JPH087886B2 - Magneto-optical recording medium - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording medium, and more particularly to a magneto-optical recording medium that records and reproduces information with a laser beam by utilizing a magneto-optical effect.

[Conventional technology]

As a conventional magneto-optical recording medium, one using a plurality of magnetic layers as a magneto-optical recording layer has been proposed for the purpose of improving recording characteristics, reproducing characteristics, and recording stability. A typical example is stacking a high coercive force layer (hereinafter referred to as a write layer) having a low Curie temperature and good recording characteristics and a low coercive force layer (hereinafter referred to as a read layer) having a good Curie temperature and good reproduction characteristics. ,
Bits written in the writing layer with a small amount of energy are transferred by exchange coupling to the reading layer having a large magneto-optical effect, and read from the reading layer side (for example, JP-A-57-78652).
issue).

As such a high coercive force layer, in the above example, Tb _x Fe _100-x
The amorphous alloy of is used as the low coercive force layer
_z (Fe _y Co _100-y ) _100-z } is used.

[Problems to be Solved by the Invention]

However, the conventional magneto-optical recording medium has a drawback that it is easily corroded, and there is a problem in putting it to practical use.

The present inventors have found a recording material having high sensitivity and high corrosion resistance while maintaining high C / N, and arrived at the present invention.

[Means for solving the problem]

The magneto-optical recording medium of the present invention comprises a high coercive force layer having a low Curie point capable of perpendicular magnetization and a low coercive force layer having a high Curie point capable of perpendicular magnetization, and the high coercive force layer and the low coercive force layer. Is an exchange-coupled magneto-optical recording medium, the high coercive force layer is an amorphous alloy of (Tb _x Fe _100-x ) _100-a Ti _a , and the low coercive force layer is {Gd _z (Fe _y Co _100-y ) _100-z } _100-b T
i _b , and x, y, z, a and b are x = 20 to 25 atom% y = 50 to 90 atom% z = 20 to 26 atom% a = 2 to 8 atom% b = 2 to 8 atom Configured to be in the% range.

Further, the magneto-optical recording medium of the present invention has a high coercive force film having a low Curie point capable of perpendicular magnetization and a low coercive force film having a high Curie point capable of perpendicular magnetization, and the high coercive force film and the low coercive force film The magnetic film is a magneto-optical recording medium that is exchange-coupled, and the high coercive film is a film in which a TbFe alloy layer and a Ti layer are alternately laminated in an atomic order thickness, and its average The composition is an amorphous alloy of (Tb _x Fe _100-x ) _100-a Ti _a ,
The low coercive force layer is a film in which layers of GdFeCo alloy and layers of Ti are alternately laminated with an atomic order thickness, and the average composition thereof is {Gd _z (Fe _y Co _100-y ) _{100- z} } _100-b Ti _b is an amorphous alloy in which x, y, z, a, and b are x = 20 to 25 atom% y = 50 to 90 atom% z = 20 to 26 atom% a = 2 -8 atom% b = 2-8 atom%

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

 FIG. 1 is a schematic sectional view showing an embodiment of the present invention.

The magneto-optical recording medium shown in FIG. 1 includes a substrate 1, a protective layer 2,
5, a low coercive force layer 3 having a high Curie point capable of perpendicular magnetization, and a high coercive force layer 4 having a low Curie point capable of perpendicular magnetization.

 The low coercive force layer 3 and the high coercive force layer 4 are exchange-coupled.

As the substrate 1, synthetic resin such as epoxy resin, polycarbonate resin, acrylic resin, or glass can be used. The low coercive force layer 3 having a high Curie point capable of perpendicular magnetization is gadolinium (Gd), iron (Fe), and cobalt (Co).
And an amorphous alloy of titanium (Ti), a Ti layer 12 and GdFe are formed on a substrate 1 on which a film is deposited as shown in a specific example in FIG.
The Co alloy layer 11 and the Co alloy layer 11 are alternately laminated in dozens of layers with the thickness of the atomic order to form the low coercive force film 3 as a whole.

High coercive force film 4 having a low Curie point capable of perpendicular magnetization
Is an amorphous alloy of terbium (Tb), iron (Fe) and titanium (Ti). As with the low coercive force film 3, as shown in the specific example of FIG. 2, the Ti layer 12 and the TbFe alloy layer 13 are And are alternately laminated in dozens of layers with an atomic thickness to form a magnetic film as a whole.

