JPS63224052A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To increase the light reflectance of a magneto-optical recording film and to improve the reproduction output or the recording-reproducing characteristics by incorporating Pt, Rh, Pd or Au into the recording film. CONSTITUTION:A film 2 having an optical effect is formed by sputtering on a substrate 1 of glass or high heat resistance resin having cleaned guide grooves and a magneto-optical recording film 3 is further formed. The film 3 is made of a magneto-optical recording material mixed with 0.5-15 atomic% at least one kind of noble metal selected among Pt, Au, Rh and Pd. The noble metal in the film 3 is preferably distributed so as to make the concn. high in the vicinity of the surface of the film 3 on which the writing and readout of informa tion are carried out and to gradually lower the concn. in the perpendicular direction. The resulting recording material can maintain high reflectance due to the noble metal as a whole over a long period.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magneto-optical recording medium in which information is written, read and erased using a laser, and in particular relates to a magneto-optical recording medium suitable for obtaining high reproduction output. Concerning recording materials.

[Conventional technology]

In recent years, high density, large capacity, and random access have become possible.
Rewritable magneto-optical disks are attracting attention. @The amorphous alloy system made of rare earth-iron group elements represented by the Tb-Fe-Go system is said to be closest to practical use as a recording material for nocturnal magnetic disks. The Kerr rotation angle for these materials is 0.33”-0.40
', and by using the Kerr enhancement layer, 0.51 ~
It can be increased to 0.6#. Shigashi, Nier
The light intensity decreases due to multiple reflections due to this Kerr enhancement provided to amplify the r effect, and the light reflectance decreases. Specifically, the light reflectance without this enhancement layer is 45. %, but by providing an enhancement layer, the light reflectance decreases to 25 to 28%.When the Kerr rotation angle of the magneto-optical recording material is 0.33° to 0.
．． If it is in the range of 38'.

However, it is not clear which has a greater effect, the improvement in reproduction output due to an increase in the Kerr rotation angle, or the improvement in reproduction output due to an increase in light reflectance.

In the conventional technology, studies have focused on magneto-optical recording media having a large Karr rotation angle, and there has been little study on improving reproduction output by improving light reflectance. Although there are few reports regarding the reflectance of the magneto-optical recording film itself, there are some reports regarding the light absorption of the magneto-optical recording film or optically functional film, such as Japanese Patent Laid-Open No. 59-227056,
Japanese Patent Publication No. 59-227054.

For example, Japanese Patent Application Laid-Open No. 59-227053 can be cited.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology mainly focuses on improving the Karr rotation angle of the magneto-optical recording film, but does not give sufficient consideration to improving the reflectance, and has the problem that it is difficult to obtain high reproduction output.

An object of the present invention is to improve the reflectance of a magneto-optical recording film without deteriorating the magneto-optical properties by adding an element that improves the reflectance to a magneto-optical recording material, and to provide a magneto-optical recording material with high reproduction output. The goal is to provide a medium.

[Means for solving problems]

The above purpose is to use Pt and Au as a magneto-optical recording material.

This is achieved by adding at least one noble metal element selected from Rh and Pd in a range of 0.5 to 15 atomic percent.

In this case, it is also preferable to add a large amount near the surface of the magneto-optical recording film on the side where information is written and read, and to create a concentration gradient such that the amount added is gradually reduced toward the opposite surface.

[Effect]

Pt, Au, Rh added to magneto-optical recording material.

Pd itself has a significantly high reflectance.

When these elements are added to the recording material in a range of 0.5 to 15 atomic percent, the high reflectance of these added elements themselves is maintained as a whole of the recording material.

Furthermore, since these elements themselves are inert to the environment, their high reflectance can be maintained for a long time.

〔Example〕

The details of the present invention will be explained below using Examples 1 and 2.

