sufficiently small, while the exchange coupling force in the second magnetic layer 25 having a sufficiently high Curie temperature is relatively large (Hc ₁ + Hb &lt; Hw _{1 (2)} ). Therefore, the sublattice magnetization of the first magnetic layer 24 coincides with the sublattice magnetization direction of the second magnetic layer 25. Then, this magnetization state is maintained until cooling advances and the temperature of the magnetic layer returns to room temperature. Therefore, the magnetization state at the time of returning to room temperature becomes as shown in FIG.

Environment IV, Environment V: All the layers in Fig. 3 ③ are sufficiently stable, so they remain intact in Environment IV and Environment V as well.

Thus, even if the TM sublattice magnetization of the first magnetic layer is in an upward state ("1") or in a downward state ("0"), the state becomes upward ("1") by "LOW recording".

`` HIGH record ''

Environment I and Environment II are the same as Environments I and II (FIG. 7 ①) in the LOW recording.

Environment III: The magnetic film in the condensing spot 16 irradiated with the laser intensity R ₁ is heated to the maximum temperature Thigh. This Thigh is To satisfy. In this Thigh, not only the first magnetic layer 24 but also the magnetization of the second magnetic layer 25 is lost. On the other hand, the Curie temperature Tc ₃ of the third magnetic layer 26 is sufficiently high to maintain the magnetization state in the environment II. Therefore, the magnetization state at this highest temperature Thigh is as shown in FIG. The magnetic layer rapidly cools away from the condensing spot 16. During the cooling process, the second magnetic layer 25 begins to appear spontaneously at a place where the temperature of the second magnetic layer 25 is slightly lower than Tc ₂ . At a temperature sufficiently higher than this Tc ₁ , the coercive force of the second magnetic layer 25 is sufficiently small, and the exchange coupling from the third magnetic layer 26 is also quite small. Therefore, it is to be noted that at this temperature, the bias magnetic field Hb.

Therefore, the magnetization of the second magnetic layer 25 is directed downward in accordance with this bias magnetic field as shown in Fig. 7?

As described above, the second magnetic layer 25 and the third magnetic layer 26 are in an unstable state. However, the second magnetic layer 25 is supported by a downward bias field having a relatively large force at this temperature (Hw _{2 (3)} -Hc ₂ &lt; Hb), and the third magnetic layer 26 has its curie temperature Tc _3. Since this is sufficiently high, the coercive force is large, and therefore the upward magnetization direction can be maintained. (Hc ₃ -Hb-Hw _{3 (2)} > O). As the temperature decreases, the coercive force of the second magnetic layer 25 and the third magnetic layer 26 becomes large and becomes more stable. When the temperature is slightly lower than Tc ₁ , the spontaneous magnetization of the first magnetic layer 24 starts to appear, and the sublattice magnetization of the first magnetic layer 24 is the same as in the case of "LOW recording". The sublattice coincides with the magnetization direction. Then, the magnetization as it is is maintained and cooled down to around room temperature (Fig. 7 (⑥)).

When cooled to room temperature, as shown in Fig. 7 (7), the second magnetic layer 25 that satisfies the formula (2) is transferred in the sublattice magnetization direction of the third magnetic layer 26, and satisfies the formula (1). The first magnetic layer 24 maintains its magnetization state.

Environment IV, Environment V: As shown in Fig. 7 (7), the first magnetic layer 24 and the second magnetic layer 25 satisfying the equations (1) and (2) maintain their magnetization states.

In this manner, the state in which the TM sublattice magnetization of the first layer is upward ("1") or downward ("0") also becomes downward ("0") by "HIGH recording".

According to the binary information imparted above, a good overwrite operation is possible by modulating the laser intensity into binary of R? And R ?.

Here, the specific structure of the used magnetic layer is shown next.

First magnetic layer Tb ₂₁ Fe ₇₄ Co ₅

2nd magnetic layer Dy ₁₉ Fe ₆₂ Co ₁₉

Third Magnetic Layer Tb ₂₀ Co ₈₀

Applying 200Oe downward as a bias magnetic field yielded a good overwrite operation of C / N = 45 dB.

