JPH04208501A - Magneto-optical material and magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To improve corrosion resistance, to increase a magneto-optic effect, and to enhance light transmission properties by mounting a holder composed of an inorganic or organic binder, which is shown in specific structural formula and to which rare-earth iron garnet fine particles having specific mean particle size are dispersed. CONSTITUTION:The magneto-optical material has rare-earth iron garnet fine particles shown in formula I and having mean particle size of 30-1000Angstrom and a holder consisting of an inorganic or organic binder, to which the rare-earth iron garnet fine particles are dispersed. Where R represents one kind or more of rare earth elements selected from a group made up of Y and a lanthanoid and M one kind or more of elements selected from a group consisting of Al, Ga, Cr, Mn, Sc, In, Ru, Rh, etc., in formula I, a+b+c+d=7.0-8.0, a+b=2.0-3.5, c+d=4.0-6.0, a=0.5-3.6, b=0-2.5, c=3.0-6.0 and d=0-2.0 hold, and (e) represents the atomicity of oxygen satisfying the valency of other elements. Accordingly, corrosion resistance is improved, an magneto-optic effect is increased, and light transmission properties are also enhanced.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a magneto-optical material that has excellent magneto-optic properties and is suitable for applications such as optical isolators, optical circulators, optical switches, optical waveguides, and optical memories, and its use. The present invention relates to magneto-optical recording media.

(Prior Art and its Problems) Conventionally, as a magnetic material with excellent magneto-optic effect, a material made of an amorphous alloy of a rare earth metal and a transition metal is known.

However, magnetic bodies made of such amorphous alloys have the drawback of being susceptible to oxidative corrosion and deteriorating their magneto-optical properties. In addition, since amorphous alloys have low light transmittance, it is necessary to use the magneto-optical effect (Kerr effect) due to reflection on the surface, or because amorphous alloys generally have a small Kerr rotation angle, there is a problem of low sensitivity. there were.

On the other hand, Japanese Patent Publication No. 56-15125 proposes a magneto-optical material using a thin film of garnet polycrystalline oxide. Magnetic materials using this oxide have excellent corrosion resistance, and the magneto-optical effect (
Since it uses the Faraday effect, it has the advantage of high sensitivity. However, because it is polycrystalline, it has the disadvantage that noise increases due to light scattering at grain boundaries, birefringence, and domain wall movement.

In addition, when producing the above-described magnetic thin film on a substrate,
Because the manufacturing temperature was high, at 500° C. or higher, there was a problem in that only heat-resistant substrates could be used.

On the other hand, JP-A-61-119758 discloses a coating type magneto-optical recording material using yttrium iron garnet particles. In such a coating type medium, whether there is an adverse effect of grain boundaries such as those in the polycrystalline oxide thin film, the garnet particles described in this publication have a particle size of 1.
The particles are as large as 5 μm, and when such particles are used, light scattering occurs, making them unsuitable for applications that utilize submicron wavelength light.

(Objective of the Invention) The present invention solves the above problems, has excellent corrosion resistance, a large magneto-optic effect, excellent optical transparency, and is an optical isolator.
It is an object of the present invention to provide a magneto-optic material suitable for applications such as an optical circulator, an optical switch, a leading waveguide, and an optical memory, and a magneto-optical recording medium using the same.

(Means for solving problems) The present invention is - large amount R, B+ bFeeM d○.

(However, R represents one or more rare earth elements selected from the group consisting of Y and lanthanum series elements, and M represents Al, G
a, Cr, Mn, Se, In, Ru, Rh
, Co, Fe(II), Cu, Ni, Zn
.

Li, Si, Ge, Zr, Ti, Hf, S
Indicates one or more elements selected from the group consisting of n, Pb, Mo, V, Nb and Ta, a + c + d
=7.0~&0, a+b=2.0~3.5, C+d=4
．． 0~6.0, a=0.5~3', 5, b=o-
z5, c=3.0 to 6.0, d=o-40, and e is the number of oxygen atoms satisfying the valences of other elements.

) and having an average particle diameter of 30 to 100 mm, and a holder made of an inorganic or organic binder in which the rare earth iron garnet particles are dispersed.

As the rare earth iron garnet particles in the present invention, R
A garnet represented by 2Fe50+2 or a garnet in which a part of the rare earth element of the garnet is substituted with Bi, and/or a garnet in which a part of Fe is substituted with M are used.

