JPH01296446A - Member for magneto-optical recording and its production - Google Patents

Abstract

PURPOSE:To greatly improve corrosion resistance without fluctuating magnetic characteristics and to form a secure protective film by providing a compd. layer in which Cr and N are bonded near to the boundary faces of magneto- optical recording films. CONSTITUTION:An underlying film 2 consisting of silicon nitride is formed by, for example, a sputtering method, to 600A film thickness on a substrate 1 and in succession, the magneto-optical recording film 3 having the compsn. Tb26Fe44Co20Cr3Pt7 is formed by a sputtering method thereon. A TbFeCoPt alloy and Cr are used for targets and Ar is used for a discharge gas at this time. The film formation is executed by two-dimensional simultaneous sputtering method and simultaneously impressing RF electric power to both the targets to form about 800A film. The discharge gas is in succession changed with N2 and an oxygen diffusion preventive layer 4 is formed to about 200A. The nitrogen layer boned to the Cr is thus formed near the boundary face. The diffusion of oxygen, etc., into the films is thereby prevented and the corrosion is suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording member for recording, reproducing, and erasing information using light, and a method for manufacturing the same, and particularly relates to a highly reliable and magneto-optical recording member. , relates to a long-life magneto-optical recording member and a method for manufacturing the same.

[Conventional technology]

With the development of an advanced information society, the need for high-density, large-capacity, and rewritable file memory is increasing. Optical disks are attracting attention as something that satisfies this requirement, and magneto-optical recording is at the closest stage to practical use.

By the way, the recording material used for magneto-optical recording is TbFe.
Amorphous alloys consisting of rare earth elements such as Co and iron group elements, and Heusler alloys mainly consisting of PtMnSb are known, but both are active against oxygen and water in the atmosphere. It corrodes easily to form hydroxides and oxides. As a result, various characteristics of the disk deteriorate over time, recorded information cannot be retained, and the life of the disk or reliability of the disk decreases.

In order to prevent this, Japanese Patent Application Laid-Open No. 61-51806
It is described that Cr, Mo, W, etc. are added to a Tb alloy, and JP-A-61-87306 describes that Cr, Ti, etc. are added to an alloy consisting of CoFe and rare earth elements.

[Problem to be solved by the invention]

The above-mentioned conventional technology does not consider simultaneously suppressing corrosion caused by water in the atmosphere and pitting corrosion caused locally in the magneto-optical recording film, and the reliability of the magneto-optical recording member is insufficient. There was a problem that it was not.

An object of the present invention is to provide a highly reliable magneto-optical recording member and a method for manufacturing the same.

[Means to solve the problem]

The above object is a magneto-optical recording member having a magneto-optical recording film having perpendicular magnetic anisotropy and recording, reproducing and erasing information using light, wherein the magneto-optical recording film contains Cr and A magneto-optical recording member characterized by having a layer in which nitrogen bonded to Cr is present on at least one of the interfaces of a magneto-optical recording film, which has perpendicular magnetic anisotropy on a substrate by sputtering or electron beam evaporation. In the method for manufacturing a magneto-optical recording member that forms a magneto-optical recording film that records, reproduces, and erases information using light, the magneto-optical recording film contains Cr, and the magneto-optical recording film contains Cr, and Alternatively, at the final stage or both, sputtering or electron beam evaporation is performed in an atmosphere containing nitrogen to form a layer containing nitrogen combined with Cr on at least one of the interfaces of the magneto-optical recording film. This is achieved by at least one method of manufacturing a magneto-optical recording member.

The magneto-optical recording film used in the present invention may have any alloy composition as long as it has perpendicular magnetic anisotropy and contains Cr. For example, it consists of rare earth elements and iron group elements,
A material containing Cr is used. Furthermore, this composition includes Pt,
At least one element selected from Au, Pd, and Rh is added and used, and in addition, Nb, Ti, and Ta are used.
, AQ is preferably used in addition. Usually, the total amount of rare earth elements and iron group elements is preferably 85 at % or more. In addition to such alloys, Heusler alloys containing Cr are also used,
In this case as well, it is preferable that the material further contains pt.