8 shows the measurement result (circle mark) in the vicinity of room temperature of the left side of Formula (1)-(3). This result shows that the overwrite operation is possible at 0 ° C-50 ° C.

In the above embodiment, the case in which the first magnetic layer 24, the second magnetic layer 25, and the third magnetic layer 26 are all TM rich is shown, but other forms are possible. Table 5 shows an example of checking the overwrite. However, the direction of the bias magnetic field is a case where the third magnetic layer is magnetized upward. Moreover, (RE) in the term of the form of each layer shows that it is RE sublattice magnetization dominance at room temperature, but turns into TM sublattice magnetization dominance at high temperature (compensation temperature or more).

The conditions for recording / reproducing with the above overwriteable three-layer film can be summarized as follows. At room temperature,

However, Hc ₁ : coercive force of the first magnetic layer, Hc ₂ : coercive force of the second magnetic layer, Hc ₃ : coercive force of the third magnetic layer, Hb: applied magnetic field during recording, Hwi (j): between j and i layers The shift amount of the inverting magnetic field of the i layer by the exchange coupling force acting on a, a = 1: when the second layer has a compensation temperature above room temperature, a = -1: the second layer does not have a compensation temperature above room temperature. Otherwise, b = 1: when both the first layer and the second layer are transition metal dominance or both lanthanide dominance, b = -1: otherwise, c = 1: the second layer and the third layer When the layers are all transition metal dominance or mode lanthanide dominance, c = -1: otherwise.

TABLE 5

TM: Transition metal sublattice magnetization advantage Hb is Oe, + is upward,-is downward

RE: Rare earth sublattice magnetization dominance C / N is dB

When one or more magnetic layers having a lower Curie temperature than the second magnetic layer is provided between the second magnetic layer and the third magnetic layer of the above-described three-layer film magneto-optical recording medium, more stable recording and reproduction can be performed, resulting in more stable C / N may be improved. 9 is a sectional view of an essential part of the magneto-optical recording medium of one embodiment of the present invention. (27), (28) and (29) are the second magnetic layer, the third magnetic layer and the fourth magnetic layer, respectively. Here, the third magnetic layer is a layer newly added, the fourth magnetic layer is a layer in contact with the third magnetic layer of the three-layer film medium, the recording medium 30 is a sputtering method or the like on a glass substrate, for example,

1st magnetic layer: Dy ₂₃ Fe ₃₈ Co ₉ 500Å [Compensation composition (room temperature)]

2nd magnetic layer: Tb ₂₅ Fe ₃₀ Co ₁₅ 700Å [RE RICH]

Third magnetic layer: Tb ₁₆ Fe ₈₄ 200 Å [TM Rich]

Fourth Magnetic Layer: Tb ₃₀ Co ₇₀ 700Å [RE Rich]

It is formed of ferrimagnetic material, and adjacent magnetic layers are bonded by exchange force. The fourth magnetic layer 29 is 700? It has a coercive force of e or more, and the fourth magnetic layer 29 does not cause magnetization reversal in the operating range with respect to the temperature rise by laser irradiation. In addition, the second magnetic layer has a compensation temperature above room temperature. External magnet (18) is 200-400 It generates a magnetic field of e. The fourth magnetic layer 29 is magnetized constantly once only, for example, upwardly, by first recording the recording medium 30 in a magnetic field greater than or equal to the magnetization anti-magnetic field of the fourth magnetic layer 29. At this time, the magnetic field by the external magnet 18 is generated upward.

The temperature characteristics of each layer and the magnetic properties between each layer are as follows.

