JP3380621B2 - Magneto-optical recording medium reproducing method, magneto-optical recording medium and magneto-optical recording and reproducing apparatus using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium for recording / reproducing by modulating light and / or magnetic field, a reproducing method thereof, and a magneto-optical recording / reproducing apparatus using the same.

[0002]

2. Description of the Related Art Magneto-optical recording is optical recording capable of recording, reproducing and erasing information. Recording / reproduction of the magneto-optical disk currently used is limited to the spot diameter of light. Various methods such as partial response, magnetic super-resolution, optical super-resolution, and crosstalk cancellation of two-dimensional information have been considered for reproducing a minute magnetic domain having a size equal to or smaller than half the spot diameter. However, none of the methods is a method of reproducing a minute magnetic domain by increasing the resolution of a light spot, and is not a method of essentially improving the signal amount.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to substantially improve the reproduction signal amount of the above-mentioned minute magnetic domain.

[0004]

SUMMARY OF THE INVENTION The above problem is that in a disc using an exchange-coupling three-layer magnetic film as a recording film, the magnetic domain of the recording layer is transferred to a reproducing layer which is heated in a light spot and has a reduced coercive force. This can be solved by expanding this with a reproducing magnetic field.

The present invention is a reproducing method of a magneto-optical recording medium for reproducing information by irradiating a magneto-optical recording medium having at least a recording layer and a reproducing layer on a substrate with light to detect a signal of the reproducing layer. , The coercive force of the reproducing layer is reduced by the irradiation of the light to transfer the magnetic domain of the recording layer to the reproducing layer, and a magnetic field having a magnetic field strength not less than the coercive force of the reproducing layer and not more than the coercive force of the reproducing layer is applied. A reproducing method of a magneto-optical recording medium is characterized in that the magnetic domain transferred to the reproducing layer by being applied to the magneto-optical recording medium is enlarged and then reduced.

The present invention also provides a magneto-optical recording medium in which at least a first dielectric film, then first, second and third magnetic layers and a protective film are sequentially laminated on a substrate, wherein the first magnetic layer is the same. Is a rare earth transition metal having a compensation temperature above room temperature, the Curie temperature of which is lower than the recording temperature of the minute magnetic domain, and the magnetic domain of the third magnetic layer is transferred by irradiation of reproducing light. While irradiating light during reproduction, a magnetic field having a magnetic field strength not less than the coercive force of the magnetic wall of the reproducing layer and not more than the coercive force of the reproducing layer is applied to the magneto-optical recording medium to enlarge and then reduce the magnetic domain transferred to the reproducing layer. A magneto-optical recording medium is characterized in that information is reproduced by doing so.

Further, the present invention uses a magneto-optical recording medium in which at least a first dielectric film, then first, second and third magnetic layers and a protective film are sequentially laminated on a substrate, and the first magnetic film is used. By irradiating the laser beam from the layer side and utilizing the reflected light to receive the magneto-optical effect, in the device for reproducing information, the information reproducing means is arranged on the substrate side and the magnetic field generating means is arranged on the film side. A magneto-optical recording / reproducing apparatus having a unit for modulating and reproducing a magnetic field and / or reproducing light at the time of reproducing.

Furthermore, the present invention relates to a magneto-optical recording medium which reproduces information by irradiating a magneto-optical recording medium having at least a recording layer and a reproducing layer on a substrate with light to detect a signal of the reproducing layer. In the reproducing method, the coercive force of the reproducing layer is lowered by the irradiation of the light to transfer the magnetic domain of the recording layer to the reproducing layer, and the magnetic field in the same direction as the magnetic domain of the recording layer is applied and transferred to the reproducing layer. A reproducing method of a magneto-optical recording medium is characterized in that after the magnetic domain is expanded, the magnetic domain expanded in the reproducing layer is contracted by applying a magnetic field in a direction opposite to the magnetic domain of the recording layer.

