JPH0791067B2 - Method for producing garnet fine particle powder - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing garnet fine particle powder, which has excellent magneto-optical properties and is suitable for applications such as optical isolators, optical circulators, optical switches, optical waveguides, and optical memories. .

(Prior Art and Problems Thereof) Conventionally, as a material having an excellent magneto-optical effect, an amorphous alloy of a rare earth metal and a transition metal is known.

However, such an amorphous alloy material has a drawback that it is susceptible to oxidative corrosion and deteriorates magneto-optical characteristics.
In addition, since the amorphous alloy has low light transmittance, the magneto-optical effect (Kerr effect) due to reflection on the surface is used. there were.

On the other hand, Japanese Patent Publication No. 56-15125 discloses a magneto-optical material using a garnet polycrystalline oxide thin film. A magnetic material using this oxide has excellent corrosion resistance and, since it utilizes the magneto-optical effect (Faraday effect) due to the light transmitted through the magnetic film, it has the advantage of high sensitivity. However, since it is polycrystalline, there is a drawback in that noise increases due to light scattering at the grain boundaries, birefringence, and domain wall motion.

When the above-mentioned magnetic thin film is formed on a substrate,
Since the fabrication temperature is as high as 500 ° C. or higher, there is a problem that only a heat resistant substrate can be used.

On the other hand, JP-A-62-119758 discloses a coating type magneto-optical recording material using yttrium iron garnet particles. In such a coating type medium, there is no adverse effect of the crystal grain boundary like the polycrystalline oxide thin film, but the garnet particles described in this publication have a large particle size of 1.5 μm. When used, light is scattered, which is not suitable for applications using light of submicron wavelength.

(Object of the Invention) The present invention solves the above-mentioned problems, is excellent in corrosion resistance, has a large magneto-optical effect, and is also excellent in optical transparency.
An object of the present invention is to provide a method for producing a garnet fine particle powder suitable for applications such as an optical circulator, an optical switch, an optical waveguide, and an optical memory.

(Means for Solving Problems) The present invention provides a compound represented by the general formula R _a Bi _b Fe _c M _d O _e (wherein R represents one or more rare earth elements selected from the group consisting of Y and lanthanum series elements, M is Al, Ga, Cr, M
n, Sc, In, Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti,
Hf, Sn, Pb, Mo, V and Nb represent one or more elements selected from the group consisting of a + b + c + d = 7.5 to 8.0, a + b = 2.
0-3.5, c + d = 4.5-6.0, a = 0.5-3.5, b = 0.25-
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. ) Is mixed with a solution containing each element ion selected in a ratio that constitutes the rare earth iron garnet and alkali hydroxide so that the alkali hydroxide concentration after mixing is 0.1 to 8 mol / A precipitate is formed and the slurry containing the precipitate is added to 150-300
The present invention relates to a method for producing a garnet fine particle powder, characterized by obtaining a rare earth iron garnet fine particle represented by the above general formula and having an average particle diameter of 30 to 1000Å by hydrothermal treatment at ℃.

The rare earth iron garnet fine particles in the present invention are R ₃ Fe ₅ O ₁₂
A part of the rare earth element of garnet represented by is replaced with Bi, or a part of Fe is further replaced with M.

R in the general formula is Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,
One or more rare earth elements selected from the group consisting of Tb, Dy, Ho, Er, Tm, Yb and Lu.

In addition, M is an element that can replace iron, and Al, Ga, Cr, Mn, S
c, In, Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, Hf,
Indicates one or more elements selected from the group consisting of Sn, Pb, Mo, V and Nb. Among M elements, trivalent elements Al, Ga, Cr, Mn, Sc, I
n, Ru, Rh and Co are divalent elements such as Co, Fe, Cu, Ni and Z.
n or monovalent element Li is tetravalent element Si, Ge, Zr, Ti, Hf, S
It is preferable to substitute n, Pb and Mo or a pentavalent element with V and Nb as an element equivalent to trivalent.

The proportion of each element in the general formula is a + b +
c + d = 7.5-8.0, a + b = 2.0-3.5, c + d = 4.5-
6.0, a = 0.5 to 3.5, b = 0.25 to 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.

In the present invention, a part of the rare earth element of garnet is 0.25
By replacing with Bi of ~ 2.5, the Faraday rotation angle can be increased. Also, part of the iron is preferably
By substituting with M of 0.3 to 2.0, the Curie temperature can be lowered and the saturation magnetization can be reduced.

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

The average particle diameter of the rare earth iron garnet fine particles in the present invention is 30 to 1000Å, preferably 100 to 600Å. If the average particle size is smaller than 30Å, it becomes superparamagnetic due to thermal agitation. Further, if it is larger than 1000Å, light scattering occurs and noise is generated, which is not preferable. Further, the particle shape is preferably optically symmetrical, preferably spherical, but may be polyhedral or plate-like.

