JPS607633A - Photothermomagnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a photothermomagnetic recording medium having excellent corrosion resistance in the recording layer itself without spoiling the magnetic characteristics thereof by incorporating B in an amorphous magnetic alloy and forming the recording layer having the axis of easy vertical magnetization on the film plane. CONSTITUTION:B is incorporated at 0.1-30atom% in an amorphous alloy such as GdTbFe, TbFeCo of GdTbFeCo and a recording layer having an axis of easy magnetization in the direction perpendicular to the film plane is formed on a base plate. The recording layer is formed on the base plate by, for example, arraying uniformly square pieces of Gd and Tb and a small piece of B on an Fe plate, using such plate as a target and sputtering simultaneously the respective components. The excellent corrosion is thus provided to the recording layer itself without spoiling the magnetic characteristics of the amorphous alloy. Such magnetic recording medium may be used for either of an air sandwich structure and a laminated structure.

Description

[Detailed Description of the Invention] This invention relates to a photothermal magnetic recording medium that is used in magnetic fields and can be read using magneto-optical effects such as the magnetic Kerr effect or the Faraday effect, and in particular, it relates to a magnetic thin film with improved corrosion resistance. It is related to recording media.

Conventionally, as a photothermal magnetic recording medium, MnI3i,
Polycrystalline thin films such as MnCuBi, Ga Co, Ga
Fe, TbFe, Dyke, GdTbFe, Tbl
) amorphous thin film such as yFe, Ga. Single crystal such as IG! ! Exchanges, etc. are known.

Among these thin films, the film-forming efficiency of producing a large-area thin film at a temperature close to room temperature, the writing efficiency of writing signals with small photothermal energy, and the ability of reading written signals with a good S/N ratio are important. Considering read efficiency and the like, the amorphous thin film is recently considered to be excellent as a photothermal magnetic recording medium.

In particular, GdTbFe has a large force-rotation angle, /
Since it has a single Curie point around the SOC, it is most suitable as a photothermal magnetic recording medium. Furthermore, as a result of our research aimed at improving the force-rotation angle, we found that TbJi''eCo, especially Gd.TbFeCo, has a sufficiently large Kerr rotation angle and S
It was discovered that this is a photothermal magnetic recording medium that can be read with a good /N ratio.

However, GdTbFe or TbFeCo
.

A characteristic of other amorphous magnetic materials including GdTbFeCo is that they have poor lt1 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.

An object of the present invention is to provide an amorphous photothermal magnetic recording medium with improved corrosion resistance by imparting corrosion resistance to the magnetic recording layer itself without impairing magnetic properties.

The object of the present invention is achieved by the following photothermal magnetic recording medium.

A photothermal magnetic recording medium in which a recording layer made of a thin film of an amorphous magnetic alloy having an axis of easy magnetization perpendicular to the film surface is formed on a substrate, characterized in that the amorphous magnetic alloy contains boron. A photothermal magnetic recording medium.

The amorphous magnetic alloy used in the present invention is, for example, G
a TbFe, TbFeCo, GaT
b FeC0, etc., but are not limited to these. In order to incorporate boron into these magnetic alloys,
For example, as described in the Examples below, there is a method of incorporating boron into the film when forming a thin film of an amorphous magnetic alloy on a substrate using a high frequency sputtering device.

The boron content is preferably 0/atom to 30 atom. This is because if the ratio is less than 0/atom, the corrosion resistance cannot be sufficiently improved, and if the ratio is more than 30/atom, the magnetic properties are affected.

The substrate used may be made of glass, metal 1-quartz, acrylic resin, polycarbonate-1, polyethylene terephthalate, or the like. After forming a thin film of an amorphous magnetic alloy containing boron on these substrates,
Second, corrosion resistance can be further improved by providing a protective layer made of various substances, a reflective layer 9 that also serves as a protective layer, an antireflection layer, a heat insulating layer, etc. Alternatively, the heat insulating layer 9 and the antireflection layer may be sequentially provided between the substrate and the magnetic recording layer from the substrate side. Additionally, boron, aluminum, silicon, and chromium are contained in the amorphous magnetic alloy thin film.

Excellent corrosion resistance can be achieved by adding seven or two or more elements such as nitrogen.

The magnetic recording medium of the present invention may have either a well-known air sandwich structure or a bonded structure.

According to the present invention, by incorporating boron into a thin film made of an amorphous magnetic alloy, the corrosion resistance of this thin film itself is improved, and the amorphous magnetic medium has better corrosion resistance than conventional ones. A magnetic recording medium is provided.

EXAMPLES The present invention will be explained in more detail with reference to Examples below.

Example / In a high-frequency sputtering device, a 3-inch square white glass plate is used as a substrate, and an F with a diameter of q inches is used as the first target.
A 5 mm square Gd and Tb piece, a 4mm diameter boron piece, and even smaller boron pieces were used. After making the inside of the device a vacuum of 15 × 1 O-5 Pa or less, Ar gas was
4, and set the Ar pressure to 3 Pa by operating the main valve of the vacuum exhaust system. By setting the sputtering power to 230 W from a high-frequency power source and changing the number of Ga, Tb, and B pieces, the following various compositions of Gd' and T were obtained.
b A P e B film was fabricated on the substrate.