It is preferable that 0.5 at % or more of Cr is present near the interface of the recording film. The composition of the elements may be changed in the thickness direction of the recording film, and the amount of Cr may be changed in this way so that it becomes 100 at % near the interface. The bond M of Cr and N (hereinafter referred to as the oxygen diffusion prevention layer) is preferably present in a thickness of 20 to 200 nm near the interface of the recording film. The effect is not significant for less than 20 people. The upper limit of thickness is 2
Although the number of layers may exceed 0.00, it takes a long time to form this layer, so it is not preferable to make it unnecessarily thick.

In the oxygen diffusion prevention layer, N is preferably 0.1 to 4 at%, more preferably 0.2 to 3 at%. If the amount is less than 0.1 at%, the effect is not significant. Although the amount of N may exceed 4 at%, it is difficult to contain a large amount of N using normal methods.

[Effect]

By providing a nitrogen layer bonded to Cr near the interface of the magneto-optical recording film, it is possible to prevent oxygen and the like from diffusing into the recording film, thereby suppressing corrosion of the recording film.

〔Example〕

Hereinafter, the details of the present invention will be explained in detail using Examples.

Example 1 FIG. 1 shows a schematic diagram of the cross-sectional structure of a magneto-optical disk manufactured by the method described below. On a substrate 1 having a guide groove,
A base film 2 of silicon nitride was formed to a thickness of 600 mm by sputtering. The refractive index of the produced film was 2.5. Following that, Tb2cFe44Co2゜Cr5P
A magneto-optical recording film 3 having a composition of t7 was formed by a sputtering method. The target was T b FeCo P alloyed with Cr, and the discharge gas was Ar. Film formation was performed by a two-dimensional simultaneous sputtering method. That is, RF power was applied to the first target at the same time to form a film of 800 layers. Then, the discharge scum was switched to N, and the sputtering continued without stopping the discharge, and about 200 people made an oxygen diffusion prevention layer 4.
was formed to produce a magneto-optical disk.

The characteristics of the disc manufactured in this way are: carrier-to-noise ratio (C/N) 58 dB (pulse width: 50011S
eC, frequency: IMHz, externally applied magnetic field: 4000e.

N A =0.5 + laser power 8 mW, rotation speed 1200 rpm). This disc at 60℃-9
The results are shown in Fig. 2, showing the changes over time in Error Ray 1 when left in 0% RH. As a comparative example, a disk was used in which the entire film was formed using only Ar. As a result, when the disk was left in this environment, the error rate was 1.
- No increase was observed and the value remained constant at 2X]0-+ (cases/bit), whereas when using the membrane of the comparative example, it increased approximately three times to 6X10-6 (cases/bit) after 3000 hours. did.

By the way, when the state of nitrogen in the surface layer was analyzed using xPS, it was found that Cr did not exist as a single substance but in a bonded state. In addition, results suggesting a bond between Cr and nitrogen were obtained from measurements using a Mössbauer.

The amount of nitrogen in the oxygen diffusion prevention layer is about 0.5 to Eat%. The reason why no increase in error to 1 is observed is due to the presence of Cr nitride.

On the other hand, in the comparative example without the oxygen diffusion prevention layer,
Although the progress of corrosion is suppressed by the effect of the additive elements, it is insufficient. It can be seen that this is due to the difference in the density of the passive film mainly composed of Cr.

Example 2 In this example, a disk was manufactured using an ion beam sputtering apparatus, and a schematic diagram of the apparatus is shown in FIG. The apparatus shown in FIG. 4, which is a schematic diagram of the cross-sectional structure of the manufactured disk, is of a load-lock type, and the figure shows the main parts for sputtering. In normal sputtering, argon gas is introduced to the depot gun side, ionized and accelerated, and the alloy target Tb1g Nd
Sputtering is performed by colliding the ions of s Fe37COz8CraPtt) with its ions. To manufacture the disc, prior to forming the recording film, nitrogen ions are fired from a milling gun.
The surface of the substrate with guide grooves was clarified. Then, with the milling gun operating, the depot gun was also operated at the same time, and a film was formed while milling to provide the oxygen diffusion prevention layer 4. When the thickness reached 100 layers, the milling gun was stopped, and the depot gun was used to form a film. A recording film 3 is formed, and 80
When the thickness reached 0 mm, milling was performed again, and an oxygen diffusion prevention layer 4 of 200 mm was formed thereon to obtain a desired magneto-optical disk. As a comparative example, a magneto-optical disk was used in which 1,100 films were formed using only a deposit gun without using a milling gun.

