JPH0714226A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To perform recording and reproduction for a magneto-optical recording medium with a large capacity and at a high transferring rate by improving the S/N and, at the same time, reducing cross talk when the recording bit length is short. CONSTITUTION:The recording film of a magneto-optical recording medium is constituted of two magnetic films, a first and second magnetic films 3 and 4 in the order from the light incident side. The first film 3 is a vertically magnetized film and the second film 4 is an intrasurface magnetized film, the temperature rising section of which reaches the Curie temperature when the section is irradiated with reproduced light 1. In addition, a switched connecting force is made to act between the films 3 and 4.

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 / erasing a signal by utilizing a temperature rise caused by laser light irradiation and reproducing a signal by utilizing a magneto-optical effect.

[0002]

2. Description of the Related Art It is important for a magneto-optical recording medium to improve the data transfer rate in order to expand its application field as a memory. Therefore, it is known to improve the recording sensitivity of the magneto-optical recording medium itself, as disclosed in Japanese Patent Laid-Open No. 2-247846.

Recording on a magneto-optical recording medium is carried out by locally irradiating a laser beam to a temperature having a small coercive force higher than the compensation temperature or a Curie temperature to irradiate the recording film in the irradiated portion with an external magnetic field. It is performed by magnetizing (thermomagnetic recording). In addition, the reproduction of the recording signal detects the situation in which the polarization plane of the reflected light or the transmitted light rotates depending on the recording state (magnetization direction) of the recording film by irradiation with laser light having a power lower than the laser power at the time of recording / erasing. By doing. A conventional recording method is a method of irradiating a laser beam of a constant intensity to raise the temperature of a recording film and performing thermomagnetic recording with an external magnetic field whose direction is modulated according to a recording signal (magnetic field modulation recording method), and There is a system (optical modulation recording system) of irradiating a laser beam whose intensity is modulated according to a recording signal under an external magnetic field of a constant intensity to locally raise the temperature of a recording film and performing thermomagnetic recording.

FIG. 4 shows an example of the structure of a conventional magneto-optical disk. In FIG. 4, 11 is a substrate made of glass or plastic, 12 and 13 are protective films made of a ZnSe film, and 14 is a recording film made of a TbFeCo film. For the recording film of the magneto-optical recording medium, a rare earth metal-transition metal alloy film such as a TbFeCo film having perpendicular magnetic anisotropy is used as a magnetic material for high density recording, and oxidation of this recording film is prevented. For protection, it is protected by a dielectric film such as ZnSe.

[0005]

However, in the conventional magneto-optical recording medium as described above, when the recording bit becomes smaller than the size of the reproduction light, the reproduction signal becomes small due to the interference from the recording bits before and after S. There is a problem that / N decreases and high density recording cannot be realized. Further, if the distance between the recording tracks is smaller than the size of the reproducing light, crosstalk from the adjacent tracks increases and reproduction jitter occurs, which hinders the increase in capacity.

The present invention solves the above-mentioned problems, and provides a magneto-optical recording medium capable of recording / reproducing with a large capacity and a high transfer rate by reducing waveform interference of recording bits and crosstalk from adjacent tracks. Is intended.

[0007]

In order to achieve the above object, the magneto-optical recording medium of the present invention comprises a recording film composed of two magnetic films, a first magnetic film and a second magnetic film from the light incident side. The first magnetic film is a perpendicular magnetic film, the second magnetic film is an in-plane magnetic film that has a Curie temperature at a temperature rising portion due to the irradiation of the reproducing light, and the first magnetic film and the second magnetic film. It has a structure in which an exchange coupling force acts between the membranes.

[0008]

According to the present invention, the exchange coupling force acts between the first magnetic film and the second magnetic film in the above-described structure, so that the second magnetic film is not affected by the second magnetic film in the region above the Curie temperature.
The exchange coupling force from the magnetic film disappears, the force for directing the first magnetic film in the in-plane direction disappears, and the magnetization direction of the first magnetic film becomes perpendicular. For this reason, the Kerr rotation angle from the first magnetic film in this region is increased, and the information on the magnetization of the first magnetic film can be emphasized and read as a reproduction signal.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magneto-optical recording medium according to an embodiment of the present invention will be described below with reference to FIGS. Figure 1
1 shows a configuration of a magneto-optical recording medium according to an embodiment of the present invention. Figure 1
In the figure, 1 is reproduction light, and 2 is a substrate made of glass or plastic. 3 is a first magnetic film, TbGdFe
Co film, 4 is a second magnetic film made of TbFe film, and 5 and 6 are protective films made of ZnSe film. Each film on the substrate 2 is formed by a sputtering method.