The composition of the low coercive force film 3 {Gd _z (Fe _y Co _100-y ) _100-z } _100-b Ti _b and the composition of the high coercive force film 4 (Tb _x Fe _100-x ) _100-a Ti _a are It is desirable that x, y, z be in the range of x = 20 to 25 atom%, y = 50 to 90 atom%, z = 20 to 26 atom%, from the viewpoint of recording and reproducing characteristics.

It is desirable that a and b are in the range of a = 2 to 8 atomic% and b = 2 to 8 atomic% from the viewpoint of corrosion resistance of recording / reproducing characteristics.

The magnetic films of the low coercive force film 3 and the high coercive force film 4 alternately laminated in dozens of layers with the thickness of the atomic order as described above can be formed by the sputtering apparatus as shown in FIG. .

The sputtering apparatus shown in FIG. 3 includes a substrate holder 31, sputtering sources 32 and 33, sputtering targets 34 and 35, and a mask.
It consists of 36 and.

Several substrates 1 are concentrically attached to the substrate holder 31 apart from the rotation axis (OO ').

A sputter source 32 and a sputter source 33 are provided at positions facing the substrate holder 31, and the sputter target 3
4, Sputter target 35 is attached. Sputter source 32,3
A mask 36 is provided between the substrate 3 and the substrate holder 31 so that a film is formed only right above the sputtering sources 32 and 33.

In the sputtering apparatus shown in FIG. 3, the sputtering target 34 of the sputtering source 32 is GdFeCo, the sputtering target 35 of the sputtering source 33 is Ti, and the power input to the sputtering sources 32 and 33 is adjusted to adjust the sputtering sources 32 and 33. By forming a film on the substrate 1 while rotating the substrate holder 31 at an appropriate film forming speed, the low coercive force is alternately laminated in dozens of layers with an atomic order of thickness as shown in FIG. The membrane 3 can be created. Sputter target 34 is TbFe and sputter target 35 is Ti.
By similarly forming a film, a high coercive force film 4 having dozens of layers alternately stacked with an atomic order thickness as shown in FIG. 2 can be manufactured. Thus sputter target 3
Since 4,35 is divided into GdFeCo and Ti and TbFe and Ti, a recording medium having the same characteristics can be obtained even when the sputter targets 34 and 35 are used for a long time. When GdFeCoTi or TbFeTi is used as the sputter targets 34 and 35, the film formation rate decreases after long-term use, and the composition in the film changes from the initial value, which changes the characteristics of the recording medium.

Next, a specific example of the embodiment shown in FIG. 1 will be described.

First, a silicon nitride film was formed as a protective film 2 on a substrate 1 of an epoxy disk with a guide groove having a diameter of 200 mm and a thickness of 1.2 mm.
The film was formed with a thickness of 0Å.

Next, by co-sputtering the GdFeCo target and the Ti target with the sputtering apparatus shown in FIG. 3, the GdFeCo alloy layer 11 and the Ti layer 12 are alternately laminated in dozens of layers in atomic order thickness, and the average composition Is 23.0 vs 58.4 vs 14.6 vs 4.0 in atomic%
A 200 Å thick readout film of a pair of GdFeCoTi was formed. (Note that
Ti layer 12 at this time is not a complete layer).

Continue to use Tb with the sputtering device shown in Fig. 3.
By co-sputtering a Fe target and a Ti target, the TbFe alloy layer 13 and the Ti layer 12 are alternately laminated in dozens of layers with an atomic order thickness, and the average composition is 20.2 vs. 75.8 vs.
A 1000 Å thick writing film of 4.0 TbFeTi was formed. (Note that
Ti layer 12 at this time is also not completely layered).

Finally, a silicon nitride film was formed thereon as a protective film 5 having a thickness of 800 Å to prepare a magneto-optical recording medium.

This magneto-optical recording medium was rotated at 3600 rpm, and a semiconductor laser having a wavelength of 830 nm was radiated through the substrate 1 at a recording frequency of 10
When a MHz signal was recorded with a recording power of 11.6 mW and reproduced with a reproduction power of 3.9 mW, a C / N of 60 dB was obtained, and it was confirmed that the magneto-optical recording medium had high sensitivity and high C / N. It was

Sputtering was performed many times from the surface state of the GdFeCo target at this time, and when it was offset by about 1 mm, the film was formed under the same sputtering conditions as above, and the recording and reproducing characteristics were measured and compared. Results were obtained.

