JP2696726B2 - Garnet fine particle powder - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to garnet fine particles having excellent magneto-optical properties and 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 has been known.

However, such an amorphous alloy material has a drawback that it is susceptible to oxidative corrosion and the magneto-optical characteristics are deteriorated. Also, amorphous alloys use the magneto-optical effect (Kerr effect) due to reflection on the surface because of their low light transmittance. However, amorphous alloys generally have a small Kerr rotation angle and thus have a problem of low sensitivity. Was.

On the other hand, JP-B-56-15125 proposes a magneto-optical material using a garnet polycrystalline oxide thin film. A magnetic body using this oxide has excellent corrosion resistance, and has an advantage of high sensitivity because it utilizes a magneto-optical effect (Faraday effect) due to light transmitted through the magnetic film. However, since it is polycrystalline, there is a disadvantage that noise is increased due to light scattering, birefringence, and domain wall motion at crystal grain boundaries.

Further, when the above-described magnetic thin film is formed on a substrate, there is a problem that only a substrate having heat resistance can be used because the manufacturing temperature is as high as 500 ° C. or higher.

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 as in the polycrystalline oxide thin film, but the garnet particles described in the publication have a large particle size of 1.5 μm, and In the case where is used, since light scattering occurs, it is not suitable for applications utilizing high submicron wavelengths.

(Objects of the Invention) The present invention solves the above-mentioned problems, is excellent in corrosion resistance, has a large magneto-optical effect, is excellent in light transmittance, and is used in optical isolators, optical circulators, optical switches, optical waveguides, optical memories, and the like. It is to provide a garnet fine particle powder suitable for the above.

(Means for Solving the Problems) The present invention provides a compound represented by the general formula: R _a Bi _b F _c M _d O _e (where 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,
One or more elements selected from the group consisting of Hf, Sn, Pb, Mo, V and Nb, wherein 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 valence of another element. ), The specific surface area is 10 to 200 m ² / g, and the tapping filling rate is 1
The present invention relates to a rare earth iron garnet fine particle powder having a content of 5% or more.

The rare earth iron garnet fine particles in the present invention are R ₃ Fe ₅ O
Garnet represented by ₁₂ or a garnet in which a part of rare earth elements of the garnet is substituted by Bi, and / or a part of Fe is M
Is replaced by

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

M is an element that can be substituted for iron, and Al, Ga, Cr, Mn,
Sc, In, Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti, H
One or more elements selected from the group consisting of f, Sn, Pb, Mo, V and Nb. Among the elements of M, the trivalent elements Al, Ga, Mn, Sc, I
n, Ru, Rh and Co alone are the divalent elements Co, Fe, Cu, Ni and Z
n or monovalent element Li is tetravalent element Si, Ge, Zr, Ti, Hf, S
It is preferable that n, Pb and Mo, or a combination of pentavalent elements V and Nb be substituted as an element equivalent to trivalent.

The ratio of each element in the above general formula is 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 ~ 6.0, d
= 0 to 2.0, and e is the number of oxygen atoms satisfying the valence of another element.

In the present invention, 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. Further, by partially replacing iron with M of preferably 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 by a divalent element such as Pb, Ca, and Mg. In this case, the tetravalent or pentavalent element of M may be used. Charge compensation may be performed.

The specific surface area of the rare earth iron garnet fine particles in the present invention is 10 to ²⁰⁰ m ² / g, preferably 15 to 100 m ² / g. If the specific surface area is larger than 200 m ² / g, it becomes superparamagnetic due to thermal disturbance. On the other hand, if it is less than 10 m ² / g, light scattering occurs and noise is generated, which is not preferable.
Also, the particle shape is preferably optically symmetric,
A spherical shape is desirable, but it may be a polyhedral shape, a plate shape, or an irregular shape.

The tapping filling ratio of the rare earth iron garnet fine particles in the present invention is 15% or more.

The tapping filling rate is the value obtained by dropping a long cylindrical container containing powder from a certain height (4 cm) and dividing the weight of the powder at that time by the volume occupied by the powder. The value divided by the true specific gravity is expressed as a percentage.

