JPH06263448A - Method for producing rare earth iron garnet polyhedral particles - Google Patents

Abstract

(57) [Summary] [Object] 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, an optical waveguide, and an optical memory. Provided is a novel method for producing rare earth iron garnet polyhedral particles suitable for applications such as [Configuration] formula _{(Bi a R 3-a)} x Fe 5-b M b O c ( where
R is a rare earth element, M is Al, Ga, Cr, Mn, Sc, In,
Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, Ge, Zr, T
Indicates one or more elements selected from i, Hf, Sn, Pb, Mo, V and Nb, and a = 0 to 2.5, b = 0 to 2, x = 1.0
2 to 2 and c are the number of oxygen atoms satisfying the valences of other elements. ) Is mixed with a coprecipitate containing each element in a proportion corresponding to the rare earth iron garnet, and 200 wt% or more of the flux is mixed, and this is the melting point of the flux or more, and Bi and the rare earth element from the garnet phase are main components. It is characterized in that the solid solution oxide is fired at a temperature not lower than the phase separation of the solid solution oxide.

Description

Detailed Description of the Invention

[0001]

The present invention has excellent magneto-optical characteristics,
The present invention relates to a method for producing rare earth iron garnet polyhedral particles suitable for applications such as an optical isolator, an optical circulator, an optical switch, an optical waveguide and an optical memory.

[0002]

2. Description of the Related Art Conventionally, as a magnetic material used for magneto-optical recording, there is known one made of an amorphous alloy of a rare earth metal and a transition metal. However, such a magnetic material of an amorphous alloy is susceptible to oxidative corrosion and has a drawback that the magneto-optical characteristics are deteriorated. Further, since the amorphous alloy has low light transmittance, the magneto-optical effect (curring effect) due to reflection on the surface is used, but the amorphous alloy generally has a small curl rotation angle and thus has low sensitivity. There was a problem. On the other hand, Japanese Patent Publication No. 56-15125 discloses that
A magneto-optical material using a Garnet's polycrystalline oxide thin film has been proposed. The magnetic material using this oxide has excellent corrosion resistance and has the advantage of high sensitivity because reproduction is performed by utilizing the magneto-optical effect (Faraday effect) due to the transmitted light of the magnetic film. However, since it is a polycrystal, it has a drawback that noise increases due to light scattering at the grain boundaries, birefringence and domain wall motion.

Further, when the above-mentioned magnetic thin film is formed on a substrate, there is a problem that only a substrate having heat resistance can be used because the production temperature is as high as 500 ° C. or higher.
On the other hand, Japanese Patent Application Laid-Open No. 62-119758 discloses a coating type magneto-optical recording material using yttrium iron garnet particles. In such a coating type medium, the grain boundaries of the polycrystalline oxide thin film are not adversely affected, but the garnet particles described in this publication have a particle size of 1.5.
The particle size is as large as μm, and when such particles are used, light scattering occurs, which is not suitable for high-density recording using light of submicron wavelength.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, is excellent in corrosion resistance, has a large magneto-optical effect, and is excellent in light transmission, and has an optical isolator, an optical circulator, an optical switch, an optical switch. It is an object of the present invention to provide a method for producing rare earth iron garnet polyhedral particles suitable for applications such as waveguides and optical memories.

[0005]

The present invention is based on the general formula (Bi
200 wt of flux is added to the coprecipitate containing each element in a ratio corresponding to the rare earth iron garnet represented by _a R _3-a ) _x Fe _5-b M _b O _c.
% Or more, and firing at a temperature above the melting point of the flux and above the temperature at which the solid solution oxide containing Bi and the rare earth element as the main component is phase separated from the garnet phase. It relates to a manufacturing method. R in the general formula is Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd,
It represents one or more rare earth elements selected from the group consisting of Tb, Dy, Ho, Er, Tm, Yb and Lu. M is an element capable of substituting for iron, and Al, Ga, Cr, Mn, Sc, In, Ru, Rh, Co, Fe (I
I), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, Hf, Sn, Pb, M
Indicates one or more elements selected from the group consisting of o, V and Nb. Also, a = 0 to 2.5, b = 0 to 2, x = 1.0
2 to 2 and c are the number of oxygen atoms satisfying the valences of other elements.