[Example 1] In this example, the case where Rh is added to the magneto-optical recording material will be explained.6 A schematic diagram of the cross-sectional structure of the produced magneto-optical disk is shown in Fig. 1. On a glass or high heat resistant resin substrate 1 having a guide groove,
Optical effect film 2 was created by a sputtering method. At that time, a 5iaNa sintered body was used as a sputtering target, and A r / N z = 95 / 5 (% /
%) mixed standard gases were used, respectively. The sputtering conditions were a discharge gas pressure of 5 X IQ-8 Torr, a substrate rotation speed of 30 rpm, and an input RF power of 4.5 W/caI.
The refractive index n of the film sputtered for 10 minutes was 2.05. The film thickness is 850 people. Subsequently, a magneto-optical recording film 3 was formed. Target is T bzeF es
An eco1g sintered target, a Nb target, and a Rh target for adding noble metal elements according to the present invention were used. The film was formed by a three-source simultaneous sputtering method.

The sputtering conditions were Ar for the discharge gas, and a discharge gas pressure of 5 x 10-
' (Torr), Substrate rotation speed: 60rp+*, Input RF power; TbFeCo: 5 W/cym",
Nb: 0, 2W/cm", Pt: 0
, I W/am", sputtering time: 10 minutes. The thickness of the resulting magneto-optical recording film is 1000 mm. The film composition is (Tbz7FasaCotsNba)ee, 5Rh
o, n.

Note that a protection m4 made of 5iaNa or the like is usually formed on this magneto-optical recording film.

By the way, the magnetic properties of this magnetic recording film are as follows: err rotation angle: θh = 0.35', coercive force Ha = 5 KOe
.

Curie temperature: Tc = 200°C. Centering on this point, the concentration of Rh, i.e. (Tbz7FaISaCoxII) zoo;xRhx
FIG. 2 shows the relationship between the light reflectance and the Curie temperature 'rc when X is varied from O to 2 Qatm%.

The dependence of light reflectance on Rh concentration is the same for T with no Rh added.
The light reflectance of b Fe Co N b was 29%, but when Rh was added to this, the light reflectance increased rapidly as shown in curve 5, and the light reflectance was 0.5% of Rh. When Rh was added, it was 42%, when 1.0% was added, it was 46%, and when 2.0% was added, it was 47%, and thereafter it increased slightly with the addition of Rh. On the other hand, the change in the Curie temperature Tc, which is one of the magnetic properties of magneto-optical disks made with varying amounts of Rh added, was 180°C for TbFeCoNb without any Rh added, but as Rh was added, 1 As shown in curve 6, Rh
The temperature rises in proportion to the amount, with 5% addition at 240℃ and 10% addition at 240℃.
The temperature was 310°C at 65'C and 20%. The optimal Curie temperature (Tc) of the recording material for a magneto-optical disk is around 200°C. However, as Rh is added, the reflectance improves as mentioned above, but the Curie temperature also increases, making it impossible to operate the disk.Also, if the amount of Rh added exceeds 12%, the Tb-rich composition (rare earth sub-component) When the addition amount was further increased, the magnetism disappeared. The Curie temperature can be lowered by adjusting the composition, such as increasing the amount of Nb in the recording material, but there is a problem that if the amount of Nb is increased too much, magnetism will be lost. There is also a limit to the control of Curi temperature by controlling the temperature of the cucumber. Nbt and bo
The control range of the Curie temperature by optimizing the amount or the ratio of rare earth elements and iron group elements is approximately 90°C, and the R
The maximum amount of h added was 15%. When 15% or more of Rh is added, the film deviates from this range, making it impossible to control the Curie temperature, Kerr rotation angle, and coercive force by controlling the film composition. This means that the concentration range in which Rh addition improves the reflectance and has practical magneto-optical properties is 0.
It is 5 to 15 at+w%.

In addition, almost similar results were obtained when Rt, Au, and Pd were added.

When we measured the recording and reproducing characteristics of the magneto-optical disks prepared in this way, we found that the one with 0.5% Rh added had a C/N=
C/N = 60 dB, whereas C/N = 57 dB was improved by 3 dB compared to the conventional C/N without adding Rh. This effect is similar to that of other Pt, Au.

The results were almost the same when Pd was added.

