JPH01154334A - magneto-optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] R Satori Ikou! The present invention relates to a magneto-optical recording medium having excellent oxidation resistance, and more particularly to a magneto-optical recording medium having an axis of easy magnetization in a direction perpendicular to the film surface and having excellent oxidation resistance.

Technical background of Ming and its problems Transition metals such as iron and cobalt, delbium (Tb),
An amorphous thin film made of an alloy with rare earth elements such as gadolinium (Gd) has an axis of easy magnetization perpendicular to the film surface, and a film surface that is entirely magnetized in one direction has an axis of easy magnetization that is opposite to this direction of magnetization. It is known that it is possible to form magnetic domains whose orientations are slightly reversed.

By associating the presence or absence of this inverted magnetic domain with "1" and "O", it becomes possible to record digital signals in the amorphous thin film as described above.

For example, Japanese Patent Publication No. 57-20691 discloses an amorphous thin film made of a transition metal and a rare earth element used as such a magneto-optical recording medium.
An l'-b-Fe based alloy amorphous thin film containing the following is disclosed. Also, an alloy amorphous thin film made by adding a third metal to Tb-Fe is also used as a magneto-optical recording medium. In general, magneto-optical recording media such as Tb-Co and Tb-Fe-Co are also known.

Magneto-optical recording media made of these alloy amorphous thin films have excellent recording and reproducing properties, but during use, these amorphous thin films undergo oxidation and their properties change over time. There were major practical problems.

The mechanism of oxidative deterioration of magneto-optical recording media made of alloyed amorphous thin films containing transition metals and rare earth elements is as follows.
For example, Journal of the Japan Society of Applied Magnetics, Vol. 9, No. 12, No. 93.
It has been discussed on pages 96 to 96, and it has been reported that there are three types as shown below.

b) Pitting corrosion Pitting corrosion refers to the formation of pinholes in the amorphous thin film of the alloy, but this corrosion typically progresses in a high humidity atmosphere. It progresses markedly.

) A surface oxidation layer is formed on the amorphous thin film of the surface oxidation alloy, and the Kerr rotation angle θ
k changes over time, and the Kerr rotation angle θk eventually decreases.

c) Selective oxidation of rare earth metal The rare earth metal in the alloy amorphous thin film is selectively oxidized, and the coercive force Hc changes significantly over time.

In order to prevent the oxidative deterioration of alloy amorphous thin films as described above, various methods have been tried in the past.

For example, an alloy amorphous thin film can be formed using 3i 3 N4, Si
A method of creating a three-layer structure sandwiched between oxidation-preventing protective films such as O, Si 02 , and AIN is being considered. However, even if this reservation film is formed, there is a problem in that it is not always possible to sufficiently prevent oxidative deterioration of the alloy amorphous thin film.

That is, if a pinhole or the like exists in the above-mentioned oxidation-preventing protective film, it is impossible to prevent the oxidative deterioration of the alloy amorphous thin film from progressing through the pinhole.

In addition, in order to improve the oxidation resistance of the thin film, a third layer is added to the amorphous thin film of alloys such as Tb-Fe and Tb-C0.
Various methods of adding metals have been attempted.

For example, in the above-mentioned Journal of the Japan Society of Applied Magnetics, 1'-b4
``e or Tb-Go, Co, Ni5Pt.

3.5 atomic% of tertiary metal oxides such as AI, Or, li, etc.
Attempts have been made to improve the oxidation resistance of l'-b-Fe-based or Tb-Co-based alloy amorphous thin films by adding 1'-b-Fe or Tb-Co alloys. Adding Co, Ni, and PT to Tb-Fe or Tb-Co is effective in preventing surface oxidation and pitting corrosion, but it is effective in preventing surface oxidation and pitting corrosion. It is reported that it is not effective in preventing selective oxidation of Tb, which is a rare earth metal. This means that T b - Fe or Tb - Co has 9 pairs of C.
When O, Ni, and Pt are added, Tb is selectively oxidized in the resulting alloy amorphous thin film, and the coercive force Hc
This means that it changes significantly over time.

Therefore, TTb-Fect5 or 3.5 for Tb-Co
Even when small amounts of Co, Ni, and Pt are added, down to atomic percent, the oxidation resistance of the resulting alloy amorphous thin film is not sufficiently improved.

