JPH01118244A - Magneto-optical recording film - Google Patents

Abstract

PURPOSE:To obtain a recording film having excellent oxidation resistance, large C/N ratio and excellent dependency on bias magnetic fields by specifying the contents of Pt and/or Pd, Fe and/or Co and incorporating a rare earth element into said film. CONSTITUTION:The Pt and/or Pd is incorporated at 10-30atom.% into the magneto-optical recording film. The Fe and/or Co is incorporated at 40-70atom.% therein and the Co/(Fe+Co) ratio [atomic ratio] is specified to 0-0.3. Nd, Sm, Pr, Ce, Eu, Gd, Tb, Dy or Ho is used for the rare earth element. The magneto-optical recording film having such compsn. has the excellent oxidation resistance and is free from pitting corrosion even after long-term use. The film has the large C/N ratio and the excellent dependency on bias magnetic fields.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magneto-optical recording film having excellent oxidation resistance and magneto-optical recording properties. The present invention relates to a magneto-optical recording film having excellent oxidation resistance and magneto-optical recording properties.

Transition metals such as iron and cobalt, terbium (Tb),
A magneto-optical recording film made of an alloy with a rare earth element such as cadrinium (Gd) has an axis of easy magnetization in a direction perpendicular to the film surface, and a film surface that is entirely magnetized in one direction is opposite to this direction of magnetization. It is known that it is possible to form magnetic domains with small orientation reversals.

By associating the presence or absence of this inverted magnetic domain with "1" and "0", it becomes possible to record digital signals on the magneto-optical recording film as described above.

As a magneto-optical recording film made of such a transition metal and a rare earth element, for example, a 'rb-r;'e-based magneto-optical recording film containing 15 to 30 atom % of Tb is disclosed in Japanese Patent Publication No. 57-20691. Magnetic recording film. Also, a magneto-optical recording film made of Tb-Fe added with a third metal is also used. Furthermore, magneto-optical recording films such as Tb-Co and Tl1-Fe-Co are also known.

These magneto-optical recording films have excellent recording and reproducing properties, but there is a major practical problem in that the magneto-optical recording film undergoes oxidation during use and its properties change over time. there were.

The mechanism of oxidative deterioration of magneto-optical recording films containing transition metals and rare earth elements is discussed, for example, in the Journal of the Japan Society of Applied Magnetics, Vol. 9, No. 2, pp. 93-96, and is as follows. It has been reported that there are three types.

b) Pitting corrosion Pitting corrosion refers to the formation of pinholes in the magneto-optical recording film, and this corrosion mainly progresses in a high humidity atmosphere, such as Tb-F'c system, Tb-C system.

The disease progresses markedly in some systems.

(a) A surface oxidation layer is formed on the surface oxidized magneto-optical recording film, and the Kerr rotation angle θk
changes over time, and eventually the Kerr rotation angle θk decreases.

c) Selective oxidation of rare earth metal The rare earth metal in the magneto-optical recording film is selectively oxidized, and the coercive force Ho changes significantly over time.

In order to prevent the oxidative deterioration of the magneto-optical recording film as described above,
Conventionally, various methods have been tried. For example, the magneto-optical recording film is made of Si3N4.5iO2S i 02 , A
A method of creating a three-layer structure sandwiched with an oxidation-preventing protective film such as IN is being considered. However, this oxidation-preventing protective film is expensive and time-consuming to form, and there is also the problem that even if this protective film is formed, it is not always possible to sufficiently prevent oxidative deterioration of the magneto-optical recording film. Ta.

Also, magneto-optical systems such as Tb-Fe system and Tb-Co system!
In order to improve the oxidation resistance of this R film during aWA,
Various methods of adding a third metal have been attempted.

For example, in the journal of the Japanese Society of Applied Magnetics mentioned above, Tb-Fe
Or Tb-Co, Co, Ni, Pt, A
By adding a third metal such as I, Cr, Ti, or Pd in an amount of up to 3.5 at. Attempts have been made to add a small amount of Co, Ni, or Pt to Tb-Fe or 'rb-co, which is effective in preventing surface oxidation and pitting corrosion. It has been reported that there is no effect in preventing selective oxidation of Tb, which is a rare earth metal in the film.This indicates that a small amount of Co in Tb-Fc or Tb-Co
, Ni, and Pt, Tb is selectively oxidized in the resulting magneto-optical recording film, and the coercive force H
This means that o changes significantly over time.

Therefore, even if a small amount of Co, Ni, or Pt (up to 3.5 atomic %) is added to Tb--Fe or Tb--Co, the oxidation resistance of the resulting magneto-optical recording film is not sufficiently improved.

Also, the summary of the 9th Academic Audience Program of the Japanese Society of Applied Magnetics (1985)
(November 2013), p. 209, for the purpose of improving the oxidation resistance of the magneto-optical recording film, Pt, AI, Cr, and Ti are added to 'rb-r;'e or Tb-Fe-Co.
Magneto-optical recording films doped with up to 0 atomic percent have been taught. However, Tb-Fe or T b-F a
-Co with amounts of Pt, AI, Cr up to 10 at%
Although surface oxidation and pitting corrosion can be prevented quite effectively even if Ti is added, Tb in the resulting magneto-optical recording film is
The oxidation prevention property against selective oxidation of is not sufficient, and there still remains the problem that the coercive force Hc changes greatly over time, and eventually the coercive force Ho decreases significantly.

