JPH087350A - Magneto-optical recording medium and magneto-optical recording and reproducing apparatus - Google Patents

Abstract

PURPOSE:To essentially improve amount of reproduced signal of a fine magnetic domain by transferring a magnetic domain of a recording layer to a reproducing layer where a coercive force is lowered because the layer is heated within an optical spot and then enlarging such magnetic domain with the reproduced magnetic field. CONSTITUTION:A recording magnetic domain 16 exists within a reproduced spot, a transferred and enlarged magnetic domain 17 appears when the enlarged magnetic field 7 is generated by a recording and reproduced magnetic field generator and thereby a signal is increased. Next, the magnetic field 7 is changed to the deleting direction to reproduce the adjacent magnetic domain 18. Thereby, the magnetic domain 17 disappears and the reproduced signal becomes zero. When the magnetic field is inverted to reproduce again the recording magnetic domain 18, the transferred enlarged magnetic domain 19 appears. When the magnetic field 7 is inverted again, the transferred and enlarged magnetic domain disappears. The compensating temperature of the intermediate layer is adequately set lower than the temperature at the center thereof to prevent that the enlarged magnetic domain is too widened to be deleted. Moreover, intensity of reproduced magnetic field must be set higher than the anti-magnetic force of magnetic wall but is lower than the coercive force of the reproducing layer at the temperature near the center temperature.

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 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. For example, as shown in FIG. 1, (1) there is a recording magnetic domain 16 in the 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. Transfer expansion magnetic domain 1 as in (2)
7 disappears and the reproduction signal becomes 0. When the magnetic field 7 is reversed like (3) to reproduce the recording magnetic domain 18 again,
The transfer magnifying 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. When it passes through the initialization magnet, it becomes a magnetized state as shown in FIG. 3, and the recording magnetic domain cannot be seen from the substrate side. When a transfer magnetic field 7 is applied by irradiating laser light, the recording magnetic domain is transferred. (FIG. 5) Further, when the magnetic field 7 is increased as shown in FIG. 6, only the magnetic domains of the magnetic layers 2 and 3 have a small coercive force and are expanded, so that a large reproduced signal can be obtained. To read the next magnetic domain, we need to erase it. With the above contents, the S / N can be further improved by making the reproduction light into a pulse shape. This is because the transfer 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 erasing is completed as shown in FIG. FIG. 9 shows a block diagram of the apparatus.
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. Particularly, 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 becoming too wide 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 expanding 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.

[0006]

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.

[0007]

【Example】

(Example 1) A sample was prepared by a sputtering method. The creation conditions are as follows. Ultimate vacuum 5X10 ^-7 Tor
r or less, Ar is used as the sputtering gas, and the gas pressure is 5 mTo
rr, input power is 500 W, and sputtering rate is 0.1 to 0.2 nm / sec. A nitride is used for the dielectric film, a GdTbFeCo alloy having a Curie temperature of 350 ° C. and a compensation temperature of room temperature or less of 40 nm is used for the first magnetic layer, and a GdDyFe alloy having a Curie temperature of 120 ° and a compensation temperature of 60 ° is used for the second magnetic layer. 20 nm was laminated. TbF having a compensation temperature of 170 degrees and a Curie temperature of 240 degrees is used as the third magnetic layer.
eCo was laminated in a thickness of 40 nm. A sample servo substrate having 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 the 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 approximately 100 Oe, only the recording magnetic domain was transferred and expanded, and when the reproducing magnetic field was approximately 150 Oe, the entire reproducing layer was inverted. Also, the reproducing magnetic field is about -1
When 00 Oe was applied, the reproducing magnetic domain was erased. The reproduction was performed at a wavelength of 680 nm, and the S / N was improved by 3 dB as compared with the case where the reproduction light and the magnetic field were not modulated. When this signal change was reproduced through a differentiating circuit, the S / N was further improved by 1 dB.

[0009]

According to the present invention, when the recording signal is reproduced by modulating the light and the magnetic field, it is possible to enlarge the minute magnetic domains to essentially increase the signal amount. 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 (5)

[Claims] 1. 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 second magnetic layer has room temperature or higher. A magneto-optical recording medium, which is a rare earth transition metal having a compensation temperature, wherein the Curie temperature of the second magnetic layer is lower than the micro domain recording temperature. 2. The magneto-optical recording medium according to claim 1, wherein the third magnetic layer is made of a rare earth-transition metal alloy, and the magnetic moment of the whole is oriented in the same direction as the magnetic moment of the rare earth at room temperature. . 3. 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 is used, and from the side of the first magnetic layer. In an apparatus that reproduces information by utilizing the fact that the reflected light receives a magneto-optical effect by irradiating a laser beam, the information reproducing means is arranged on the substrate side and the magnetic field generating means is arranged on the film side, and the magnetic field and And / or a magneto-optical recording / reproducing apparatus having means for modulating and reproducing reproduction light. 4. A magneto-optical recording / reproducing apparatus according to claim 3, wherein positive and negative magnetic fields are alternately reproduced when reproducing one recording domain. 5. A magneto-optical recording / reproducing apparatus according to claim 3, wherein when reproducing one recording domain, positive and negative magnetic fields are alternated to differentially detect a reproduced signal.