JPH02304751A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium with high recording sensitivity and high signal quality by constituting a magnetic recording layer of three-layer structure containing recording layer, read-out layer and switching layer. CONSTITUTION:The read-out layer 3 consists of a material having high Curie temp. and large Kerr rotation angle, while the recording layer 5 has lower Curie point than the read-out layer and the switching layer 4 has lower Curie point than the read out layer 3. The switching layer 4 is provided between the read-out layer 3 and the recording layer 5. The temp. of the medium required for recording is near the Curie temp. of the recording layer, so that the switching layer 4 is demagnetized at the temp. where pits are formed in the recording layer, which prevents magnetic exchange interaction between the recording layer 5 and read-out layer 3. Thereby, recording sensitivity and signal quality can be independently controlled and the obtd. medium has high recording sensitivity and signal qualities.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magneto-optical recording medium that records and reproduces information using laser light.

BACKGROUND OF THE INVENTION Optical disk memories are considered as a new memory to replace current magnetic disk memories because they are capable of high density, large capacity, and high-speed access. Among them, magneto-optical disks using magneto-optical recording media have attracted the most attention because of their rewritability, and have been actively researched and developed in recent years.

FIG. 4 is a sectional view showing an example of a conventional magneto-optical recording medium. This magneto-optical recording medium is manufactured by sequentially depositing an intermediate layer 2, a magneto-optical recording layer 7, and a protective layer 6 on a support substrate 1 made of glass or organic resin. middle layer 2
And the protective layer 6 contains Si3N4, AJ! N,S
i02, ZrO2, A2203, etc. are used, and the magneto-optical recording layer 7 is an amorphous material made by a combination of rare earth metals such as Tb, Gd, Dy, and Nd and iron group transition metals such as Fe and Go. Alloy thin films are mainly used.

In recent years, the processing speed of information has been increasing, and a memory system with a high information transfer speed has become necessary. Along with this, in order to increase the transfer speed of magneto-optical disks as well, it has become necessary to increase the number of rotations of the disk. Under these circumstances, there is a need to improve the recording sensitivity of magneto-optical recording media.

One method for improving recording sensitivity is to use a two-layer film that combines a readout layer with a high Curie temperature and a large Kerr rotation angle and a recording layer with a low Curie temperature.

[Problems to be Solved by the Invention] When an amorphous rare earth-transition metal is used as a single-layer recording medium, it is necessary to lower the magnetic Curie temperature Tc of the medium in order to improve recording sensitivity. On the other hand, the Kerr rotation angle θ of the medium, which determines the width of the read signal, decreases as the magnetic Curie temperature decreases. Therefore, if you try to improve sensitivity by lowering the magnetic Curie temperature of the medium,
The imaging width of the readout signal decreases, and the signal quality deteriorates.

Another problem with the two-layer film method is that during the recording process, the recording layer loses its magnetization and bits are first formed on the readout layer, but this bit shape is easily distorted, resulting in an increase in recording noise and a decrease in signal quality. There is a point.

An object of the present invention is to provide a magneto-optical recording medium with high recording sensitivity and high signal quality by independently controlling the recording sensitivity and signal quality of the medium.

[Means for Solving the Problems] The present invention provides a magneto-optical recording layer including a readout layer having a relatively large Kerr rotation angle and a high magnetic Curie temperature, and a recording layer having a lower magnetic Curie temperature than the readout layer. and a switching layer having a magnetic Curie temperature lower than that of the readout layer, and the switching layer is located between the readout layer and the recording layer.

[Function] The function of the magneto-optical recording medium of the present invention will be explained based on FIG. 5.

FIG. 5(a) shows the initialized state, and the magnetization of each layer is 8.
are aligned upward. FIG. 5(b) is a diagram when the medium temperature is raised to the Curie temperature of the recording layer by irradiating the laser beam, and the recording layer 5 and switching layer 4 in the laser irradiated area lose their magnetization. ing. Figure 5 (
C) is a diagram showing a state in which the laser beam irradiation is stopped and the medium temperature is gradually decreasing. When the medium temperature becomes lower than the magnetic Curie temperature of the recording layer 5, magnetization appears in the direction of the external magnetic field 1-1ex. At this time, switching layer 4
is still in a state where magnetization has disappeared, so there is no exchange magnetic coupling between the recording layer 5 and the readout layer 3, and a clean bit is formed in the recording layer 5 without being affected by the magnetic influence of the readout layer 3. Figure 5(d), where the medium temperature has decreased drastically.
Then, magnetization appears in the switching layer 4, and this magnetization is aligned in the direction of the external magnetic field Hex and the magnetization of the recording layer 5. At the same time, the magnetization of the readout layer 3 is aligned in the direction of the magnetization of the switching layer 4 due to exchange coupling with the magnetization of the switching layer 4.