((GdO,5TbO,5) +121FeO,79)
0.997[30,003((GdO,5TbO,5)
0.21FeO,79) 0.99 130.01(
(GdO,5Tb0.5) 0.21 FeO,79
) 0.95 Bo, 05 ((GdO,5TbO,5)
0.22FeO,78) 0.9 130.1((GdO
,5Tb0.5) 0.20Fe0.80 io, ss
'3o,ts((GdO,5Tb0.5)0.19''
""0.81) 0.8 Bo, 2" Ga of two-note configuration,
T1) The F e T3 film was subjected to a corrosion resistance test in a constant temperature and humidity chamber at g, t'O, and relative humidity ss.

The results are shown in Figure 1. In FIG. 1, the vertical axis shows the ratio of coercive force to the initial value, and the horizontal axis shows time, and a decrease in coercive force indicates progress of corrosion.

As is clear from Figure 1, Ga containing no boron
Significant corrosion was observed in the T,bFe film after about 700 hours.As the boron content of the GdTbFe film increases, the coercive force decreases less and the corrosion resistance increases.

In addition, amorphous magnetic films tend to undergo structural changes such as crystallization at relatively low temperatures, and their properties as photothermal air materials may be impaired; however, the addition of boron increases the crystallization temperature. Thermal stability was also improved.

In addition, GaTbFeB containing 30 or more atomic ratios of boron
A film was also formed, but this film did not have an axis of easy magnetization perpendicular to the film surface.

Example 2 In a high-frequency sputtering device, a 3-inch square white plate glass was used as a substrate, and a 3-mm square Ga,
A Ga Tb Fe Co J3 film having the following composition was fabricated on a substrate in the same manner as in Example 1 by uniformly arranging Tb, Co pieces, boron pieces with a diameter of O mm, and boron pieces cut into smaller pieces.

((Gd05TbO,5) 0.21 (FeO,90
00,1) 0.79 Jo,997”0f106((
Gdo, 5Tbo, s) 0.2'l' (Feo, c
+COo,t) 0.79 )0.99 Bonx((
GdO,5Tb0.5 )0.21 (FeO,9CO
O, 1) 0.79) 0.95"0.05< (G
dO,5TbO,5') 0.21 (FeO,9CO
O,1) 0.79)(19Bo,1((GdO,5T
bO,5) 0.21 (FeQ,9C00,1) 0
．． 79) 0B5B0.15((GdO, 5TbO,
5) 0.21 (FeO,,QCoO,1) 0.7
9) 013 Bo, 2 GdTbFeCo B above
The film and the GaTbFeCo film were subjected to the same corrosion test as in Example 1, and as a result, significant corrosion was observed on the surface of the GdTbFeCo film after approximately 1,000 hours. The above Ga T 1-
The decrease in coercive force of the I Fe Co B film after 500 hours of testing is shown in Table 1.

Table 1: GaTbFeC containing 30 or more atomic proportions of boron
An oB film was also formed, but this film did not have an axis of easy magnetization perpendicular to the film surface.

Example 3 Example! Similarly, a TbFeCoB film having the following composition was fabricated on a substrate using Fe, i, "b, Co, and B.

(Tb20(FeO,9COO,1)80)0.99
7B0.003(Tb20(FeO,9CoO,1)
80) 0.99130.01(Tb20”eO,9
COO, 1) 80 ) 0.95 Bo, 05 (Tb20
(FeO,'9Co0.1)80)0.9 Bo,1[
Tb20 (FeO,9COO,1) 80) 0.
85 Bo, 15(Tb20(FeO,9C00,1)
80') 0.8 Bo, 2 Tb re Co B above
The film, 'I', and bFeCo film were subjected to the same corrosion test as in Example/, and as a result, TbFeC.

Significant corrosion was observed on the surface of the film after approximately 3'0 hours.

Table 1 shows the decrease in coercive force of the above TbFeCoB film after 500 hours of testing.

Table λ In addition, containing 30 or more atomic proportions of boron'],' b
Although an FeCoB film was also formed, this film did not have an axis of easy magnetization in the direction perpendicular to the film surface.

[Brief explanation of the drawing]

Figure 1 shows GaTb of various compositions obtained in Examples/
1 is a chart showing the results of a corrosion resistance test of a photothermal magnetic recording medium having an FeB film. Figure 1 Proceedings Amendment (Spontaneous) Spring 1, 1988 1-1 1 Director-General of the Licensing Agency 1 Indication of another matter 1982 Patent No. 112927 2 Name of the invention Photothermal magnetic recording medium 3 , Relationship with the person making the amendment Patent applicant (+00) Canon Co., Ltd. 4, Agent address 5-9-20, 1-9, Akasaka, Minato-ku, Tokyo, Claims column of the specification to be amended. Claim 1: A photothermal magnetic recording medium in which a recording layer consisting of a thin film of an amorphous magnetic alloy having an axis of easy magnetization perpendicular to the film surface is formed on a substrate, wherein the amorphous Fe gold alloy boron A photothermal magnetic recording medium characterized by containing. 2. The monothermal #1'' recording body according to claim 1, wherein the boron content is 0.1 to 30 at%. 3. The amorphous magnetic alloy is made of Gd Tb Fe, Tb F
9. The embodiment according to claim 1, which is e Co or Gd Tb Fe Co.

Claims (1)

[Scope of Claims] 1. A photothermal magnetic recording medium in which a recording layer made of a thin film of an amorphous magnetic alloy having an axis of easy magnetization perpendicular to the film surface is formed on a substrate. A photothermal magnetic recording medium characterized by containing boron. 2. The method according to claim 1, wherein the boron content is 0.7 to 30 atoms. 3 The amorphous magnetic alloy is GdTbFe, TbPaCo
or GdTbFe'Co, the method according to claim 1.