Tc ₄ ＞ Tc ₂ ＞ Tc ₁ ＞ Tc ₃ ＞ O (Room temperature)

-Hw _{1 (2)} + Hc ₁ -Hb ＞ O (room temperature)

Hw _{1 (2)} -Hc ₁ -Hb> O (Reference temperature: any temperature from room temperature to Tc ₁ )

Hw _{2 (3)} -Hw _{2 (1)} + Hc ₂ + Hb> O (Room temperature)

Hw _{3 (4)} -Hw _{3 (2)} -Hc ₃ -Hb> O (any temperature change from Tc ₃ to room temperature)

-Hw _{4 (3)} + Hc ₄ ＞ O (all operating range temperatures)

Next, the operation will be described. During regeneration, the laser output is increased to exceed the reference temperature at the portion within the condensing spot 16, and the magnetization reversal temperature of the second magnetic layer 27 (the coercivity becomes smaller than the external magnetic field due to the increase in temperature, causing magnetization in the direction of the external magnetic field. When the temperature is not inverted), the magnetization directions of the sublattice magnetizations of the TM and RE of the second magnetic layer 27 do not change, so that the magnetization direction of the second magnetic layer 27 at the reference temperature of the first magnetic layer 24 is the first. Transferred to the magnetic layer 24, the magnetization direction of the TM sublattice of the first magnetic layer 24 becomes downward as shown in FIG. At the reference temperature, the first magnetic layer is TM rich (LOW recording). In this case, the third magnetic layer 28 and the fourth magnetic layer 29 have no contribution to the drawing, and even if the magnetization of the third magnetic layer 28 is lost, the third magnetic layer 28 and the fourth magnetic layer 29 are again changed in a predetermined direction by the exchange force with the fourth magnetic layer 29. Magnetized in the same direction. Thereafter, the condensing spot is removed and cooled to around room temperature, and the first magnetic layer 24 returns to compensation adjustment (FIG. 9). When the magnetization inversion temperature of the second magnetic layer 27 is not exceeded and the magnetization inversion temperature of the fourth magnetic layer 29 is not reached, the magnetization of the first and third magnetic layers is lost, but the fourth magnetic layer 29 is a sublattice. The magnetization direction does not change. In addition, since the compensation temperature of the second magnetic layer is exceeded, the second magnetic layer is TM rich (Fig. 10 ②). The magnetization direction of the second magnetic layer 27 becomes upward due to the magnetic field by the external magnet 18 due to the exchange force between the first and third magnetic layers at the magnetization inversion temperature of the second magnetic layer 27 (10th ③ The magnetization direction of the second magnetic layer 27 is transferred to the first magnetic layer 24 so that the magnetization direction of the first magnetic layer is upward. The first magnetic layer 24, the second magnetic layer 27, the second magnetic layer 27, and the third magnetic layer 28 increase the exchange force between the third magnetic layer 28 and the fourth magnetic layer 27. At this time, the sublattice magnetization of the third magnetic layer 28 below the Curie temperature of the third magnetic layer 28 coincides with the sublattice magnetization of the fourth magnetic layer 29 (Fig. 10 ⑤), and the temperature is lowered. When the exchange force becomes large, the sublattice magnetization of the second magnetic layer 27 returns to the initial state in accordance with the sublattice magnetization of the fourth magnetic layer 29 via the third magnetic layer 28 (FIG. 10 ⑥).

By modulating only the laser light intensity in the above operation, direct modulation of light modulation is possible. In a magneto-optical recording medium provided with a dielectric dielectric layer on a substrate having grooves spaced 1.6 mu m apart, and provided with the magnetic layer, 1 m / sec, a pit length 0.76 mu m, an applied magnetic field 2000 e, the laser power is optically modulated at a peak power of 18 mW and a bottom power of 7 mW to obtain characteristics of 45 dB of C / N ratio and 40 dB of cancellation ratio.

Example 16

The recording medium of Table 6 was formed on the glass substrate by the sputtering method as in the above embodiment. By almost optimizing the recording conditions of any recording medium, almost complete optical modulation direct overwrite is possible.

TABLE 6

11 to 91 describe patterns for all cases in which the composition of the alloy of the transition metal and the rare earth metal is different in each layer. In these drawings, the definition of each symbol is as follows.

