JPH0380725B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Industrial Application] The present invention relates to a crystalline anisotropic oxide magnetic material used in magnetic application fields such as magnetic recording media and resin magnets, and a method for producing the same. The present invention relates to a novel plate-shaped crystal anisotropic oxide magnetic material having a coercive force having low temperature dependence, and a method for manufacturing the same. [Prior art and problems] General formula MO・6Fe ₂ O ₃ (M is Ba, Sr, Pb, Ca,
So-called hexagonal ferrites, which are represented by at least one metallic element selected from By adjusting the properties, a wide range of coercive forces can be obtained, and by taking advantage of the fact that the axis of easy magnetization is the 001 axis, it has been used in magnetic recording media, resin magnets, and other magnetic application products. However, it has been pointed out that the drawbacks of the hexagonal ferrite are that its saturation magnetization is lower than that of other oxide magnetic materials, and that its coercive force has a large temperature dependence and cannot be adjusted to an arbitrary value. It has been. Incidentally, the saturation magnetization of these hexagonal ferrites varies depending on the production, but is approximately 50 to 58 emu/g, while the temperature dependence of coercive force is in the range of +3 to +50 e/°C. In general, the higher the saturation magnetization is, the better, and it gives any magnetic product a large output. On the other hand, when magnetic products using hexagonal ferrite powder are used in environments with large temperature changes, they are no longer able to exhibit the desired performance as designed in advance, causing various troubles.
The magnetic properties of hexagonal ferrite powder, especially the coercive force, change with temperature. For example, taking a magnetic recording medium using hexagonal ferrite powder as an example, the coercive force of the magnetic recording medium has a large effect on the electromagnetic conversion characteristics, and when this electromagnetic conversion characteristic changes, recording, reproduction, and erasure immediately occur. This will cause variations in characteristics. In other words, if a magnetic recording medium whose coercive force changes greatly with temperature is used in locations where the environmental temperature is significantly different, recording failures, reductions in reproduction output, or recording failures may occur, resulting in poor performance as a magnetic recording medium. There was a problem that the functionality deteriorated significantly. On the other hand, conventional crystalline anisotropic spinel ferrite has a higher saturation magnetization than the above-mentioned hexagonal ferrite, and a value of 70 to 80 emu/g has been reported at a practical level. Also, the temperature dependence of coercive force is 0
A range including ~-60e/°C and around 0 (0e/°C) has been reported. However, crystal anisotropic spinel ferrite has a higher saturation magnetization than hexagonal ferrite, and although it has the advantage of reducing the temperature dependence of its coercive force, those with a small temperature dependence of coercive force are The problem is that the range is low, for example below 400 (0e). An even more fatal drawback is that magnetic products using plate-shaped hexagonal ferrite utilize the fact that the axis of easy magnetization of the hexagonal ferrite is in the uniaxial direction of the 001 axis (direction perpendicular to the plate surface). On the other hand, the crystalline anisotropic spinel ferrite is
Since the axis of easy magnetization lies in the (001) plane, there was a problem that it could not be applied to hexagonal ferrite magnetic products in principle. For example, a resin magnet using plate-shaped hexagonal ferrite uses the fact that the axis of easy magnetization of the hexagonal ferrite is perpendicular to the particle plate surface [(001) axis] to connect the ferrite particles to the resin. It is manufactured by forming a sheet into a sheet using a roll forming machine, and then laminating the sheets. At this time, the plate surfaces of the ferrite particles are aligned parallel to the sheet surface, and the axes of easy magnetization are aligned perpendicular to the sheet surface. The resin magnet created in this way has a strong magnetic force in the direction perpendicular to the laminated sheet surface. It cannot be applied. In addition, in recent years, perpendicular magnetic recording has been considered as a new magnetic recording method, but plate-shaped hexagonal ferrite is used as the magnetic recording medium for this method, and it is dispersed in a resin and used as a support. It has been proposed to manufacture perpendicular magnetic recording media by coating the perpendicular magnetic recording medium. Since the hexagonal ferrite has a plate-like shape and the axis of easy magnetization is perpendicular to the surface of the particle plate, simply by coating it on a support, the axis of easy magnetization can be easily set perpendicular to the surface of the medium. It is possible to make a coating-type perpendicular magnetic recording medium, but in crystalline anisotropic spinel ferrite, even if the shape is plate-like, the axis of easy magnetization exists on the particle plate plane [(001) plane]. Therefore, it is unsuitable for perpendicular magnetic recording media. If it is possible to make the axis of easy magnetization of plate-like spinel ferrite in the uniaxial direction of the (001) axis, that is, in the direction perpendicular to the particle plate surface, spinel has high saturation magnetization and coercive force. While taking advantage of its low temperature dependence,
It will be possible to apply it to the field of hexagonal ferrite magnetic products, and it will solve the problem of high temperature dependence and low saturation magnetization of hexagonal ferrite, which will bring immeasurable advantages to this field. Dew. However, this is contrary to the common sense of those skilled in the art, and no attempt has ever been made to create a new ferrite for such a purpose. In the past, attempts were made to stack hexagonal ferrite and spinel ferrite to compensate for the advantages and disadvantages of both.For example,
In JP-A No. 60-255629, the surface of plate-shaped hexagonal ferrite powder is coated with magnetite (FeO _Y
Magnetic materials coated (modified) with Fe ₂ O ₃ ) have been proposed. However, this is because two crystal structures, hexagonal ferrite and spinel ferrite, exist independently and have the unique properties of each crystal structure. It is not a novel crystal structure that can essentially eliminate these drawbacks. [Object of the Invention] The object of the present invention is to solve the drawbacks of plate-shaped hexagonal ferrite, such as high temperature dependence and low saturation magnetization, and the aforementioned problem that spinel ferrite cannot be applied to the field of hexagonal ferrite magnetic products. The aim is to solve these problems at the same time. [Structure of the Invention] The present invention provides an oxide magnetic powder consisting of plate-like crystals with an average particle size of 0.01 to 1.0 μm and a platelet ratio of 2 to 30, which contains at least one of Ba, Sr, Pb, or Ca. The metal element is included in the ferrite crystal structure as an element constituting the crystal, and the crystal has an X-ray diffraction peak substantially as a spinel, and the easy axis of magnetization is the (001) axis in the same direction as the hexagonal ferrite. The present invention provides a novel oxide magnetic material having crystal anisotropy in a uniaxial direction (perpendicular to the plate surface). As a manufacturing method for this new ferrite magnetic material, at least one of Ba, Sr, Pb or Ca is used.