When the characteristics of this disk were evaluated, C/N=52d
B (Frequency: IMHz, pulse width: 500ns.

Externally applied magnetic field: 4000e, N^=0.5. Recording laser power 10mW, readout laser power 1.5mW)
Met. In addition, the magnetic properties of the recording film are Curie temperature: T
c=250°C, compensation temperature: T comp = 90°
C, Kerr rotation angle: 0K=0.34°, coercive crab Hc
=9KOe.

Next, Fig. S shows the results of the change in error rate over time when this disk was left at 60° C. and 90% RH. From this figure, the error rate of the disk manufactured according to the present invention remained constant at 2 Xl0-6 (items/bit), with no change at all from the initial stage of manufacture until it was left for 1500 hours.
After that, it gradually increased in thickness to 3X10- after 3000 hours.
'(case/bit). On the other hand, in a comparative example that does not use the present invention, 2X10-' (items/bi
t) gradually increases after 1000 hours, and after 3000 hours I
-5 (cases/bit). It can be seen that by using the present invention as described above, the occurrence of errors can be significantly suppressed.

By the way, when we investigated the bonding state between the metal material and nitrogen on the surface of the recording film using Auger electron spectroscopy and Mossbauer spectroscopy, we found that mainly Cr and nitrogen in the material were strongly bonded. .

In addition to Cr, some Fe was also bonded to nitrogen. Since this compound of Cr and nitrogen is stable and dense and has a significantly high protective effect, it may be provided not only as a surface layer but also as a protective film. Note that the amount of nitrogen in the oxygen diffusion prevention layer was about 0.5 to lat%.

Example 3 The structure of the magneto-optical disk manufactured in this example is the same as that of Example 2, as shown in FIG. The disk was manufactured by a DC dual-sputtering method. A schematic diagram of the device is shown in FIG. The apparatus used consisted of two evaporation sources, a TbFeCoPt alloy target and a Cr target, and a N2 plasma source, and the discharge gas was mainly Ar, with N2 for nitriding being turned into plasma. The disk manufacturing procedure was as follows: First, the surface of the substrate 1 with guide grooves was irradiated with plasma from an N2 plasma gun, and then a Cr target was discharged to form a film of about 50 layers.
The recording layer 3 was formed by gradually decreasing the amount of plasma irradiation and the current flowing through the Cr target, and discharging the TbFeCoPt target.

When the film thickness reached 100 people, the nitrogen plasma irradiation was stopped. Then, when the total film thickness reached 800 wafers, the current applied to the T b Fe Co P t was gradually lowered, and stopped completely when the total film thickness reached 900 wafers. On the contrary, the current flowing through the Cr target was gradually increased and the amount of N2 plasma irradiation was increased. Then, the film formation was stopped when the total film thickness reached 1100 layers. The composition of the recording layer is Tb26Fe44C
o2oCr3Pt7, and the composition of the oxygen diffusion prevention layer is the same as the recording layer on the side in contact with the recording layer, and changes toward the outside so that the amount of Cr increases and the amount of other metal elements decreases, and on the surface. The metal element is only Cr.

When the C/N of the disc thus produced was measured under the same recording and reproducing conditions as in Example 2, it was 53 dB. A life test was conducted using this disk, and the results are shown in FIG. As a comparative example, one manufactured without irradiation with N2 plasma was used. As a test method, the discs were left in the same environment as in Example 1 at <60° C. and 90% RH, and changes in error rays 1 to 1 were measured over time. As a result, disks manufactured without using the present invention had an error rate of 2X10-' (cases/bit) at the initial stage of manufacture, but the error rate was 1
It started to gradually increase after 000 hours and reached 5x1o-'(cases/bit) after 3000 hours. On the other hand, the error rate of the disc manufactured using the present invention did not change at all both at the initial stage of manufacture and after being left for 3000 hours.
×10-' (items/bit).

The bonding state of nitrogen and Cr in the surface layer of this disk was examined using XPS.
and Mössbauer, results suggesting that Cr and nitrogen are also bonded were obtained. Further, FIG. 8 shows the results of examining the distribution of Cr, N, and O among the elements constituting the recording film of the disk manufactured in this example. Oxygen exists only near the surface of the recording layer, and Cr creates a composition gradient from the surface to the inside of the film.
Since it was possible to further strengthen the bond with nitrogen and suppress layer peeling, it was possible to obtain the greatest protective effect. Note that the amount of nitrogen in the oxygen diffusion prevention layer was about 0.5 to lat%.