TM: Transition metal-rare earth metal alloy which is a transition metal rich and has no compensation temperature between room temperature and Curie temperature

RE: Transition metal-rare earth metal alloy which is rare earth metal rich and does not have compensation temperature between room temperature and Curie temperature

re: Transition metal-rare earth metal alloy that is a rare earth metal rich and does not have a compensation temperature between room temperature and Curie temperature.

t: film thickness

Ms: Saturated magnetic moment [emu.cc ^-1 ]

Hc: Coercivity [? E]

Tc: Curie temperature [℃]

Sw (≡σW): interfacial wall energy [erg.cm ^-2 ]

Hwi: Total exchange power received by i

Hwi (j): Exchange force exerted on the i-layer by the j-layer (≡σwij / (2 | Mis | ti))

Where i and j are layers from the substrate side

↑: TM sublattice magnetization direction

: Magnetization of the sum of TM sublattice magnetization and RE sublattice magnetization

Tstor: All temperatures within the storage temperature range (ex. -10 ℃ -60 ℃)

Tread: All temperatures at which the media reaches the temperature during regeneration at the minimum operating temperature

: Any temperature higher than the temperature during regeneration and below which Tc ₁ causes the magnetization of the first magnetic layer to be transferred by the magnetization direction of the second magnetic layer.

Tini: All temperatures under the operating temperature condition (or the temperature at the part prepared for the initialization operation except the laser irradiation part)

Tall: All temperatures within the operating temperature (0 ℃-)

Tuse: Operating device operating temperature (0 ℃ -50 ℃)

In addition, in each figure, (a1) shows the state which recorded the information # 0 ', (a2) shows the state which recorded the information # 1'. out of (a2) Represents the wall.

Next, the configuration of the magneto-optical recording medium of another overwriteable three-layer film will be described. The relationship between the Curie temperature of each layer and the magnetization between each layer is as follows.

An embodiment of a magneto-optical recording medium having such a relationship is shown in FIG. 92A. In the figure, reference numeral 31 denotes the first magnetic layer Tb ₂₃ (Fe ₃₂ Co ₈ ) ₇₇ , reference numeral 32 denotes the second magnetic layer Tb ₂₆ (Fe ₈₅ Co ₁₅ ) ₇₄ , and reference numeral 33 denotes the third magnetic layer Tb ₂₆ Fe ₇₄ . The second magnetic layer 32 has a compensation point above room temperature, as shown in FIG. 92B.

Next, the operation of the overwrite will be described. The magnetization direction of the third magnetic layer 33 is magnetized upward over the entire surface in advance. For example, it can magnetize easily using the electromagnet which produces the magnetic field of about 20 KOe. The upwardly magnetized third magnetic layer 33 may rise in temperature above its Curie temperature Tc ₃ by irradiation of a condensing spot and lose its magnetization. However, magnetization becomes upward again under the influence of the upward bias magnetic field Hb at the time of cooling. In addition, although the cooling force Hw may be received downward from the second magnetic layer 32 when cooled,

Therefore, the magnetization of the third magnetic layer 33 is maintained upward and cooled to room temperature (However, Hc ₃ and Hw _{3 (2)} in equation ₍₆₎ are values near room temperature as in equations _{(3) and (} 5). The value of the third magnetic layer at the time of cooling is a value below the temperature determined, and therefore, the formula (6) is satisfied at all temperatures at the time of cooling). As described above, the magnetization direction of the third magnetic layer 33 is always upward except for the laser spot irradiation portion. As indicated above, the exchange train Hw _{2 (3)} and the bias magnetic field Hb from the third magnetic layer 33 magnetized upward act to raise the magnetization of the second magnetic layer 32 (32). The magnetization of the second magnetic layer 32 is higher than that of the exchange force Hw _{2 (1)} or the coercive force Hc ₂ from the first magnetic layer 31 to lower the magnetization of the second magnetic layer 32. This is called initialization of the second magnetic layer 32.

In the above, the case where the bias magnetic field Hb acts on the recording medium at room temperature is considered. This situation is achieved in some parts of the recording medium that are directly above the bias magnetic field and are not under irradiation by the light collecting spot. In the actual recording and reproducing apparatus, there is a laser spot at the center of the region in which the bias magnetic field Hb is acting, so that the initialization of the second magnetic layer occurs immediately before and immediately after recording. For this reason, the magnetization direction of the second magnetic layer 32 is always upward except for the laser spot irradiating portion as in the magnetization direction of the third magnetic layer 33.