Furthermore, Japanese Patent Application Laid-open No. 61-255546 discloses that a magneto-optical recording film made of rare earth elements and transition dead water is coated with Pt, Au, and Al.
A magneto-optical recording film with improved oxidation resistance is disclosed in which noble metal elements such as a, Ru, Rh, 'Pd, Os, and Ir are added within a range that provides the Kerr rotation angle necessary for reproduction. .

Furthermore, in JP-A-58-7806, Pt
A magneto-optical recording film comprising a polycrystalline thin film having a composition of Co and containing Pt in an amount of 10 to 30 atomic % is disclosed.

However, since this polycrystalline thin film having a composition of Pt co is polycrystalline, it requires heat treatment such as annealing after film formation, and the grain boundaries between crystals may generate noise signals. This polycrystalline thin film had a problem in that it had a high Curie point.

In this way, in the conventional Tb-Pa or Tb-Co, C
o, Ni, Pt, AN, Cr, Ti, Pd
Magneto-optical recording films doped with third metals, such as Both of these problems include the fact that a high C/N ratio cannot be obtained unless a high and large bias magnetic field is applied (poor bias magnetic field dependence).

The present inventors have discovered that the C
As a result of intensive research aimed at providing a magneto-optical recording film with excellent bias magnetic field dependence that can obtain a /N ratio, it was found that
The present invention was completed based on the discovery that a magneto-optical recording film containing a specific amount of e and/or Co and also containing a rare earth element such as Tb has excellent properties.

The present invention aims to solve the problems associated with the prior art as described above, and has excellent oxidation resistance, can be used for a long period of time, and has a low C/N ratio. It is an object of the present invention to provide a magneto-optical recording film having excellent bias magnetic field dependence, which has a large ratio, a low noise level, and can obtain a sufficiently high C/N ratio even with a small bias magnetic field.

The magneto-optical recording film according to the present invention contains (i) Pt and/or Pd (11) rare earth element (RE) and (ii) Fc and/or Co, Pt and/or Pd is
Fe and/or Co are present in an amount of more than 10 atom % and less than 3o atom %, and Fe and/or Co are present in an amount of more than 40 atom % and less than 70 atom %, and the Co/(PcmoCo) ratio [J
It is characterized in that the jX ratio is 0 to 0.3.

As described above, the magneto-optical recording film according to the present invention contains a specific amount of Pt and/or Pd, and contains Fc and y'j.
, or Co in a specific amount, and rare earth elements such as Tb, it has low oxidation resistance, can be used for a long period of time, has a high C/N ratio, and has a low noise level. is low, and has excellent bias magnetic field dependence.

The magneto-optical recording film according to the present invention will be specifically described below.

The magneto-optical recording film according to the present invention contains the following components (i) Pt and/or Pd (ii) rare earth elements (iii) Fe and/or Co as essential components. Further, the magneto-optical recording film of the present invention is preferably substantially amorphous when analyzed by wide-angle X-ray diffraction.

i Pt and/or Pd The magneto-optical recording film according to the present invention contains Pt and/or Pd.
is present in the magneto-optical recording film in an amount of more than 10 atomic % and less than 30 atomic %, preferably more than 10 atomic % and less than 20 atomic %, and more preferably 11 atomic % and less than 19 atomic %. .

The amount of Pt and /''& or Pd in the magneto-optical recording film is 10
When present in an amount exceeding atomic %, the magneto-optical recording film has excellent oxidation resistance, and has the advantage that pitting corrosion does not occur even after long-term use, and the C/N ratio does not deteriorate.

Figure 1 shows Pt and/or P in the magneto-optical recording film.
The d-containing material and magneto-optical recording film were heated at 85% relative humidity and 80°C.
The relationship with the He/N ratio when maintained for 1000 hours under the following environment is shown.

From FIG. 1, it can be seen that when the amount of Pt and/or Pd in the magneto-optical recording film exceeds 10 Ei%, the W4 oxidation property of the magneto-optical recording film improves and pores remain even after long-term use. It can be seen that no eclipse occurs and the C/N ratio does not deteriorate.

For example, P j 13T b 2s F C5ac O
9 or P d 12T b 28 F e s3C
In the magneto-optical recording film according to the present invention having the composition shown by 07, the C/N ratio does not change at all even if it is kept in an environment of 85% relative humidity and 80° C. for 1000 hours. On the other hand, P
T b25 F G as C that does not contain t or Pd
When a magneto-optical recording film having the composition shown by o7 is kept in an environment of 85% relative humidity and 80°C for 1000 hours, it becomes C
/N ratio decreases greatly.