A group consisting of hexagonal ferrite powder in which a metal element is included in the crystal structure as an element constituting the crystal and has an average particle size of 5 μm or less, and glycosides, saccharides, polyhydric alcohols, oxycarboxylic acids, or their salts. at least one selected substance;
X essentially as a spinel by contacting in the presence of an alkali in a medium above 100°C
Provided is a method for producing a crystalline anisotropic oxide magnetic material having linear diffraction lines and an easy axis of magnetization in the uniaxial direction (perpendicular to the plate surface) of the (001) axis in the same direction as the hexagonal ferrite. It is. As will be demonstrated later, the crystal anisotropic plate-shaped oxide magnetic material powder (ferrite powder) according to the present invention has the following properties:
It has an X-ray diffraction peak as a spinel, but like hexagonal ferrite, its axis of easy magnetization is in the uniaxial direction of the (001) axis (direction perpendicular to the plate surface). The temperature dependence of its coercive force is in the range of +2 to -50e/°C, which cannot be obtained with conventional hexagonal ferrite. The temperature dependence of coercive force (θ _HC ) is generally evaluated as follows. θ _HC = Hc − Hc ⁰ /T − T ₀ where T is the measurement temperature (°C), T ₀ is the room temperature (°C), and Hc is the temperature measured when the temperature of the magnetic material is T (°C). The coercive force (Oe) and Hc ⁰ are the coercive force (Oe) measured when the temperature of the magnetic material is T ₀ (°C). θ _HC of the ferrite powder of the present invention is +2≧θ _HC ≧−
5 Oe/℃, and θ _HC of conventional hexagonal ferrite
It has an excellent feature of less temperature dependence than those with ≧+3. The saturation magnetization of conventional hexagonal ferrite varies depending on the manufacturing process, but commercial products are approximately 50 to 58 emu/g, but the ferrite powder of the present invention can sufficiently secure this and even exceed this. I can do it. The ferrite powder of the present invention has a spinel crystal structure, but its easy magnetization axis is in the uniaxial direction of the (001) axis (perpendicular to the plate surface), which is the same direction as the hexagonal ferrite.
This provides a completely new type of magnetic material in that it has the following characteristics. Even in the case of a spinel type, at least one metal element of Ba, Sr, Pb, or Ca is present in the crystal structure as an element constituting the crystal. That is, at least one of Ba, Sr, Pb, or Ca, which is an element constituting hexagonal ferrite,
It contains certain metal elements, and as a result, like hexagonal ferrite, it has an axis of easy magnetization in the uniaxial direction of the (001) axis. Therefore, in the present invention, at least one metal element of Ba, Sr, Pb, or Ca has an easy magnetization axis in the uniaxial direction of the (001) axis in a crystal anisotropic oxide having a substantially spinel crystal structure. It is an essential metallic element for imparting. Note that "substantially" spinel means that a small amount of hexagonal ferrite phase may coexist. The present invention may be more advantageously achieved if a small amount of hexagonal ferrite phase coexists. In any case, the ferrite crystal of the present invention has at least one metal element of Ba, Sr, Pb, or Ca present as a crystal-constituting element throughout the crystal, both inside and on the surface, and is spinel. It can be said that it is an unprecedented new crystalline anisotropic ferrite in that it exhibits a crystal structure of Conventional spinel ferrite, whose magnetization mechanism is based on crystal anisotropy, has the following formula: (a) General formula MO・Fe ₂ O ₃ (where M is Fe ²⁺ ,
At least one selected from Mg, Mn, Zn, Ni
(b) C ₀ O Fe ₂ O ₃ , (c) γ-Fe ₂ O ₃ or γ-Fe ₂ O ₃ metamorphosed with C ₀
can be mentioned. Among the above, spinel-type ferrite (a) is called a soft magnetic material, and the temperature dependence of coercive force (θ _HC )
is θ _HC ≒ 0, but the coercive force (Hc) is Hc <
It is as low as 400 Oe, and the axis of easy magnetization is on the (001) plane, which is completely different from the spinel type ferrite of the present invention. Cobalt ferrite (b) has a high coercive force, but its temperature dependence is -
The oxide magnetic material is as large as 5 to -6 (Oe/°C), and has its easy axis of magnetization in the (001) plane, and has the easy axis of magnetization in the (001) axis, which is the object of the present invention. Essentially different. Furthermore, γ-Fe ₂ O ₃ or (c)
γ-Fe ₂ O ₃ metamorphosed with Co is usually used as acicular particles, and in this case, the magnetization generation mechanism is based on formation anisotropy, so as in the present invention, the magnetization generation mechanism is based on crystal anisotropy. This is different from those based on orientation. On the other hand, a plate-shaped magnetic powder made of crystals belonging to the cubic system is disclosed in JP-A-62-41717.