Next, when the information # 1 is recorded, that is, when the magnetization direction of the first magnetic layer 31 is made upward, the following description will be given. At this time, the laser power is R _1, and the temperature of the condensing spot portion rises to Thigh at 92 ° B.

That is, the temperature becomes near Tc ₂ or above Tc ₂ at which the coercive force of the second magnetic layer 32 is higher than the Curie temperature Tc ₁ of the first magnetic layer 31 and smaller than Hb. As a result, the magnetization in the condensing spot of the first magnetic layer 31 is lost (Fig. 93), and is higher than the compensation temperature by the upward bias magnetic field Hb. Thus, the TM sublattice of the second magnetic layer 32, which is TM rich, is formed. Magnetization is upward (Fig. 93 ②). In addition, the magnetization direction of the second magnetic layer 32 is transferred by the exchange force to the first magnetic layer 31 when the temperature of the first magnetic layer 31 is lower than the Curie temperature Tc ₁ , and the first magnetic layer 31 is transferred to the first magnetic layer 31. The magnetization direction of the TM sublattices is upward, that is, the direction corresponding to the information # 1 '(Fig. 93 (3)). When the temperature is lowered and lower than the Curie temperature Tc ₃ , the total magnetization of the sublattice of the third magnetic layer is increased by the bias magnetic field Hb (the RE sublattice magnetization is upward). At this temperature, the second magnetic layer is also at or below the compensation temperature and is RE rich. As described above, the sum of the sublattice magnetization of the second magnetic layer is changed upward by the exchange force from the third magnetic layer and the bias magnetic field Hb. 93 degrees ④).

Further, the description will be given when the information # 0 is recorded, that is, when the magnetization direction of the first magnetic layer 31 is made downward. At this time, the laser power is R _0, and the temperature of the condensing spot portion rises to Tlow of FIG. 92b. That is, the temperature of the condensing spot portion is sufficiently lower than the Curie temperature Tc ₂ of the second magnetic layer 32 before and after the Curie temperature Tc ₁ of the first magnetic layer 31. As a result, the magnetization of the first magnetic layer 31 is lost or unstable. When the cooling starts, the sublattice magnetization direction of each of the second magnetic layers 32 is transferred to the first magnetic layer, and the magnetization direction of the TM sublattice of the first magnetic layer 31 is downward, that is, at 93 ° ⑤. The direction corresponds to the information # 0 'as shown. When cooled to room temperature, the state of Fig. 93 is taken as described when recording # 1 is recorded. By overwriting by the above operation, the laser power is modulated according to the binary codes # 0 and # 1 of the information so that overwriting can be performed in real time without initializing magnets on the old data.

Even if a fourth magnetic layer is newly provided between the second magnetic layer 32 and the third magnetic layer 33 of the three magneto-optical recording medium, good overwrite operation is possible. In this case, it is essential that the Curie temperature Tc ₄ of the fourth magnetic layer is lower than the Curie temperature of the third magnetic layer. As the fourth magnetic layer, for example, Dy ₂₃ Fe ₇₇ (t = 500 kPa) may be used.

This magneto-optical medium satisfies the following conditions at room temperature,

In addition, there exists respectively the temperature which satisfies the following conditions: Tc between ₄ at room temperature.

By providing this fourth magnetic layer, the operation in which the third magnetic layer is magnetized by the bias magnetic field during cooling can be made smoother. Because when the third magnetic layer is magnetized by the bias magnetic field, it is the exchange force from the second magnetic layer that interferes with it. The temperature Td at which magnetization of the third magnetic layer is determined is a temperature slightly lower than Tc ₃ .

If Tc _3> Td> When high the Curie temperature Tc ₄ satisfying Tc ₄ has a fourth magnetic layer, a fourth magnetic layer is noted that in the temperature Td for the third magnetic layer magnetization is confirmed the magnetization and the loss, and since the second The exchange force from the magnetic layer does not act on the third magnetic layer and thus the magnetization of the third magnetic layer smoothly coincides with the bias magnetic field.

Subsequently, the sublattice magnetization of the third magnetic layer is transferred to the fourth magnetic layer in Equation (4), and the sublattice magnetization of the fourth magnetic layer is transferred to the second magnetic layer in Equation (3). In other words, the second magnetic layer is initialized as described above.

