JPH0636367A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To control the exchange power between 1st and 2nd magnetic layers and to enhance recording and reproducing characteristics and productivity by forming a magnetic layer for controlling exchange power with a rare earth metal-transition metal alloy in which the magnetization of the sub-lattices of the rare earth metal is predominant. CONSTITUTION:This magneto-optical recording medium has a magnetic layer for controlling exchange power formed between the 1st and 2nd magnetic layers 13, 14 with a rare earth metal-transition metal alloy in which the magnetization of the sub-lattices of the rare earth metal is predominant. The saturation magnetization of the alloy at room temp. is 200-550emu/cm<3>. The thickness of the magnetic layer for controlling exchange power is <=400Angstrom , the rare earth metal is essentially based on Gd and the transition metal includes at least one of Fe and Co. The exchange power between the 1st and 2nd magnetic layers can be effectively controlled and recording and reproducing characteristics and productivity can be enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an overwritable magneto-optical recording medium, and more particularly to improvement of recording / reproducing characteristics and productivity.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a conventional magneto-optical recording medium disclosed in, for example, Japanese Patent Laid-Open No. 3-219449, and FIG. 5 shows a recording device for recording on the magneto-optical recording medium shown in FIG. It is a perspective view which shows an outline. In the figure, 1 is a substrate, 2
Is formed on the substrate 1 and has a perpendicular magnetic anisotropy.
The magnetic layers 3 are provided on the first magnetic layer 2 and are exchanged with each other to make the first
The second magnetic layer 4 coupled to the magnetic layer 2 is the third magnetic layer 5
Is a fourth magnetic layer, and the recording medium 10 is composed of these 1 to 5. 6 is a drive motor for rotationally driving the recording medium 10,
Reference numeral 7 is a semiconductor laser that emits a laser beam 8, and 9 is a laser beam 8 that is emitted from the semiconductor laser 7 and is focused on the recording medium 1.
A condenser lens that is incident on 0 and a bias magnet 11 that generates a bias magnetic field.

Next, the overwrite operation of the conventional magneto-optical recording medium having the above structure will be described. First, after the recording medium 10 is formed, the second to fourth magnetic layers 3, 4,
The transition metal sublattice magnetic moment of No. 5 is first oriented downward only once, and the bias magnetic field is
1 raises upward. In FIG. 6, a white arrow indicates magnetization, an arrow in the white arrow or an arrow shown alone indicates a transition metal sublattice magnetic moment, a shaded portion indicates a state in which domain walls are generated between the magnetic layers, and a horizontal bar indicates The states in which the temperature is raised above the Curie temperature and the ferromagnetism is lost are shown.

In FIG. 6A, first, the output of the semiconductor laser 7 is made higher than that at the time of reproduction, and each magnetic layer in the focused spot of the laser beam 8 is heated to near the Curie temperature of the first magnetic layer 2. Then, the sub-lattice magnetization direction of the second magnetic layer 3 does not change, the sub-lattice magnetization of the second magnetic layer 3 is transferred to the first magnetic layer 2, and the sub-lattice magnetization of the first magnetic layer 2 faces downward. At this time, the third and fourth magnetic layers 4 and 5 do not particularly contribute to the operation, and even if the magnetization of the third magnetic layer 4 disappears, the third magnetic layer 4 and 5 again move in the same direction by the exchange force with the fourth magnetic layer 5. Magnetized to state "0", a low power process.

Further, in FIG. 6B, when the temperature is raised to near the Curie temperature of the second magnetic layer 3 in the same manner as in the low power process, the magnetizations of the first and third magnetic layers 2 and 4 disappear. However, the sublattice magnetization direction of the fourth magnetic layer 5 does not change. Then, the sublattice magnetization of the second magnetic layer 3 is directed upward by the bias magnetic field without receiving the exchange force from the first and third magnetic layers 2 and 4. Next, when the temperature is lowered from the Curie temperature of the first magnetic layer 2, the sub-lattice magnetization of the second magnetic layer 3 is transferred to the first magnetic layer 2, and the sub-lattice magnetization of the first magnetic layer 2 is directed upward. When the temperature is lowered below the Curie temperature of the third magnetic layer 4, the sub-lattice magnetization of the third magnetic layer 4 is aligned with the fourth magnetic layer 5 and faces downward. As the temperature further decreases, the sub-lattice magnetization of the second magnetic layer 3 is aligned downward with the sub-lattice magnetization of the fourth magnetic layer 5 through the third magnetic layer 4, and the state "1", that is, the high power process is performed. . As described above, overwriting becomes possible by modulating the recording laser intensity into at least two values.

