JPS60237655A - Optomagnetic recording medium - Google Patents

Abstract

PURPOSE:To provide high saturation magnetization and coercive force and to improve C/N by using 15-25atom% Dy as a rare earth element and FeCo contg. 5-20atom% Co as a transition metal. CONSTITUTION:Rare earth metal layers 4 and transition metal layers 5 are alternately laminated in a way as to be mixed with each other on a disk base body 1 consisting of, for example, glass, etc. to form an optomagnetic recording medium 3 having an optomagnetic recording layer 2. 15-25atom% Dy is used for the layers 4 and the FeCo contg. 5-20atom% Co is used for the layer 5. The optomagnetic recording medium by Curie point recording is formed in the above- mentioned way, by which the high saturation magnetization and coercive force are provided and the C/N is improved. The reduction in the diameter of recording bits is also possible and high-density recording is made possible.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a rewritable magneto-optical recording medium.

Background Art and Problems Magneto-optical recording, such as a rewritable magneto-optical disk, is capable of writing with laser light, for example semiconductor laser light, that is, formation of a magnetic bubble, and reading based on the Kerr rotation angle. TbFe as a medium,
Some are made of rare earth metal-transition metal based amorphous materials such as GdCo and GdTbFe.

This magneto-optical recording medium made of an amorphous material has the advantage of being free from so-called grain noise caused by crystal grain boundaries.

There are two types of recording on this type of magneto-optical recording medium: Curie single-point recording and compensation point recording.The recording material for Curie single-point recording has Fe as its main component, but it still has sufficient characteristics, especially C. /H has not been proposed to be fully satisfactory.

OBJECTS OF THE INVENTION The present invention provides a magneto-optical recording medium based on Curie single point recording using a rare earth metal-transition metal magnetic recording material.
This is intended to improve C/N.

Summary of the Invention The present invention provides a magneto-optical recording medium using a rare earth metal-transition metal based magneto-optical recording material.
This is a magneto-optical recording medium in which PeCo containing 5 at % of Oy and 5 to 20 at % of Co as a transition metal is used.

Examples Example 1 A magneto-optical recording medium was prepared using a magneto-optical recording material made of a transition metal of FeCo5 (5 at. % Co - balance Pa) and a rare earth metal Dy. As shown in FIG. 1, this medium has a magneto-optical recording layer (2) containing the rare earth metal oy and the transition metal FeCo on a disk base (11, for example, glass, acrylic, polycarbonate, etc.).
constitutes a magneto-optical recording medium (3) having the following properties, and the composition ratio of the above-mentioned rare earth metal and transition metal in this recording layer (2) changes periodically in the thickness direction of the recording layer (2). do. That is, as shown in FIGS. 2A and B, which compare and contrast the respective distributions of the rare earth metal content and the transition metal content in the thickness direction of the recording layer (2), when one is large, the other is large. Change it periodically so that it becomes smaller. In order to obtain a magneto-optical recording medium with this configuration, a rare earth metal and a transition metal are provided as different sputtering sources, and the respective metals are simultaneously sputtered from both sputtering sources toward the substrate (11. In this case, both sputtering sources from the substrate il
The positional relationship between both sputtering sources and the substrate and the mask to be placed between both sputtering sources and the substrate are selected so that the main sputtering positions with respect to l are different from each other. Then, by relatively rotating and moving these child batter sources and the substrate, a rare earth metal layer (4) and a transition metal layer (5) are formed on the substrate (1) as shown in FIG. The layers are stacked alternately and intermixed with each other, so that the composition ratio of the rare earth metal and the transition metal changes periodically in the film thickness direction, as described above. In this case, each rare earth metal layer and transition metal layer is made of only a rare earth metal or only a transition metal so that each metal at least diffuses into the transition metal layer and rare earth metal layer deposited before it. Make sure there are no layers.

In this case, the growth rate of each metal layer by sputtering on the substrate is 2 to 25 people/second, especially 5 to 20 people/second.
It is desirable to select the relative rotational speed of the substrate and sputtering source and other sputtering conditions so that the sputtering time is within seconds. That is, if the relative rotational speed between the substrate and the sputtering source is too high and the growth rate is less than 2 per second, it becomes difficult to form layers of the transition metal and the rare earth metal, and if the growth rate is less than 20 per second. It was observed that when the temperature exceeds 100%, the magnetic properties deteriorate.

The sputtering apparatus for performing this sputtering may have a magnetron type structure, but this is a special structure. FIG. 3 shows the linear configuration of an example of a sputtering device. In this case, a base (6
), and for example, on the bottom surface thereof, there is a base (1) made of a glass plate, a resin plate, etc. that constitutes the intended magneto-optical distribution/recording medium.
is placed. Two sputter sources 17 and (8) are arranged facing the base body (11) at equal angular intervals, that is, at an angular interval of 180°, about the axis 0-0'.

Between these sputtering sources (7) and (8) and the base (6), that is, the base +11, there is a mask (9) for regulating the sputtering position of the metal sputtered from the sputtering sources (7) and (8), respectively. ). In this example, the sputter source (7) has a target OI consisting of a plate of the rare earth metal Dy, and the sputter source (8) has a target OI consisting of a plate of the rare earth metal Dy.
It has a target (11) made of a plate-shaped body of eCo5.

(12) and (13) each indicate a magnet.

For example, as shown in FIG. 4, the mask (9) has, for example, a ginkgo-shaped portion extending outward in the direction of a straight line Windows (14) and (15) are drilled therein. In Fig. 4, the inner window (14) and (
15) are chosen to be the same size, but these windows (
The areas of 14) and (15) can be formed at a ratio corresponding to the ratio of rare earth metal and transition metal in the recording layer formed on the substrate (1).