Specific overwrite operations are the same as those described above. In each of the above inventions, it is important to appropriately control the exchange force between the magnetic layers. For this reason, you may interpose an interface control layer between each magnetic layer. For example, in a two-layer magnetic layer medium, sputtering is performed on a glass substrate.

1st magnetic layer Tb ₂₃ Fe ₇₂ Co ₅ 500 Å

Interface Control Layer Tb ₂₆ Fe ₇₀ Co ₄ 50 ₄

2nd magnetic layer Tb ₃₀ Fe ₇₀ 1500Å

Ferrimagnetic material of was formed in turn. Here, the interface control layer was formed by increasing the pressure of the rare gas Ar introduced at the time of sputtering to about 6 times the pressure of the first magnetic layer. Peak velocity 9-17 mW, bottom power 4-7.5 mW, bias magnetic field 300 ± 80 Showed good overwrite characteristics.

In the fourth magnetic layer medium, sputtering is performed on a glass substrate.

1st magnetic layer Dy ₂₃ Fe ₆₈ Co ₉ 500 Å

Interface Control Layer SiNx 10Å

2nd magnetic layer Gd ₁₃ Dy ₁₂ Fe ₆₀ Co ₁₅ 1200Å

Third Magnetic Layer Tb ₁₆ Fe ₈₄ 200Å

4th magnetic layer Tb ₃₀ Co ₇₀ 700Å

Ferrimagnetic material and dielectric of the. At this time, the adjacent magnetic layers, including those which have passed through the interface control layer, are bonded to each other by an exchange force. In this medium, flux 11 m / sec, bias magnetic field 200 The laser power was modulated with peak power of 18 mW and bottom power of 7 mW, showing good overwrite characteristics with a C / N ratio of 45 dB.

As the interface control layer, those shown above may be used, including the above.

1. It is formed as a pressure 5 times or more of the sputtering gas pressure normally used for formation of a magnetic layer.

2. A dielectric of nitride (SiN, AlN, or oxide (SiOx, etc.)) is used.

3. The normal magnetic layer is formed by the neutral sputtering method of Ar alone, but at this time, a reactive gas (oxygen, nitrogen) is mixed to form a reactive sputtering method.

4. When rare earth (RE) -transition metal (TM) alloy film is used, the RE composition is 30 at% or more. In this case, the sputtering gas pressure may be a normal value.

5. Use non-magnetic metal (Al, Cu, etc.).

6. A magnetic film whose magnetizing side is in-plane direction is used.

Although the interface control layer can be formed by the above method, as long as the exchange bonding force can be controlled, the method shown here may be sufficient.

As described above, the two-, three- and four-layer media may be provided with an interface control layer which does not essentially contribute to the operation, and therefore may be located at any interface of the magnetic layer.

Although a magneto-optical recording medium capable of being overwritten even without such an initializing magnet has been described, a method of manufacturing such a recording medium will now be described using a four-layer film as an example. As shown in FIG. 94, the SiNx film was formed on the polycarbonate body 2 as the dielectric film 34 by the sputtering apparatus, and then the first layer 35 and the second layer 36 were sequentially sputtered. ), The third layer 37 and the fourth layer 38 are formed, and the protective film 39 is formed last.

In this case, after sputtering film formation, the magnetic domain of the 4th layer 38 which is an initialization layer becomes random.

Therefore, it is necessary to coincide the magnetization direction of the fourth layer 38 in one direction. First, the method shown in FIG. 95ab as the first direction is considered. In the figure, reference numeral 41 denotes an initial magnetic field applying means, and 42 is an adhesive layer.

First, the magnetic field He ?? of coercive force Hc ₄ or more at room temperature of the fourth layer 38 is applied before joining each other to match the magnetization direction of the fourth layer 38. Subsequently, an adhesive layer is formed of an ethoxy adhesive or a hot melt, and the like is bonded together.

In the second method, the coercive forces Hc ₄ (A) and Hc ₄ (B) (A and B are two film-forming substrates bonded to each other) of each of the fourth layers to be bonded to each other are | He (A) | >> | Hc ₄ (A) |> | He ₄ (B) |> | Hc (B) | (He (A) and He (B) have the characteristics of the applicator field of the grass field application means).

