JPH01124131A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a magneto-optical recording medium having excellent recording and reproducing characteristics by using a recording film having a two- layered structure constituted of a 1st magnetic layer which contains at least Nd and Gd and a 2nd magnetic layer which does not contain the Nd and Gd. CONSTITUTION:The magnetic film having the two-layered structure constituted of the 1st magnetic layer 3 consisting of at least 1 kind of rare earth elements and transition metals among the Nd and Gd and the 2nd magnetic layer 4 consisting of at least 1 kind of the rare earth elements and transition metals among the rare earth elements except the Nd and Gd is used as the recording film. The 1st magnetic layer 3 which contains the Nd and Gd and has a large Kerr rotating effect is used as an information reading-out layer by laser light irradiation and, therefore, a large reproduced output is obtd. On the other hand, the magnetic layer having a low Curie temp. and the perpendicular magnetic anisotropy and coercive force of sufficient magnitudes is selected as the 2nd magnetic layer 4, by which the decrease of recording sensitivity and the increase of a noise level are prevented. The magneto-optical recording medium having the good recording and reproducing characteristics is thereby obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a magneto-optical recording medium in which recording, reproduction and erasing are performed by irradiation with laser light, and particularly relates to a recording medium suitable for obtaining good recording and reproduction characteristics. The present invention relates to a magneto-optical recording medium having a film.

[Conventional technology]

Magneto-optical recording media that use an amorphous magnetic film made of rare earth elements and transition metals as a recording film are capable of rewriting information and can perform high-density recording. However, in order to handle even larger amounts of information at higher speeds, it is necessary to further improve the recording and reproducing characteristics of magneto-optical recording media.

The magnitude of the reproduction signal of a magneto-optical recording medium is mainly determined by Kerr (Ke
rr) Determined by the magnitude of the rotation angle.

In recent years, a method of adding Nd or Gd, which is a rare earth element, to a recording film has been known as a method of increasing the Kerr rotation angle of the recording film. For example, as a recording film containing both Nd and Gd, a NdGdFe film is used in Japanese Patent Laid-Open No. 60-11743.
It is proposed in No. 6. Also.

Journal of the Japanese Society of Applied Magnetics, Volume 11, Pages 193-19
Page 6 shows that the Kerr rotation angle of a recording film containing Nd tends to increase in the short wavelength region of laser light.

This is particularly effective when writing minute pits using short wavelength laser light to perform high-density recording.

[Problem that the invention seeks to solve]

However, in the above conventional technology, Nd and Gd
No consideration has been given to the structure of the recording film to maximize the effect of increasing the Kerr rotation angle due to the addition of However, there was a problem in that practically superior recording and reproducing characteristics could not be obtained.

That is, in a conventional configuration using a single layer recording film, it is necessary to set the Curie temperature to a low temperature so as to obtain good recording sensitivity, and the amounts of Nd and Gd added are limited. Also, since it contains Nd and Gd, the perpendicular magnetic anisotropy and coercive force are not large enough, and the magnetization within the recording domain is tilted from the perpendicular direction of the recording film surface, making it impossible to obtain a large reproduction output. There was also the problem that the recorded information was unstable.

An object of the present invention is to provide a magneto-optical recording medium with excellent recording and reproducing characteristics by using a magnetic layer containing rare earth elements Nd and Gd as part of a recording film.

[Means for solving problems]

The above object is achieved by using a recording film having a two-layer structure consisting of a first magnetic layer containing at least Nd and Gd and a second magnetic layer not containing Nd and Gd.

achieved.

The recording film does not necessarily have to have a two-layer structure.

A structure in which a large number of first magnetic layers and second magnetic layers are laminated may be used.

It is desirable that the first magnetic layer is placed on the laser beam incidence plane, and the optimal film thickness of the first magnetic layer is 50 Å or more, 3
00 Å or less.

The most desirable configuration of the recording film is to laminate 50 to 150 first magnetic layers on the substrate surface onto which the laser beam is incident.

Furthermore, a second magnetic layer is stacked on top of this by 700 to 1000 layers. Of course, when reproducing is performed by inputting a laser beam from the film surface side of the recording film, the stacking order is reversed to the above.

Moreover, the above-described laminated structure does not necessarily have to have a composition distribution in the film thickness direction that changes discontinuously, but may have a structure in which the two composition distributions change continuously.

