JP3148017B2 - Magneto-optical recording medium and method of manufacturing 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 having a recording layer made of a rare earth-transition metal amorphous alloy and a method of manufacturing the same, and more particularly to a technique for improving recording characteristics under the action of a low external magnetic field. About.

[0002]

2. Description of the Related Art Among various optical recording elements, a magneto-optical recording medium capable of recording and erasing information has already been put to practical use. As a recording film of this magneto-optical recording medium,
Thin films made of rare earth-transition metal amorphous alloys are most often used because of their excellent overall properties. This recording film is generally formed by laminating a plurality of layers such as a first dielectric layer, a recording layer, a second dielectric layer, and a reflective layer, and the recording layer includes a rare earth-transition metal amorphous alloy. Is used. Recording of information is performed using a change in the magnetization direction in the perpendicular magnetization thin film.

As a recording method utilizing the change in the magnetization direction of the perpendicular magnetization thin film, an optical modulation method has been practically used. This involves irradiating a recording layer with a laser beam having a diameter of about 1 μm in a pulsed manner under the action of a relatively strong external magnetic field of 200 to 300 Oersteds (Oe) to reach the Curie temperature. By heating up to that point, the magnetization direction of that portion is magnetized in the same direction as the external magnetic field, and signal information is recorded. However, in recent years, while continuously irradiating a laser beam of a constant intensity, an external magnetic field is applied, the direction of the magnetic field is switched (modulated) at a high speed, and a binarized signal distinguished by a difference in magnetization direction. Has been developed, and this method has received particular attention because it is possible to overwrite a recording medium.

[0004]

By the way, in the above-mentioned magnetic field modulation method, it is necessary to reverse the direction of the magnetic field at a high speed. For this high-speed magnetic field modulation, a large coil which generates a large external magnetic field is required. It is better to use a small coil that generates an external magnetic field as small as possible,
The smaller the coil, the smaller the whole device
In addition, the configuration can be simplified. However, since the strength of the available external magnetic field is low, the signal quality is degraded. Therefore, in the recording medium, the magnetization direction of the recording layer is reversed even under the action of the small external magnetic field, in other words, the recording layer is It is necessary to improve the magnetic field sensitivity. Specifically, it is necessary to realize sufficient signal recording characteristics, for example, a signal carrier-to-noise ratio (CNR) of 36 dB or more at an external magnetic field strength of −50 to +50 (Oe).

The present invention has been made to solve the above problems, and provides a magneto-optical recording medium capable of obtaining a sufficient signal quality even under the action of a low external magnetic field, and a method of manufacturing the same. The purpose is to:

[0006]

In order to achieve the above object, the present invention is directed to a first dielectric layer, a rare earth-transition metal amorphous alloy recording layer, and a second dielectric layer. in the dielectric layer are sequentially stacked magneto-optical recording medium, between the recording layer and the second dielectric layer, in which a layer consisting of the following gold average thickness 8 angstroms is formed. According to a second aspect of the present invention, there is provided a method for manufacturing a magneto-optical recording medium comprising sequentially laminating a first dielectric layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a second dielectric layer on a substrate. in, after forming the recording layer, the surface of the on the recording layer to form a layer composed of the following gold 8 angstroms average thickness, producing intermediate obtained magneto-optical recording medium, including oxygen Exposure to gas. Furthermore, a third aspect of the present invention is a method for manufacturing a magneto-optical recording medium in which a first dielectric layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a second dielectric layer are sequentially laminated on a substrate. in, after forming the recording layer, the surface of the on the recording layer to form a layer composed of the following gold 8 angstroms average thickness, producing intermediate obtained magneto-optical recording medium, in a vacuum This is to perform plasma etching.

[0007]

[Action] In the above, the average thickness of a layer of gold is seen microscopically be completely uniform, the thickness of the case where deemed completely covering the surface of the recording layer with a constant thickness, in fact , not a layer of gold is completely covering the surface of the recording layer, between the gold particles and the gold particles, it is a state in which the portion where the surface of the recording layer is exposed exists. As described above, the state in which the portion covered with the gold particles and the portion not covered with the gold particles coexist on the surface of the recording layer has a desirable effect on the properties of the domain wall of the recording layer, and as a result, the small external magnetic field However, it is presumed that a recording medium capable of recording and erasing information and having characteristics suitable for the magnetic field modulation method will be manufactured. The layer made of gold, when it is to cover all portions of the surface of the recording layer to improve the recording characteristics in a small external magnetic field is not observed.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to a magneto-optical disk as a typical magneto-optical recording medium. FIG. 1 is a sectional view showing a basic configuration of a magneto-optical disk (hereinafter, a disk). In FIG.
A first dielectric layer 3, a recording layer 4 that is a perpendicular magnetization film, a gold layer 5 made of gold (Au), a second dielectric layer 6, and a reflective layer 7 are formed on a light-transmitting substrate 2. It is constructed by sequentially laminating.

The substrate 2 is made of an optically transparent material such as a transparent plastic such as polycarbonate, epoxy resin or polyolefin resin, or transparent glass. The first dielectric layer 3 and the second dielectric layer 6 are made of Si
It is formed using N, AlSiON, SiO, or the like as a material. The recording layer 4 is formed of a rare earth-transition metal amorphous alloy composed of elements such as Tb, Fe, Co, Cr, and Ti. The reflection layer 7 is composed mainly of Al and Ti,
It is formed of an alloy obtained by adding Cr or the like.