The R in the above-large quantity is Y, La, Ce, P
r, Nd, Pm.

Sn+, Eu, Gd, Tb, Dy, Ha,
Indicates one or more rare earth elements selected from the group consisting of Er, T[El, Yb, and Lu.

Further, M is an element that can be substituted for iron, such as Al or Ga.

Cr, Mn, Se, In, Ru, Rh, C
o, Fe(II), Cu, Ni, Zn,
Sl.

Ge, Zr, Ti, Hf, Sn, Pb, M
Indicates one or more elements selected from the group consisting of o, V, Nb, and Ta. Among the elements of M, the trivalent element Al,
Ga, Cr, Mn, Se, In, Ru,
Rh and Co alone are divalent elements Co, Fe, C
u, Ni and Zn, or the monovalent element Li, the tetravalent element Si, Ge, Zr, Ti, Hf, Sn,
It is preferable to substitute Pb and Mo, or a combination of pentavalent elements V, Nb, and Ta as an element equivalent to trivalent.

The proportion of each element in the general formula is a +
b + c + d = 7.0-8.0, preferably 7.2-8.0. a+b=2.0-3.5, preferably 2.5-3°5, c+d=4.0-6.0, preferably 4.0-5.5, a=0.5-3.5, Preferably 0
．． 5-2.5, b=.

~Z5, preferably 0.5-2.5, C=3.0-6.
0, preferably 3.5 to 580, d=o to 2.0, preferably 0 to 1.5, and e is the number of oxygen atoms satisfying the valences of other elements.

In the present invention, some of the rare earth elements of garnet are replaced with Bi.
By replacing it with , the Faraday rotation angle can be increased. Moreover, by substituting a part of iron with M, the Curie temperature can be lowered and the saturation magnetization can be reduced.

Further, in the present invention, a part of R in the rare earth iron garnet fine particles may be further substituted with a divalent element such as Pb, Ca, Mg, etc. In that case, M's tetravalent or
Charge compensation may be performed using a valence element.

The average particle diameter of the rare earth iron garnet fine particles in the present invention is 30 to 1000 particles, preferably 100 to 600 particles. When the average particle size is smaller than 30 particles, it becomes superparamagnetic due to thermal disturbance. Moreover, if the number of people exceeds 1,000, light scattering occurs and noise is generated, which is not preferable.

In addition, it is preferable that the particle shape is optically symmetrical,
A spherical shape is preferable, but a polyhedral shape or a plate shape may also be used.

The method for producing the rare earth iron garnet fine particles is not particularly limited as long as particles having the above-mentioned characteristics can be obtained, and production methods such as a hydrothermal synthesis method, a coprecipitation method, a melting method, an alkoxide method, a gas phase method, etc. can be used. It will be done.

Below, a method for producing rare earth iron garnet fine particles by a coprecipitation method will be described.

A solution containing ions of each element selected in proportions constituting the rare earth iron garnet represented by the above general formula and an alkali are mixed so that the alkali concentration after mixing is 0.1 to 8 mol/l. to produce a precipitate, and the precipitate was heated to 600 to 9
Rare earth iron garnet fine particles are obtained by firing at 00°C.

The solution containing ions of each element is obtained by dissolving compounds of each element, such as nitrates, sulfates, chlorides, etc., in a solvent.

The solvent may be any solvent as long as it can dissolve the compounds of each of the above elements, and usually water, alcohols, ethers, or mixed solvents thereof are used.

It is desirable that the solution containing each of the elemental ions is prepared so that the total ion concentration contained in the slurry after precipitation is 0.01 to 2.0 mol/l.

If the total ion concentration is less than 0.01 mol/l, the amount of garnet produced will be small, and if it is more than 2.0 mol/l, the particles will become large or a different phase will be formed, which is not preferable.

Further, the proportion of each element ion can be set to the proportion of each element constituting the rare earth iron garnet represented by the above general formula, but for R and Bi, the proportion is 1 less than the required amount.
It may be used in an excess amount of up to about 0 mol%.

As the alkali, sodium hydroxide, potassium hydroxide, aqueous ammonia, diethylamine, ethanolamine, etc. are used. The amount of alkali used should be selected so that the alkali concentration in the solution after mixing the alkali is O, 1 to 8 mol/l, preferably 0.5 to 2 mol/l. If the amount of alkali is too small, the particles produced will become thick (or unreacted substances will remain).Also, it is not economical to increase the amount of alkali excessively.

Examples of methods for mixing the solution containing ions of each element and an alkali include a method of adding a solution containing ions of each element to an aqueous alkali solution, and a method of continuously mixing the two. Further, the precipitation may be formed at once or in multiple stages.

Next, the obtained precipitate is washed with water to remove free alkali, and then filtered, dried, and fired to obtain rare earth iron garnet fine particles. The firing temperature varies depending on the composition of the rare earth iron garnet, but is usually 600 to 9
00°C. If the firing temperature is too low, crystallization will not be sufficient, and if the firing temperature is too high, the particles will become large or sintering will occur, which is undesirable. Appropriate firing time is about 10 minutes to 30 hours. Further, the firing atmosphere is not particularly limited, or an air atmosphere is generally convenient.

The magneto-optical material of the present invention can be obtained by dispersing rare earth iron garnet fine particles in a carrier comprising an inorganic or organic binder.

The rutting machine binder that serves as a holding body includes a nitrate aqueous solution that conforms to the garnet composition, a peptized co-precipitation neutralized product that conforms to the garnet composition, metal alcoholades, silanol compounds and their derivatives, organosilicon compounds, and acetylacetone metals. Examples include amorphous inorganic oxides and molten glass produced by heat-treating salts and the like.

Examples of organic binders include vinyl chloride-vinylacetate copolymers, vinyl chloride-vinylidene chloride copolymers, cellulose derivatives such as nitrocellulose resins, acrylic resins, polyvinyl butyral resins, epoxy resins, polyurethane resins, phenoxy resins, and polyesters. Examples include resins, phenol resins, polyamide resins, melamine resins, and the like.

In particular, in order to reduce noise due to light scattering, it is desirable that the refractive index of the binder be matched with the refractive index of the rare earth iron garnet fine particles, and the deviation from the refractive index of the rare earth iron garnet fine particles should be ±20% or less, especially ± 10
% or less.

The magneto-optical material of the present invention has rare earth iron garnet fine particles and a binder dispersed or dissolved in water or an organic solvent,
After coating on a suitable substrate or pouring into a suitable mold,
It is obtained by performing a hardening treatment such as heat treatment.

The magneto-optical material of the present invention has excellent corrosion resistance, a large magneto-optic effect, and excellent optical transparency, and can be used as an optical isolator,
It is suitably used for applications such as optical circulators, optical switches, optical waveguides, and optical memories.

For example, a magneto-optical recording medium can be obtained by providing a magnetic layer made of the magneto-optic material of the present invention on a substrate.

The thickness of the magnetic layer is 0.05 to 2.0 μrn, particularly 0.05 to 2.0 μrn.
A range of 2 to 1.0 μm is preferable in terms of stability of recording bits.

The substrate is not particularly limited, and may be a single crystal substrate, a polycrystalline substrate, an amorphous substrate such as glass, another inorganic material substrate such as a composite substrate, or acrylic resin, polycarbonate resin,
An organic material substrate such as polyester resin, polyamide resin, polyimide resin, etc. can be used.

Furthermore, a light reflecting layer can be provided between the substrate and the magnetic layer or on the magnetic layer. As the light reflecting layer, Cu, Cr,
Al, Ag, Au, TiN, etc. are used. This light-reflecting layer is formed on the substrate or magnetic layer by a coating method, plating method, vapor deposition method, or the like.

As such a magneto-optical recording medium, in the above-mentioned large amount RaBi bFecM a Oa, a = 0.5 to 3.0, preferably 1.0 to 2.0.
, b=0°25-2.5, preferably 1.0-2.0.
c=3.0-5.0, preferably 3.8-5.0, d=
It is preferably 0 to 2.0, preferably 0 to 1.2.

In particular, by including at least Co and/or Rh as M, it is possible to have magnetocrystalline anisotropy, have a low Curie temperature, and have low saturation magnetization. in this case,
As M, CO and/or Rh should be in the range of 0.1 to 2.0, preferably 0.2 to 1.5, and the remaining elements should be in the range of θ to 2.0, preferably 0.1 to 1.5. or desirable.

When M contains at least CO and/or Rh, the rare earth iron garnet fine particles have magnetocrystalline anisotropy, so when producing a magneto-optical recording medium, the rare earth iron garnet fine particles and a binder are dissolved or dispersed in a solvent. By applying the magnetic paint onto the substrate and then performing an orientation treatment, the magnetization of the rare earth iron garnet fine particles can be aligned in the direction perpendicular to the substrate.

The orientation treatment may be carried out by passing a substrate coated with magnetic paint in a direction across the magnetic flux in a magnetic field to orient the magnetization of the rare earth iron garnet fine particles in the direction of the magnetic flux, or by rolling the coated layer. Good too.

On the other hand, by inducing perpendicular magnetic anisotropy in the rare earth iron garnet fine particles in the magnetic film through the inverse magnetostriction effect, the magnetization of the rare earth iron garnet fine particles can be aligned perpendicularly to the substrate.

The perpendicular magnetic anisotropy due to the inverse magnetostriction effect is generally expressed as follows, where the magnetostriction constant of the magnetic particle is λ8, the magnetization is M8, and the in-plane stress applied to the particle is σ (σ>0 in the case of tensile stress). It is expressed when the perpendicular magnetic anisotropy expressed as K=-3/2λ, σ-2πIVI'' satisfies K=0.

Therefore, λ8, σ, and M8 in the above equation may be appropriately set so as to satisfy K〉0.

For example, depending on the sign of the magnetostriction constant λ, if λ8〉0, a pressure stress of σ〈0 may be applied to the fine particles, and conversely, if λ8〉0, σ〉0. What is necessary is to apply tensile stress to the fine particles.

Specifically, by employing a binder that can apply stress to magnetic fine particles by shrinking or expanding during curing, or by using a substrate that compresses or expands by heat treatment, radiation irradiation, etc. By applying stress to the magnetic film,
Perpendicular magnetic anisotropy can be induced in the magnetic particles in the magnetic film by the inverse magnetostriction effect. Thereby, the magnetization of the magnetic fine particles can be aligned in the direction perpendicular to the substrate.

The coercive force of the film containing magnetic fine particles that develops perpendicular magnetic anisotropy expressed by the inverse magnetostriction effect is 0.5 koe or more,
In particular, it is preferably 1 to 20 kOe.

In the above-mentioned magneto-optical recording medium provided with a magnetic layer consisting of a binder and magnetic fine particles having perpendicular magnetic anisotropy due to the inverse magnetostriction effect, in addition to the above-mentioned rare earth iron garnet fine particles, as the magnetic fine particles, A similar magneto-optical recording medium can be obtained by using a material that is ferromagnetic and has a cubic crystal structure, such as spinel ferrite such as cobalt ferrite and magnetite.

(Example) The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example 1 1.93 mol of sodium hydroxide (NaOH) was dissolved in 80 ml of water, and separately, bismuth nitrate [Bi(NO3
)-・5H20] 0.030 mol, dysprosium nitrate [DY(NO2)s ・5HzO] 0.030 mol
, iron nitrate [Fe(No2)z・9HtO] 0.085m
ol and aluminum nitrate [Al(NOs)s・9H2
0]0.01611101 was dissolved in 220 d of 5N nitric acid solution. Next, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise to neutralize the solution to form a precipitate.

The obtained precipitate was washed with water, filtered, and dried at 700°C.
and fired to obtain garnet fine particles.

The obtained garnet fine particles had an average particle size of 380 mm, and as a result of X-ray powder diffraction spectrum and composition analysis, they were found to be DY+, sBl+, 5Fe4. zAlo, so
+z, and was a garnet single phase.

Moreover, the refractive index of this fine particle was Z6.

Next, this fine particle powder was mixed with bismuth nitrate, yttrium nitrate, and ferric nitrate with Bi:Y:Fe=28
:10:62 molar ratio.
After sufficient dispersion, it was applied onto a glass substrate with a diameter of 3 inches and a thickness of Im. Next, by thermal decomposition at 250°C, an amorphous BiYPe oxide film containing rare earth iron garnet fine particles was formed.

The refractive index of this binder was 2.6.

The thickness of the resulting coating film was 0.5 μm.

A reflective film of aluminum was formed on this coating film by vapor deposition to obtain a magneto-optical recording medium.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of nm light was measured using the polarization plane modulation method, 1. It was Odeg.

Also, when evaluating the S/N of this medium, it was found to be 60.
It was found that the noise level was extremely high (dB) and the noise was low.

Example 2 1.93 mol of sodium hydroxide was dissolved in 8 mol of water (W),
Separately, 0.030 mol of bismuth nitrate, 0.007 mol of gadolinium nitrate [Gd(NOz)2”6HzO]
, dysprosium nitrate 0.023 mol, iron nitrate 0.023 mol.
085 mol and 0.016 mol of aluminum nitrate were dissolved in 220 rILl of 5N nitric acid solution. Next, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise to neutralize the solution to form a precipitate.

The obtained precipitate was washed with water, filtered, and dried at 700°C.
and fired to obtain garnet fine particles.

The obtained garnet fine particles had an average particle size of 420 mm, and as a result of X-ray powder diffraction spectrum and composition analysis, D)' l+5Gdo *sBl+, 5Fei, t
Alo, 801! It was a single phase of garnet.

Moreover, the refractive index of this fine particle was 2.6.

A magneto-optical recording medium was manufactured in the same manner as in Example 1 using these fine particles.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of nm light was measured using the polarization plane modulation method, 1. It was Odeg.

In addition, when evaluating the S/N of this medium, it was found to be 59.
dB was very high and the noise was low.

Example 3 1.93 mol of sodium hydroxide was dissolved in 80 m of water,
Separately, 0.030 mol of bismuth nitrate, 0.030 mol of dysprosium nitrate, 0.085 mol of iron nitrate, and gallium nitrate [Ga(NO,), 9H,010,016
mol was dissolved in a 5N nitric acid solution 22 (7i).Next, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise to neutralize the solution to form a precipitate.

The obtained precipitate was washed with water, filtered, and dried at 700°C.
and fired to obtain garnet fine particles.

The obtained garnet fine particles had an average particle size of 420 mm, and as a result of X-ray powder diffraction spectrum and composition analysis, D'll'1. J1+, 5Fe4. zGa(+,
*O4 and garnet single phase.

Moreover, the refractive index of this fine particle was 2.6.

A magneto-optical recording medium was manufactured in the same manner as in Example 1 using these fine particles.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of nm light was measured using the polarization plane modulation method, 1. It was Odeg.

Also, when evaluating the S/N for this medium, it was 62.
Very high dB and very little noise.

Example 4 Using the same rare earth iron garnet fine particles as those obtained in Example 1, yttrium nitrate and ferric nitrate were mixed with Y:
This fine particle powder was added to an aqueous solution containing Fe at a molar ratio of 38:62, thoroughly dispersed, and then coated on a glass substrate with a diameter of 3 inches and a thickness of IIul. Then 2
By thermal decomposition at 50° C., an amorphous YFe oxide film containing rare earth iron garnet fine particles was formed. The refractive index of this binder was 2.0.

The thickness of the resulting coating film was 0.5 μm.

A reflective film of aluminum was formed on this coating film by vapor deposition to obtain a magneto-optical recording medium.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of nrn light was measured using the polarization plane modulation method, 1. It was Odeg.

Also, when evaluating the S/N for this medium, it was found to be 50.
It was dB.

Comparative Example 1 Bismuth oxide [BizOz] 0.030 mol, dysprosium oxide [Dy 202 ] 0.030 mol
l, iron oxide [pe2o2]o, 085+nol, aluminum oxide [Al2O510,016aiol to N
By mixing with aCl and firing at 1200 °C,
Garnet fine particles were obtained.

The obtained garnet fine particles had an average particle diameter of 3 μm, and as a result of X-ray powder diffraction spectrum and composition analysis, Dy+ 5Bil sFe<, tAlo *Oit, and a garnet single phase.

A magneto-optical recording medium was manufactured in the same manner as in Example 1 using these particles.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
The Faraday rotation angle of nm light was measured by the polarization plane modulation method and was found to be 0.9 degrees.

Also, when evaluating the S/N for this medium, it was found to be 20
It was as low as dB.

Comparative Example 2 An amorphous coating was formed on a glass substrate with a diameter of 3 inches and a thickness of 11 by sputtering using a sintered body having a composition of DyIIBi+ 5Fe4.2AiO, so it as a target.

Next, heat treatment was performed at 630° C. for 1 hour to obtain a polycrystalline oxide thin film.

The thickness of the obtained film was 0.4 μm. A reflective film of aluminum was formed on this film by vapor deposition to obtain a magneto-optical recording medium.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
The Faraday rotation angle of nm light was measured using the polarization plane modulation method.2. It was Odeg.

Also, when evaluating 87 antis for this medium, 42
It was as low as dB.

Example 5 Diethylamine [(C,H6)2NH] 1.27m01
was dissolved in 800 rIL of water, and separately, bismuth nitrate [B
t(Now)z・5H20]0゜015mo1. Gadolinium nitrate [Gd(NOs)*-6H2olo, ot5
mo 1, iron nitrate [Fe(Not)2.9HzO] 0.
041mol, cobalt nitrate [Co(NOs)z・6H
20] 0.006 mol and vanadium oxysulfate [V
0.003 mol of 0.003 mol of O3O4.5H20 was dissolved in 800 ml of 0.7N nitric acid solution. Next, while stirring the diethylamine solution, a nitric acid solution was gradually added dropwise to neutralize the solution to form a precipitate.

The obtained precipitate was washed with water, filtered, and dried at 730°C.
and fired to obtain garnet fine particles.

The obtained garnet fine particles had an average particle size of 500 mm, and as a result of X-ray powder diffraction spectrum and composition analysis, they contained Bj +, iGd +, 5Fe4. +COo, e
Vo, s 012, and a single garnet phase.

4.5 g of these garnet fine particles and 0.45 g of a polyoxyethylene alkyl ether type surfactant (Hycol 02; manufactured by Nikko Chemicals ■) were mixed with an organic solvent (4.5 g of toluene, 4.5 g of methyl ethyl ketone, and 4.5 g of cyclohexanone). In addition, a dispersion treatment was performed for 75 minutes using a paint conditioner dispersion machine.

Next, a vinyl chloride-vinyl acetate copolymer (MPR-DSA2; 8 manufactured by Shin Kagaku) was added to this dispersion as a binder.
A magnetic paint was prepared by adding 0.9 g of the mixture and a mixed organic solvent (4.5 g of toluene, 4.5 g of methyl ethyl ketone, and 4.5 g of cyclohexanone) and dispersing the mixture in a paint conditioner disperser for 300 minutes.

The obtained magnetic paint was applied onto a glass substrate using a spin coater, and then dried in a magnetic field of 5 kOe to obtain a magneto-optical recording medium.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of nm light was measured using the polarization plane modulation method, 1. It was Odeg.

Further, the perpendicular coercive force of this medium was 11,000e.

Example 6 1.27 ml of diethylamine was dissolved in 800 ml of water,
Separately, 0.015 mol of bismuth nitrate, 0.015 mol of dysprosium nitrate [Dy(NOs)z-5HzO]
, iron nitrate 0.041 moL cobalt nitrate 0.006 moL
1 and 0.7 mol of vanadium oxysulfate
N-nitric acid solution 80% (dissolved in W) Next, while stirring the diethylamine solution, the nitric acid solution was gradually added dropwise to neutralize it and form a precipitate.

The obtained precipitate was washed with water, filtered, and dried at 730°C.
and fired to obtain garnet fine particles.

The obtained garnet fine particles had an average particle diameter of 490 mm, and as a result of X-ray powder diffraction spectrum and composition analysis, Bib, sD)'+, sFe<, +Coo, @
V6. to +2, and had a single garnet phase.

Using these garnet fine particles, a magneto-optical recording medium was obtained in the same manner as in Example 5.

633 for the magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of nm light was measured using the polarization plane modulation method, 1. It was Odeg.

Further, the perpendicular coercive force of this medium was 10,800e.

Example 7 1.93 mol of sodium hydroxide (NaOH) was dissolved in 80 mJ of water, and separately, bismuth nitrate [Bi(NOz
)z・5H,0] 0.020 mol, dysprosium nitrate [Dy(NOx)2・5HzO] 0. '040mol
, iron nitrate [Fe(NOs)z-9HzO] 0.085m
o-1 and aluminum nitrate [Al(NO,)2-9H
,0]0.016 mol was dissolved in 5N nitric acid solution 220-. Next, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise to neutralize the solution to form a precipitate.

The obtained precipitate was washed with water, filtered, and dried at 700°C.
and fired to obtain garnet fine particles.

The obtained garnet fine particles had an average particle size of 380 mm, and as a result of X-ray powder diffraction spectrum and composition analysis, B1+ OD! /2 oFe4. zAle, 101
2, and had a single garnet phase.

15 g of the garnet fine particles and 1.5 g of a polyoxyethylene alkyl ether type surfactant (Hicor 02, manufactured by Nikko Chemicals ■) were added to 97.2 g of ethanol, and dispersed for 75 minutes using a paint conditioner disperser.