Also, the 9th Academic Lecture Summary of the Japanese Society of Applied Magnetics (1985)
(November 2013), page 209 of the publication also states that Pt, AI, Cr, and Ti are added to T b-Fe or T b-Fe-Co for the purpose of improving the oxidation resistance of the alloy amorphous thin film. 1
Alloy amorphous thin films with additions of up to 0 atomic percent are taught. However, Tb-Fe or Tb-Fe-
■ Pt, AI, Cr, up to 10 atomic % in Co
Even if Ti is applied as a splint, surface oxidation and pitting corrosion can be prevented quite effectively.
The antioxidant property against selective oxidation of b is not sufficient, and the coercive force 1-1c changes greatly over time,
There still remained the problem that the coercive force Hc eventually decreased significantly.

Furthermore, in Japanese Patent Application Laid-open No. 58-7806, pt.
A magnetic thin film material comprising a polycrystalline thin film having a composition of Co and containing at most 10 to 30 at. % of pt is disclosed.

However, since this polycrystalline thin film with the composition ptCo is polycrystalline, heat treatment such as annealing is required after film formation, and the grain boundaries between the crystals may generate noise signals. Furthermore, this polycrystalline thin film had the problem of a high Curie point.

In order to solve such problems, the present inventors have developed Pt
We have proposed an amorphous alloy thin film containing Pd and/or Pd at ω of 15 atomic % or more and having an axis of easy magnetization perpendicular to the film surface. This amorphous alloy a film has excellent oxidation resistance and excellent magneto-optical properties such as a large Kerr rotation angle.

Purpose of the Invention The present invention aims to solve the above-mentioned problems, and has excellent magneto-optical properties such as a large coercive force and a large Kerr rotation angle and a large Faraday rotation angle. The object of the present invention is to provide a magneto-optical recording medium that has excellent oxidation resistance and does not change its coercive force or Kerr rotation angle over time.

1. The magneto-optical recording medium according to the present invention includes a first protective film, a magneto-optical recording film, and a second protective film, which are sequentially laminated in this order on a transparent substrate, and includes the following steps: The magnetic recording film is (Pt and/or Pd).

[RExTMl-x] 1-y (wherein, RE is Nd s Sm , Pr , Ce ,
At least one element selected from the group consisting of Eu, Gd, Tb, Dy and HO, TM is Fe and/or CO, 0.2<x<0.7.0.0
It is characterized by being an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface, which is expressed as 4<y<0.10.

The above-mentioned magneto-optical recording medium according to the present invention has excellent magneto-optical properties such as a large coercive force and a large Kerr rotation angle and a large Faraday rotation angle, and has excellent oxidation resistance.
It has an excellent property that the coercive force or Kerr rotation angle does not change over time.

DETAILED DESCRIPTION OF THE INVENTION The magneto-optical recording medium according to the present invention will be specifically described below.

As shown in FIG. 1, the magneto-optical recording medium according to the present invention has a first protective film 2, a magneto-optical recording film 3, and a second protective film 4 laminated in this order on a transparent substrate 1. The magneto-optical recording film is made of (Pt and/or Pd).

[RExTMl-x] 1-y (wherein, RE is Nd, Sm, Pr, Ce, Eu
, Gd , Tb , DV and HO, and TM is Fe and/or
or Co and 0.2<x<0.7.0.04<V
It is an amorphous alloy thin film having an axis of easy magnetization perpendicular to the film surface expressed by <0.10).

As the transparent substrate 1, a wide variety of materials that have been conventionally used as transparent substrates can be used, but specific examples include glass, polymethyl methacrylate, polycarbonate, a polymer alloy of polycarbonate and polystyrene, and U.S. Patent No. 4,614. Use of amorphous polyolefin, poly4-methyl-1-pentene, epoxy resin, polyether sulfone, polyneedlelimide, ethylene/tetracyclododecene copolymer, etc. as shown in No. 778 Can be done.

The thickness of this transparent substrate 1 is 0.5 to 2.5 mm, preferably 1.0 to 1.5 mm. It is about Sm.

As the first protective film 2 provided on the transparent substrate 1 as described above, S! 3N4, AI N, AI Si N,
Nitride such as BN, 5102, Tb-3! 02, M
g-3l 02 , AI 203 , S! 0゜-Al
203, M(]-3! 02- AI 203, Tb
-3! 02-AI 203, [3a-3i 02
, Ba-Al 203 , Ba-wrinkle strength alumina, T
e-Al2O3, IVH)-A1203, T! 02,
Si O, Ti01zno, Z ('02, Ta205,
Oxides such as Nb2O5, CeO2, SnO2, TeO2, indium-tin oxide, sulfides such as ZnS, CdS, ZnSe, SiC, Si, etc. are used.