For example, as shown in FIG. 1, (1) there is a recording magnetic domain 16 in a reproduction spot, and an expansion magnetic field 7 is generated by a recording / reproducing magnetic field generating device so that a transfer expansion magnetic domain 17 appears and a signal increases. Next, the magnetic field 7 is switched to the erasing direction in order to reproduce the adjacent magnetic domain 18. As in (2), the transfer expansion magnetic domain 17 disappears and the reproduction signal becomes zero. When the magnetic field 7 is reversed as in (3) in order to reproduce the recording magnetic domain 18 again, the transfer enlarged magnetic domain 19 appears. When the magnetic field is reversed again as in (4), the transfer expansion magnetic domain disappears. 2 to 8 show how the magnetization state of the recording film changes.
In the magnetization state, the white arrow indicates the overall magnetic moment, and the black arrow indicates the magnetic moment of the transition metal. After magnetization, the magnetized state is as shown in FIG. Next, the magnetization state after recording is shown in FIG. When this is passed through an initialization magnet and an initialization magnetic field 8 is applied, the magnetization state becomes as shown in FIG. 4, and the recording magnetic domain cannot be seen from the substrate 6 side. Then, by irradiating a laser beam and applying a transfer magnetic field 7, the recording magnetic domain is transferred as shown in FIG. Further, when the magnetic field 7 is increased as shown in FIG. 6, only the magnetic domains of the magnetic layers 3 and 4 (the magnetic domains transferred at the time of reproduction) have a small coercive force and are expanded, and a large reproduced signal can be obtained. In order to read the next magnetic domain, it is necessary to erase the magnetic domain transferred during reproduction. This is because the transferred magnetic domain is reduced by applying the magnetic field 7 in the opposite direction as shown in FIG. 7, and when the magnetic field is further increased, the magnetic domain transferred at the time of reproduction is completely erased as shown in FIG.
FIG. 9 is a block diagram of an apparatus (optical magnetic field modulation magneto-optical recording / reproducing apparatus). In the figure, 9 is a magneto-optical disk, 10 is a flying magnetic head, 11 is a flying magnetic head drive apparatus, 12 is a recording / reproducing control apparatus, Reference numeral 13 is an optical head, 14 is a spindle motor, and 15 is an initialization magnet. As the third magnetic film, a rare earth transition metal alloy, which is excellent in the stability of recording in the small magnetic domain, is preferable. In particular, a composition in which the magnetic moment of the rare earth metal is preferential at room temperature is preferable.

In order to prevent the enlarged magnetic domain from being too widened to be erased, the compensation temperature of the intermediate layer may be set appropriately lower than the center temperature of the reproducing light spot. Further, the reproducing magnetic field strength needs to be set to be not less than the domain wall coercive force of the reproducing layer and not more than the coercive force near the center temperature of the light spot at the time of reproducing. Further, there is a method of detecting the change in the signal amount as a differential signal in addition to the signal amount improving operation by enlarging the minute magnetic domain. Further, in order to record the minute magnetic domain, it is necessary to set the Curie temperature of the second magnetic layer lower than the minute magnetic domain recording temperature.

[0011]

By the above means, the signal-to-noise ratio S / N is greatly improved. In addition, since reproduction crosstalk between adjacent magnetic domains is significantly improved, both track density and mark pitch can be reduced, so that high density recording becomes possible. S / N can be further increased by making the reproduction light into a pulse shape.

[0012]

Example (Example 1) A sample was prepared by a sputtering method. The creation conditions are as follows. The ultimate vacuum is 5 × 10 ⁻⁷ Torr or less, Ar is used as the sputtering gas, the gas pressure is 5 mTorr, the input power is 500 W, and the sputtering rate is 0.1 to 0.2 n.
m / sec. Nitride is used for the dielectric film, and the first magnetic layer has a Curie temperature of 350 ° C. and a compensation temperature of Gd of room temperature or less.
TbFeCo alloy 40nm, Curie temperature 12 in the second magnetic layer
A 20 nm layer of GdDyFe alloy having a temperature of 0 ° and a compensation temperature of 60 ° was laminated.
The third magnetic layer has a compensation temperature of 170 degrees and a Curie temperature of 2
40 degree TbFeCo of 40 nm was laminated. A sample servo substrate with a track pitch of 1.6 μm was used as the substrate.

The modulating magnetic field used for recording was 200 Oe, and the linear velocity of the disk was 2.1 m / sec. The magnetic domain recorded at a modulation frequency of 2.5 MHz was reproduced by modulating the optical pulse and the magnetic field at 5 MHz with the timing of the sample clock. When the reproducing magnetic field was about 100 Oe, only the silver magnetic domain was transferred and expanded, and when the reproducing magnetic field was set to about 150 Oe, the entire reproducing layer was inverted. In addition, the reproducing magnetic field is about -100
When Oe was applied, the reproducing magnetic domain was erased. Regeneration has a wavelength of 6
The S / N was improved by 3 dB as compared with the case where this was not performed by modulating the reproduction light and the magnetic field at 80 nm.
When this signal change was reproduced through a differentiating circuit, the S / N was further improved by 1 dB.