Note that the targets (11) of both sputtering sources (8) are not limited to being made of an alloy, but may also have a structure in which they are glued together with an area ratio that corresponds to the intended composition ratio.

Then, while rotating the base (6), DC sputtering was performed with the targets 001 and (11) on the negative electrode side.

The metal layer thus formed has a layer structure in which Dν, that is, a layer rich in rare earth metals, and layers rich in Fe and Co, that is, transition metals, are sequentially alternately formed as explained in FIG. It became.

When a 2 MHz signal is recorded on the magneto-optical recording medium, that is, a disk obtained in this way, at a Kerr rotation angle θ = 0.3° and a disk rotation speed of 180 rpm using a semiconductor laser beam, the reproduction characteristic is C/N. was 54dB.

Example 2 A magneto-optical recording medium (disk) was obtained in the same manner as in Example 1, but in this Example 2, the composition of the recording material was changed to D.
y-FeC+o. In this case, the C/N is
was 55 dB.

Example 3 A magneto-optical recording medium (disc) was obtained in the same manner as in Example 1, but in this Example 3, the composition of the recording material was Dy-FeC+5. In this case, C/
N was 54 dB.

FIG. 5 shows the saturation magnetization Ms and coercive force He when a magneto-optical recording medium was produced by the method shown in Example 1 and oy was varied in the composition of the recording material.

The curves (51M), (52M), and (53M) indicate the curves (51M), (52M), and (53M) for Gy-Fe (i.e., Co content o) and Dy-Fe, respectively. In the case of FeCo5o and Dy-FeCo
Showing the old measurement results for 2o, the curve (51M)
(52H) and (53M) are respectively similar Dy-pEl
The measurement results of He in the case of Dy-FeCo+o and Dy-FeCo2° are shown, and the curve (51T) (52T
) and (53T) are similar Dy −Fe+ D
T for y-FeCo+o and Dy-FeCo2o
The measurement results of c are shown.

Further, FIG. 6 shows a magneto-optical recording medium manufactured by the same method as in Example 1, with the composition of the magneto-optical recording material being DV.
The value of y as Fet-yCoy, ie C.

It shows the measurement results of the characteristics when the amount is changed, and the curves (60M), (60θ), (60T) and (60T) are shown.
0x) are the measurement results of the saturation magnetization Ms, the Kerr rotation angle θ, the Curie temperature Tc, and the temperature Tx at which crystallization begins, respectively.

Furthermore, FIG. 7 shows a magneto-optical recording medium manufactured by the same method as in Example 1, in which the magneto-optical recording material is Dy.
peloo-X Cox, x = 5, x =
I.Q.

The holding force He was measured when the amount of Dy was changed when x-20 and x=30, and the black circles in the figure indicate X-5
In this case, the white circle indicates the measurement result when X=10, the triangle mark indicates the measurement result when X-20, and the square mark indicates the measurement result when x=30.

In the present invention, as described above, D is used as an optical recording material.
y-FeCo configuration, and the rare earth metal y is 1
In Co-Fe as a transition metal, CO is 4 to 20 atom%, but the reason why oy is selected to be 15 to 25 atom% is due to the following reason. Ru. In other words, magneto-optical recording media need to have a good squareness ratio in order to make effective use of the originally small Kerr rotation angle, and must prevent records from being easily erased. It is desired that He is 1 kOe or more, but if the Oy content is less than 15 at%, as is clear from Figure 6, He will be lower than 1 kOe, and the o
This is because if y exceeds 25 atom %, Hc becomes too high, making erasing and rewriting difficult, so it was confirmed that y is desirably 25 atom % or less. Incidentally, when oy was 26 atomic %, the composition became a compensation composition and Hc became infinite.

In addition, the reason for selecting 5 to 20 atomic % of Co in FeCo is that the Kerr rotation angle θk is small in the magneto-optical material of DyFe, and the Curie point Tc is low, but as a transition metal, FeCo is
It has been recognized that these improvements can be made by adding 5 atomic % or more of Co to this using 2.
When it exceeds 0 atomic %, the temperature Tx at which crystallization begins becomes lower than the Curie temperature Tc, as shown in Figure 6.
This is because it would be inconvenient to record only one curri.

In the magneto-optical recording medium according to the present invention, the C/N is improved by 2 to 5 dB compared to, for example, a case using a conventional magneto-optical recording material such as TbFeCo or TbGd-Fe.

Effects of the Invention As described above, according to the present invention, high saturation magnetization Ms and coercive force He can be obtained, and C/N can be improved.

Incidentally, since the diameter of the recording focus is inversely proportional to Ms and Hc, it is possible to reduce the bit diameter, thereby achieving high-density recording.

[Brief explanation of drawings]

FIG. 1 is an enlarged linear sectional view of a magneto-optical recording medium according to the present invention, FIG. 2 is a component distribution diagram thereof, FIG. 3 is a linear configuration diagram of an example of a sputtering apparatus for implementing the manufacturing method of the present invention, and FIG.
The figure is a plan view of the main part, and FIGS. 5 to 7 are measurement curve diagrams of each characteristic of the magneto-optical recording medium. (11 is the substrate, and (2) is the magneto-optical recording layer. Hidemori Matsukuma, I. N. 1-1j Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Y (C6 Kaisuke)

Claims (1)

[Claims] In a magneto-optical recording medium using a rare earth metal-transition metal based magneto-optical recording material, PaC contains 15 to 25 atom % h as a rare earth metal and 5 to 20 atom % Co as a transition metal.
Magneto-optical recording medium using o.