Further, as the first protective film 2, a plasma polymerized film of CH4, C82, Teflon, etc., or an organic coat film such as a UV-curable organic coat film can also be used.

This first protection film 2 functions as a protective film that protects the magneto-optical recording film from oxidation and the like, and also functions as an enhancement film.

The thickness of the first protective film 2 must be about 50 to 5,000, preferably about 100 to 2,000.

The magneto-optical recording film provided on such a first protective film is
Although the composition expressed by the above formula is acceptable, this magneto-optical recording film will be specifically explained below.

(i> In the above formula, TM is Fe or Co, or both. When the magneto-optical recording film is represented by the above formula [I], TM is ]-X (where 0.2<
x<0.7, preferably 0.25<x<0.5, more preferably 0.3<x<0.5).

As TM, it is preferable that both Fe and Co exist, and in particular, as this TM, Ee is 100 to 100.
Preferably, Co is present at ω of 35 at. % and from 0 to 65 at. %.

Note that the TM may contain 5 atomic % or more, preferably 3 atomic % or less of Ni.

(ii) Pt and/or Pd is added to the magneto-optical recording film.
It is present in an amount of up to 10 atom %, preferably 6 to 10 atom %.

If the content of pt and/or Pd is less than 4 at. If this happens, the magneto-optical recording film will be oxidized and the coercive force HC will change over time or the Kerr rotation angle θk will decrease, which is not preferable.

pt or Pd may each be used alone,
They may also be used in combination.

(iii>The magneto-optical recording film according to the present invention has the above-mentioned (i>
In addition to and <ii), it is configured to contain at least one rare earth element (RE).

This RE has Nd, Sm, Pr, Qe,
EU.

At least one element selected from the group consisting of Gd, Tb, oy and HO. Preferably 60 RE
At least atomic% is Tb, and the remainder is Dy, Ntl, Gd
, Ce, Eu, Pr, Ho or 3m.

More preferably, 80 atomic % or more of RE is Tb, particularly preferably 90 atomic % or more, and the remainder is Dy, Nd.
, Gd, Ce, Eu, Pr, Ho or 5Ill
It is.

When the amorphous alloy thin film is represented by the above formula [I], the rare earth element RE as described above is 0.2<x0.7, preferably 0.25<x<0.5, more preferably 0. .3<x
<0.5.

In the present invention, the thickness of the magneto-optical recording film made of the amorphous alloy thin film having the axis of easy magnetization perpendicular to the film surface is 2.
00 to 2,000 people, preferably about 200 to 1,000 people.

The second protective film 4 provided on the magneto-optical recording film 3 as described above is made of 513N4, ΔIN, At Si N
, nitrides such as BN, Si 02 , Tb-3i 02
, M(]-3i○2 , Te-A I 203 , M
'J-AI O, Tb-3i O-At 203,
MLS! 02- Al 203 , [3a-3i 0
2, Ba-A1203.3a-3i 02-AI 2
C3, T! 02, S! O, T! 0Szno, Z
l'02, Ta2o5, N1)205, CeO2
, 5n02, TeO2, oxides such as indium-tin oxide, ZnS, CdS': which sulfides, ZnSe
, Si, C, Si, etc. are used.

Further, as the second protective film 4, a PT film, a PCI film, a Ti film,
Metal films such as CrpIA, Zr film, l'Ji film, and N1-Cr film can also be used.

Furthermore, as the second protective film, it is also possible to use a plasma polymerized film such as CH4, C82, Teflon, or the like, or an organic coat film such as a UV-curable organic coat film.

This second protective film 4 functions as a protective film for protecting the magneto-optical recording film from oxidation, etc., and may also function as a reflective film.

The film thickness of such a second protective film 4 is 5 in the case of an inorganic material.
The number is about 0 to 5,000 people, preferably about 100 to 2,000 people, and in the case of organic materials, it is about 100 to 100tiTrL, preferably about 300A to 500Iim.

The magneto-optical recording medium according to the present invention having the above-described structure has an axis of easy magnetization perpendicular to the film surface, and often exhibits a rectangular loop with good Kerr hysteresis.

In this specification, a square loop with good Kerr hysteresis means that the saturation Kerr rotation angle (Ok, ) is the Kerr rotation angle at 43 times the maximum external magnetic field and the residual m, which is the Kerr rotation angle at zero external magnetic field. This means that the ratio θ to the Kerr rotation angle (θk) is 210k1 or 0.8 or more.