[Effect]

Since the first magnetic layer containing Nd and Gd and having a large Kerr rotation angle is used as an information readout layer by laser beam irradiation, a large reproduction output can be obtained. On the other hand, as the second magnetic layer,
By selecting a magnetic layer with a low Curie temperature and sufficient perpendicular magnetic anisotropy and coercive force, it is possible to prevent a decrease in recording sensitivity and an increase in noise level.

Both magnetic layers constituting the recording film are magnetically coupled, and during recording and reproduction by laser beam irradiation.

- Since the layer behaves like a recording film, good recording and reproducing characteristics can be obtained.

〔Example〕

Hereinafter, two embodiments of the present invention will be described in more detail with reference to the drawings.

(Example 1) A magneto-optical disk having the configuration shown in FIG. 1 was manufactured according to the procedure shown below. A silicon nitride film (dielectric film 2) of 850 layers was laminated on a transparent resin substrate 1 with a diameter of 13cm by magnetron high frequency sputtering.
d1. Gd! 2Fe,. Co, , film (first magnetic film 3
) and 900 Tb, Fe, and □Co films (second magnetic layer 4) were laminated in this order. Pure Ar gas was used as the sputtering gas, and the high frequency output was 1.5 kW. Furthermore, 1,500 silicon nitride films (protective film 4) were laminated as a protective film. The Kerr rotation angle measured from the substrate side of the produced magneto-optical disk was 0.9 degrees, and the coercive force was 6.0 kOe.

FIG. 2 shows the recording and reproducing characteristics of the magneto-optical disk manufactured in this example.

This was performed from the substrate side using a semiconductor laser. The recording and reproduction conditions were: recording laser output 8mW, recording magnetic field 4000s, disk rotation speed 240Orpm, reproduction laser output 2,0
It is aW. As shown in Figure 2, the recording frequency is 10MH
C/N (carrier-to-noise ratio) of 45 dB even at z
was obtained, and it was found that good recording and reproducing characteristics were obtained.

Note that it has the same configuration as the magneto-optical disk described above, and the first magnetic layer includes Nd, Gd□, Tb, Fe4.
Co.

Membrane, Nd. Gd0. D31t Fe,, Go,
, C/N of 45 dB and 43 dB were obtained at the recording frequency of IOM Hz, respectively, when using the film.

Here, 1000 people stacked the above-mentioned NdGdFeCo films.

In magneto-optical disks using this as a recording film,
Good recording and reproducing characteristics could not be obtained. This is shown in Figure 3 (
This is because, as shown in b), the squareness of the Kerr hysteresis curve is poor. That is, it can be seen that the perpendicular magnetic anisotropy and coercive force are not large enough to be used as a magneto-optical recording film.

On the other hand, as shown in FIG. 3(a), in the structure of the two magneto-optical disks according to the present invention, a Kerr hysteresis curve with good squareness was obtained.

Furthermore, as shown in Figure 4, 60 people's thickness of NdGd
A total of 8 FeCo films and a TbFeCo film with a thickness of 190
A magneto-optical disk using a layered recording film was fabricated.

A vacuum evaporation apparatus having two evaporation sources of NdGdFeCo alloy and TbFeCo alloy was used, and the disk substrate was rotated so as to pass over each evaporation source. Also in the magneto-optical disk produced in this way, a C/N of 43 dB or more was obtained at a recording frequency of 1OMHz.

(Example 2) Next, using an NdGdFeCo film as the first magnetic layer,
A magneto-optical disk was fabricated using a T b F a Co film as the second magnetic layer. What are the steps to make the disc?

This is the same as in Example 1. However, the NdGdFeCo alloy target (first
target) and 'l'b Feco alloy target (second target), first discharge both targets at the same time, and then pass the disk substrate over the first target and the second target in sequence. Ta. The thickness of the recording film including the first magnetic layer and the second magnetic layer was 1000 mm. in this case.

The interface between the first magnetic layer and the second magnetic layer is not clear.

The composition changed continuously.

Figure 5 is based on Auger analysis. FIG. 3 is a diagram showing the concentration distribution of rare earth elements in a recording film. Sputtering was performed with Ar ions from the protective film 4 side, and the recording film was analyzed in the depth direction. The composition of the first magnetic layer is Nd, Gd, Tb4F
e7. Cot (atomic %).

The composition of the second magnetic layer is Tb2! Fe@4CO□. Met.