[0014]

According to the present invention, when a recording signal is reproduced by modulating light and a magnetic field, it is possible to enlarge a minute magnetic domain to essentially increase the signal amount, so that a large signal-to-noise ratio can be obtained. This can be improved, and since the magnetic domains that have expanded immediately after reproduction can be erased, reproduction crosstalk can be greatly improved.

[Brief description of drawings]

FIG. 1 is a principle diagram of magnetic field modulation reproduction according to the present invention.

FIG. 2 is a state diagram of magnetization after magnetization.

FIG. 3 is a state diagram of magnetization after recording.

FIG. 4 is a state diagram of magnetization after passing through an initialization magnet.

FIG. 5 is a state diagram of magnetization when a recording magnetic domain is transferred during reproduction.

FIG. 6 is a state diagram of magnetization when a magnetic domain transferred during reproduction is enlarged.

FIG. 7 is a state diagram of magnetization when erasing a magnetic domain transferred during reproduction.

FIG. 8 is a state diagram of magnetization when a transfer magnetic domain is completely erased during reproduction.

FIG. 9 is a block diagram of a magneto-optical field modulation magneto-optical recording / reproducing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Protective film, 2 ... 3rd magnetic film, 3 ... 2nd magnetic film, 4 ... 1st magnetic film, 5 ... Dielectric film, 6 ... Substrate, 7 ... Magnetic field by a recording / reproducing magnetic field generator, 8 ... Initialization Magnetic field, 9 ... Magneto-optical disk, 10 ... Levitating magnetic head, 11 ... Levitating magnetic head drive device, 12 ... Recording / reproducing control device, 13 ... Optical head,
14 ... Spindle motor, 15 ... Initializing magnet, 16 ...
Magnetic domains which are transferred and expanded and reproduced, 17 ... Magnetic domains which are transferred and expanded and reproduced, 18 ... Adjacent magnetic domains, 19 ... Magnetic domains which are transferred and expanded and reproduced.

Claims (6)

(57) [Claims] 1. A reproducing method of a magneto-optical recording medium, wherein information is reproduced by irradiating a magneto-optical recording medium having at least a recording layer and a reproducing layer on a substrate with light and detecting a signal of the reproducing layer, The magnetic field of the recording layer is transferred to the reproducing layer by lowering the coercive force of the reproducing layer by irradiation of light, and a magnetic field having a magnetic field strength not less than the coercive force of the magnetic wall of the reproducing layer and not more than the coercive force of the reproducing layer is magneto-optical. A reproducing method of a magneto-optical recording medium, comprising enlarging a magnetic domain applied to a recording medium and transferred to the reproducing layer, and then reducing and eliminating the magnetic domain. 2. The reproducing method of the magneto-optical recording medium according to claim 1, wherein the expansion and contraction of the transfer magnetic domain is performed within the spot of the light. 3. The reproducing method of the magneto-optical recording medium according to claim 2, wherein the magnetic field applied when expanding the magnetic domain is in the same direction as the recording magnetic domain. 4. The method of reproducing a magneto-optical recording medium according to claim 3, further comprising applying a magnetic field in a direction opposite to the recording magnetic domain when the magnetic domain expanded in the reproducing layer is reduced. 5. The method of reproducing a magneto-optical recording medium according to claim 1, further comprising differentially detecting the reproduction signal. 6. A reproducing method of a magneto-optical recording medium, which reproduces information by irradiating a magneto-optical recording medium having at least a recording layer and a reproducing layer on a substrate with light to detect a signal of the reproducing layer, wherein After the coercive force of the reproducing layer is lowered by irradiation of light, the magnetic domain of the recording layer is transferred to the reproducing layer, and a magnetic field in the same direction as the magnetic domain of the recording layer is applied to expand the magnetic domain transferred to the reproducing layer. A reproducing method for a magneto-optical recording medium, characterized in that the magnetic domain expanded in the reproducing layer is erased by applying a magnetic field in a direction opposite to the magnetic domain of the recording layer.