Then, after joining such two substrates together, as shown in FIG. 96A, first, the magnetic field applying means 43 applies the magnetic field He (A) exceeding Hc ₄ (A) of the disk with the A surface. Is applied to match the magnetization of the initialization layer on the A plane. Next, as shown in FIG. 96B, a magnetic field He (B) opposite to He (A) that exceeds Hc ₄ (B) and does not exceed Hc ₄ (A) is applied, and an initialization layer on the B surface is applied. Match the magnetization of This method can similarly initialize the disk even if the disk is reversed in the middle as shown in 97ab. FIG. 98 shows the disks joined together in FIG. 97A. After detecting the A side and the B side on the apparatus side of the disks in which the fourth layers of the substrates 40A and 40B are initialized in one direction, the bias magnetic field is changed and the signal processing circuit is changed. After determining that the direction of the recording bit has changed, the final playback signal processing may be executed.

Although the above-mentioned manufacturing method has been described in the case of a four-layer film, the three-layer film and the two-layer film can be executed by the same method.

Industrial availability

The method of manufacturing the magneto-optical recording medium and the magneto-optical recording medium according to the present invention can be widely used as a method of manufacturing the recording medium and the recording medium which can record audio information, visual information and data information at high density and high speed.

Claims (12)

A first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in an exchange force, wherein Tc ₁ &lt; Tc ₂ , Tc ₁ : Curie temperature of the first magnetic layer, Tc ₂ : satisfies the Curie temperature of the second magnetic layer, and at room temperature, Hc ₁ > Hw ₁ , Hc ₂ > Hw ₂ , Hc ₁ : coercive force of the first magnetic layer Hc ₂ : coercive force of the second magnetic layer, Hw ₁ : first The magnetism of the inverse magnetic field due to the exchange force of the magnetic layer, Hw ₂ : The magnetism of the inverse magnetic field due to the exchange force of the second magnetic layer is satisfied, the second magnetic layer is not magnetized inverted during recording and reproduction Record carrier. A first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in an exchange force, and a third magnetic layer provided in the second magnetic layer and exchanged with the second magnetic layer. Tc ₁ &lt; Tc ₂ &lt; Tc ₃ , Tc ₁ : Curie temperature of the first magnetic layer, Tc ₂ : Curie temperature of the second magnetic layer, Tc ₃ : Curie temperature of the third magnetic layer, and Hc ₁ at room temperature. > Hw _{1 (2)} , Hc ₃ > Hw _{3 (2)} is satisfied, and Hc ₂ <Hw _{2 (3)} -Hw _{2 (1)} is different from room temperature to Tc ₁ except that Hc ₁ : first magnetic layer The coercive force of Hc ₂ : the coercive force of the second magnetic layer, Hw ₃ : the coercive force of the third magnetic layer, Hwi (j): the amount of inverse magnetic field inversion of the inverted magnetic field of the i layer by the exchange coupling force acting between the j layer and the i layer Magneto-optical recording medium, characterized in that there exists a temperature that satisfies. A first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in exchange force, a third magnetic layer provided in the second magnetic layer and exchanged with the second magnetic layer, A fourth magnetic layer provided on the third magnetic layer and coupled to the third magnetic layer by an exchange force, wherein Tc ₁ <Tc ₂ , Tc ₃ <Tc ₂ , Tc ₁ <Tc ₄ , Tc ₃ <Tc ₄ , and Tc ₁ : Curie temperature of the first magnetic layer, Tc ₂ : Curie temperature of the second magnetic layer, Tc ₃ : Curie temperature of the third magnetic layer, Tc ₄ : Curie temperature of the fourth magnetic layer, and Hc ₁ > Hw _{1 (2 ), Hc 4> Hc 2 <} Hw 2 (3) -Hw 2 (1), Hc 3 <Hw 3 among the satisfying Hw _{4 (3),} and also at room temperature to Tc ₁ and Tc ₃ low temperature solution of _{( 4)} -Hw _{3 (2) where} Hc ₁ : coercive force of the first magnetic layer, Hc ₂ : coercive force of the second magnetic layer, Hw ₃ : coercive force of the third magnetic layer, Hc ₄ : coercive force of the fourth magnetic layer, Hwi (j) : Exchange between the j-th layer and the i-th layer The magneto-optical