Specific substances include γ-Fe ₂ O ₃ and Co metamorphosed γ-
_{Fe2O3 and Fe3O4 are} shown. However, it has been described that all of them are characterized by in-plane magnetization in the (001) plane, which is essentially different from the uniaxial crystal anisotropy along the (001) axis like the material of the present invention. These are magnetic powders with different characteristics. Further, JP-A No. 60-255629 discloses a plate-shaped Ba ferrite fine particle powder whose particle surface is modified with magnetite (FeO _y . Fe ₂ O ₃ where O<y≦1) as described above. However, according to the publication, the only metal element distributed on the surface of the Ba ferrite particles is Fe. On the other hand, in the crystal anisotropic oxide according to the present invention, Ba, Sr,
At least one kind of metal element such as Pb or Ca is distributed, and the above-mentioned purpose is achieved by distributing the metal element as an element constituting the crystal to the particle surface. Therefore, in this respect, it is essentially different from the magnetite-modified plate-shaped Ba ferrite fine particle powder described in the publication. In the present invention, the reason why the platelet ratio of the particles is set to 2 to 30 is because, for example, when used in the above-mentioned resin magnets or perpendicular magnetic recording media, if it is less than 2, the orientation of the particles will decrease, whereas if it exceeds 30, the orientation of the particles will decrease. This is because the thinner particles become bulky, which is unfavorable in terms of handling. Furthermore, the reason why the average grain size is defined as 0.01 μm to 1.0 μm is because when the grain size becomes smaller than 0.01 μm, superparamagnetism occurs and the saturation magnetization decreases significantly.
This is because if the particle size is larger than 1.0 μm, it tends to become multi-domain particles, which reduces residual magnetization, which is not preferable. The novel crystalline anisotropic oxide magnetic material of the present invention can be produced by the method described below. That is, hexagonal ferrite powder containing at least one metal element of Ba, Sr, Pb, or Ca as an element constituting the crystal in the crystal structure and having an average particle size of 5 μm or less, glycosides, sugars, and polyhydric alcohols. and at least one substance selected from the group consisting of oxycarboxylic acids, oxycarboxylic acids, or salts thereof, in the presence of an alkali in a medium at a temperature of over 100°C. The composition of the hexagonal ferrite that can be used in the method of the present invention can be represented by the composition formula (1) shown below, and its manufacturing method can be a coprecipitation method, a glass method, a hydrothermal synthesis method, or a normal method. Any dry method may be used. Composition formula (1): M ¹ O・n (Fe _2-x M ² _x O ₃ )... (1) However, in formula (1), M ¹ is at least one selected from Ba, Sr, Ca, and Pb. Metal element, n is 4≦n≦6, x is 0≦x≦0.7 ^M2 is at least one metal element selected from Sb, V, Ti, Sn, Ta, Zr, Si, and Mg, Mn ，
At least one selected from Ni, Fe ²⁺ , Cu, Co, and Zn is in combination with a metal element, and this M ²
does not necessarily have to exist (if x=0)
However, the presence of this allows the coercive force to be adjusted more effectively and higher saturation magnetization to be obtained more advantageously. It is also useful as an element for adjusting the temperature dependence of coercive force to a desired value. In the following, the method for producing the spinel crystal anisotropic oxide magnetic material of the present invention will be explained, taking as an example the case where hexagonal ferrite having the composition (1) above is produced by a hydrothermal synthesis method. First, a method for producing hexagonal ferrite having the composition of the above compositional formula (1) by hydrothermal synthesis is carried out as follows. In an H ₂ O medium containing a predetermined ratio of metal components represented by the above compositional formula (1) at a temperature exceeding 100°C and in the presence of an alkali in an amount whose alkali equivalent ratio to acid radical exceeds 1.0, or at the pH of the reaction system. Hexagonal ferrite particles are generated by hydrothermal treatment in the presence of an alkali with a 11 or more. Composition formula (1) substantially corresponds to the required proportions of metal components to be present during hydrothermal synthesis. Molar ratio n in the formula
is set to 4 to 6 because the desired hexagonal ferrite cannot be obtained with a molar ratio outside this range. In addition, the substituent component M ² is a component useful for controlling the coercive force, and the substituent x is 0.