FIG. 7 is a block diagram of a conventional magneto-optical recording medium having a magnetic layer for controlling exchange force, as shown in Japanese Patent Laid-Open No. 121103/1990, and the recording medium 10 is as shown in the figure. And between the first magnetic layer 2 and the second magnetic layer 3,
Fifth magnetic layer 1 made of rare earth-dominant metal film and controlling exchange force
Have two. When the optical modulation direct overwrite is performed on the recording medium 20, the direction of the sub-lattice magnetization of the second magnetic layer 3 must be aligned in one direction in advance, so that the bias magnet 11 shown in FIG. Others,
An external auxiliary magnetic field device 13 for generating a magnetic field strength of several KOe is required for the initialization process.

[0007]

The conventional magneto-optical recording medium is configured as described above, and at a temperature at which the first magnetic layer 2 is aligned with the direction of the transition metal sublattice magnetization of the second magnetic layer 3,
Since the exchange force between the first magnetic layer 2 and the second magnetic layer 3 is strong, the external auxiliary magnetic field device 13 is used during the initialization process near room temperature.
Therefore, it is necessary to weaken the exchange force, which complicates the device, and in order to weaken the exchange force, the first and second
For example, because the magnetic layers 2 and 3 must be made thicker, the margin for creating the film thicknesses of the first and second magnetic layers 2 and 3 is narrowed, and stable production is difficult. There was a problem.

The present invention has been made in order to solve the above-mentioned problems, and the first aspect of the present invention does not complicate the apparatus.
An object of the present invention is to provide a magneto-optical recording medium capable of effectively controlling the exchange force between the magnetic layer and the second magnetic layer to improve the recording / reproducing characteristics and the productivity. is there.

[0009]

[Means for Solving the Problems] Claim 1 according to the present invention
Is a rare earth-transition metal alloy having a saturation magnetization at room temperature of 200 to 550 emu / cm ³ between the first magnetic layer and the second magnetic layer and having a rare earth sublattice magnetization dominant. The magneto-optical recording medium according to claim 2 is the magneto-optical recording medium according to claim 1, wherein the magnetic layer for exchange force control has a thickness of 400 angstroms or less, and the rare earth metal is Cd as a main component. At least Fe for the transition metal
Alternatively, either one of Co and Co is included.

[0010]

The magnetic layer for controlling the exchange force of the magneto-optical recording medium according to the present invention effectively controls the exchange force between the first magnetic layer and the second magnetic layer.

[0011]

【Example】

Example 1. Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing a magneto-optical recording medium according to Embodiment 1 of the present invention. In the figure, 11 is a bias magnet for generating a bias magnetic field, 12 is a glass or plastic transparent substrate, and 13 to 16 are exchange-coupled first magnetic layer, second magnetic layer, third magnetic layer and fourth magnetic layer. , 17 is a fifth magnetic layer which is provided between the first magnetic layer 13 and the second magnetic layer 14 and controls the exchange force between the magnetic layers 13 and 14, and these magnetic layers 13 to 17 are transparent. Board 1
The recording medium 20 is formed by sequentially depositing films on the film 2 by sputtering. Although not shown, the magnetic layer thus formed is sandwiched from both sides by the dielectric layer and the protective layer.

The details of each of the above components will be described below. Substrate 12: PC substrate with 1.2 mmt groove Dielectric layer: SiN _x First magnetic layer 13: TbFeCo ternary amorphous alloy Tb ₂₄ Fe ₇₂ Co ₄ film thickness: 300 angstrom Fifth magnetic layer 17: GdFeCo ternary non Crystalline alloy Gd ₃₀ Fe ₄₉ Co ₂₁ Film thickness: 150 Å [Saturation magnetization Ms = 456 emu / cm ³ ] Second magnetic layer 14: DyFeCo ternary amorphous alloy Dy ₂₅ Fe ₄₅ Co ₃₀ Film thickness: 500 angstrom Third Magnetic layer 15: TbFe binary amorphous alloy Tb ₁₈ Fe ₈₄ film thickness: 200 angstrom Fourth magnetic layer 16: TbCo binary binary amorphous alloy Tb ₃₀ Co ₇₀ film thickness: 400 angstrom protective layer: SiN _x