In the present invention, a solution containing each element ion selected in a ratio constituting the rare earth iron garnet represented by the above general formula and an alkali hydroxide, the alkali hydroxide concentration after mixing is 0.1 to 8 mol / Rare earth iron garnet fine particles are obtained by mixing the above components to form a precipitate, and subjecting the slurry containing the precipitate to hydrothermal treatment at 150 to 300 ° C.

In the present invention, first, a solution containing each element ion selected in a ratio constituting the rare earth iron garnet represented by the above general formula is mixed with alkali hydroxide to form a precipitate.

The solution containing each element ion can be obtained by dissolving a compound of each element, for example, a nitrate, a sulfate or a chloride in a solvent.

Any solvent can be used as long as it can dissolve the compounds of the above-mentioned elements, and water, alcohols, ethers and mixed solvents thereof are usually used.

The solution containing each elemental ion is preferably prepared so that the total concentration of ions contained in the slurry after the precipitation is 0.01 to 2.0 mol / l. When the total ion concentration is less than 0.01 mol /, the amount of garnet produced is small, and when it is more than 2.0 mol / particle, the particles become large and a different phase is produced, which is not preferable.

Further, the ratio of each element ion is determined by the ratio of each element constituting the rare earth iron garnet represented by the general formula,
R and Bi may be used in excess to the required amount up to about 10 mol%.

As the alkali hydroxide, sodium hydroxide, potassium hydroxide, ammonium water or the like is used. The amount of alkali hydroxide used is required to be such that the alkali hydroxide concentration in the solution after mixing the alkali hydroxide is 0.1 to 8 mol /. If the amount of alkali hydroxide is too small, the particles become large and unreacted substances remain. Also, it is not economical to increase the amount of alkali hydroxide excessively.

Examples of the method of mixing the solution containing each element ion with the alkali hydroxide include a method of adding the solution containing each element ion to an aqueous solution of alkali hydroxide, and a method of continuously mixing the two. The precipitation may be performed at once or in multiple stages.

Next, the slurry containing the precipitate is hydrothermally treated at 150 to 300 ° C. If the temperature is too low, the formation of crystals is not sufficient, and if the temperature is too high, the particles become large, which is not preferable. The hydrothermal treatment time is usually about 0.5 to 20 hours, and an autoclave is usually adopted for the hydrothermal treatment.

Next, the obtained precipitate is washed with water to remove free alkali, filtered and dried to obtain rare earth iron garnet fine particles.

In the present invention, the rare earth iron garnet fine particles may be further fired. The firing sufficiently crystallizes the particles.

The firing temperature varies depending on the composition of the rare earth iron garnet, but is preferably 600 to 900 ° C. If the temperature is too low, crystallization does not proceed, and if the temperature is too high, the particles become large,
It is not preferable because sintering occurs. A firing time of 10 minutes to 30 hours is suitable. The firing atmosphere is not particularly limited, but an air atmosphere is generally convenient.

The garnet fine particle powder obtained by the present invention is an optical isolator, an optical circulator, an optical switch, an optical waveguide,
Used for applications such as optical memory.

For example, a magneto-optical recording medium can be obtained by providing a magnetic layer composed of garnet fine particle powder and a binder on a substrate.

As the binder, an amorphous inorganic oxide binder or an organic binder is used. In particular, in order to reduce noise due to light scattering, it is desirable that the refractive index of the binder matches the refractive index of the rare earth iron garnet fine particles, and the deviation with respect to the refractive index of the rare earth iron garnet fine particles is ± 20% or less, particularly ± It is preferably 10% or less.

The thickness of the magnetic layer is preferably 0.05 to 2.0 μm, more preferably 0.2 to 1.0 μm in terms of the stability of the recording bit.

The magnetic layer is formed by dispersing or dissolving the rare earth iron garnet fine particles and the binder in water or an organic solvent, applying the dispersion on a substrate, and then curing the binder by heat treatment or the like. At this time, the rare earth iron garnet fine particles are subjected to stress due to the curing of the binder, so that the magnetization is aligned in the direction perpendicular to the substrate. Alternatively, the alignment treatment may be performed by applying a magnetic field in a direction perpendicular to the substrate.

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

Further, a light reflecting layer can be provided between the substrate and the magnetic layer or on the magnetic layer. As the light reflection layer, Cu, Cr, Al, Ag, A
u, TiN, etc. are used. The light reflecting layer is formed on the substrate or the magnetic layer by a coating method, a plating method, a vapor deposition method or the like.

(Examples) Hereinafter, the present invention will be described in more detail by showing Examples and Comparative Examples.

EXAMPLE 1 Sodium hydroxide 2.67mol dissolved in water 80 ml, separately, bismuth nitrate _{[Bi (NO 3) 3 ·} 5H 2 O] 0.033mol, yttrium nitrate 0.033 mol and iron nitrate 0.109 mol 5 N- nitric acid solution 22
It was dissolved in 0 ml. Next, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate.