Furthermore, by adding Pt and/or Pd in the above-mentioned range to the magneto-optical recording film, a small bias magnetic field is sufficient when recording or reading information from the magneto-optical recording film. A high C/N ratio can be obtained. If a sufficiently high C/N ratio can be obtained with a small bias magnetic field, the magnet for generating the bias magnetic field can be made smaller, and heat generation from the magnet can also be suppressed.
An optical disk drive device having a magneto-optical DB can be simplified. Moreover, since a sufficiently large C/N ratio can be obtained with a small bias magnetic field, it becomes easy to design a magnet for magnetic field modulation recording that can be overridden.

In Figure 2, P j 13T b 28 F e soCo
Bias magnetic field dependence and C/N ratio (dB) of the magneto-optical recording film according to the present invention having the composition shown by 9 and the magneto-optical recording film having the composition shown by Tb25Fe68Co□
Indicates the relationship between

From FIG. 2, it can be seen that in the conventionally known magneto-optical recording film shown by Tb25F068Co□, the C/N ratio does not saturate unless a bias magnetic field of 2500 seconds or more is applied, whereas the P t 13T b 28F e according to the present invention 50Co
It can be seen that in the magneto-optical recording film indicated by g, sufficient recording is possible even with a small bias magnetic field, and the C/N ratio is saturated at 12,000 or more. In the Examples and Comparative Examples shown below, the C/N of each magneto-optical recording film is shown in the table.
The smaller Efi Hsat, which indicates the value of the minimum bias magnetic field Hsat necessary for the ratio to be saturated, means that the C/N ratio will be saturated with a smaller bias magnetic field.

Furthermore, FIG. 3 shows the relationship between the content of Pt and/or Pd in the Pt Tb Fe Co-based magneto-optical recording film and the Pd:Tb Fe Co-based magneto-optical recording film and the minimum bias magnetic field (Hsat, (Oe)). shows.

From this Figure 3, it can be seen that the content of P [and/or Pd is 1
It can be seen that when it exceeds 0 atomic %, the minimum bias magnetic field Hsat becomes sufficiently small.

:i "-U The magneto-optical recording film according to the present invention contains a rare earth element (RE
), and these rare earth elements include Nd,
Sn+, Pr, Ce, Eu, Gd,
Tb.

D'/or Ho is used.

Among these, Nd, Pr, Gd, Tb, Dy
are preferably used, and Tb is particularly preferred.

Further, two or more kinds of rare earth elements may be used in combination, and in this case, it is preferable that Tb is contained in an amount of 50 atomic % or more.

This rare earth element has the advantage of providing magnetism with an axis of easy magnetization perpendicular to the film surface, so that RE/(RE+Fe +
Co ) ratio [atomic ratio] is expressed as X, 0.25
It is desirable that it be present in the magneto-optical recording film in an amount such that ≦X≦0.45, preferably 0.3≦X≦0.4.

(iii) Fe and/or Co The magneto-optical recording film according to the present invention contains Fe and/or Co.
is present in an amount of 40 atomic % or more and 70 atomic % or less, preferably 40 atomic % or more and less than 60 atomic %, and more preferably 40 atomic % or more and 59 atomic % or less.

Furthermore, Fe and/or Co are Co/(FQ +C
o) Present in the magneto-optical recording film in such an amount that the ratio [atomic ratio] is 0 or more and 0.3 or less, preferably 0 or more and 0.2 or less, and more preferably 0.01 or more and 0.2 or less. This is desirable.

When the amount of Fe and/or Co is in the range of 40 atomic % or more and 70 atomic % or less, a magneto-optical recording film with excellent oxidation resistance and an axis of easy magnetization in the direction perpendicular to the film surface can be obtained. It has the advantage of

By the way, when Co is added to the magneto-optical recording film, (a)
It has been observed that the Curie point of the magneto-optical recording film increases and the Kerr rotation angle (θk) increases, and as a result, the recording sensitivity of the magneto-optical recording film can be adjusted by adjusting the amount of Co added. Moreover, by adding Co, the carrier level of the reproduced signal can be increased. However, according to the study by the present inventors, Co is magneto-optical with jM4
It has been found that if too much is added to the film, the noise level of the reproduced signal increases and the C/N ratio decreases. Therefore, in the magneto-optical recording film according to the present invention, Co/(Fe +
Co ) ratio [atomic ratio Co is 0 or more and 0.3 or less, preferably 0
It is desirable that the range is 0.01 or more and 0.2 or less, more preferably 0.01 or more and 0.2 or less.

Figure 4 shows the relationship between the Co/(Co+-Fe) ratio [atomic ratio ko] and the noise level (dBn) in a PtTbFeCo-based magneto-optical recording film, and Figure 5
Co/(C
o +Fe) ratio atomic ratio and noise level (dBn+
).

Specifically, P j 13T b 28 Fe sa
A magneto-optical recording film according to the present invention having a composition represented by cO9 (Co/(Fe +Co) ratio [atomic ratio]: 0
．． 15), the noise level is 156dlll, while P j 13T b 28 F e 3ec 0
Magneto-optical SAM (Co
/ (Fe + Co ) ratio [atomic ratio]: 0.39) has a noise level of 150 dBn, which is a large noise level.