Using the recording medium 20 configured as described above, a signal having a bit length of 2 μm, a signal having a bit length of 0.76 μm, a linear velocity of 11 m / sec, an applied magnetic field of 300 Oe, and light beam intensities of 13 mW and 5 mW are used. As a result of performing optical modulation and confirming the operation of the optical modulation direct overwrite, a CN ratio of 47 dB was obtained at an erasing ratio of 45 dB or more. FIG. 2 shows the saturation magnetization Ms dependence of the CN ratio at a bit length of 0.76 μm (recording frequency 4.93 MHz, linear velocity 7.5 m / sec) when the saturation magnetization Ms of the fifth magnetic layer 17 is changed. As is clear from the figure, when the saturation magnetization Ms of the fifth magnetic layer 17 is 200 to 550 emu / cm ³ ,
A good CN ratio of 45 dB or more was obtained. At this time, the film thickness of the fifth magnetic layer 17 was 200 Å. That is, 200 emu / cm ³ is applied to the fifth magnetic layer 17.
When the following saturation magnetization Ms is used, the exchange force between the first and second magnetic layers 13 and 14 cannot be sufficiently controlled and the noise level rises, and the saturation magnetization Ms of 550 emu / cm ³ or more is used. In the case of using No. 1, the CN ratio is deteriorated because the erasing ratio after the optical modulation direct overwrite recording is lowered due to the lack of exchange power.

FIG. 3 shows the first and second magnetic layers 13 and 14.
The dependence of the exchange force σw at room temperature during this period on the saturation magnetization Ms of the fifth magnetic layer 17 is shown. As shown in the figure, the exchange force σw decreases as the saturation magnetization Ms increases, and the fifth magnetic layer 17
The film thickness decreases as the film thickness increases. This is explained by the reduction of the perpendicular magnetic anisotropy energy of the fifth magnetic layer 17. From this, the exchange force σw at room temperature between the first and second magnetic layers 13 and 14 is that a high saturation magnetization film is used for the fifth magnetic layer 17,
And it is clear that the film thickness is reduced by making it thinner. The exchange force σw can be reduced by increasing the film thickness even with a low saturation magnetization film, but the recording sensitivity is deteriorated by increasing the total film thickness. For example, when a film of about 200 emu / cm ³ is used for the fifth magnetic layer 17, it is necessary to increase the thickness of the fifth magnetic layer 17 to control the exchange force, but 400 angstrom is a practical problem in recording sensitivity. There is no upper limit film thickness. Therefore, it is preferable to use the high saturation magnetization film because the thickness of the fifth magnetic film 17 can be made thinner and the recording sensitivity is improved. From the above, considering the saturation magnetization Ms and the film thickness t, the fifth magnetic layer 17 is preferably Ms × t <10 ⁻³ emu / cm ³ .

[0015]

As described above, according to the present invention, the saturation magnetization at room temperature is 200 between the first magnetic layer and the second magnetic layer.
A magnetic layer for controlling the exchange force, which is made of a rare earth-transition metal alloy in which the rare earth sublattice magnetization is dominant at 550 emu / cm ³ , and the thickness of the magnetic layer for controlling the exchange force is 400 angstroms or less, and the rare earth When the metal is Cd as a main component and the transition metal contains at least one of Fe and Co, the exchange force between the first magnetic layer and the second magnetic layer is effectively controlled, and recording, It is possible to provide a magneto-optical recording medium capable of improving reproduction characteristics and productivity.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a magneto-optical recording medium according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the dependency of the CN ratio on the saturation magnetization Ms when the saturation magnetization Ms of the fifth magnetic layer is changed.

FIG. 3 is a characteristic diagram showing the dependency of the exchange force σw between the first and second magnetic layers at room temperature on the saturation magnetization Ms of the fifth magnetic layer.

FIG. 4 is a block diagram showing a conventional magneto-optical recording medium.

5 is a perspective view showing an outline of a recording device for recording on the magneto-optical recording medium shown in FIG.

FIG. 6 is a schematic diagram for explaining a recording operation on the magneto-optical recording medium shown in FIG.

FIG. 7 is a block diagram showing a conventional magneto-optical recording medium having a magnetic layer for controlling exchange force.

[Explanation of symbols]

 1, 12 Substrate 2, 13 First magnetic layer 3, 14 Second magnetic layer 4, 15 Third magnetic layer 5, 16 Fourth magnetic layer 7 Semiconductor laser 8 Laser light 9 Condensing lens 10, 20 Recording medium 11 Bias magnet 17 Fifth magnetic layer (magnetic layer for exchange force adjustment)

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[Procedure amendment]

[Submission date] November 10, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 2

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

FIG. 7 is a block diagram of a conventional magneto-optical recording medium having a magnetic layer for controlling exchange force, as shown in Japanese Patent Laid-Open No. 121103/1990, and the recording medium 10 is as shown in the figure. And between the first magnetic layer 2 and the second magnetic layer 3,
Fifth magnetic layer 1 made of rare earth-dominant metal film and controlling exchange force
Have two. When the optical modulation direct overwrite is performed on the recording medium 20, the direction of the sub-lattice magnetization of the second magnetic layer 3 must be aligned in one direction in advance, so that the bias magnet 11 shown in FIG. Others,
An external auxiliary magnetic field device 13 that generates a magnetic field strength of several kOe is required for the initialization process.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