[Example 2] The cross-sectional structure of the produced magneto-optical disk was the same as in Example 1, and a schematic diagram is shown in FIG. First, a 5iaNa optical effect film 2 was formed thereon by sputtering. The preparation conditions and film thickness at that time were the same as in Example 1. Subsequently, a magneto-optical recording film 3 was formed. The target is (Gdo, sT bo, z) o, 27Fao, 5
aCoo, tsNbo, oa sintered targets and an Au plate for adding noble metal elements according to the present invention were used. The film was formed by a two-source simultaneous sputtering method. The conditions at that time were
It is as follows. Ar was used as the discharge gas, the discharge gas pressure was 5X 10-a (Torr), and the number of rotations of the substrate was 80.
rpm, input RF power; 5 W for magneto-optical recording @ membrane
/am”.

Sputtering was carried out for 10 minutes at 0.1 W/cm" for Au. Here, the input RF force for Au was 0.1 W/am" for the first 3 minutes, and after 3 minutes it was sputtered at 5.
After 5 minutes, sputtering was performed using only the G d T b Fe Co N b based sintered body as a target from 5 minutes until the end of sputtering, to form a recording film. A magneto-optical recording film with a concentration gradient of additive elements in the recording film has the effect of being resistant to corrosion from the film surface.The composition of the created film at the interface between the enhancement film and the recording film was determined by analysis. , (Gdo, aT
bo, z) o, zsFθo, +5scoo*
It was t2INbo, on)o, esAuo, ot.

The protective film 4 provided thereon is also the same as in the first embodiment. The optical reflectance measured through the substrate of the magneto-optical disk thus prepared was 45%, and the optical reflectance of the system not containing Au was 30%, but by adding 1% Au, the optical reflectance was 1%.
We were able to improve this by 5%. When the recording and reproducing characteristics of this disk were measured, the C/N was 60 dB, whereas the one with 1% Au added had a C/N of 60 dB.

In the case of the one not containing Au, the C/N was 57 dB, which was improved by 3 dB as in Example 1 by adding Au to improve the light reflectance. This effect is due to Pt, Rh, Pd
The results were almost the same even when . Also, A u added to the recording film.

When the amounts of Pd, Pt, and Rh were increased, the light reflectance improved to 51% with addition of 15%. However, as explained in Example 1, if more than this is added, the magneto-optical properties are lost and information cannot be recorded, reproduced or erased. Furthermore, by creating a concentration gradient in the additive elements as in this example, the corrosion resistance of the film was greatly improved.

In other words, if the prepared film is stored in a high temperature and high humidity environment of 80'C and 95% RH (relative humidity), the change in the saturation magnetization of the film after 300 hours rm will be different from that of the film (((Gdo ,5Tbo,z)o,zoFeo,!Ia
coo, taNbo, oalo, ellAuo, os)
In contrast, when a composition gradient was set and a recording film whose composition at the interface was equal to the composition described above was used, the change was 11%.
We were able to significantly reduce it to less than 1/2.

〔Effect of the invention〕 According to the present invention, the magneto-optical recording film contains Pt and Rh.

By adding Pd and Au, the light reflectance of the recording film can be greatly improved, so strong light intensity can be obtained and the reproduction output or recording-reproduction characteristics can be improved. be.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the cross-sectional structure of a magneto-optical disk according to the present invention, and FIG. 2 is a diagram showing the relationship between light reflectance and Curie temperature with respect to the amount of Rh added in the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Optical effect film, 3... Magneto-optical recording film, 4... Protective film, 5... Rh concentration dependence of reflectance, 6... Curie temperature Rh'a degree dependence. Agent Patent attorney Katsuo Ogawa□ Pa＼

Claims (1)

[Claims] 1. In a magneto-optical recording medium using a metal alloy having perpendicular magnetic anisotropy as a magneto-optical recording material, Pt, Au, Rh,
1. A magneto-optical recording medium characterized in that a magneto-optical recording material is doped with at least one noble metal element selected from Pd in a range of 0.5 to 15 atomic percent. 2. When adding at least one noble metal element selected from the above-mentioned Pt, Au, Rh, and Pd, a concentration gradient is created in the added element in the magneto-optical recording film to improve information writing and
2. The magneto-optical recording medium according to claim 1, wherein the magneto-optical recording medium is present in larger quantities near the surface on the side from which reading is performed than near the surface on the opposite side.