Further, the magneto-optical recording film (Co
/(Fe÷Co) ratio [atomic ratio Koni 0.12], while the noise level is 155 dBl, P d 14
Magneto-optical distribution SAW (Co/(Fe-t-Co) ratio [
Atomic ratio]: 0.31) has a noise level of 151 dBn
+, indicating a large noise level.

Also, the co / (Fe + cO) ratio [atomic ratio] is 0.3
If it exceeds this, erasing deterioration will be observed in the magneto-optical recording film. That is, Co/(Fe −+−Co ) in the magneto-optical recording film
If the ratio (atomic ratio) is more than 0.3, more precisely, more than 0.2, - when the energy irradiated to the magneto-optical recording film is increased when erasing information recorded on the magneto-optical recording film,
This is not preferable because the magneto-optical arrangement 3jt and FA may be altered in quality.

Figure 6 shows Pt Tb Fe Co or Pd TbP.
The relationship between the Co/(Fe +Co) ratio [atomic ratio] and erasure deterioration (ΔC/N ratio (dB)) in a magneto-optical recording film having a composition represented by a Co is shown.

Specifically, P j 13T b 28F according to the present invention
F3s.

Magneto-optical recording 11m having a composition of Co9 (Co/
(Fe + Co) atomic ratio]: 0.155>,
- When erasing recorded information, no alteration occurs even if the energy irradiated to the film is increased, and the new information has the same C/N ratio value as before erasing. Can be done. On the other hand, Co is Co / (Fe +
Co ) ratio [atomic ratio] containing more than 0.3 r' t1
3T b 28F 04oc O19 or Pi
If a magneto-optical recording film having a composition of 13T b 28F O3eC023 is erased with more energy than necessary, it will cause alteration and the magneto-optical properties will deteriorate, and the C/N ratio of newly recorded information will also decrease. The C/N ratio becomes smaller than the one before erasing.

Furthermore, the magneto-optical recording film according to the present invention does not cause any altered quality even after repeated recording and erasing, for example, the P t 13T b 28F e s
A magneto-optical recording film having a composition of ac O9 shows no decrease in C/N ratio even after 100,000 recording and erasing operations are repeated.

In the present invention, small amounts of various elements may be added to the magneto-optical recording film to improve the Curie temperature, compensation temperature, coercive force Hc, Kerr rotation angle θ, or to reduce costs. These elements can be used in a proportion of, for example, less than 10 atomic % based on the total number of atoms constituting the recording film.

Examples of other elements that can be used in combination include the following elements.

(I) 3dEI transfer elements other than Fe and Co Specifically,
Sc, Ti, V, Cr, Mn, Ni, Cu, Zn
is used.

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

(ff) 4d transition elements other than Pd, specifically Y, Zr, Nb, Mo, Tc, Ru
, Rh, Ag, and Cd are used.

Among these, Zr and Nb are preferably used.

(■) 5d transition elements other than Pt Specifically, Hf, Ta, W, Re, Os, Ir
, Au, and HiJ are used.

Among these, Ta is preferably used.

(IV) Group IIIB 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.

Among these, Si, Ga, Sm, and Pb are preferably used.

(Vl) VB group element Specifically, N, P, As, Sb, and Bi are used.

Among these, sb is preferably used.

(■) VIB group elements Specifically, S-Sa, Ta, and Pa are used.

Among these, Ta is preferably used.

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

Sputtering or electron beam evaporation is performed by keeping the substrate temperature at about room temperature and using a composite target or an alloy target having a predetermined composition, in which chips made of each element constituting the magneto-optical recording film according to the present invention are arranged in a predetermined ratio. A magneto-optical recording film of a predetermined composition is deposited on this substrate (the substrate may be fixed, or may be rotating or revolving around its axis) using conventionally known film-forming conditions such as the method By this, the magneto-optical recording film according to the present invention can be formed.

Such a magneto-optical recording film according to the present invention can be formed at room temperature, and it is not necessarily necessary 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. .

Note that, if necessary, the amorphous alloy J film can be formed on the substrate while heating the substrate temperature 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, the ions of an inert gas such as argon accelerated by the electric field will hit not only the target material but also the magneto-optical recording film that is being formed, resulting in a magneto-optical recording film with the characteristics of being beaten. It may happen.

The alloy target used for forming +1A on the magneto-optical recording film according to the present invention includes (i) Pt and/or Pd;
(ii) contains rare earth elements and (iii) Fe and/or Co, Pt and/or Pd is 5 at.%
Fe and /:& or Co are present in an amount exceeding 30HX% and below 80W%, and the Co/(Fe + Co) ratio [atomic ratio J is 0 to 0.4.

Such an alloy target can be created using each of the metals mentioned above by either a melting method or a sintering method.

The melting method is a method in which metals are melted and cast in a low-frequency melting furnace, and a better alloy target can be obtained by removing impurities such as oxygen using a calcining pot or the like.

On the other hand, the sintering method is a method of sintering powders of various metals,
An alloy target can be obtained by sintering individual powders of each elemental metal, sintering alloy powders of each element, or sintering a mixture of alloy powders of several metals and elemental metals. .