The reason why the range is 0.7 is that if it exceeds 0.7, the saturation magnetization of the crystal anisotropic oxide of the present invention will be less than 40 emu/g. Substitution components ^M2 for Fe atoms in the ferrite lattice include Sb, V, Ti, Sn, Ta,
At least one element selected from the group consisting of Zr and Si, or this element and Ni, Co, Cu,
A combination with at least one component selected from the group consisting of Mg, Mn, Fe ²⁺ and Zn can most effectively adjust the coercive force. Next, hexagonal ferrite is produced in a H ₂ O medium at a temperature of over 100°C and in the presence of an alkali with an alkali equivalent ratio of over 1.0 or such that the pH of the reaction system is 11 or higher. However, this is done by using a raw material mixture with water as a medium adjusted to have the composition of formula (1) at a temperature exceeding 100°C in the presence of a specified alkali, that is, using an autoclave ( (Temperatures exceeding 100℃ cannot be obtained without autoclaving.)
This means that the ferrite production reaction proceeds. Hydrothermal synthesis refers to a ferrite synthesis reaction in an autoclave using water as a medium. In carrying out this hydrothermal synthesis,
First, it is necessary to adjust the mixture of red raw materials and adjust the alkali. The raw material is prepared by preparing a mixture in which metal components are uniformly mixed in a predetermined ratio based on the ferrite composition of formula (1). The raw materials providing these metal components may be hagelonides, nitrates, or other water-soluble metal salts or hydroxides. At this time, when all the raw materials are water-soluble metal salts, the raw material mixture is an aqueous solution containing metal ions in a predetermined ratio, whereas when hydroxide is selected as the raw material, the raw material mixture is a slurry-like mixture. . Moreover, when a water-soluble metal salt and a hydroxide are allowed to coexist, a slurry containing metal ions and metal hydroxide is obtained.
Note that iron oxyhydroxide can also be applied to the method of the present invention as a raw material that provides the Fe component. Next, this raw material mixture adjusted to a predetermined ratio and an alkali (an alkaline solution containing an alkaline substance) are added.
This usually results in the formation of a precipitate and an alkaline slurry-like material. The amount of alkali used is determined by the ratio of alkali equivalent to acid radical.
The amount exceeds 1.0. In the absence of acid radicals, the pH of the alkaline slurry obtained by contacting the above raw material mixture with an alkaline solution is
The amount of alkali is 11.0 or higher. In any case, the alkaline slurry-like substance is a slurry containing a metal oxide, a slurry containing a metal hydroxide and an iron oxyhydroxide, or a slurry-like substance containing metal ions therein. The reason for specifying the amount of alkali within this range is that if it is outside this range, the amount of hexagonal ferrite phase produced will be significantly reduced. The alkaline solution to be used is
It is selected from solutions of NaOH, KOH, LiOH, NH ₄ OH, mixed solutions thereof, and solutions containing other strongly alkaline substances. Regarding the reaction temperature of the ferritization reaction in an autoclave, a temperature exceeding 100°C, preferably 120 to 400°C is suitable. If the temperature inside the autoclave exceeds 400°C, the pressure will be extremely high, which is economically disadvantageous. On the other hand, below 120° C., the amount of hexagonal ferrite produced is small, making it unsuitable as the raw material hexagonal ferrite used in the present invention. It is sufficient to maintain this temperature and pressure within 10 hours, and in some cases even about 1 hour may be enough to achieve the purpose. The crystalline anisotropic oxide magnetic material of the present invention includes the hexagonal ferrite of compositional formula (1) thus prepared and at least one selected from glycosides, sugars, polyhydric alcohols, oxycarboxylic acids, or salts thereof. One or more substances (hereinafter referred to as agent A) at 100℃
in H ₂ O medium and in the presence of an alkali,
It can be produced by bringing them into contact. In this case, there are three cases regarding the timing of addition of agent A: (1) When producing hexagonal ferrite of composition formula (1), agent A is added in the process of preparing the raw material alkaline slurry material to be subjected to the autoclave (before the hydrothermal synthesis reaction of hexagonal ferrite in the autoclave). do. In this case, in the process of hydrothermal synthesis in an autoclave using the alkaline slurry material containing Agent A as a raw material, first the hexagonal ferrite of the composition formula (1) is produced, and then the crystal anisotropic oxidation A step can be taken in which a magneto-magnetic material is produced. (2) Agent A is added during the process of hydrothermally synthesizing the hexagonal ferrite of compositional formula (1). In this case, a solution containing a predetermined amount of agent A is supplied at high pressure into an autoclave that has reached a predetermined temperature and pressure. (3) Separately synthesized hexagonal ferrite of compositional formula (1) is used as a starting material. In this case, a predetermined amount of hexagonal ferrite and agent A are mixed and adjusted in an alkaline solution containing an alkaline substance in the atmosphere, and then subjected to hydrothermal treatment. In the case of (3), it is of course not necessary to use hexagonal ferrite produced by a hydrothermal synthesis method as a starting material. In either case, although the timing of addition of Agent A is different, the present invention can be achieved by contacting Agent A with fine hexagonal ferrite with an average particle size of 5 μm or less in the presence of an alkali in a medium over 100°C. A new crystalline anisotropic oxide magnetic material can be produced. Specific examples of Agent A that can be used in the method of the present invention include:
Glycosides such as β-methyl glucoside and arbutin; Saccharides such as monosose, diose, maltose, sucrose, cellulose, dextran, glycogen, dextrin, starch, and algenic acid; Sugars and alcohols such as tetritol, pentitol, and hexitol; ethylene glycol , polyhydric alcohols such as diethylene glycol, polyethylene glycol, propylene glycol, glycerin, cholesterol, and stigmasterol; esters such as mononitrate and benzoate;
At least one substance selected from oxycarboxylic acids or their salts such as alcorbins, tartaric acid, and sodium citrate, and the amount added is 0.1 based on the amount of hexagonal ferrite in composition formula (1).
weight percent or more. If it is less than 0.1 weight percent, the purpose of the present invention cannot be fully achieved. Note that the method for hydrothermally synthesizing magnetoplumbite ferrite in the presence of the organic substances described above has already been described in Japanese Patent Application Laid-Open No. 1983-1981 by the present inventors.