The composition of the rare earth iron garnet particles obtained according to the present invention has a composition in which a part of the rare earth element of garnet represented by R ₃ Fe ₅ O ₁₂ is replaced with Bi, and / or a part of Fe is M. It has been replaced with. The Faraday rotation angle can be increased by substituting a part of the rare earth element of garnet with Bi of preferably 0.2 to 2.5. By substituting a part of Fe with M of preferably 0.3 to 2, the Curie temperature can be lowered and the saturation magnetization can be reduced.

In the present invention, the excess Bi and the solid solution oxide mainly composed of a rare earth element are phase-separated from the garnet phase during the firing process, so that the amount of the phase-separated elements is smaller than the charge composition. The feature is that
In other words, the general formula _{(Bi a R 3-a)} x Fe 5-b M b O x in _c to produce a coprecipitate with a composition deviated from 1.02 to 2 and the stoichiometric composition. As a result, excessive Bi and solid solution oxides containing rare earth elements as main components are phase-separated from the garnet phase during the firing process, and garnet having an optimum composition at the firing temperature is produced. As a result, the obtained garnet particles have an increased stress-induced magnetic anisotropy, and when a stress is applied thereto, a large coercive force and a high squareness ratio can be obtained. x is 1.
If it is less than 02, phase separation between Bi and the solid solution oxide containing a rare earth element as a main component does not occur in the firing process, and garnet particles having the optimum composition at the firing temperature are not obtained. No increase is observed, and the increase in coercive force when stress is applied is small. The average particle size of the rare earth iron garnet particles in the present invention is 30 to 100.
It is preferably 0Å. 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, which causes noise, which is not preferable.

The method for producing the rare earth iron garnet particles is not particularly limited as long as the particles having the above-mentioned characteristics can be obtained, and any of the coprecipitation method, the alkoxide method and the like may be used. The method for producing rare earth iron garnet particles by the coprecipitation method will be described below. The alkali hydroxide concentration after mixing a solution containing each element ion selected in a ratio corresponding to the rare earth iron garnet represented by the general formula with alkali hydroxide is 0.1 to 8 mol / l. 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, or a mixed solvent thereof is 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. The total ion concentration is 0.
If it is less than 01 mol / l, the amount of garnet produced is small, and if it is more than 2.0 mol / l, the particles become large and a hetero phase is produced, which is not preferable. As the alkali, sodium hydroxide, potassium hydroxide, aqueous ammonia or the like is used. The amount of alkali used is required to be such that the alkali concentration is 0.01 to 8 mol / l. If the amount of alkali is too small, the particles become large and unreacted substances remain. In addition, it is not economical to use too much alkali. Examples of the method of mixing the solution containing each element ion with the alkali include a method of adding a solution containing each element ion to an alkaline aqueous solution, and a method of continuously mixing both. The precipitation may be performed at once or in multiple stages.

Next, the obtained precipitate is washed with water to remove free alkali content, and then 200 wt% or more of a fluxing agent is mixed therein, which is above the melting point of the fluxing agent and from the garnet phase Bi and rare earths. Firing is performed at a temperature at which the solid solution oxide containing an element as a main component undergoes phase separation or higher. A firing time of about 10 minutes to 30 hours is suitable. The firing atmosphere is not particularly limited,
Generally, an air atmosphere is convenient. As a flux, Na,
One or more selected from K, Li chloride, bromide, iodide, fluoride, sulfate or nitrate. The mixing ratio of the flux is 200 wt% or more, preferably 200 to 1000 wt%. The rare earth iron garnet obtained by mixing the flux with 200 wt% or more is
The surface of the particles is a polyhedral particle having crystal faces, that is, a so-called self-shaped particle. Since the self-shaped particles have less variation in composition, the characteristics of the particles are improved and the dispersibility is also improved.