The alloy target used in the present invention is Tb
Compared to Fe-Co alloy targets, it has excellent oxidation resistance and toughness, and the alloy target is prevented from cracking after casting and processing. Therefore, the alloy target used in the present invention is Tb Fe, which has been conventionally used.
It is not necessarily necessary to perform pre-sputtering as with a Co alloy target.

In addition, in the target of the present invention, the magnetic permeability of the target is also reduced, the thickness of the target can be increased compared to the conventional Tb Fe Co, and the utilization efficiency of the target can be improved.

In general, the composition of an alloy target and the composition of a film obtained from this alloy target differ by a maximum of about 10 atomic percent depending on sputtering conditions.

Therefore, the composition of the alloy target is determined depending on the film composition and sputtering conditions.

Since the magneto-optical recording film of the present invention has an axis of easy magnetization perpendicular to the film surface, it can be used in the field of magnetic recording materials such as perpendicular magnetic recording films, magnetic bubble memories, or magneto-optical recording films, and utilizes the magneto-optic effect. It can be applied to various fields such as optical modulators.

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

In the present invention, a rectangular loop with good Kerr hysteresis means a saturated Kerr rotation angle (1 for θ), which is the Kerr rotation angle at the maximum external magnetic field, and a residual Kerr rotation, which is the Kerr rotation angle at zero external magnetic field. This means that the ratio θ of 2/θ of 1 to the angle (θk) is 0.8 or more.

In the present invention, the film thickness of the magneto-optical recording film is 20 to 5 μm, preferably 50 to 5,000 μm, and more preferably 100 to 3 μm.
Kashima is desirable because it has about 1,000 people.

A case where the magneto-optical recording film of the present invention is applied as a recording film of a magneto-optical disk will be described below.

The magneto-optical recording film of 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 rectangular 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 θ at the maximum external magnetic field and the coercive force Hc is large, it is suitable as a magneto-optical recording film. Furthermore, a good value of θk means a good value of θf, and therefore it can be used in either the Kerr effect type or the Faraday effect type.

In addition, since the magneto-optical recording film of the present invention has excellent oxidation resistance, it can be protected against oxidation as in the case of conventional heavy rare earth-3d transition metal alloy thin films such as Tb-Fe-Tb-Fc-Co. It is not necessarily necessary to use a membrane.

Furthermore, it is not necessary to use anti-oxidant materials for the substrate, other functional films (for example, enhancement film, reflective film), adhesive layers for bonding, etc. that are in contact with the recording film.

Furthermore, when forming enhancement films, reflective films, etc., in addition to dry HI film formation methods such as vacuum evaporation and sputtering, wet film formation methods such as spin code and spray methods, which could not be performed conventionally, can also be used. .

Therefore, the structure of a magneto-optical disk using the magneto-optical recording film of the present invention as a recording film is as follows: N) Substrate/recording film (ii) Substrate/enhancement film/recording film (i) Substrate/recording film/reflection film (IV ) Substrate/Enhancement [/Recording M/Reflection film (V)
Substrate/enhanced JLQ/recording plA/enhanced film/
A reflective film is mentioned, and TI4, which is a magneto-optical disk, has a protective film or protective label formed on the outermost layer on the side of the recording film to provide scratch resistance or oxidation resistance.
It can also be set to m.

The enhancement film may be made of any organic or inorganic material as long as its refractive index is greater than the refractive index of the substrate.

Substrates include inorganic materials such as glass or aluminum, polymethyl methacrylate, polycarbonate, polymer alloys of polycarbonate and polystyrene, amorphous polyolefins such as those shown in U.S. Pat. No. 4,614,778, and poly(4-methyl). -1-pentene,
Organic materials such as epoxy resin, polyether sulfon, polysulfon, and polyetherimide can be used.

The reflective film may be made of any material as long as it has a reflectance of 50% or more.

Furthermore, the configuration of the magneto-optical disk is as follows (1) to (V
) The structure is not limited to the structure shown in (), but may be laminated with a base layer, an oxidation prevention film, or a high permeability soft magnetic film as necessary, and it is also possible to use them in combination in addition to a single plate. It is.

It is also possible to form a magneto-optical SAM by providing a 2reJ magneto-optical recording film on the substrate. In that case, the coercive force of the first magneto-optical recording film is Hcl, the Curie temperature is TCl, and the second optical When the coercive force of the magnetic recording film is 11C2 and the Curie temperature is TC2, Hc1>Hc2 and TCl<TC2, and at least the outer layer (
The layer on the side opposite to the substrate (ie, the second magneto-optical recording film layer) is preferably a magneto-optical recording film as specified in the present invention.

Such a 2RjJ side magneto-optical recording film can be overridden. A recording method for overriding such a two-layered magneto-optical recording film will be described.

A magneto-optical recording device has a magnetic field (Ho) that generates an upward magnetic field (or downward magnetic field) for writing directly below a head that irradiates a laser beam, and in front of the magnetic field, that is, on the upstream side, there is a magnetic field HCl>Hb>Hc2. A downward magnetic field with the relationship (
It has a magnetic field (1-tb) that generates an upward magnetic field).