It is disclosed in Publication No. 40823. Here, the organic substances corresponding to glycosides, saccharides, polyhydric alcohols, oxycarboxylic acids, or salts thereof are those described as agents O in the above publication. However, the effects of this agent B described in the above publication are as follows. When hydrothermally synthesizing magnetoplumbite-type ferrite, the ferrite powder obtained by the conventional hydrothermal synthesis method has a low saturation magnetization. It is said that the saturation magnetization was significantly improved by being present as the main reaction aid, and in some cases by using agent A in combination to further enhance the effects of agent A. As described above, the action of the agent O in this publication is aimed at providing an auxiliary effect to improve the saturation magnetization of the ferrite powder when magnetoplumbite-type ferrite is hydrothermally synthesized, which is the purpose of the present invention. The action is different from the formation of spinel-type ferrite. Furthermore, +2≧θ _HC ≧−5Oe/℃ as the object of the present invention
As will be demonstrated in Comparative Example 3 and Examples below, in order to obtain a ferrite powder having The manufacturing method of the invention must be used. Next, the amount of alkali used in the alkali adjustment (alkali adjustment when the hexagonal ferrite and Agent A are contacted) is such that free alkali can exist in the alkaline slurry material after the adjustment. The reason why the amount of alkali is defined in this way is that if it is outside this range, a crystalline anisotropic oxide magnetic material having the predetermined characteristics aimed at by the present invention cannot be obtained. Alkaline solutions include NaOH, KOH, LiOH,
A solution of NH ₄ OH or a mixed solution thereof, or a solution containing other strongly alkaline substances can be used. Regarding the hydrothermal treatment temperature in the autoclave (the temperature at which the hexagonal ferrite and Agent A are brought into contact),
Temperatures above 100℃, more preferably 120-300℃
is appropriate. The temperature inside the autoclave is 300℃
If the temperature exceeds 120°C, coarse particles will be produced in large quantities and the particle size distribution will deteriorate. On the other hand, if it is below 120°C, the amount of magnetic material produced, which is the object of the present invention, will decrease. The purpose is usually achieved within about 1 to 3 hours while maintaining this temperature and pressure. Since the slurry-like material containing the crystalline anisotropic oxide magnetic material thus obtained exhibits high alkalinity, it is repeatedly filtered and washed with water to sufficiently remove impurities. After this washing, acid treatment may be performed using a known acidic substance such as HCl, HClO ₄ , HNO ₃ , HCOOH, H ₃ PO ₄ or the like. In this case, after the treatment, further washing with water is added to remove acidic substances. In this way, a crystalline anisotropic oxide magnetic material according to the present invention is obtained, which has a plate-like particle shape, a platelet ratio of 2 to 30, and an average particle size of 0.01 to 1.0 μm. As shown in the examples below, this powder was
When the substance is identified by line diffraction, it is found that it has a substantially spinel structure, and in some cases, a small amount of hexagonal ferrite phase is also observed. Furthermore, when measuring the metal components present on the particle surface, for example using Auger electrons, it is found that at least one element of ^M1 of composition formula (1) (i.e., at least one of Ba, Sr, Pb, or Ca) is present in the surface layer of the particle. It is recognized that the metal elements) are distributed. These crystalline anisotropic oxide magnetic materials according to the present invention have a temperature dependence (θ _HC ) of coercive force measured in a 10 (KOe) magnetic field of +2≧θ _HC ≧−5 (Oe/°C),
In the results obtained by the present inventors, 63 emu/g was obtained as the largest value of saturation magnetization (δ _S ). Furthermore, although the details will be shown in Examples below, although the magnetic material has X-ray diffraction lines as a spinel as described above, its easy axis of magnetization is in the direction perpendicular to the particle plate surface [ (001) axis). For example, using the ferrite powder of the present invention with a platelet ratio of 10, a magnetic paint with the following composition is prepared with a dispersion time of 4 hours, the resulting paint is applied onto a polyethylene terephthalate film using an applicator, and after drying, it is calendered. A comparison was made between a tape made by applying the above method and a tape made by the same method as above using hexagonal ferrite powder with a plate ratio of 10 as a control example, and the following results were obtained. [Composition of magnetic paint] Ferrite powder 100 parts by weight Vinyl chloride, vinyl acetate, vinyl alcohol copolymer 5 parts by weight Lecithin 1 part by weight Polyurethane resin 5 parts by weight Methyl ethyl ketone 70 parts by weight Cyclohexanone 70 parts by weight Toluene 70 parts by weight Squareness ratio and orientation The ratio was as follows. Squareness ratio Orientation ratio SQ (⊥) SQ (⊥) / SQ (=) (A): Product of the present invention 0.816 2.71 (B): Hexagonal product 0.821 2.73 Here, SQ (⊥) is relative to the surface of the base film. The squareness ratio in the vertical direction, SQ (=) indicates the squareness ratio in the direction parallel to the base film surface. Further, the temperature dependence (θ HC ) of the coercive force of the tape prepared above was measured in a magnetic field of 10 (KOe) using a VSM magnetic measuring device, and the temperature dependence (θ _HC ) was as follows. (A) Inventive product: θ _HC = −0.1 (Oe/℃) (B) Hexagonal crystal product; θ _HC = +3.5 (Oe/℃) Regarding θ _HC of the magnetic powder itself, sample (A) : θ _HC = −0.05 (Oe/°C) Sample (B): θ _HC = +3.4 (Oe/°C). The crystalline anisotropic oxide magnetic tape obtained in this way has a large SQ (⊥) of 0.816.