When the tapping filling ratio is 15% or more, the filling property of the powder is good, the shape of the powder is uniform, the gap between the powders is small, and the particle size distribution is sharp. Further, when a coating type magneto-optical recording medium is used, the packing density in the medium is large, and the Faraday rotation angle related to the output can be increased, which is useful.

If the tapping filling ratio is less than 15%, the dispersibility is poor, and strong agglomeration of the powder occurs.

The method for producing the rare earth iron garnet fine particle powder is not particularly limited as long as particles having the above-mentioned characteristics can be obtained, but a flux method is preferably used.

Hereinafter, a method for producing rare earth iron garnet fine particle powder by a flux method will be described.

Mixed with one or more fluxes selected from the group consisting of chlorides, bromides, iodides, fluorides, sulfates and nitrates of Na, K and Li, to the precursor particles of the rare earth iron garnet represented by the general formula. By heating this at a temperature equal to or higher than the melting point of the flux, rare earth iron garnet fine particle powder is obtained.

As the precursor particles of the rare-earth iron garnet, those that are crystallized by performing a heat treatment to generate rare-earth iron garnet are used. As such precursor particles, for example, a solution containing each element ion selected in a ratio constituting the rare earth iron garnet represented by the general formula,
A precipitate obtained by mixing a precipitate-forming agent such as alkali hydroxide or the like, or a powder obtained by subjecting the precipitate to a hydrothermal treatment is exemplified.

Hereinafter, a method for producing precursor particles of rare earth iron garnet will be described by way of an example.

A solution containing each element ion selected at a ratio constituting the rare earth iron garnet represented by the above general formula and an alkali hydroxide are mixed so that the alkali hydroxide concentration after mixing becomes 0.01 to 8 mol /. Thus, a precipitate is formed to obtain precursor particles of rare earth iron garnet.

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

Any solvent may be used as long as the compound of each of the above-mentioned elements can be dissolved, and water, alcohols, ethers or a mixed solvent thereof is usually used.

It is desirable that the solution containing each of the element ions is prepared so that the concentration of the total ions contained in the slurry after the precipitation is from 0.01 to 2.0 mol /. When the total ion concentration is less than 0.01 mol /, the production amount of garnet is small,
If the amount is more than 2.0 mol /, the particles become large,
It is not preferable because a different phase is formed.

Further, the ratio of each element ion is determined by the ratio of each element constituting the rare earth iron garnet represented by the above general formula, and R and Bi are used in excess of about 10 mol% from their required amounts. Is also good.

As the alkali hydroxide, sodium hydroxide, potassium hydroxide, aqueous ammonia or the like is used. The amount of alkali hydroxide used must be such that the alkali hydroxide concentration in the solution after mixing with the alkali hydroxide is 0.01 to 8 mol /. If the amount of the alkali hydroxide is too small, the particles become large or unreacted substances remain. It is not economical to use an excessive amount of alkali hydroxide.

As a method of mixing the solution containing each element ion and alkali hydroxide, for example, there is a method of adding a solution containing each element ion to an aqueous solution of alkali hydroxide, or 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 components, thereby obtaining precursor particles of rare earth iron garnet.

By mixing a flux with the precursor particles and heating the mixture at a temperature equal to or higher than the melting point of the flux, rare earth iron garnet fine particle powder is obtained.

As the flux, at least one selected from the group consisting of chlorides, bromides, iodides, fluorides, sulfates and nitrates of Na, K and Li is used.

The amount of the flux used is 5 to 100% by weight based on the precursor particles.
Is preferred. If the amount of the flux is too small, sintering of the particles occurs, and if the amount is too large, there is no advantage due to the increased amount, and it is not economical.

The method of mixing the precursor particles and the flux is not particularly limited.For example, after adding the flux to the slurry of the precursor particles and performing wet mixing,
The slurry may be dried, or after the precursor particles are dried, a flux may be added and dry-mixed.

Next, the obtained mixture is heated and fired at a temperature equal to or higher than the melting point of the flux. The firing temperature varies depending on the composition of the rare earth iron garnet, but is 600 to 900 ° C. If the temperature is too low, crystallization is not sufficient, and if the temperature is too high, the particles become large or sintering occurs, which is not preferable. Firing time is
About 10 minutes to 30 hours is appropriate. The firing atmosphere is not particularly limited, but an air atmosphere is generally convenient.

The obtained fired product is washed, filtered, and dried to obtain rare earth iron garnet fine particles.

Garnet fine particle powder of the present invention, an optical isolator,
It is 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 composed of garnet fine particle powder and a binder on a substrate.

As the binder, an amorphous binder of an inorganic oxide or an organic binder is used.

The thickness of the magnetic layer is preferably in the range of 0.05 to 2.0 μm, particularly 0.2 to 10 μm, from the viewpoint of the stability of the recording bit.

The magnetic layer is formed by dispersing or dissolving rare earth iron garnet fine particles and a 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 stress is applied to the rare-earth iron garnet fine particles by the curing of the binder, so that the magnetization is aligned in the direction perpendicular to the substrate. Alternatively, the orientation treatment may be performed by applying a magnetic field in a direction perpendicular to the substrate.

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

Further, a light reflection layer can be provided between the substrate and the magnetic layer or on the magnetic layer. Cu, Cr, Al, Ag,
Au, TiN, etc. are used. This light reflection layer is formed on a substrate or a magnetic layer by a coating method, a plating method, an evaporation method, or the like.

(Examples) Examples and comparative examples are shown below, and the present invention will be described in more detail.

Example 1 Sodium hydroxide (NaOH) 2.67 mol was dissolved in water 80 ml, separately, bismuth nitrate _{[Bi [NO 3) 3 ·} 5H 2 O] 0.033mo
l, yttrium nitrate _{[Y (NO 3) 3 ·} 6H 2 O] 0.033mol and ferric nitrate _{[Fe (NO 3 · 9H 2} O] 0.109mol the 5N- nitric acid solution 220
Dissolved in ml. Then, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise to neutralize the solution, thereby producing a precipitate.

The obtained precipitate was washed with water, filtered, and dried, and a mixture of NaCl and KCl at a weight ratio of 1: 1 as a flux was added to the precipitate by 50% by weight and mixed. This mixture was calcined at 660 ° C. under an air atmosphere. The obtained fired product was sufficiently washed with water, filtered and dried to obtain garnet fine particles.

The obtained garnet fine particles have a specific surface area of 26 m ² / g,
The tapping filling factor was 17%, and as a result of X-ray powder diffraction spectrum and composition analysis, the powder was Y _1.5 Bi _1.5 Fe _5.0 O ₁₂ and was a garnet single phase.

After this fine particle powder was sufficiently dispersed in an organic binder, it was coated on a glass substrate having a diameter of 3 inches and a thickness of 1 mm to form a film containing rare earth iron garnet fine particles. The thickness of the obtained coating film was 0.5 μm.

The surface glossiness of this coating film was measured and found to be 85%, indicating good dispersibility.

Example 2 1.93 mol of ammonia was dissolved in 80 ml of water. Separately, 0.030 mol of dysprosium nitrate [Dy (NO ₃ ) ₃ .5H ₂ O], 0.030 mol of bismuth nitrate, 0.085 mol of iron nitrate and aluminum nitrate [Al (NO ₃ )] the ₃ · 9H ₂ O] _0.016mol dissolved in 5N- nitric acid solution 220 ml. Then, while stirring the ammonia solution, a nitric acid solution was gradually added dropwise to neutralize the solution, thereby producing a precipitate.

The obtained precipitate was washed with water, filtered and dried, and a mixture of NaCl and LiCl at a weight ratio of 3: 7 as a flux was added to the precipitate by 100% by weight and mixed. This mixture was calcined at 640 ° C. in an air atmosphere. The obtained fired product was sufficiently washed with water, filtered and dried to obtain garnet fine particles.

The obtained garnet fine particles have a specific surface area of 24 m ² / g,
A tapping packing rate 19%, X-ray powder diffraction spectra and the composition analysis result, a _{Dy 1.5 Bi 1.5 Fe 4.2 Al 0.8} O 12, was garnet single phase.

After this fine particle powder was sufficiently dispersed in an organic binder, it was coated on a glass substrate having a diameter of 3 inches and a thickness of 1 mm to form a film containing rare earth iron garnet fine particles. The thickness of the obtained coating film was 0.5 μm.

The surface gloss of this coating film was measured and found to be 87%.

EXAMPLE 3 Sodium hydroxide 2.67mol dissolved in water 80 ml, apart from gadolinium chloride _{[GdCl 3 .6H 2 O] 0.033mol} , bismuth chloride [BiCl _3] 0.033 mol, iron chloride _{[FeCl 3 · 6H 2 O]} 0.083mol ,
0.013 mol of cobalt chloride [CoCl ₂ .6H ₂ O] and 0.013 mol of titanium chloride [TiCl ₄ ] were dissolved in 220 ml of a 5N nitric acid solution. Then, while stirring the sodium hydroxide solution, a nitric acid solution was gradually added dropwise to neutralize the solution, thereby producing a precipitate.

The obtained precipitate was washed with water, filtered and dried, and a mixture of NaCl and KCl at a weight ratio of 1: 1 as a flux was added to the precipitate at 30% by weight and mixed. This mixture was calcined at 660 ° C. under an air atmosphere. The obtained fired product was sufficiently washed with water, filtered and dried to obtain garnet fine particles.

The obtained garnet fine particles have a specific surface area of 25 m ² / g,
The tapping filling factor was 18%, and as a result of X-ray powder diffraction spectrum and composition analysis, it was Ga _1.5 Bi _1.5 Fe _3.8 Co _0.6 Ti _0.6 O ₁₂ and was a garnet single phase.

After this fine particle powder was sufficiently dispersed in an organic binder, it was coated on a glass substrate having a diameter of 3 inches and a thickness of 1 mm to form a film containing rare earth iron garnet fine particles. The thickness of the obtained coating film was 0.5 μm.

The surface gloss of this coating film was measured and found to be 82%.

Comparative Example 1 0.030 mol of bismuth oxide [Bi ₂ O ₃ ], 0.030 mol of dysprosium oxide [Dy ₂ O ₃ ], 0.085 mol of iron oxide [Fe ₂ O ₃ ], and 0.016 mol of aluminum oxide [Al ₂ O ₃ ] mixed with NaCl Then 1200
By baking at ℃, garnet fine particles were obtained.

The obtained garnet fine particles have a specific surface area of 3 m ² / g,
A tapping packing rate 12%, X-ray powder diffraction spectra and the composition analysis result, a _{Dy 1.5 Bi 1.5 Fe 4.2 Al 0.8} O 12, was garnet single phase.

After sufficiently dispersing this powder in an organic binder,
It was applied on a glass substrate having a diameter of 3 inches and a thickness of 1 mm to form a film containing fine particles of rare earth iron garnet. The thickness of the obtained coating film was 0.5 μm.

When the surface glossiness of this coating film was measured, it was 40%.

(Effect of the Invention) The garnet fine particle powder obtained by the present invention is excellent in corrosion resistance, large in magneto-optical effect, and excellent in light transmittance, and is used for optical isolators, optical circulators, optical switches, optical waveguides, optical memories, etc. It is suitable for use.
Also, productivity is good.

Continuation of the front page (72) Inventor Yuji Hisamura 5-1978 Kogushi, Ube City, Ube City, Yamaguchi Prefecture Examiner at Ube Research Laboratory, Ube Industries, Ltd. Masahiro Hiratsuka (56) References JP-A-3-159915 (JP, A)

Claims (1)

(57) [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 lanthanides, M is Al, Ga, Cr, M
n, Sc, In, Ru, Rh, Co, Fe (II), Cu, Ni, Zn, Li, Si, Ge, Zr, Ti,
One or more elements selected from the group consisting of Hf, Sn, Pb, Mo, V and Nb, wherein 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 valence of another element. ), The specific surface area is 10 to 200 m ² / g, and the tapping filling rate is 1
Rare earth iron garnet fine particle powder having a content of 5% or more.