Further, a transparent magnetic material can be obtained by dispersing the rare earth iron garnet particles of the present invention in a support made of an inorganic binder such as an amorphous inorganic oxide. The translucent magnetic material is obtained by dispersing or dissolving rare earth iron garnet particles and an inorganic binder in water or an organic solvent, applying the solution on a substrate, and then curing the binder by heat treatment or the like. At this time, by selecting an appropriate binder, the rare earth iron garnet particles are stressed by the curing of the binder, and the magnetization can be aligned in the direction perpendicular to the substrate. This translucent magnetic material has a large magnetic anisotropy, excellent corrosion resistance, a large magneto-optical effect, and excellent light transmittance, and can be used in optical isolators, optical circulators, optical switches, optical waveguides, optical memories, etc. Suitable for use.

For example, a magneto-optical recording medium can be obtained by providing a magnetic layer made of a translucent magnetic material on a substrate.
The magnetic layer has a thickness of 0.05 to 2.0 μm, particularly 0.2 to
The range of 1.0 μm is preferable in terms of stability of recorded bits. The substrate is not particularly limited, single crystal substrate, polycrystalline substrate, amorphous substrate such as glass, other inorganic substrate such as composite substrate, or acrylic resin, polycarbonate resin, polyester resin, polyamide resin, polyimide resin, etc. The organic material substrate can be used. A light reflection layer may be provided between the substrate and the magnetic layer or on the magnetic layer. Cu, Cr, Al, Ag, Au, TiN or the like is used for the light reflecting layer. 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.

[0012]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 Dissolve 3.605 mol of ammonia in 700 ml of water,
Separately, bismuth nitrate 0.0864 mol, dysprosium nitrate 0.0432 mol, iron nitrate 0.184 mol,
Aluminum nitrate 0.016 mol was added to 5N-nitric acid solution 7
It was dissolved in 00 ml. Then, while stirring the ammonia solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate. The composition at this time was (Bi ₂ Dy ₁ ) _1.08 Fe
It was _4.6 Al _0.4 . After washing the obtained precipitate with water, KBr and KI in a molar ratio of 51.8: 48.2 were 40% by total weight.
0 wt% was mixed and baked at 600 ° C., and the flux was washed with water to obtain garnet particles in which Bi and a solid solution oxide containing a rare earth element as a main component were phase-separated. The obtained garnet fine particles were cubic particles whose surface was composed of crystal planes as shown in FIG. Next, 15 g of this garnet fine particle powder and methyl silicone varnish (YR3187;
51.55 g of Toshiba Silicone Co., Ltd. was added to a mixed organic solvent (15 g of toluene, 15 g of methyl ethyl ketone and 15 g of cyclohexanone), and the mixture was dispersed for 60 minutes with a paint conditioner disperser to prepare a magnetic paint.
The magnetic coating material obtained was applied onto a glass substrate having a diameter of 3 inches and a thickness of 1 mm. Then, after placing on a hot plate kept at 200 ° C. and drying treatment for 30 minutes, the temperature of the hot plate was raised to 350 ° C. and heat treatment was performed for 10 minutes to cure the binder to obtain a coating film. Then, a reflective film of aluminum was formed on this coating film by a vapor deposition method to obtain a magneto-optical recording medium. The Faraday rotation angle for light of 633 nm in the direction perpendicular to the film surface of the obtained medium was measured by the polarization plane modulation method to be 1.68 deg.
Met. The coercive force of this medium was 1100 Oe and the squareness ratio was 100%.

Comparative Example 1 3.605 mol of ammonia was dissolved in 700 ml of water,
Separately, 0.080 mol of bismuth nitrate, 0.040 mol of dysprosium nitrate, 0.184 mol of iron nitrate and 0.016 mol of aluminum nitrate were added to a 5N-nitric acid solution 700.
Dissolved in ml. Then, while stirring the ammonia solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate. The composition at this time was (Bi ₂ Dy ₁ ) ₁ Fe _4.6 Al
It was _0.4 . After washing the obtained precipitate with water, a total weight of 400 wt of KBr and KI in a molar ratio of 51.8: 48.2 was obtained.
t% mixed, fired at 600 ° C, washed the flux with water, and
Net fine particles were obtained. The obtained garnet fine particles were amorphous particles as shown in FIG. Then this Gar
A magneto-optical recording medium was obtained in the same manner as in Example 1 using the net fine particle powder. 6 in the direction perpendicular to the film surface of the obtained medium
The Faraday rotation angle with respect to the light of 33 nm was measured by the polarization plane modulation method and found to be 1.18 deg. Met. The coercive force of this medium was 500 Oe and the squareness ratio was 90%.