For comparison, a read film was formed by using a GdFeCoTi target without co-sputtering, a write film was formed by using a TbFeTi target without co-sputtering, and a magneto-optical recording medium was produced in the same manner as above, When the recording and reproducing characteristics were measured, it was 60 dB.
C / N was obtained and was equally good.

However, the C / N of the magneto-optical recording medium prepared after using the GdFeCoTi target so as to deviate by about 1 mm from the beginning had a low C / N, and good recording / reproducing characteristics could not be obtained.

This is because the amount of Ti on the target increased and sputtering was performed using such a target, so that the composition of the obtained film changed from the initial value.

Next, the magneto-optical recording medium prepared as described above is heated to 60 ° C.
The bit error rate (BER) was measured after 500 hours of storage in a high temperature and high humidity environment of 80%, and it was confirmed that the BER did not increase and the corrosion resistance was excellent.

The repeating unit film thickness of the magnetic layer of GdFeCo or TbFe is
From the viewpoint of recording and reproducing characteristics, a range of about 2 to 6Å converted from the film forming rate is desirable.

When the content of Tb is reduced, the recording sensitivity is lowered, the recording noise is slightly increased, and the C / N is lowered. Therefore, _x of Tb _x Fe _100-x is preferably 20 to 25 atomic%.

In Gd _z (Fe _y Co _100-y ) _100-z , when Co is decreased, the magneto-optical effect is lowered, and when Co is increased, the recording sensitivity is lowered. Therefore, y is preferably 50 to 90 atomic%. If the ratio is decreased, the recording sensitivity is increased, but the recording noise is increased and the C / N is decreased, so that z is preferably 20 to 26 atomic%.

If the Ti content is low, corrosion resistance will become a problem, and if it is high, C /
Since N decreases, (Tb _x Fe _100-x ) _100-a Ti _a and {Gd _z (Fe _y
Co _100-y ) _100-z } _100-b Ti _b is preferably 2 to 8 atom% as a and b.

〔The invention's effect〕

By mixing titanium (Ti), the magneto-optical recording medium of the present invention has an effect that it can have high corrosion resistance while maintaining high sensitivity and high C / N.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, FIG. 2 is a schematic view showing one specific example of the embodiment shown in FIG. 1, and FIG. 3 is a high coercive force film and a low coercive force film shown in FIG. It is a schematic sectional drawing of the sputtering apparatus for producing a coercive force film. 1 ... Substrate, 2,5 ... Protective film, 3 ... Low coercive force film, 4 ...
… High coercive force film, 11 …… GdFeCo alloy film, 12 …… Ti layer, 13…
… TbFe alloy layer, 31 …… Substrate holder, 32, 33 …… Sputter source, 34, 35 …… Sputter target, 36 …… Mask.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 63-71960 (JP, A) JP 61-117747 (JP, A) JP 62-200551 (JP, A)

Claims (2)

[Claims] 1. A low Curie point capable of perpendicular magnetization (Tb _x Fe
_100-x ) _100-a Ti _a high coercive force layer made of an amorphous alloy and a high Curie point capable of perpendicular magnetization and exchange coupled with the high coercive force layer {Gd _z (Fe _y Co _100-y ) _100-z } _100-b Ti _b including a low coercive force layer made of an amorphous alloy, and x, y, z, a, and b are x = 20 to 25 atomic% and y = 50 to 90 atomic%, respectively. A magneto-optical recording medium, characterized in that z = 20 to 26 atomic% a = 2 to 8 atomic% b = 2 to 8 atomic%. 2. A TbFe alloy layer and a Ti layer having a low Curie point capable of perpendicular magnetization are alternately laminated in an atomic order thickness, and the average composition thereof is (Tb _x Fe _100-x ) _100-a. A high coercive force film, which is an amorphous alloy of Ti _a , and a GdFeCo alloy layer and a Ti layer, which have a high Curie point capable of perpendicular magnetization without being exchange-coupled with the high coercive force film, are alternately laminated in an atomic order thickness. And its average composition includes a low coercive force film which is an amorphous alloy of {Gd _z (Fe _y Co _100-y ) _100-z } _100-b Ti _b , and the x, y, z, Each of a and b is configured to be in the range of x = 20 to 25 atomic% y = 50 to 90 atomic% z = 20 to 26 atomic% a = 2 to 8 atomic% b = 2 to 8 atomic%. A magneto-optical recording medium characterized by: