JPS60101740A - Photomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a photomagnetic recording medium having improved corrosion resistance without spoiling the magnetic characteristic thereof by adding Ni and Cr to an amorphous magnetic alloy consisting of TbFeCo having the axis of easy magnetization in the direction perpendicular to the film plane. CONSTITUTION:A photomagnetic recording layer added with Ni and Cr preferably at 8/2 Ni/Cr atom ratio so as to be incorporated at 0.1-35atom% total of Ni and Cr when the total thin magnetic film is made 100atom% is formed in the stage of forming the thin amorphous magnetic alloy film consisting of TbFeCo and having the axis of easy magnetization in the direction perpendicular to the film plane on a base plate consisting of glass, metal etc. The Kerr rotating angle of TbFeCo is increased and the corrosion resistance is improved without decreasing the property having a good S/N ratio by adding both Ni and Cr to said film in the above-mentioned way. The corrosion resistance is further improved by providing a protective layer in common use as an antireflection film on the recording layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording medium that is used in magneto-optical memory, magnetic recording, display elements, etc. and can be read using magneto-optic effects such as the magnetic Kerr effect or the Faraday effect. In particular, the present invention relates to a magnetic thin film recording medium with improved corrosion resistance.

Conventionally, MnB1 and MnCuB have been used as magneto-optical recording media.
1st grade polycrystalline thin film, GdCo, GdFe, Tb
Fe, DyFe, GdTbFe t:TbDyF
Amorphous thin films such as e, single crystal thin films such as Gd1G, etc. are known.

Among these thin films, the film-forming efficiency is required to produce a large-area thin film at a temperature close to room temperature, the writing efficiency for writing signals with small photothermal energy, and the reading efficiency for reading out written signals with a good S/N ratio. Taking these factors into consideration, the amorphous thin film has recently been considered to be excellent as a magneto-optical recording medium.

In particular, GdTbFe has a large Kerr rotation angle (150°C
It is ideal as a magneto-optical recording medium because it has one Curie point at the front and back. Furthermore, as a result of our research aimed at improving the Kerr rotation angle, we found that GdTbFeCo is a magneto-optical recording medium that has a sufficiently large Kerr rotation angle and enables readout with a good 8/N ratio.

However, a characteristic of amorphous magnetic materials such as GdTbFe and GdTbFeCo is that they have poor corrosion resistance. That is, when it comes into contact with air or water vapor, it not only deteriorates its magnetic properties but also eventually becomes completely oxidized and becomes transparent.

To this end, disk-shaped recording media have been proposed in which a protective layer is provided on the recording layer or the recording layer is further sealed with an inert gas.

The purpose of the present invention is to provide the recording medium itself with corrosion resistance, unlike conventional methods, and to create an amorphous magneto-optical recording medium with improved corrosion resistance without impairing the magnetic properties. It is about providing.

In the photothermal magnetic recording medium according to the present invention, an amorphous magnetic alloy TbFeCo having an axis of easy magnetization perpendicular to the film surface is used.
The purpose is to achieve the above object by adding Ni and Cr to the steel.

Furthermore, in the photothermal magnetic recording medium according to the present invention, %,
Ni,! : The original ratio including Cr is 1oO
When expressed as atom%, 0.1atom% ~ 35
It is desirable that the content be in the range of atom%. This is because if Ni and Cr are less than 0.1 atom%, corrosion resistance cannot be sufficiently improved, and if Ni and Cr are less than 0.1 atom%, corrosion resistance cannot be sufficiently improved.
If it exceeds .om%, the magnetic properties will be affected, making it difficult to obtain a duty magnetized film.

The present invention will be explained in more detail by way of examples below.

(Example 1) In a high frequency sputtering device, a crystal resonator plate of a film thickness meter using a crystal resonator was used as a substrate, and a 5 mm film was placed on a 50% Co-balance Fe plate with a diameter of 4 inches as the first target.
After evacuating until the corner Tb pieces are evenly arranged and a 40% Cr-balance Ni alloy is used as the second target, Ar gas is introduced to 4 x 10 Pa and the main pulp of the evacuation system is operated. By increasing the Ar pressure to 3 P
I made it a. At this time, a small amount of an 11m power source was input to the substrate side so that the self-bias voltage was 80 volts. In this way, TbFeCoN of various compositions with a thickness of 0.2 μm as shown below was prepared.
An iCr film was produced.

@pl i -1; (Tho, xs(Feo, yo
oo, s) o, 5t) o, os (Nio, eco
,4)0,O5EI)1-2; ('l'bo,
t@(Feo, qcoo, s)o, 5t)o, oo
(Nio, acre, 4) 0.10 sample 1-3;
(Too, 1s(Feo, yOoo,, s)o, 5
t) o, as(Nio, ecro, ichi) o, ts
EF) 1-4; %o, ts(Fbo, tCoo
,s)o,5t)o,1o(Nio,acro,4)0
．． s.

As a result of X-ray diffraction, these compounds were found to be amorphous.

Above configuration c7) TbFeCoNiCr film at 80°C.
Figure 1 shows the results of a corrosion resistance test in which the crystal was placed in a constant temperature and humidity chamber of 85% R,I. , it shows that the corrosion progressed as the weight increased.The numbers here are the same as the respective sample numbers.As a comparative example, a magneto-optical recording medium with a conventional composition was tested under the same conditions. By example, TbF
It was found that the eCoNiCr film has significantly improved corrosion resistance compared to the TbFeCo film that does not contain Ni or Cr. Also conventional GdTbFe.

(3dToFeCr, Ud'll'bli"eNi
It was found that this film has better corrosion resistance than other films. Furthermore, in the TbFeCoNiCr film, even if the amounts of Ni and Cr were increased, the rate of decrease in the Kerr rotation angle, which is related to readout efficiency, was small, and was about 10 degrees in Samples 1-4.

(Example 2) Films were formed in the same manner as in Example 1, or in this case, the self-bias voltage was set to zero.
A FeCoNiCr film was created.

Sample 2-1; (Too, ts(Fleo, tCoo
,suo,5t)o,os(Nio,aCro,+)o,
os sample 2-2; (Too, x@(Feo, tC
Do, s)o, 5ilo, 5o(Nio, eCro
, 0.10t+tN2-3; ('Ibo, 1s
(FIeo,ycOo,s)o,sg)o,5s(
Nio, 5cro, 4) 0.1 s The above film was placed in a constant temperature and humidity chamber at 80° C. and 85% in the same manner as in Example 1, and a corrosion resistance test was conducted. The results are shown in FIG. The same reference numerals as the sample numbers are given here as well, and the same comparative examples as in FIG. 1 are also shown with the same reference numbers.

In this example as well, the TbFeCoNiCr film is GdTbFe.
, (Ml; bljhcr.

It was found that this film has better corrosion resistance than films such as GdTbFeNk and TbFeCo.

Further, regarding the rate of decrease in the Kerr rotation angle, a similar structure appeared in Sample 2-4, and compared to Example 1, the density was smaller and corrosion was faster. From this, it was found that corrosion resistance was improved when the film was formed by applying a bias voltage.

(Example 6) In Example 2, a 20% Cr-balance Ni alloy was used as the second target, and the film was formed in exactly the same manner. In this way, the following Tb1i of various compositions with a thickness of 0.2 μm were prepared.
'eCoNiCr film was created.

"Arn5-1 + ('11] o, 1y (1'bo
,y(Eoo,a)o,5ale,as(Ni o,8
Cro, t)o, oslR6-2; ('lbo, 1
? (1i'eO,lCo0.8)0,! 8) 0.5o
(Ni O+ acro, t)o, 1043-3;
('1lbo, x7 (1'bo, 700G, so
,5sJo,ssσNio,5Cro,t)o,15''
ξ亨13-4; ('Ibo, l?(1i'eO,
? Q) 0, g) o, 5s) o, go (Nio, 5c
ro,t)o,g.

As a result of X-ray diffraction, all of these films were found to be amorphous.

The film having the above composition was placed in a constant temperature and humidity chamber at 85° C. and 85° RH in the same manner as in Example 1, and a corrosion resistance test was conducted.

The results are shown in FIG. The same reference numerals as the sample numbers are used here as well, and the same comparative examples as in Fig. h'91 are also shown with the same reference numerals 9.

In this example as well, the film of Tb1I″eCoNiCr was (3d
TbFe.

! 1”k7Eileco, GdTbFeCr,
(It was found that the corrosion resistance was improved compared to films such as 3dTbFeNi. Also, the reduction rate of the Kerr rotation angle was
-4, it was about 8 inches after 10 days. As a result of researching magneto-optical recording media made of °TbFecoNicr films with various compositions other than the examples, in order to obtain the above effects sufficiently, Ni and Cr$ were added to the total amount of Ni and Cr, respectively. It is desirable that it be present in an atomic ratio of 0.1 atom% or more. In the above example, ki, Nt
is 60 atom% with respect to the combined amount of Ni and Cr.
Good results were obtained in the range of ~F3 Q atom %.

The magneto-optical recording medium according to the present invention may be made of glass or metal.

When laminating on a substrate such as a plastic snack by the sputtering method or vacuum evaporation method of the embodiment, if a well-known protective layer, an antireflection layer that also serves as a protective layer, a heat insulating layer, etc. is provided on the recording medium, 1. Corrosion resistance is improved. Furthermore, it goes without saying that the corrosion resistance can be improved even if the conventionally known air sandwich type structure in which an inert gas is confined is used.

As described above, in the magneto-optical recording medium according to the present invention, TbF
By simultaneously adding Ni and Cr to an eCo amorphous magnetic film, a magnetic film with improved corrosion resistance than before was obtained, and excellent effects were obtained by simple means.

[Brief explanation of the drawing]

0 is a diagram showing the results of the eating test.

Claims (2)

[Claims] (1) TbFeC with easy axis of magnetization perpendicular to the film surface
. A magneto-optical recording medium characterized in that Ni and Cr are added to an amorphous magnetic alloy consisting of. (2) The combined atomic ratio of Ni and Cr is 1 as a whole.
% 0.1810m when 00 ato+n%
% to z, 5 atom %.