The operation of the above configuration will be described. FIG. 2 is a diagram showing the magnetization state of the magneto-optical recording medium of the present invention. In FIG. 2, the direction of magnetization of each magnetic film is indicated by an arrow. First
Information is recorded on the magnetic film 3 in the direction of magnetization by an optical modulation method or a magnetic field modulation method. When reproducing the magneto-optical recording medium, the temperature of the first magnetic film 3 and the second magnetic film 4 rises due to the irradiation of the reproducing light 1. The in-plane magnetized film, which has a Curie temperature at the temperature of the reproducing light irradiation section,
Since the magnetic film 4 is formed, the magnetization of the second magnetic film 4 disappears in the region where the temperature of the second magnetic film 4 is equal to or higher than the Curie temperature (mesh portion in FIG. 2), and thus the second magnetic film 4 is removed. The exchange coupling force from does not work. In the region where the second magnetic film 4 is below the Curie temperature, the magnetization direction of the first magnetic film 3 tilts in the in-plane direction due to the exchange coupling force from the second magnetic film 4, so that the region from the first magnetic film 3 in this region is inclined. The car rotation angle decreases. Further, in a region where the second magnetic film 4 has a Curie temperature or higher, the exchange coupling force from the second magnetic film 4 disappears, the force for directing the first magnetic film 3 in the in-plane direction disappears, and the first magnetic film 3 has a The magnetization direction is perpendicular. Therefore, the Kerr rotation angle from the first magnetic film 3 in this region increases. In other words, with the above configuration,
The first magnetic film 3 in the temperature rising region of the central portion of the reproduction light 1
Therefore, it is possible to emphasize the magnetization information and read it as a reproduction signal. This is equivalent to making the size of the reproducing light beam 1 at the time of reproduction equivalently smaller, and thereby recording bits smaller than the size of the reproducing light beam 1 can be read out without waveform interference of the recording bits before and after. Become. This principle also works in the traveling direction of the reproduction beam and in the direction perpendicular to the traveling direction, so that the S /
N degradation as well as crosstalk from adjacent tracks can be reduced.

Next, the respective film thicknesses are 40 nm for the first magnetic film 3, 50 nm for the second magnetic film 4, 80 nm for the protective film 5, and 6 for the protective film.
Was 100 nm. The composition of the TbFe film of the second magnetic film 4 was Tb = 50% and Fe = 50%, and its Curie temperature was 130 ° C. In addition, the TbGdF of the first magnetic film 3
The composition of the eCo film is Tb = 7%, Gd = 15%, Fe
= 69.5% and Co = 8.5%.

The dependence of the reproduction signal noise ratio (hereinafter referred to as the CN ratio) on the recording bit length of the magneto-optical recording medium having the above-mentioned structure was measured. The reproduction CN ratio is measured by using a magnetic field modulation recording method for recording, and the moving speed of the magneto-optical recording medium is 6 m / s.
I went there. The results are shown in FIG. 3, in which the relationship between the recording bit length and the CN ratio of the magneto-optical recording medium of the present invention is shown by a solid line, and the relationship between the recording bit length of the conventional magneto-optical recording medium and the CN ratio is shown by a dotted line. As is clear from FIG. 3, the CN ratio is higher than that of the conventional magneto-optical recording medium in the region where the recording bit length is short, and it can be said that the magneto-optical recording medium of the present invention is effective for high density recording. Further, in the magneto-optical recording medium of the present invention, the crosstalk amount at the track pitch of 1.4 μm is 13 dB lower than that of the conventional magneto-optical recording medium, which makes it possible to realize a magneto-optical recording medium having a narrow track pitch. It is what

In this embodiment, the second magnetic film 4 is made of T
Although the bFe film is used, the same effect can be obtained by using an in-plane magnetized film having a Curie temperature at the temperature of the central portion of the reproduction light 1. The TbFe film used in this example is also Co
Since it is possible to control the Curie temperature within a certain range by adding, even if the temperature of the central portion of the reproduction light 1 during reproduction changes due to reproduction conditions,
Optimization can be easily performed by adding Co.

[0014]

As is apparent from the above description, the magneto-optical recording medium of the present invention achieves both S / N improvement and crosstalk reduction at a short recording bit length, a large capacity and a high transfer rate. This enables the realization of the magneto-optical recording device.

[Brief description of drawings]

FIG. 1 is a sectional view of a magneto-optical recording medium according to an embodiment of the present invention.

FIG. 2 is a diagram showing a magnetization state of the magneto-optical recording medium.

FIG. 3 is a characteristic diagram showing a relationship between a reproduction CN ratio and a recording bit length of a magneto-optical recording medium according to an embodiment of the present invention and a conventional magneto-optical recording medium.

FIG. 4 is a sectional view of a conventional magneto-optical recording medium.

[Explanation of symbols]

 1 reproducing light 3 first magnetic film 4 second magnetic film

Claims (1)

[Claims] 1. A recording film is provided with a first magnetic film and a second magnetic film from the light incident side.
The first magnetic film is a perpendicular magnetization film, and the second magnetic film is an in-plane magnetization film that has a Curie temperature at a temperature rising portion due to irradiation of reproduction light. A magneto-optical recording medium in which an exchange coupling force acts between the first magnetic film and the second magnetic film.