The magneto-optical recording film first passes over Hb to form a second
The direction of magnetization of the magneto-optical recording film is aligned downward (or upward). At this time, the direction of magnetization of the first magneto-optical recording film does not change from the relationship Hc 1 > Hb when passing over the 0th order Ho. First, the magneto-optical recording film is irradiated with laser light whose level is modulated to a high level or a low level in accordance with the information signal. Since the high-level laser beam heats the magneto-optical recording film to a temperature higher than the Curie temperature TC2 of the second magneto-optical recording film, the weak external magnetic field Ho causes both the first magneto-optical recording film and the second magneto-optical recording film to be exposed to the magnetic field of the external magnetic field. The direction of magnetization is aligned upward (or downward). On the other hand, since the low-level laser beam only heats the first magneto-optical recording film 5j to a temperature higher than the Curie temperature TC1 and less than TC2 of the film, only the first magneto-optical recording film is magnetized by Ho. The direction of magnetization of the second magneto-optical recording film is downward (
or upward). Therefore, the magnetization direction of the first magneto-optical recording film is reversed to the magnetization direction of the second magneto-optical recording film in the process of returning to room temperature after passing through Ho, and becomes downward (or upward). Therefore, by modulating the energy level of the writing laser beam, it is possible to override the magneto-optical recording film.

In addition to the above, there is also a magneto-optical recording film having a two-layer structure, in which the coercive force of the first magneto-optical recording film layer (inner IU) is higher than the coercive force of the second magneto-optical recording film layer (outer layer). If the magneto-optical recording film of the present invention is small, and at least the outer layer (layer opposite to the substrate) is the magneto-optical recording film of the present invention, C.
A magneto-optical IH film with a high /N ratio and excellent long-term reliability can be obtained. In other words, the recording sensitivity depends on the Curie point of the outer layer, and the information recorded on the outer layer is transferred to the inner layer, which has a small coercive force and a large Kerr rotation angle, and when it is read out, a high C/N ratio can be obtained. be. In this case, in order to obtain a high C/N ratio, the Kerr rotation angle of the inner layer is 0.25 dcg or more, preferably 0.3 deg or more, the coercive force is 3KO8 or less, preferably 2KOe or less, and (B) the The coercive force is 3 KOe or more, preferably 4 KOa or more, and (B
) The Curie point of the layer is preferably 100 to 300°C.

In such a magneto-optical recording film, the recording sensitivity depends on the Curie point of the second magneto-optical recording film, and the information recorded on the first magneto-optical recording film is stored in the second film, which has a small coercive force and a large Kerr rotation angle. When this information is transferred to the magneto-optical recording layer and read out, a high C
/N ratio is obtained.

In the present invention, (i) Pt and/or Pd (ii) rare earth elements (RE) and (iii) Fe
and/or Co, Pt and/or Pd is present in an amount greater than 10 atom % and less than or equal to 3 o atom %, and Fe and/or Co is present in an amount of greater than or equal to 4 o atom % and less than or equal to 70 atom %. And Co/(Fe+Co)
There is provided a magneto-optical recording film characterized in that the ratio [atomic ratio ko] is 0 to 0.3.

This magneto-optical recording film has excellent oxidation resistance, can be used for a long period of time, has a large C/N ratio, has a low noise level, and has excellent bias magnetic field dependence.

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

-' 1 to 25 and 1 to 19 As targets, on Fc target or Fe, C
o Using a composite target in which chips of Pt and/or Pd and rare earth metals are arranged at a predetermined ratio on the target, sputtering was performed on a glass substrate by DC magnetron sputtering at 20 to 50°C as shown in Table 1. A magneto-optical recording film having a composition was formed. The film forming conditions were Ar pressure 5
mTOrr, Ar flow Ji 35CCI, vacuum attainment level 5
x 1O-6 Torr or less, and the thickness of the alloy thin film is 1
000 people.

The obtained magneto-optical recording film was entirely amorphous as measured by wide-angle X-ray diffraction. The composition was determined by 102 emission spectrometry.

In addition, the Kerr rotation angle is the residual Kerr rotation angle measured from the glass substrate side with zero external sensing field using the oblique incidence method (λ = 780nn).
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.
Published by Trikebbs Co., Ltd. on March 25th) pp. 261-26
It is described on page 3.

X value of the obtained magneto-optical recording film, Fe fCo mass (atomic%
), Co/(Fe +cO) ratio [atomic ratio], Kerr rotation angle (θk), and coercive force (Hc) are shown in Table 1.

In addition, a magneto-optical recording film of a predetermined composition was formed on a substrate made of a non-quality ethylene-tetracyclododecene copolymer by DC magnetron sputtering to create a single-layer magneto-optical disk with a capacity of 1,000 people. .

The obtained magneto-optical disk had a diameter of 130 cm, and the magneto-optical disk was driven by a drive device (Nakamichi 0MS-40
00), recording and reproduction were performed under the conditions of a recording frequency of 1 MH2 (duty ratio 50%), a linear velocity of 11.1 m/s, a bias magnetic field of 2000 e during writing, and a read laser power of 1.0 mW.

Table 1 shows the recording power (optimal recording power) at which the level of the second harmonic is minimized by the spectrum analyzer.
It also shows the signal-to-noise ratio (C/N ratio) and noise level when recorded.

Then, this information was erased with a power 3.0 mW higher than the optimum recording power, and new information was recorded. This operation was repeated 10 times, and the difference in the C/N ratio before and after erasing was expressed as the 0/N ratio.

Regarding the bias magnetic field dependence, the bias magnetic field dependence was set under the above conditions.
Hsat was determined from the change in C/N ratio when changing from 0 to 5000c.

Furthermore, with the promise of investigating long-term reliability, we conducted a life test in which the resulting magneto-optical disk was left in an oven at a high temperature of 80°C and 85% relative humidity for 1,000 hours. The C/N ratio was measured and shown in Table 1.

P j 13 was deposited on a non-quality polyolefin substrate as a first magneto-optical recording film by a DC magnetron splatter method.
T b 28F OssCo4 film and P j 13T b 3o F e 4ac as the second magneto-optical recording film
09 film was formed so that the outer layer was the second magneto-optical recording film. At this time, the coercive force of the first magneto-optical recording film is larger than the coercive force of the second magneto-optical recording film, and the coercive force of the first magneto-optical recording film j, &
The Curie temperature of the film had a smaller relationship than the Curie temperature of the second magneto-optical recording film.

Next, an upward magnetic field for writing (<0.2 KOa) and a downward magnetic field (5 KOa) which is larger than the coercive force of the second magneto-optical recording film and smaller than the coercive force of the first magneto-optical recording film adjacent to the upstream side of the magnetic field are applied. ), the magneto-optical disk described above was overridden by single beam modulation at a linear velocity of 11 m/s, a low level laser power of 4 mW, and a high level laser power of 6 mW.
It could be overridden.

Further, when this magneto-optical disk was subjected to a life test under conditions of 80° C. and 85% relative humidity for 1000 hours, no change was observed in the recording characteristics.

Pt was used as the first magneto-optical recording film in the same manner as in Example 25.
A Tb20Fe6oCo15 film is provided with a film thickness of 30OA, and a Pt13Tb28F film is provided as a second magneto-optical recording film (outer layer).
c519o8Wi to 800 II5! It was set thick.

This first magneto-optical recording film has θk of 0.40° and H
c was 1.2KOe, and Tc was 270°C. Further, the second magneto-optical recording film has θk of 0624° and Hc
was 8°3KOa, and Tc was 170°C.

The C/N ratio of this magneto-optical recording film was 55 dB.

Further, when a life test was carried out in which this magneto-optical disk was left for 1000 hours under conditions of 80° C. and 85% relative humidity, no change was observed in the recording characteristics.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the content (atomic %) of Pt and/or Pd in the magneto-optical recording film and the oxidation resistance (C/N ratio). FIG. 2 is a diagram showing the relationship between the bias magnetic field (Oe) of the magneto-optical recording film and the C/N ratio. Figure 3 shows the content of Pt and/or Pd in the magneto-optical recording film (
atomic%) and minimum bias magnetic field (Hsat, (Oe))
FIG. FIG. 4 is a diagram showing the relationship between the Co/(Fe +Co) ratio [atomic ratio] in a magneto-optical recording film containing P and the noise level (dll). FIG. 5 shows Co/(
Fe + Co) ratio [atomic ratio] and noise level (dBn
) is a diagram showing the relationship between FIG. 6 is a diagram showing the relationship between the Co/(FI3+Co) ratio [atomic ratio Co] and erase deterioration (to C/N ratio (dB)) in the magneto-optical recording film. Note that all the magneto-optical disks in Figures 1 to 6 are single-layer 1
It is made up of 000 people. Figure 2 Bias magnetic field (Oe) Figure 3 Pd content (atomic %) Figure 4 0, I 02 0.3
0.4Co/(Fe+Col ratio [atomic ratio] Fig. 5 co/(Few (:6) ratio [atomic ratio] Fig. 6 □ Q, I O, 20, 3Q4
('/cFeeCol ratio [atomic ratio]) (Note) The Q symbol indicates that the 0 symbol and the 0 symbol are fused.

Claims (1)