In this disc, a C/N of 46 dB was obtained under the recording and reproducing conditions shown in Example 1.

In Examples 9 and above, Go was added to the first magnetic layer. This is to suppress the decrease in the angle. Therefore, Go
The addition of N is not necessarily necessary, and as the first magnetic layer, N
Even if a dGdFe film or a N d G d T b Fe film is used, the same effect as in the above embodiment can be obtained. In addition, as the second magnetic layer, in addition to the TbFeC0 film, TbFa, DyF
e, DyFeCo film, etc. may be used, and the structure of the magneto-optical recording film shown in Table 1 also has good recording and reproducing characteristics (C
/N) was obtained.

Table 1 In addition, All and Ti are added to the first magnetic layer and the second magnetic layer for the purpose of improving corrosion resistance and stabilizing the amorphous film.

Similar effects can be obtained by adding elements such as Cr, Pt, Nb, B, C, Si, and Ge.

〔Effect of the invention〕

As explained in detail above, two first magnetic layers according to the present invention are made of at least one rare earth element among Nd and Gd and a transition metal, and at least one rare earth element among rare earth elements other than Nd and Gd. A magneto-optical recording medium that uses a two-layered magnetic film as a recording film consisting of a second magnetic layer made of a transition metal and a second magnetic layer, even if it contains Nd or Gd and has a large Kerr rotation angle, is used as a recording film. Even if it's a medium.

It is possible to suppress a decrease in recording sensitivity and an increase in noise level, and it is possible to obtain a magneto-optical recording medium having extremely good recording and reproducing characteristics.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the cross-sectional structure of the magneto-optical disk manufactured in Example 1 of the present invention, FIG. 2 is a diagram showing the recording frequency dependence of C/N of the magneto-optical disk of Example 1, and FIG.
FIG. 3(a) is a diagram showing the Kerr hysteresis curve of the magneto-optical disk of Example 1, FIG. 3(b) is a diagram showing the Kerr hysteresis curve of the magneto-optical disk using a conventional recording film, and FIG.
The figure is a schematic diagram showing the cross-sectional structure of a magneto-optical disk having a recording film with a multi-layered structure manufactured in Example 1 of the present invention, and FIG. 5 is the recording of the magneto-optical disk manufactured in Example 2 of the present invention. FIG. 2 is a diagram showing the concentration distribution of rare earth elements in the film thickness direction in a film. 1...Transparent substrate 2...Dielectric film 3=・N
dGdFeCo film (first magnetic layer) 4...TbFeC
O film (second magnetic layer) 5...Protective film Patent attorney Junnosuke Nakamura Figure 1 Figure 2 Figure (a) (b) Figure 4-rbvecagl (-fzqrAfz layer 2 Figure 5

Claims (1)

[Scope of Claims] 1. In a magneto-optical recording medium using as a recording film an amorphous magnetic film mainly composed of rare earth elements and transition metals formed directly or through an underlayer on a substrate, The film includes a first magnetic layer made of a rare earth element containing at least one element selected from Nd and Gd and at least one transition metal, and a first magnetic layer made of at least one transition metal selected from Nd and Gd. The magnetic film is composed of a second magnetic layer made of a rare earth element and at least one transition metal, and has a two-layer structure in which the first magnetic layer and the second magnetic layer are laminated. magneto-optical recording medium. 2. The magneto-optical recording medium according to claim 1, characterized in that a plurality of sets of two-layered magnetic films constituting the recording film are provided. 3. The two-layered magnetic film constituting the recording film is characterized in that the first magnetic layer is arranged on the surface on the laser beam incidence side, and the second magnetic layer is arranged on the other surface. A magneto-optical recording medium according to claim 1 or 2. 4. The composition distribution of the constituent elements of the two-layered magnetic film constituting the recording film is at the interface between the first magnetic layer and the second magnetic layer or at the interface between the second magnetic layer and the first magnetic layer. The magneto-optical recording medium according to any one of claims 1 to 3, wherein the recording film has a structure that changes discontinuously or continuously. 5. The first magnetic layer constituting the two-layer magnetic film is NdG.
dFe, NdGdFeCo, NdGdTbFeCo, N
The magneto-optical recording medium according to any one of claims 1 to 4, characterized in that the second magnetic layer is made of at least one kind selected from dGdDyFeCo, and the second magnetic layer is TbFeCo.