Example 4 The structure of the manufactured disk was the same as that of Example 2, as shown in FIG. The disk was manufactured using an electron beam (EB) evaporation device. PtMnSb alloy and Cr were used as the source for vapor deposition. First, a disk substrate with guide grooves is kept at 300°C, and N
2 After about 50 people laminated the Cr layer in an atmosphere, A
Switching to the r atmosphere, PtMnSb and Cr were deposited at the same time, and when the film thickness reached 900 layers, the atmosphere was changed again to N2 atmosphere and Cr was deposited only until the film thickness reached 1100 layers.

A life test of this disk was conducted under the same environmental conditions as in Example 1. The lifespan was evaluated based on the results of measuring changes in the thickness of the oxide layer on the surface using ellipsometry. The results are shown in FIG. Here, as a comparative example, a disk in which all film formation was performed in an Ar atmosphere was used. As a result, when using the present invention, the film thickness of the surface layer increases significantly for the first 300 hours;
Until then, there was no growth of the surface layer at all.

On the other hand, in the comparative example that was not produced in an N atmosphere, the film thickness of the surface layer changed significantly immediately after 300 hours after being left in the environment, and then a gradual increase in film thickness was observed.

This indicates that corrosion is progressing over time. It was found that the progress of corrosion can be greatly suppressed by providing a bonding layer of Cr and N as seen in this example. The composition of the recording film is P t4oM
n2s S b311Cr, and the amount of nitrogen in the oxygen diffusion prevention layer is about 1 to 1.5 at%.

In this way, the present invention is effective in improving corrosion resistance by having a compound layer of Cr and N bonded near the interface of the recording film, regardless of the type of magnetic material or the manufacturing method. There is.

〔Effect of the invention〕

According to the present invention, the presence of a compound layer in which Gr and N are combined in the vicinity of the interface of the magneto-optical recording film has the effect of significantly improving corrosion resistance without changing the magnetic properties. In addition, the surface layer can be easily formed by changing the production atmosphere, and continuous film formation is possible, making it possible to form a strong protective layer without peeling or cracking. . Furthermore, the produced nitride layer, particularly the compound of Cr and N, has extremely high hardness and high mechanical protection performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a cross-sectional structure of a magneto-optical disk according to an embodiment of the present invention; FIGS. 2, 5, and 7 are diagrams showing changes in error rate over time to explain the present invention; 3 is a schematic diagram of an ion beam sputtering device, FIG. 4 is a schematic diagram of a cross-sectional structure of a magneto-optical disk according to another embodiment of the present invention, FIG. 6 is a schematic diagram of a DC binary simultaneous sputtering device, and FIG. 8 FIG. 9 is a diagram showing the minute digit result of a magneto-optical disk according to another embodiment of the present invention.
The figure is an explanatory diagram for explaining the present invention. 1 Substrate 2... Base film 3/Magneto-optical recording film 4... Oxygen diffusion prevention layer Attorney Junnosuke Nakamura Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. A magneto-optical recording member having a magneto-optical recording film that has perpendicular magnetic anisotropy and records, reproduces and erases information using light, wherein the magneto-optical recording film contains Cr. 1. A magneto-optical recording member comprising a layer containing nitrogen bonded to Cr on at least one of the interfaces of the magneto-optical recording film. 2. The magneto-optical recording member according to claim 1, wherein the composition of the magneto-optical recording film changes in the film thickness direction, and the Cr concentration increases in a portion of the magneto-optical recording film near an interface. 3. On the substrate by sputtering or electron beam evaporation,
It has perpendicular magnetic anisotropy and can record, reproduce, and reproduce information using light.
In the method for manufacturing a magneto-optical recording member forming a magneto-optical recording film for erasing, the magneto-optical recording film contains Cr and nitrogen at the beginning or end of formation of the magneto-optical recording film or both. A method for producing a magneto-optical recording member, characterized in that a layer containing nitrogen bonded to Cr is formed on at least one of the interfaces of the magneto-optical recording film by sputtering or electron beam evaporation in an atmosphere.