The gold layer 5 is made of Au. However, the gold layer 5 does not completely cover the surface of the recording layer 4, but the portion where the surface of the recording layer 4 is exposed between the gold particles. There is a so-called sea-island structure. For example, if the gold layer 5 has an average thickness of 20 angstroms or more, the above-described sea-island structure is not formed, and the gold particles almost completely cover the recording layer 4, so that the average thickness is at least 8 angstroms or less. It must be formed as follows.

An embodiment in which the detailed structure and the manufacturing procedure are modified based on the basic structure of the disk 1 shown in FIG. In the first embodiment, the substrate 2
Is an optical grade polycarbonate, the first dielectric layer 3 and the second dielectric layer 6 are SiN, and the recording layer 4 is Tb.
FeCoCr, Au for the gold layer 5, AlTi for the reflective layer 7
Were used as materials, and laminated as shown in FIG. 1 by sputtering film formation using Ar and N ₂ gas to constitute a magneto-optical recording medium. The gold layer 5 was adjusted to have an average thickness of about 5 angstroms. In forming the gold layer 5,
Gold is sputtered so that its average thickness can be measured by the precision step measuring device, and the thickness of the gold layer obtained at this time and the net deposition time of sputter deposition are determined per unit time. The gold film formation rate was determined, and the net film formation time on the recording layer was adjusted with reference to the gold film formation rate thus obtained, so that the sputter film was formed so that the average thickness was about 5 Å. . The net deposition time in this example was 5 seconds.

A second embodiment will be described. In this embodiment, after the above-mentioned gold layer 5 is formed by sputtering, an oxygen-argon mixed gas having an oxygen volume concentration of 20% is introduced into the sputtering apparatus for about 20 minutes.
Then, the second dielectric layer was formed into a film to obtain a disk 1. Otherwise, the same materials and procedures as in the first embodiment were used.

A third embodiment will be described. In this embodiment, after forming the gold layer 5, argon plasma etching is performed for 30 minutes.
Seconds. Otherwise, the same materials and procedures as in the first embodiment were used.

Next, a comparative example to be compared with the above-mentioned embodiment will be described. In the comparative example, a disk was formed without forming the gold layer 5. Otherwise, the same materials and procedures as in the first embodiment were used.

FIG. 2 shows the results of measuring the signal recording characteristics of the disks according to the first to third embodiments and the comparative example. In the figure, under the action of a low external magnetic field in the range of −50 to +50 (Oe), the disks of the first to third embodiments provided with the gold layer 5 have a larger CNR than the disk of the comparative example. It is clear that the present invention has the effect of improving the recording characteristics.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described configuration, and various modifications are possible . As described above, the thickness of the gold layer formed on the surface of the recording layer may be such that the gold particles are formed in a sea-island structure and the surface of the recording layer is not completely covered. The thickness may be 8 Å or less, preferably 5 Å or less. Further, in order to bring the gold layer into the above-mentioned sea-island structure, it is also effective to finely process the surface by plasma etching or the like after the film formation. Further, in the above-described embodiment, the configuration example of the magneto-optical disk having the reflection layer is shown, but the reflection layer may not be formed. The present invention is widely applicable not only to magneto-optical disks but also to other magneto-optical recording media.

[0017]

As described above, according to the present invention, a signal recording characteristic under the action of a low external magnetic field is larger than that of a conventional magneto-optical recording medium, and a magneto-optical recording medium suitable for an external magnetic field modulation system is provided. can do. Further, an apparatus using this medium does not need to be provided with a large magnetic field generator, so that the apparatus can be reduced in size and cost. Further, high-speed magnetic field modulation becomes possible, and the recording operation time can be shortened.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a magnetic field sensitivity characteristic of a magneto-optical recording medium according to first to third examples and a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Substrate 3 First dielectric layer 4 Recording layer 5 Gold layer 6 Second dielectric layer 7 Reflective layer

Claims (3)

(57) [Claims] 1. A magneto-optical recording medium in which a first dielectric layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a second dielectric layer are sequentially laminated on a substrate . between the second dielectric layer, a magneto-optical recording medium, wherein the layer consisting of gold average thickness 8 angstroms is formed. 2. A method for manufacturing a magneto-optical recording medium, comprising: sequentially laminating a first dielectric layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a second dielectric layer on a substrate. after forming the, to this on the recording layer to form a layer composed of the following gold average thickness 8 angstroms, the surface of the manufacturing intermediate product obtained magneto-optical recording medium, is exposed to a gas containing oxygen A method for manufacturing a magneto-optical recording medium, comprising: 3. A method for manufacturing a magneto-optical recording medium, comprising: sequentially laminating a first dielectric layer, a recording layer made of a rare earth-transition metal amorphous alloy, and a second dielectric layer on a substrate. after forming, and the surface of the on the recording layer to form a layer composed of the following gold 8 angstroms average thickness, producing intermediate obtained magneto-optical recording medium, to plasma etching in a vacuum A method for manufacturing a magneto-optical recording medium, characterized by the following.