Next, a silanol compound (Si-100000-3G; manufactured by Tokyo Ohka Kogyo ■) was added to this dispersion as a binder.
3.7 g and a mixed organic solvent (17 g of ethyl acetate and 17 g of ethanol) were added, and the mixture was dispersed for 300 minutes using a paint conditioner 3-way dispersion machine to prepare a magnetic paint.

The obtained magnetic paint was applied onto a glass substrate using a spin coater. Then heat at 350°C on a hot plate.
A heat treatment was performed for 15 minutes to harden the binder and obtain a magneto-optical recording medium.

The coercive force of the obtained medium was determined from Faraday hysteresis with respect to 633 nm light, and as shown in FIG. 1, it was 9040e.

Comparative Example 3 15 g of garnet fine particles obtained in Example 7 and a polyoxyethylene alkyl ether type surfactant (Hicor 02; manufactured by Nikko Chemicals ■).

6 g was added to a mixed organic solvent (15 g of toluene, 15 g of methyl ethyl ketone, and 15 g of cyclohexanone), and a dispersion treatment was performed for 75 minutes using a paint conditioner disperser.

Next, 3.0 g of vinyl chloride-vinyl acetate copolymer (VAGH; manufactured by UCC) was added to this dispersion as a binder.
and a mixed organic solvent (15 g of toluene, 15 g of methyl ethyl ketone, and 15 g of cyclohexanone) were added and dispersed for 300 minutes using a paint conditioner disperser to prepare a magnetic paint.

The obtained magnetic paint was applied onto a glass substrate using a spin coater and dried to harden the binder to obtain a magneto-optical recording medium.

The coercive force of the obtained medium was determined from Faraday hysteresis with respect to light of 633 nm, and as shown in FIG. 2, it was less than 1000e.

(Effects of the Invention) The magneto-optical material of the present invention has excellent corrosion resistance, a large magneto-optic effect, and excellent optical transparency.
It is suitably used for applications such as optical circulators, optical switches, leading waveguides, and optical memories.

In particular, magneto-optical recording media using magneto-optic materials have excellent corrosion resistance, a large magneto-optic effect, and are suitable for high-density magneto-optical recording. Furthermore, since the coercive force is large, recording stability is also excellent.

Furthermore, it can be manufactured by a coating method and has good productivity.

(Effect of the invention)

[Brief explanation of the drawing]

1 and 2 are diagrams showing Faraday hysteresis with respect to 633 nm light of the magneto-optical recording media obtained in Example 7 and Comparative Example 3, respectively. Patent applicant: Ube Industries, Ltd. Figure 1 Figure 2

Claims (4)

[Claims] (1) General formula R_aBi_bFe_cM_dO_e (where, R represents one or more rare earth elements selected from the group consisting of Y and lanthanum series elements, and M represents Al, Ga, C
r, Mn, Sc, In, Ru, Rh, Co, Fe(II
), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti
, Hf, Sn, Pb, Mo, V, Nb and Ta, and a+b+c+d
=7.0~8.0, a+b=2.0~3.5, c+d=
4.0-6.0, a=0.5-3.5, b=0-2.5
, c=3.0 to 6.0, d=0 to 2.0, and e is the number of oxygen atoms satisfying the valences of other elements. ) and having an average particle diameter of 30 to 1000 Å, and a holder made of an inorganic or organic binder in which the rare earth iron garnet particles are dispersed. (2) On the substrate, the general formula R_aBi_bFe_cM_d
O_e (However, R represents one or more rare earth elements selected from the group consisting of Y and lanthanum series elements, and M represents Al
, Ga, Cr, Mn, Sc, In, Ru, Rh, Co,
Fe(II), Cu, Ni, Zn, Li, Si, Ge,
Zr, Ti, Hf, Sn, Pb, Mo, V, Nb and T
Indicates one or more elements selected from the group consisting of a, and a+
b+c+d=7.0-8.0, a+b=2.0-3.5
, c+d=4.0-6.0, a=0.5-3.0, b=
0.25-2.5, c=3.0-5.0, d=0-2.
0, and e is the number of oxygen atoms satisfying the valences of other elements. ), and the average particle diameter is 30 to 100
A magneto-optical recording medium comprising a magnetic layer comprising rare earth iron garnet fine particles having a thickness of 0 Å and a binder. (3) The magneto-optical recording medium according to claim 2, wherein M contains at least Co and/or Rh. (4) The magneto-optical recording medium according to claim 2, wherein the rare earth iron garnet fine particles have perpendicular magnetic anisotropy induced by an inverse magnetostrictive effect.