JPS6119105A - Material for photomagnetic recording - Google Patents

Abstract

PURPOSE:To improve corrosion-resisting property, to enhance the stability of recording and to increase the repeatability of writing-in and erasing operation by a method wherein a suitable quantity of W and Co is contained in the titled material. CONSTITUTION:A recording layer 2 is provided on a substrate 1. The material to be used for photomagnetic recording of the layer 2 consists of an Fe-R-M alloy. In this composition, R consists of one or two or more kinds selected from Gd, Tb and Dy of rare-earth element, M consists of the metal other than iron and rare-earth element, and M contains W and Co. The quantity of R is set at 20-35atom% of the total quantity of alloy, the quantity of W is set at 3-20atom% of the total quantity of Fe+M, and the quantity of Co is set at 3-20atom% of the total quantity of Fo+M. W and Co are contained in the above-mentioned alloy composition, the corrosion-resisting property of the material is remarkably improved mainly by the action of W, the stability of recording is enhanced by the above-mentioned improvement in corrosion-resisting property, and the repeatability of writing-in and erasing operations can also be enhanced remarkably. Moreover, the material is suitable for high density recording which is attributed to the characteristics of the alloy itself of the above-mentioned composition, and the reproduction of S/N can be enhanced by containing Co.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to optical recording materials, particularly magneto-optical recording materials.

(Prior Art) In the field of information processing technology, with the rapid increase and diversification of information, demands for further increases in magnetic memory recording capacity, number of writes, etc. have been increasing in recent years. There is. Therefore, as an alternative to the conventional recording method, an optical recording method using a recording medium is proposed, such as magazines (electronic outlook, etc.).
November issue (1983) Seibundo Shinkosha, p. 63-74)
has been disclosed.

The conventional example disclosed herein will be explained.

First, there are those using metal thin films or metal-containing polymer materials. In this method, the recorded portion of the recording medium is melted and evaporated using a laser beam, and a hole is punched for writing, making it impossible to rewrite.

On the other hand, an example of a rewritable optical recording medium is one that utilizes the photodarkening phenomenon of amorphous chalcogenide, but such amorphous chalcogenide materials generally have low recording sensitivity and have a light absorption edge with a short wavelength. Furthermore, since absorption is small at wavelengths near the absorption edge, recording sensitivity for long wavelength light is extremely low. Incidentally, since laser light generally has good directivity and can be focused to an extremely small spot, it is suitable for use as a light source for optical recording media. Furthermore, since semiconductor lasers can be made extremely compact, they are attracting particular attention as light sources. However, at present, the oscillation wavelength range of semiconductor lasers is 750 to 800 nm or more, and it will probably be a relatively long wavelength of about 700 nm in the future. In addition, He-
Even the Ne laser has a wavelength range of 832.8 nm, and the Ar, Kr, etc. lasers have short wavelengths, but they are slightly more unstable and the equipment itself is larger.

For this reason, when a semiconductor laser or a He-Ne laser is used as a light source, the recording sensitivity of the amorphous chalcogenide mentioned above becomes low, whereas when Ar, Kr
If such a laser is used, the memory device will become significantly large.

Another type of optical recording medium is a medium that combines thermoplastic and photoconductor.This recording medium has the advantage of being able to change the operating wavelength range by freely selecting the photoconductor, but it is rewritable. There are drawbacks such as the maximum number of times that can be erased is about 100, and the fact that it is not possible to selectively erase individual recorded copies (), instead of erasing the entire area. It is not possible to adequately handle the increase in quantity and diversity.

By the way, there is another recording medium using a magneto-optical recording material. This type of recording medium has no restrictions on the light source used, and is viewed as promising because it can be rewritten many times. Among these, alloys of rare earth elements such as Gd, Tb, and Dy and iron elements such as Fe and Go are particularly promising as materials for magneto-optical recording.

(Problems to be solved by the invention) However, these magneto-optical recording materials are GO-based and Fe-based.
GO-based systems have large changes in magnetic properties due to differences in alloy composition, and are disadvantageous compared to Fe-based systems in terms of larger size, etc., while Fe-based systems are extremely susceptible to oxidation, which is a practical problem. It has some disadvantages.

Furthermore, the reality is that many of the conventional optical recording media described above do not necessarily provide satisfactory rewritability and various properties during rewriting as described above.

Therefore, an object of the present invention is to provide a magneto-optical recording material that has excellent corrosion resistance, good recording stability, and significantly increases the repeatability of writing and erasing.

Another object of the present invention is to provide a magneto-optical recording material that can be used for high-density recording and has good recording sensitivity.

(Means for Solving the Problems) In order to achieve this object, a magneto-optical recording material according to the present invention is made of an Fe-R-M alloy,
is iron, R is at least one or two or more elements selected from rare earth elements Gd, Tb, and ay, and M
is a metal system other than iron and rare earth elements, M includes W and GO, and the amount of H is 2 of the total amount of the alloy.
The amount of W is 3 to 20 at % of the total amount of Fe+M, and the amount of Co is 3 to 20 at % of the total amount of Fe+M.

(Function) According to the compositional alloy of the present invention, it contains W and Co, and the erodibility is significantly improved mainly due to the action of W. The improved erodibility also increases the stability of recording. The repeatability will also increase significantly.

Furthermore, due to the properties of this compositional alloy itself, the material of the present invention is suitable for high-density recording, and the inclusion of Go further increases the Kerr rotation angle and increases the reproduction S/N ratio. ing.

(Embodiments) Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a magneto-optical recording medium using the magneto-optical recording material of the present invention to the extent that its structure can be understood and understood. In the figure, l denotes a substrate, and a sufficiently smooth and transparent glass substrate or resin substrate is used as the substrate l.

2 is a recording layer provided on the upper side of this substrate 1. This recording layer 2 is formed as an alloy layer using the above-mentioned magneto-optical recording material of the present invention.

For the magneto-optical recording medium thus formed, 10
Recording was performed using a He-Ne laser beam of less than mw in a writing time of about 1 JLs, and it was confirmed that minute records with a diameter of about IILm or less were obtained and that it could withstand repeated erasing and rewriting more than 100,000 times. did.

Moreover, Fe-R (R=
A comparative test of corrosion resistance was conducted on a recording medium made of a Tb, Gd, or Dy)-based material and a recording medium formed using the magneto-optical recording material of the present invention. It was confirmed that the medium has significantly excellent corrosion resistance. This corrosion resistance will be described below.

In general, Fe-based magneto-optical recording materials undergo pitting corrosion in a high humidity atmosphere, and this pitting corrosion penetrates through the thin film. Therefore, as the amount of pitting corrosion increases, the transmittance increases. Therefore, the edibility can be evaluated based on the magnitude of the change in transmittance.

FIG. 2 shows Tb3.
(W, CofFe90)? ,, Tbja(W,,
Go,, Fe,,)7゜or Dingb)tr (Wza
A magneto-optical recording medium in which the recording layer 2 shown in FIG.
7) Tb70Fe7D, Gd,, Fe2. Or Dy,
, Fe2. This is a characteristic curve diagram showing the change in transmittance of each magneto-optical recording medium when the magneto-optical recording medium in which the recording layer 2 is formed using is kept in an atmosphere with a temperature of 85° C. and a relative humidity of 85%. be. Note that for the purpose of comparison, the same figure shows Tb3. to which W is not added. CCo1B Fe12
)7. and T b) 6 (Co to Fe F,)?
The results for , are also shown. In Figure 2, the retention time/h of each magneto-optical recording medium in the atmosphere is plotted on the horizontal axis, and the transmittance T after each retention time and the transmittance before being placed in this atmosphere are plotted on the horizontal axis. Rate (referred to as initial value) To
The transmittance ratio T/To, expressed as a ratio of T/To, is plotted on the vertical axis. When the recording layer 2 is not corroded, this transmittance ratio is l, and the greater the amount of corrosion, the larger this ratio becomes.

As can be understood from the experimental results shown in Figure 2, Tb)
6 (W y Cab Fep, ),,, Tb3
a (Wlo Cata Fezo) 7.7 and Tb
The transmittance ratio of the recording layer 2 using Tb, .
Fe, , Gd, , Feg and D y3. Fe
1/10 to 1/1000 under the same conditions compared to 7B
T b 36 (c o l
o Fe ya ) q6 and Tb, (Co2.
Fe,,)2. Compared to , it is - by several orders of magnitude.

Therefore, it can be seen that the magneto-optical recording medium of the present invention is significantly better in corrosion resistance than conventional recording media. Furthermore, the second
Although only Tb alloy system is shown in the figure, Gd alloy system, D
In the y alloy system, the T, M: d alloy system, and the TbDy alloy system, the effect of adding W and Go was similar to that in the Tb alloy system.