[0009]

[Means for Solving the Problems] Claim 1 according to the present invention
Is a rare earth-transition metal alloy having a saturation magnetization at room temperature of 200 to 550 emu / cm ³ between the first magnetic layer and the second magnetic layer and having a rare earth sublattice magnetization dominant. In the magneto-optical recording medium according to claim 2, the magnetic layer for controlling exchange force has a thickness of 400 angstroms or less, and the rare earth metal contains Gd as a main component. At least Fe for the transition metal
Alternatively, either one of Co and Co is included.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

The details of each of the above components will be described below. Substrate 12: PC substrate with 1.2 mmt groove Dielectric layer: SiN _x First magnetic layer 13: TbFeCo ternary amorphous alloy Tb ₂₄ Fe ₇₂ Co ₄ film thickness: 300 angstrom Fifth magnetic layer 17: GdFeCo ternary non Crystalline alloy Gd ₃₀ Fe ₄₉ Co ₂₁ Film thickness: 150 Å [Saturation magnetization Ms = 456 emu / cm ³ ] Second magnetic layer 14: DyFeCo ternary amorphous alloy Dy ₂₅ Fe ₄₅ Co ₃₀ Film thickness: 500 angstrom Third Magnetic layer 15: TbFe binary amorphous alloy Tb ₁₆ Fe ₈₄ Film thickness: 200 angstrom Fourth magnetic layer 16: TbCo binary binary amorphous alloy Tb ₃₀ Co ₇₀ Film thickness: 400 angstrom Protective layer: SiN _X

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

FIG. 3 shows the first and second magnetic layers 13 and 14.
Interfacial domain wall energy σ that determines the exchange force at room temperature between
The saturation magnetization M of the fifth magnetic layer 17 having w (hereinafter, exchange force σw)
Shows s dependency. As shown in the figure, the exchange force σw decreases as the saturation magnetization Ms increases, and also decreases as the thickness of the fifth magnetic layer 17 increases. This is explained by the reduction of the perpendicular magnetic anisotropy energy of the fifth magnetic layer 17. From this, the exchange force σw between the first and second magnetic layers 13 and 14 at room temperature
It is the use of a high saturation magnetization film to a fifth magnetic layer 17, and it is clear that reduced by thicker film thickness. The exchange force σw can be reduced by increasing the film thickness even with a low saturation magnetization film, but the recording sensitivity is deteriorated by increasing the total film thickness. For example,
When a film of about 200 emu / cm ³ is used for the fifth magnetic layer 17, it is necessary to increase the thickness of the fifth magnetic layer 17 to control the exchange force, but 400 angstrom is practically no problem in recording sensitivity. This is the upper limit film thickness. Therefore,
It is preferable to use a high saturation magnetization film because the thickness of the fifth magnetic film 17 can be made thinner and the recording sensitivity is improved. From the above,
Considering the saturation magnetization Ms and the film thickness t, the fifth magnetic layer 17 preferably has Ms × t <10 ⁻³ emu / cm ³ .

[Procedure correction 6]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

[0015]

As described above, according to the present invention, the saturation magnetization at room temperature is 200 between the first magnetic layer and the second magnetic layer.
A magnetic layer for controlling the exchange force, which is made of a rare earth-transition metal alloy in which the rare earth sublattice magnetization is dominant at 550 emu / cm ³ , and the thickness of the magnetic layer for controlling the exchange force is 400 angstroms or less, and the rare earth The metal is Gd as a main component, and the transition metal contains at least one of Fe and Co to effectively control the exchange force between the first magnetic layer and the second magnetic layer for recording, It is possible to provide a magneto-optical recording medium capable of improving reproduction characteristics and productivity.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsuya Fukami 8-1-1 Tsukaguchihonmachi, Amagasaki City Mitsubishi Electric Corporation Material Device Research Center (72) Inventor Yuji Kawano 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Electric Device Co., Ltd. Material Device Research Center

Claims (2)

[Claims] 1. A first magnetic layer having perpendicular magnetic anisotropy,
A second magnetic layer provided on the first magnetic layer and coupled to the first magnetic layer by exchange force, and a saturation magnetization at room temperature of 200 to 200 provided between the first magnetic layer and the second magnetic layer. 550em
A magneto-optical recording medium comprising a magnetic layer for controlling exchange force, which is made of a rare earth-transition metal alloy having a rare earth sublattice magnetization predominant at u / cm ³ . 2. The film thickness of the magnetic layer for controlling the exchange force is 400 angstroms or less, the rare earth metal is Cd as a main component, and the transition metal contains at least one of Fe and Co. The magneto-optical recording medium according to claim 1.