Since it was comparable to hexagonal ferrite powder, it was confirmed that its axis of easy magnetization was perpendicular to the particle plate surface ((001) axis). When the novel crystalline anisotropic oxide magnetic material of the present invention is used in a magnetic application product, for example, the temperature dependence of the coercive force of a tape coated on a base film by turning the magnetic material into a paint is also observed. holds the same value as in the case of powder, +2 (Oe/℃) ≧θ _HC
It was confirmed that a value in the range of ≧-5 (Oe/°C) could be sufficiently secured. The advantages of magnetic products using the crystalline anisotropic oxide magnetic material of the present invention are as follows. The magnetic product possesses the improved temperature dependence of coercive force, which is a characteristic of the magnetic material itself, and can exhibit the desired performance designed in advance even when used in an environment with large temperature changes. Magnetic products using the magnetic material of the present invention have higher saturation magnetization than conventional hexagonal ferrite products and are expected to have improved output. Although the oxide magnetic material of the present invention is plate-shaped and has a spinel structure, the axis of easy magnetization is in the direction [(001) axis] perpendicular to the particle plate surface [(001) plane]. Therefore, it is advantageously used in resin magnets, perpendicular magnetic recording media, etc., and since the temperature dependence of coercive force is small, stable characteristics can be obtained against significant changes in environmental temperature. As described above, the magnetic material according to the present invention has the same characteristics as hexagonal ferrite except that the temperature dependence of the coercive force is adjusted to an arbitrary value and the saturation magnetization is high. It can be advantageously applied to the magnetic products used. The structure and effects of the present invention will be described in more detail below using comparative examples and examples. Comparative example 1 In the composition formula M ¹ O・n (Fe _2-x M ² _x O ₃ ), M ¹ =
Ba, M ² = Zr + Cu, n = 5.95, x = 0.2, 280 ml of 3.1 mol FeCl ₃ aqueous solution, 0.29 mol
BaCl ₂ 162ml, zirconium oxychloride 30.67gr,
After thoroughly mixing and cupric chloride 23.16gr.
Add 9.0M NaOH aqueous solution to this mixed solution at room temperature.
495 ml was added to obtain a highly alkaline slurry containing a brown precipitate. This slurry material was then reacted in an autoclave at 280°C for 60 minutes. The reaction product thus obtained was sufficiently washed to remove impurities, and then dried and pulverized to obtain Ba-ferrite powder. As a result of X-ray diffraction, no spinel-type ferrite was observed in the obtained magnetic powder, and only magnetoplumbite-type ferrite was observed. Further, from photographic observation, the shape was plate-like, the plate-like ratio was 10, and the average particle size was 0.11 μm. Also, when measured with VSM in a magnetic field of 10 (KOe), the coercive force was 723 (Oe), the temperature dependence of the coercive force was +3.5 (Oe/℃), and the saturation magnetization was 40.1 emu/g.
It was hot. Comparative Example 2 In the composition formula M ¹ O・n (Fe _2-x M ² _x O ₃ ), M ¹ =
Ba, M ² = Zr + Cu, n = 5.95, x = 0.2, 3.1 molar ratio FeCl ₃ aqueous solution 280 ml, 0.29 mol
BaCl ₂ 162ml, zirconium oxychloride 30.67gr,
After thoroughly mixing and cupric chloride 23.16gr.
Add 9.0M NaOH aqueous solution to this mixed solution at room temperature.
495 ml was added to obtain a highly alkaline slurry containing a brown precipitate. Next, this slurry material was sufficiently washed to remove impurities, and then dried and granulated. The coprecipitate thus obtained was calcined in an electric furnace in the atmosphere at 900°C for 1 hour, then disintegrated using a pulperizer, and the disintegrated product was processed using a ball mill to achieve pulp density.
Water was added to give a concentration of 50%, and the mixture was pulverized for 4 hours, followed by dehydration, drying, and pulverization to obtain Ba-ferrite powder. As a result of X-ray diffraction, no spinel-type ferrite was observed in the obtained magnetic powder, and only magnetoplumbite-type ferrite was observed. Further, from photographic observation, the shape was plate-like, the plate-like ratio was 2, and the average particle size was 0.5 μm. When measured with VSM in a magnetic field of 10 (KOe), the coercive force was 1050 (Oe), the temperature dependence of the coercive force was +4.1 (Oe/°C), and the saturation magnetization was 56 emu/g. Comparative example 3 280 ml of 3.1 mol FeCl ₃ aqueous solution, 0.29 mol BaCl ₂ 162
ml, 30.67gr of zirconium oxychloride, and 23.16gr cupric chloride, and then 495ml of 9.0M NaOH aqueous solution was added to this mixed solution at room temperature to form a highly alkaline slurry containing brown precipitate. Obtained. Next, an aqueous solution containing 33.7 gr of diethylene glycol and 13.9 gr of sodium lignin sulfonate (Part A) was added to this slurry.