[Claims] 1) Contains (i) Pt and/or Pd (ii) rare earth element (RE) and (iii) Fe and/or Co, in which Pt and/or Pd exceeds 10 atomic % and 30 Fe and/or Co are present in an amount of 40 atomic % or more and 70 atomic % or less, and the Co/(Fe + Co) ratio [atomic ratio] is 0 to 0.3. A magneto-optical recording film characterized by: 2) The magneto-optical recording film according to claim 1, wherein the crystalline state of the magneto-optical recording film is substantially amorphous. 3) Pt and/or Pd exceeds 10 atomic %2
3. The magneto-optical recording film according to claim 1, wherein the magneto-optical recording film is present in an amount of less than 0 atomic %. 4) The magneto-optical recording film according to claim 1 or 2, wherein Pt and/or Pd are present in an amount of 11 atomic % to 19 atomic %. 5) Fe and/or Co is 40 atomic % or more and 60
3. The magneto-optical recording film according to claim 1, wherein the magneto-optical recording film is present in an amount of less than atomic percent. 6) Co/(Fe+Co) ratio [atomic ratio] is 0 or more
．． 2. The magneto-optical recording film according to claim 1 or 2, wherein the magneto-optical recording film is 2 or less. 7) The magneto-optical recording film according to claim 1 or 2, wherein the Co/(Fe+Co) ratio [atomic ratio] is 0.01 to 0.2. 8) Rare earth elements are Nd, Sm, Pr, Ce, Eu, G
d, Tb, Dy or Ho.
The magneto-optical recording film described in . 9) The magneto-optical recording film has a two-layer structure, the coercive force of the first magneto-optical recording film is Hc_1, the Curie temperature is Tc_1, the coercive force of the second magneto-optical recording film is Hc_2, and the Curie temperature is Tc_2. Then, Hc_1>Hc_2 and Tc_1<Tc_2, and furthermore, at least the outer layer (the layer on the opposite side of the substrate, ie, the second magneto-optical recording film) contains (i) Pt and/or Pd (ii) rare earth elements ( RE) and (iii) Fe and/or Co, Pt and/or Pd is present in an amount of more than 10 atom % and less than 30 atom %, Fc and/or Co is present in an amount of more than 40 atom % and 70 atom % A magneto-optical recording film characterized by being present in an amount of at most atomic % and having a Co/(Fe+Co) ratio [atomic ratio] of 0 to 0.3. 10) The magneto-optical recording film according to claim 9, wherein the crystalline state of the second magneto-optical recording film is substantially amorphous. 11) The magneto-optical recording film according to claim 9 or 10, wherein in the second magneto-optical recording film, Pt and/or Pd are present in an amount of more than 10 atomic % and less than 20 atomic %. 12) The magneto-optical recording film according to claim 9 or 10, wherein in the second magneto-optical recording film, Pt and/or Pd are present in an amount of 11 atomic % to 19 atomic %. 13) The magneto-optical recording film according to claim 9 or 10, wherein in the second magneto-optical recording film, Fe and/or Co are present in an amount of 40 atomic % or more and less than 60 atomic %. 14) In the second magneto-optical recording film, Co/(Fe+Co
) ratio [atomic ratio] is 0 or more and 0.2 or less
The magneto-optical recording film according to item 1 or item 10. 15) In the second magneto-optical recording film, Co/(Fe+Co
) ratio [atomic ratio] is 0.01 to 0.2. The magneto-optical recording film according to claim 9 or 10. 16) In the second magneto-optical recording film, the rare earth element is Nd
, Sm, Pr, Ce, Eu, Gd, Tb, Dy and Ho
The magneto-optical recording film according to claim 9 or 10. 17) The magneto-optical recording film has a two-layer structure, the coercive force of the first magneto-optical recording film (inner layer) is smaller than the coercive force of the second magneto-optical recording film (outer layer), and at least the outer layer (on the side opposite to the substrate (i) Pt and/or Pd (ii) rare earth element (RE) and (iii) Fe and/or Co, Pt and/or Pd is more than 10 atomic % and 30 atomic % or less Fe and/or Co are present in an amount of 40 atomic % or more and 70 atomic % or less, and the Co/(Fe + Co) ratio [atomic ratio] is 0 to 0.3. magneto-optical recording film. 18) The magneto-optical recording film according to claim 17, wherein the crystalline state of the second magneto-optical recording film is substantially amorphous. 19) The magneto-optical recording film according to claim 17 or 18, wherein in the second magneto-optical recording film, Pt and/or Pd are present in an amount of more than 10 atomic % and less than 20 atomic %. 20) The magneto-optical recording film according to claim 17 or 18, wherein in the second magneto-optical recording film, Pt and/or Pd are present in an amount of 11 atomic % to 19 atomic %. 21) The magneto-optical recording film according to claim 17 or 18, wherein in the second magneto-optical recording film, Fe and/or Co are present in an amount of 40 atomic % or more and less than 60 atomic %. 22) In the second magneto-optical recording film, Co/(Fe+Co
) ratio [atomic ratio] is 0 or more and 0.2 or less
The magneto-optical recording film according to item 7 or 18. 23) In the second magneto-optical recording film, Co/(Fe+Co
) ratio [atomic ratio] is 0.01 to 0.2. Claim 17
19. The magneto-optical recording film according to item 1 or 18. 24) In the second magneto-optical recording film, the rare earth element is Nd
, Sm, Pr, Ce, Eu, Gd, Tb, Dy and Ho
The magneto-optical recording film according to claim 17 or 18. 25) Contains (i) Pt and/or Pd, (ii) rare earth elements and (iii) Fe and/or Co,
Pt and/or Pd is present in an amount of more than 5 atom % and less than 40 atom %, Fe and/or Co is present in an amount of more than 30 atom % and less than 80 atom %, and Co/(
An alloy target having an Fe+Co) ratio [atomic ratio] of 0 to 0.4.