Furthermore, the magneto-optical recording medium according to the present invention as described above has excellent oxidation resistance, and as shown in FIG.
l) An amorphous alloy thin film having a composition of 2BFe51Co13, a first protective film 513N4, and a second protective film S!
For example, a magneto-optical recording medium made of 3N4 is heated at 85°C,
Even if kept in an environment with relative humidity of 85% for more than 240 hours,
Its coercive force hardly changes. On the other hand, pt
Tfi 251CO75 or Tb 25 without
An amorphous alloy thin film having a composition of Fe66CO9 has a composition of 8
When kept in an environment of 5° C. and 85% relative humidity, the coercive force changes greatly over time. Furthermore, if this environmental test is continued for 1000 hours, pt and/or P
In the system containing d, the coercive force hardly changes, whereas in the system not containing pt and/or Pd, the coercive force decreases to such a degree that it can hardly be measured.

Furthermore, from the experimental examples described later, it has been found that in the magneto-optical recording medium according to the present invention containing an amorphous alloy thin film containing pt and/or Pd, even if there are pinholes in the protective film, the θ after the environmental test is It can be seen that surface oxidation is prevented because the change in .

In the present invention, various elements other than those mentioned above may be added to the magneto-optical recording film in order to improve the Curie temperature, the compensation temperature, f-(c and θ), or to reduce the cost. These elements can be substituted, for example, at a rate of less than 50 atomic % with respect to the rare earth element.

Examples of other elements that can be used in combination include (I)Fe, 3d transition elements other than Co, specifically S
c STi, V, Cr, Mn, Ni, Cu, Z
ll is using irarel.

Among these, Ti, Ni, Cu, Zn, etc. are preferably used.

(II) 4d transition elements other than Pd Specifically, Y, Zr, Nb, IVIO, 'Tc, Ru
, Rh, Ag, and Cd are used.

Among these, Z' and Nb are preferably used.

(III) 5d transition sources other than Pt Specifically, Hf', Ta, W, Re, Os, I
r, Au, and Hg are used.

Among these, Ta is preferably used.

(IV) I [IB group element Specifically, B, AI, Ga, In, and TI are used.

Among these, B, AI, and Ga are preferably used.

(V) IVB group element Specifically, C, Si, Ge, Sn, and Pb are used.

Preferably, Si, Ge, Sn, and Pb are used.

(Vl>VB group element Specifically, N, P, As, 3b, and Bi are used.

Among these, sb is preferably used.

(VI[)VIBllj, element Specifically, S, Se, Te, and PO are used.

Among these, Te is preferably used.

Next, a method for manufacturing a magneto-optical recording medium according to the present invention will be explained.

First, a first protective film is formed on a transparent substrate.

To form the first protective film on the transparent substrate, a conventionally known method such as a vacuum evaporation method, a sputtering method, an electron beam evaporation method, a spin code method, etc. can be employed.

Next, in order to form a magneto-optical recording film on the first protective film provided on the transparent substrate, the substrate temperature is kept at around room temperature, and chips made of each element that constitutes and covers the magneto-optical recording film according to the present invention are used. This substrate (the substrate is not fixed) is formed using a composite target or an alloy target having a predetermined composition of A magneto-optical recording film of a predetermined composition may be deposited on top of the magneto-optical recording film.

As described above, the magneto-optical recording film according to the present invention can be formed at room temperature, and there is no need to perform heat treatment such as annealing treatment after film formation in order to have an axis of easy magnetization perpendicular to the film surface.

If necessary, the magneto-optical recording film can be formed on the substrate while heating the substrate to 50 to 600°C or cooling it to -50°C.

Further, during sputtering, the substrate can be biased to a negative potential. In this way, ions of an inert gas such as argon accelerated by an electric field will strike not only the target material but also the perpendicularly magnetized film being formed, resulting in a perpendicularly magnetized film with excellent properties. There is.

Next, a second protective film is formed on the magneto-optical recording film formed as described above, and at this time, a conventionally known method such as a vacuum evaporation method, a sputtering method, or an electron beam evaporation method is used. etc. can be adopted.

The magneto-optical recording medium according to the present invention is a perpendicularly magnetized film having an axis of easy magnetization perpendicular to the film surface, and in many cases, the Kerr hysteresis loop has a square shape, so that it can be easily magnetized in the absence of an external magnetic field. Since θk is almost the same as the saturation Ok at the maximum external magnetic field and the coercive force 1-1c is also large, it is suitable as a magneto-optical recording film. In addition, a good θk means that
This means that θf is also good, so it can be used in either the Kerr effect type or Faraday effect type.