After adding 114gr and forcibly stirring for 10 minutes,
This mixture was reacted in an autoclave at 280°C for 60 minutes. After thoroughly washing the reaction product obtained in this way and removing impurities,
Dry pulverization was performed to obtain Ba-ferrite powder. As a result of X-ray diffraction, no spinel-type ferrite was observed in the obtained magnetic powder, and only magnetoplumbite-type ferrite was observed. Further, from photographic observation, the shape was plate-like, the plate-like ratio was 26, and the average particle size was 0.18 μm. When measured with VSM in a magnetic field of 10 (KOe),
The coercive force is 650 (Oe), and the temperature dependence of the coercive force is +
2.4 (Oe/°C), and the saturation magnetization was 52 emu/g. Example 1 Ba- obtained by the hydrothermal synthesis method of Comparative Example 1
117 g of ferrite powder was suspended in 480 ml of an aqueous solution containing 0.547 mol of sodium hydroxide, then 520 ml of an aqueous solution containing 5.85 g of diethylene glycol was added to this suspension and thoroughly stirred and mixed to prepare an alkaline slurry. The alkaline slurry was hydrothermally treated at 280° C. for 60 minutes in an autoclave. The thus obtained reaction product was sufficiently washed to remove impurities, and then dried and granulated to obtain an oxide magnetic powder. As a result of X-ray diffraction, the obtained magnetic powder was found to have a spinel structure, as a strong diffraction line of spinel-type ferrite was observed as shown in FIG. In addition, in FIG. 1, a minute diffraction line of hexagonal Be ferrite was also observed. FIG. 2 is a microscopic photograph (magnification: 30,000 times) of the magnetic powder obtained in this example, and as seen in the photograph, the magnetic powder has a plate-like shape. Its plate ratio is 10
The average particle size was 0.15 μm. Furthermore, when measured with VSM in a magnetic field of 10 (KOe), the temperature dependence of coercive force was -0.1 (Oe/℃),
The coercive force was 650 (Oe) and the saturation magnetization was 56 emu/g. In addition, when we measured the metal components present on the particle surface of this magnetic powder using Auger electrons, we found that Ba,
The presence of Zr, Cu, and Fe was confirmed. Furthermore, using the magnetic powder, a magnetic paint having the composition shown below was prepared with a dispersion time of 4 hours, and the resulting paint was applied onto a polyethylene terephthalate film using an applicator, and after drying, it was calendered and a tape was applied. Created. [Composition of magnetic paint] Ferrite powder 100 parts by weight Vinyl chloride, vinyl acetate, vinyl alcohol copolymer 5 parts by weight Lecithin 1 part by weight Polyurethane resin 5 parts by weight Methyl ethyl ketone 70 parts by weight Cyclohexanone 70 parts by weight Toluene 70 parts by weight As a result of measuring the prepared tape with VSM, the squareness ratio SQ (⊥) in the direction perpendicular to the surface of the base film was 0.816, and SQ (⊥)
and the squareness ratio SQ in the direction parallel to the base film surface.
Orientation ratio SQ(⊥)/SQ(=) expressed as a ratio with (=)
was 2.71. Therefore, it was found that the magnetic powder had its axis of easy magnetization in the direction [001 axis] perpendicular to the particle plate surface. Examples 2 to 8 Magnetic powder was obtained by carrying out the same operation as in Example 1, except that diethylene glycol was replaced with arbutin, diose, tetritol, cholesterol, stigmasterol, butyl mononitrate, or ascorbic acid. The amounts added and hydrothermal conditions are shown in Table 1. The obtained magnetic powders were evaluated in the same manner as in Example 1, and as in Example 1, most of the powders were spinel phase and had a plate-like shape. The metal components present on the particle surface of the magnetic powder were also the same as in Example 1. Furthermore, it was confirmed in the same manner as in Example 1 that in each case, the axis of easy magnetization existed in a direction perpendicular to the particle plate surface. These evaluation results are summarized in Table 1. Example 9 The same procedure _was carried out, except that _the raw material _hexagonal ferrite powder was _replaced with one whose composition was SrO. The same operation as in Example 1 was performed to obtain magnetic powder. When the obtained magnetic powder was evaluated in the same manner as in Example 1, it was found that, as in Example 1, most of the powder was in the spinel phase and the shape was plate-like. The metal components present on the particle surface of the magnetic powder were measured using Auger electrons.
The presence of Sr, Ti, Zn, and Fe was confirmed. Furthermore, when the tape was evaluated in the same manner as in Example 1, it was confirmed that the axis of easy magnetization existed in a direction perpendicular to the particle plate surface. Note that these evaluation results are also listed in Table 1. Example 10 Comparative example 2 as the raw material hexagonal ferrite powder
Magnetic powder was obtained by carrying out the same operation as in Example 1, except that Ba-ferrite powder obtained by the coprecipitation method was used. When the obtained magnetic powder was evaluated in the same manner as in Example 1, it was found that, as in Example 1, the majority of the powder was in the spinel phase and the shape was plate-like. The metal components present on the particle surface of the magnetic powder were measured using Auger electrons.