recording medium, characterized in that the temperature that satisfies the soup teuryang the switching magnetic field of the i-layer is present by the force. The magneto-optical recording medium according to claim 3, wherein Tc ₂ ≤ Tc ₄ . A first magnetic layer having perpendicular magnetic anisotropy, a second magnetic layer provided in the first magnetic layer and coupled to the first magnetic layer in an exchange force, and a third magnetic layer provided in the second magnetic layer and exchanged with the second magnetic layer. Tc ₁ <Tc ₂ , Tc ₃ <Tc ₂ , Tc ₁ : Curie temperature of the first magnetic layer, Tc ₂ : Curie temperature of the second magnetic layer, Tc ₃ : Curie temperature of the third magnetic layer, and room temperature in _{Hc 1> Hw 1 (2)} , Hc 3> Hc between the Tc to meet Hw _{3 (2),} and further at room temperature for _{2 <Hw 2 (3) -Hw} 2 (1) However, Hc _1: the Coercive force of one magnetic layer, Hc ₂ : Coercive force of second magnetic layer, Hc ₃ : Coercive force of third magnetic layer, Hwi (j): Inverted magnetic field of layer i by exchange coupling force acting between j and i layers A magneto-optical recording medium, characterized in that there is a temperature that satisfies the amount of the ft. The magneto-optical recording medium according to claim 5, wherein Tc ₃ ≤ Tc ₂ A fourth magnetic layer provided between the second magnetic layer and the third magnetic layer, the fourth magnetic layer being coupled to the second magnetic layer and the third magnetic layer by an exchange force, respectively; and Tc ₄ <Tc ₃ <Tc ₂ , Tc ₁ <Tc ₂ However, Tc ₄ : satisfies the Curie temperature of the fourth magnetic layer, and satisfies Hc ₁ > Hw _{1 (2)} and Hc ₃ > Hw _{3 (4)} at room temperature, and Hc ₂ at room temperature up to Tc ₄ . <Hw _{2 (4)} -Hw _{2 (1)} , Hc ₄ <Hw _{4 (3)} -Hw _{4 (2) The} temperature to satisfy each of the claims, characterized in that the magneto-optical Record carrier. The magneto-optical recording medium according to any one of claims 1 to 7, wherein an interface control layer is provided at the interface between the magnetic layers to control the exchange force. In a method of manufacturing an over-writable magneto-optical recording medium having an initialization layer which does not invert magnetization during recording and reproducing, the magnetic field applying direction of a substrate having the initialization layer in an atmosphere in which a magnetic field is applied in one direction by a magnetic field applying means. And the substrate surface perpendicular to each other, and the initialization layer is initialized in advance. In a method of manufacturing an over-writable magneto-optical recording medium having an initialization layer which does not invert magnetization during recording and reproducing, the magnetic field applying direction of a substrate having the initialization layer in an atmosphere in which a magnetic field is applied in one direction by a magnetic field applying means. And the substrate surface so as to be perpendicular to each other, and the initialization layer is initialized in advance and then bonded to each other. In the method of manufacturing an over-writable magneto-optical recording medium having an initialization layer which does not invert magnetization during recording and reproducing, the substrates bonded to each other in an atmosphere in which magnetic fields are applied in one direction after the substrates having the initialization layers are bonded to each other are bonded to each other. And a direction in which the application direction and the substrate surface are perpendicular to each other. In the method of manufacturing an over-writable magneto-optical recording medium having an initialization layer which does not invert magnetization during recording and reproducing, the coercivity of one initialization layer is greater than that after joining two substrates each having an initialization layer having different coercivity. A magnetic field is applied vertically to the substrate, and then the magnetic field in the opposite direction to the magnetic field is applied perpendicularly to the substrate, wherein the one initialization layer is smaller than the coercive force and larger than the coercive force of the other initialization layer. Method of manufacturing magnetic recording medium.