The magneto-optical recording medium according to the present invention is not limited to the above-mentioned structure, but may be laminated with an underlayer, an anti-oxidation film, or a high permeability soft magnetic film as necessary. In addition to being used as a single board, it is also possible to use the board by laminating it together.

Effects of the Invention The magneto-optical recording medium according to the present invention includes a first protective film, a magneto-optical recording film, and a second protective film that are sequentially laminated in this order on a transparent substrate, and the magneto-optical recording medium comprises: The membrane is (Pt and/or Pd).

[RE, TM 1. 1-V (in the formula, REL
, tNd, Sm, Pr, Ce, Eu, Gd,
TM is at least one element selected from the group consisting of Go, DV, and Ho, and TM is Fe and/or Go.
and 0.2<x<0.7.0.04<y<O,'t
Since it is an amorphous alloy thin film with an axis of easy magnetization perpendicular to the film surface, expressed as Furthermore, it has excellent oxidation resistance, and even if there are pinholes in the protective film, the coercive force or Kerr rotation angle will not change over time. There is. Further, when forming the magneto-optical recording film according to the present invention on a substrate, the film can be formed at room temperature, and there is no need for heat treatment after film formation.

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

EXAMPLE On a glass substrate, a first protective film, a magneto-optical recording film, and a second protective film were sequentially formed by sputtering to a predetermined thickness.

When a dielectric film such as nitride or oxide was selected as the heat-retaining film, each sintered target was subjected to RF blasting. On the other hand, when a metal film was selected as the protective film, it was formed by DC magnetron sputtering.

As for the magneto-optical recording film, the target is
pt on the Fe target or on the eSCo target.
And/or using a composite target in which chips of Pd, light rare earth metals, and heavy rare earth metals are arranged at a predetermined ratio, the substrate is placed on a glass substrate at 20 to 30°C by water cooling.
An amorphous alloy thin film having the composition shown in Table 1 was formed by DC magnetron sputtering while controlling the temperature to be around room temperature. Film forming conditions are Ar pressure 5ffl
Torr, Ar flow 13sec, vacuum attainment 5
X 10-6Torr Wl There is a lower temperature.

The crystalline state of the obtained alloy thin film was measured by wide-angle X-ray diffraction, and the composition was determined by ICP spectroscopy.

In addition, the Kerr rotation angle is the residual bacteria Kerr rotation angle measured from the glass substrate side with zero external magnetic field using the oblique incidence method (λ = 633 nm).
It was measured with Specific measurement methods and equipment for the oblique incidence method are available in "Measurement Techniques for Magnetic Materials" (December 1985) supervised by Aibe Yamakawa.
March 25th 1-Published by Rikezos Co., Ltd.) Pages 261-2
It is described on page 63.

The X value and coercive force (HCO
) are shown in Table 1.

Furthermore, in order to confirm the oxidation resistance of the amorphous alloy thin film of the present invention, the strips 1'1 formed on the glass substrate were
An environmental test was conducted in which the high-temperature, high-humidity strip 1'1 was left in an oven at 5°C and 85% RH, and the Kerr rotation angle (θk) and coercive force (HC>) were measured after 240 hours or more. A comparison was made with the initial surface values θko and Hco.These results are shown in Table 1.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a magneto-optical recording medium according to the present invention,
FIG. 2 shows changes in coercive force of the magneto-optical recording medium according to the present invention and Tb 25CO75 and Tb 25 according to comparative examples.
FIG. 3 is a diagram showing changes in coercive force of Fe 66Co 9. 1... Transparent substrate 2... First protective film 3...
Magneto-optical recording film 4...Second protective film Agent: Patent attorney Shunichi Suzuki

Claims (1)

[Claims] 1) A first protective film, a magneto-optical recording film, and a second protective film are sequentially laminated in this order on a transparent substrate, and the magneto-optical recording film is made of (Pt and/or Pd) [RE_xTM_1_-_x]_1_-_y (wherein R
E is Nd, Sm, Pr, Ce, Eu, Gd, Tb, Dy
and Ho, TM is Fe and/or Co, and 0.
2<x<0.7, 0.04<y<0.10. 2) The magneto-optical recording medium according to claim 1, wherein 0.25<x<0.5. 3) At least 60 atomic % or more of RE is Tb, and the remainder is Dy, Sm, Pr, Ce, Eu, Gd, or Ho
A magneto-optical recording medium according to claim 1.