The presence of Ti, Co, and Fe was confirmed. Furthermore, when the tape was evaluated in the same manner as in Example 1, it was confirmed that the axis of easy magnetization existed in a direction perpendicular to the particle plate surface. Note that these evaluation results are also listed in Table 1.

【table】

[Table] Example 11 Ferric chloride 0.90 mol, cobalt chloride 0.043 mol,
500 ml of a mixed solution containing 0.043 mol of titanium chloride and 0.10 mol of barium chloride, and 5.5 ml of sodium hydroxide.
Thoroughly stir and mix 500 ml of an aqueous solution containing 4.60 g of diethylene glycol, and then add 100 ml of an aqueous solution containing 4.60 g of diethylene glycol. After stirring and mixing thoroughly, the alkaline slurry was heated in an autoclave at 250°C.
Hydrothermally treated for 60 minutes. This was quickly cooled to 100°C, then heated again and hydrothermally treated at 300°C for 2 hours. The reaction product thus obtained was thoroughly washed to remove impurities, and then dried and granulated to obtain magnetic powder. When the obtained magnetic powder was evaluated using the same method as in Example 1, it was found that, as in Example 1, most of it was in the spinel phase, and the shape was plate-like, with a plate-like ratio of 10 and an average particle size of was 0.14 μm. Furthermore, when measured with VSM in a magnetic field of 10 (kOe), the temperature dependence of coercive force was -1.2 (Oe/°C), the coercive force was 720 (Oe), and the saturation magnetization was 57 emu/g. In addition, when the metal components present on the particle surface of the magnetic powder were measured using Auger electrons, Ba, Ti,
The presence of Co and Fe was confirmed. Furthermore, when the tape was evaluated in the same manner as in Example 1, the squareness ratio SQ (⊥) in the direction perpendicular to the surface of the base film was 0.821, and SQ (⊥) and
Squareness ratio SQ (=) in the direction parallel to the base film surface
The orientation ratio SQ(⊥)/SQ(=) expressed as the ratio of
3.104, it was confirmed that the axis of easy magnetization exists in a direction perpendicular to the particle plate surface. Example 12 After thoroughly stirring and mixing 500 ml of a mixed solution containing 0.90 mol of ferric chloride, 0.043 mol of cobalt chloride, 0.043 mol of titanium chloride, and 0.10 mol of barium chloride, and 500 ml of an aqueous solution containing 5.5 mol of sodium hydroxide, the alkaline slurry was 300℃ in autoclave
After hydrothermal treatment for 60 minutes, 4.60 g of diethylene glycol was immediately dissolved. 100 ml of an aqueous solution was supplied under high pressure, followed by hydrothermal treatment at 300°C for 2 hours.
The reaction product thus obtained was thoroughly washed to remove impurities, and then dried and granulated to obtain magnetic powder. When the obtained magnetic powder was evaluated using the same method as in Example 1, it was found that, as in Example 1, most of it was in the spinel phase, and the shape was also plate-like, with a plate-like ratio of 8 and an average particle size. was 0.11μm. Furthermore, when measured in a VSM in a magnetic field of 10 (kOe), the temperature dependence of the coercive force was -2.5 (Oe/°C), the coercive force was 818 (Oe), and the saturation magnetization was 61 emu/g. The metal components present on the particle surface of the magnetic powder were measured using Auger electrons and found to be Ba, Ti,
The presence of Co and Fe was confirmed. Furthermore, when the tape was evaluated in the same manner as in Example 1, the squareness ratio SQ
(⊥) is 0.795, orientation ratio SQ (⊥) / SQ (=) is 2.65
It was confirmed that the axis of easy magnetization was perpendicular to the particle plate surface.

[Brief explanation of drawings]

Figure 1 shows the X-ray diffraction diagram of the crystalline anisotropic oxide magnetic material obtained in Example 1, and Figure 2 shows the crystal state of the crystalline anisotropic oxide magnetic material obtained in Example 1. This is an electron micrograph (30,000x magnification).

Claims (1)

[Scope of Claims] 1. An oxide magnetic powder consisting of plate crystals with an average particle size of 0.01 to 1.0 μm and a plate ratio of 2 to 30, comprising Ba,
At least one metal element of Sr, Pb, or Ca is included in the ferrite crystal structure as an element constituting the crystal, the crystal has an X-ray diffraction line substantially as a spinel, and the easy axis of magnetization is hexagonal. A crystal anisotropic oxide magnetic material that has a (001) axis in the same direction as ferrite (perpendicular to the plate surface). 2 Hexagonal ferrite containing at least one metal element of Ba, Sr, Pb or Ca as an element constituting the crystal in the crystal structure and having an average particle size of 5 μm or less, glycosides, sugars, polyhydric alcohols,
The product is made by contacting at least one substance selected from the group consisting of oxycarboxylic acids or salts thereof in the presence of an alkali in a medium exceeding 100°C, and has an X-ray diffraction line substantially as a spinel. A method for manufacturing a crystalline anisotropic oxide magnetic material having an easy axis of magnetization in the uniaxial direction of the (001) axis (perpendicular to the plate surface) in the same direction as that of hexagonal ferrite.