Example 2 3.605 mol of ammonia was dissolved in 700 ml of water,
Separately, bismuth nitrate 0.0636 mol, dysprosium nitrate 0.0636 mol, iron nitrate 0.184 mol,
Aluminum nitrate 0.016 mol was added to 5N-nitric acid solution 7
It was dissolved in 00 ml. Then, while stirring the ammonia solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate. The composition at this time is (Bi _1.5 Dy _1.5 )
_{It was 1.06} Fe _4.6 Al _0.4 . After washing the obtained precipitate with water, KBr and KI with a molar ratio of 51.8: 48.2 were mixed in a total weight of 500 wt% and baked at 600 ° C., and the flux was washed with water to remove Bi and rare earth elements. Garnet fine particles in which the solid solution oxide as the main component was phase separated were obtained. The obtained garnet fine particles were cubic particles whose surface was composed of crystal planes. Then, using this garnet fine particle powder, a magneto-optical recording medium was obtained in the same manner as in Example 1. The Faraday rotation angle for light of 633 nm in the direction perpendicular to the film surface of the obtained medium was measured by the polarization plane modulation method to be 1.26 deg. Met. The coercive force of this medium was 1500 Oe and the squareness ratio was 100%.

Comparative Example 2 3.605 mol of ammonia was dissolved in 700 ml of water,
Separately, bismuth nitrate 0.060 mol, dysprosium nitrate 0.060 mol, iron nitrate 0.184 mol, and aluminum nitrate 0.016 mol were added to a 5N-nitric acid solution 700.
Dissolved in ml. Then, while stirring the ammonia solution, a nitric acid solution was gradually added dropwise for neutralization to form a precipitate. The composition at this time was (Bi _1.5 Dy _1.5 ) ₁ Fe _4.6
It was Al _0.4 . After the obtained precipitate was washed with water, the total weight of KBr and KI was 51.8: 48.2 (500).
wt% was mixed and baked at 600 ° C., and the flux was washed with water to obtain garnet fine particles. The obtained garnet particles are
It was an amorphous particle. Then, using this garnet fine particle powder, a magneto-optical recording medium was obtained in the same manner as in Example 1. The Faraday rotation angle for light of 633 nm in the direction perpendicular to the film surface of the obtained medium was measured by the polarization plane modulation method to be 0.88 deg. Met. The coercive force of this medium was 900 Oe and the squareness ratio was 90%.

[0016]

According to the present invention, the optical isolator, which is excellent in corrosion resistance, has a large magneto-optical effect, and has excellent optical transparency,
Rare earth iron garnet polyhedral particles suitable for applications such as optical circulators, optical switches, optical waveguides, and optical memories can be produced.

[Brief description of drawings]

FIG. 1 is a transmission electron micrograph as a substitute for a drawing, which shows the particle structure of rare earth iron garnet particles obtained in Example 1 of the present invention.

FIG. 2 is a transmission electron micrograph as a substitute for a drawing, which shows the particle structure of the rare earth iron garnet particles obtained in Comparative Example 1 of the present invention.

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Claims (1)

[Claims] 1. A general formula _{(Bi a R 3-a)} x Fe 5-b M b O c ( wherein, R represents one or more rare earth elements selected from the group consisting of Y and lanthanides, M is Al, Ga, Cr, Mn,
Sc, In, Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, G
represents one or more elements selected from the group consisting of e, Zr, Ti, Hf, Sn, Pb, Mo, V and Nb, and a = 0 to 2.5, b =
0 to 2, x = 1.02 to 2, and c is the number of oxygen atoms satisfying the valences of other elements. ) Is mixed with a coprecipitate containing each element in a proportion corresponding to the rare earth iron garnet, and 200 wt% or more of the flux is mixed, and this is the melting point of the flux or more, and Bi and the rare earth element from the garnet phase are main components. A method for producing rare earth iron garnet polyhedral particles, which comprises calcination at a temperature at which the solid solution oxide is phase separated.