In such a recording process, the medium temperature required for recording is around the magnetic Curie temperature of the recording layer, so it is possible to improve the recording sensitivity by lowering the magnetic Curie temperature of the recording layer.

In addition, at the time when bits are formed in the recording diagram, the magnetization of the switching layer has disappeared and there is no magnetic exchange coupling between the recording layer and the readout layer, so the magnetic properties of the readout layer are not affected. Bits are formed in the layer.

Therefore, by using a medium with a high magnetic Curie temperature and a large Kerr rotation angle in the readout layer, it is possible to improve signal quality without reducing recording sensitivity.

As described above, in the magneto-optical recording medium of the present invention, recording sensitivity and signal quality can be controlled independently.
A magneto-optical recording medium with high sensitivity and high signal quality can be provided.

[Example] Next, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention. SiN intermediate layer 2 and GdFeC0 readout layer 3 on support substrate 1
, DyFeC○ switching layer 4, TbD"y'FeC
0 recording@5 and a Si3N4 protective layer 6 were sequentially formed by sputtering.

FIG. 2 shows the temperature characteristics of the coercive force HC of each magnetic layer. GdFeCo@ (readout layer) has a magnetic Curie temperature of high < (TC= 4) for the purpose of increasing the Kerr rotation angle.
00'C) was selected.

For the TbDVFeCo layer (recording layer), a composition with a low Curie temperature was selected for the purpose of improving recording sensitivity, and a composition with a magnetic Curie temperature of 160'C (TbDyFeCo(a)) and 1
Two types of compositions were prepared at 20°C (TbDyFeCo(b)). The DyFeCo layer (switching layer) was fabricated with a composition having a magnetic Curie temperature of 90'C.

FIG. 3 shows the recording and reproducing characteristics of the magneto-optical recording medium thus produced. Disk (a) is a sample using a TbD'y'FeC0 layer with a composition with a magnetic Curie temperature of 160'C, and disk (b) is a sample with a TbDVFeCo layer with a composition with a magnetic Curie temperature of 120°C.10 measurements. The conditions were a disc rotation speed of 360 rpm.

The radius was set to r=iaomm. Disk (b) has a recording threshold power of 2m1Il compared to disk (a).
Smaller size and improved sensitivity. C/corresponding to signal quality
N was 60 dB for both disks. As described above, in the magneto-optical recording medium of the present invention, recording sensitivity can be improved without impairing signal quality.

In this example, an example was shown in which the recording sensitivity was controlled by changing the magnetic Curie temperature of the recording layer, but by increasing the Kerr rotation angle of the readout layer, the signal quality could be improved without reducing the recording sensitivity. It is also possible to improve this.

[Effect of the invention 1 As explained above, the magneto-optical recording medium of the present invention has a magnetic recording layer composed of three layers: a recording layer, a readout layer, and a switching layer.
The layered structure makes it possible to independently control recording sensitivity and signal quality.

This has the effect that recording sensitivity can be improved without impairing signal quality, and signal quality can be improved without reducing recording sensitivity.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of the present invention, FIG. 2 is a characteristic diagram showing the temperature dependence of the coercive force of the magnetic recording layer in one embodiment of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of an example of a conventional magneto-optical disk, and FIG. 5 is an explanatory diagram for explaining the recording method of the magneto-optical recording medium of the present invention.

Claims (1)

[Claims] (1) The magneto-optical recording layer includes a readout layer having a relatively large Kerr rotation angle and a high magnetic Curie temperature, a recording layer having a magnetic Curie temperature lower than that of the readout layer, and a magnetic Curie temperature lower than that of the readout layer. 1. A magneto-optical recording medium comprising a low switching layer, and having a film structure in which the switching layer is located between a readout layer and a recording layer.