The slurry containing the obtained precipitate was placed in an autoclave,
Hydrothermal treatment was performed at 250 ° C. for 3 hours. Then, the obtained precipitate was sufficiently washed with water, filtered and dried to obtain garnet fine particles.

The obtained garnet fine particles had an average particle diameter of 450Å, X-ray powder diffraction spectrum and compositional analysis showed Y _1.5 Bi _1.5 Fe _5.0 O ₁₂ , and a garnet single phase.

Example 2 1.93 mol of sodium hydroxide was dissolved in 80 ml of water, and separately, 0.030 mol of bismuth nitrate and gadolinium nitrate [Gd (NO ₃ ) ₃
· 6H ₂ O] 0.030mol, iron nitrate 0.085mol and aluminum _{nitrate, [Al (NO 3) 3} · 9H 2 O] nitrate 5N- the 0.016mol solution 220
dissolved in ml. Then, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate.

The slurry containing the obtained precipitate was placed in an autoclave,
Hydrothermal treatment was performed at 220 ° C. for 3 hours. Then, the obtained precipitate was sufficiently washed with water, filtered and dried to obtain garnet fine particles.

The obtained garnet fine particles had an average particle diameter of 400Å, and as a result of X-ray powder diffraction spectrum and composition analysis, were Gd _1.5 Bi _1.5 Fe _4.2 Al _0.8 O ₁₂ , and were garnet single phase.

Example 3 1.93 mol of sodium hydroxide was dissolved in 80 ml of water, and separately, 0.030 mol of bismuth nitrate and dysprosium nitrate [Dy (NO ₃ ).
₃ · 5H ₂ O] 0.030mol, dissolved iron nitrate 0.085mol and aluminum nitrate 0.016mol the 5N- nitric acid solution 220 ml. Then, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate.

The slurry containing the obtained precipitate was placed in an autoclave,
Hydrothermal treatment was performed at 200 ° C. for 3 hours. Then, the obtained precipitate was sufficiently washed with water, filtered and dried to obtain garnet fine particles.

The obtained garnet fine particles had an average particle diameter of 400Å, and as a result of X-ray powder diffraction spectrum and composition analysis, were Dy _1.5 Bi _1.5 Fe _4.2 Al _0.8 O ₁₂ , and were garnet single phase.

The refractive index of these fine particles was 2.6.

This fine particle powder was added to an aqueous solution containing bismuth nitrate, yttrium nitrate, and ferric nitrate in a molar ratio of Bi: Y: Fe = 28: 10: 62, and after being sufficiently dispersed, a diameter of 3 inches and a thickness of 3 inches were obtained. It was applied on a 1 mm glass substrate. Next, by heating and decomposing at 250 ° C., an amorphous BiYFe oxide film containing rare earth iron garnet fine particles was formed. The refractive index of this binder was 2.6.

The thickness of the obtained coating film was 0.5 μm.

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

633 nm for a magnetic field in the direction perpendicular to the film surface of the obtained medium
When the Faraday rotation angle of the light was measured by the polarization plane modulation method, it was 1.0 deg.

Moreover, the S / N of this medium was evaluated, and it was found that it was very high at 60 dB and had little noise.

Comparative Example 1 Bismuth oxide [Bi ₂ O ₃ ] 0.030 mol, dysprosium oxide [Dy ₂ O ₃ ] 0.030 mol, iron oxide [Fe ₂ O ₃ ] 0.085 mol, aluminum oxide [Al ₂ O ₃ ] 0.016 mol were mixed with NaCl. Then 1200 ℃
Garnet particles were obtained by firing at.

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, were Dy _1.5 Bi _1.5 Fe _4.2 Al _0.8 O ₁₂ , and were garnet single phase.

Using these particles, a magneto-optical recording medium was manufactured in the same manner as in Example 4.

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

The S / N ratio of this medium was evaluated to be as low as 20 dB.

(Effect of the invention) The garnet fine particle powder obtained by the present invention is excellent in corrosion resistance, has a large magneto-optical effect, and is also excellent in light transmission, and has an optical isolator, an optical circulator, an optical switch,
It is preferably used for applications such as optical waveguides and optical memories. Also, the productivity is good.

Claims (1)

[Claims] 1. A general formula R _a Bi _b Fe _c M _d O _e (wherein 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, M).
n, Sc, In, Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti,
Hf, Sn, Pb, Mo, V and Nb represent one or more elements selected from the group consisting of a + b + c + d = 7.5 to 8.0, a + b = 2.
0-3.5, c + d = 4.5-6.0, a = 0.5-3.5, b = 0.25-
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. ) Is mixed with a solution containing each element ion selected in a ratio that constitutes the rare earth iron garnet and alkali hydroxide so that the alkali hydroxide concentration after mixing is 0.1 to 8 mol / A precipitate is formed and the slurry containing the precipitate is added to 150-300
A process for producing a garnet fine particle powder, which comprises subjecting a rare earth iron garnet represented by the above general formula and having an average particle size of 30 to 1000Å to a hydrothermal treatment at ℃.