Next, the Kerr rotation angle of the magneto-optical recording medium of the present invention will be described. It is known that when the Kerr rotation angle is large, the S/N ratio becomes large and the read characteristics are good. While the corrosion resistance increases significantly by adding W, the Kerr rotation angle decreases, but when the amount of W is 3 to 20
In the M% range, the amount of decrease in the Kerr rotation angle is small, and the addition of Go can suppress the decrease in the Kerr rotation angle. Alternatively, this small Kerr rotation angle can be compensated for by applying a dielectric film to the protective layer 2 and utilizing its enhancement effect, so that there is no problem in practice.

As described above, it has been found that, according to the magneto-optical recording medium of the present invention, the erodibility is significantly improved mainly due to the addition of W, and the reason for this is currently believed to be as follows. W is a more chemically active metal than Fe. In an environment where Fe is actively dissolved, W becomes passive. Therefore, when the alloy is actively dissolved, W, which is more active than the main metal element (Fe) constituting the alloy, becomes a reaction product and is concentrated in a large amount in the corrosion product to form a corrosion product film. Subsequent corrosion progresses through the diffusion of metal ions through this corrosion product film, which acts as a barrier to the progress of corrosion, and thus improves the corrosion resistance of the alloy.

On the other hand, although Go also has a certain degree of anti-corrosion effect, this anti-corrosion effect of Go is due to the inertness of Co, and its effect is significantly smaller than that of W at the level of content in this invention.

Alloys of the above composition range according to the present invention, namely Fe
-RM alloy, Fe is iron, R is Gd, Tb.

Contains at least one or two or more of Dy, the amount of R is 20 to 35 atomic% of the entire alloy, M always includes W and Co, and the amount of W is 3% of the total amount of Fe+M. Regarding magneto-optical recording media using materials with a Go content of ~20 at% and a Go content of 3 to 20 at% of the total amount of Fe+M, conventional Fe-R system (R=Cd, Tb, or Dy) In addition to having the same characteristics as magneto-optical recording media using at least one type of magneto-optical recording medium, it also has significantly improved corrosion resistance and recording stability compared to conventional media, and also has improved repeatability of writing and erasing. It was confirmed that the amount increased significantly. The reason why the amount of Co is set at 3 to 20 atomic % is to prevent the addition of Co, which can increase the Kerr rotation angle, since the Curie point increases rapidly, and the magneto-optical recording sensitivity decreases when excessively added. be. Within this range, a suitable Curie point value can be obtained, and a decrease in the Kerr rotation angle due to W addition can be suppressed. Further, the amount of H is set to 20 to 35 atomic percent of the entire alloy, but this is done in consideration of the fact that a perpendicularly magnetized film can be easily obtained. Such a magneto-optical recording material according to the present invention is not only applied to the above-mentioned transparent glass, but also can be applied in the form of a plate, sheet, tape, or other shape, regardless of whether it is transparent or opaque, and can be made of any desired material. It can be deposited as an alloy layer on a substrate.

(Effects of the Invention) As is clear from the above, the magneto-optical recording material according to the present invention contains W and Go, so it has better corrosion resistance than conventional recording materials of this type. It has the advantage of good recording stability and the ability to significantly increase the repeatability of writing and erasing.The material itself also has the advantage of enabling high-density recording and good recording sensitivity.

Further, the magneto-optical recording material of the present invention can be written and erased using a laser beam, and has the advantage that various conventional restrictions regarding the light source used are significantly alleviated.

The magneto-optical recording material of the present invention is particularly suitable for use in recording media.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing a magneto-optical recording medium formed by applying the magneto-optical recording material of the present invention, and FIG. 2 is a diagram showing light transmission for explaining the characteristics of the magneto-optical recording material of the present invention. It is a curve diagram showing experimental results of gravity ratio. 1...Substrate, 2...Recording layer.

Claims (1)

[Claims] Fe-R-M alloy, Fe is iron, R is at least one or more elements selected from rare earth elements Gd, Tb, and Dy, and M is an element other than iron and rare earth elements. metal-based, the M includes W and Co,
The amount of R is 20 to 35 at% of the total amount of the alloy, and the amount of W is 3 to 20 at% of the total amount of Fe+M.
A magneto-optical recording material characterized in that the amount of Co is 3 to 20 at % of the total amount of Fe+M.