JP2002363607A - Rare earth based magnetic powder, its manufacturing method, and magnet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare rare earth based magnetic powder with which corrosion resistance and weather resistance can be improved without deteriorating magnetic properties and also a bonded magnet, or the like, can be manufactured easily and efficiently without increasing the thickness of an oxidation-resistant film on the surface of the magnetic powder and further time deteriorations under its actual-use environment can be reduced, to provide its manufacturing method, and a magnet using the same. SOLUTION: The rare earth based magnetic powder is composed of an alloy or an intermetallic compound containing one or more kinds selected among rare-earth elements and one or more transition-metal elements selected from the group consisting of Fe, Co, Ni and Mn, and further, at least >=80% of the surface of the particle of this magnetic powder is coated with an aluminum oxide film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare-earth magnetic powder, a method for producing the same, and a magnet using the same. A rare earth magnetic powder capable of easily and efficiently producing a bonded magnet or the like without increasing the thickness of the oxidation-resistant coating, and capable of reducing deterioration over time in a practical environment, a method for producing the same, and a method for producing the same. About magnets.

[0002]

2. Description of the Related Art Rare earth magnets have high magnetic properties.
The shape can be remarkably reduced as compared with the conventional one, and today it is an indispensable material as a component to be incorporated in electronic products such as audio equipment and OA equipment. In particular, rare-earth bonded magnets have been expanding their applications year by year because they have not only excellent shape workability but also enable thin-walled minute molding. A typical rare earth bonded magnet material is SmC
Materials such as o-based, NdFeB-based, and SmFeN-based are known. However, since these rare earth magnets contain a rare earth element as a component, they have a drawback that they are easily oxidized by oxygen in the air. Was.

[0003] In order to improve the characteristics of such rare earth magnets and to improve the durability against oxygen and moisture (referred to as oxidation resistance, corrosion resistance, or weather resistance) in a use environment, a magnet or its magnetic powder is used. Methods for treating the surface by various means are being studied. For example, in Japanese Patent Application Laid-Open No. Sho 62-152107, by providing a silicic acid anhydride or silicate coating on the surface of a magnetic powder for a synthetic resin magnet containing a rare earth element, it is excellent in oxidation resistance and relatively high temperature. Under these circumstances, means for suppressing a decrease in magnetic properties is disclosed. Japanese Patent Application Laid-Open No. 2-265222 discloses a highly corrosion-resistant rare earth-based bonded magnet having improved corrosion resistance by mechanically applying a zinc-based metal and a silica powder to a rare-earth-based magnet powder.

Further, Japanese Patent Application Laid-Open No. 3-280404 describes a method for improving the corrosion resistance of a rare earth-Fe-B-based permanent magnet by providing a glass coating in which inorganic fine particles are dispersed on the surface of a magnet. . The fine particles are used as a dispersant, and are resistant to oxidation such as flake stainless steel powder, lead tin, lead suboxide, cyanamide lead, basic lead chromate, zinc chromate, carbon black, zinc white, iron oxide, alumina, and titania. Examples include a permeable material, an impermeable material, and an oxidizing agent for passivating the magnet surface. This method attempts to improve the corrosion resistance by providing a relatively thick glass coating on the surface of the resin-bound magnet.
There is no description about application to magnet powder. Also, Japanese Patent Application Laid-Open No. H08-111306 discloses that a sol-gel reaction using ethyl silicate or a plasma
A method for obtaining a bonded magnet powder having excellent corrosion resistance by providing a protective coating of silicon dioxide on the surface of an Fe-B-based magnet powder is disclosed.

However, in the method of coating the surface of the rare-earth magnetic powder or magnet with a Si-based oxide film such as glass, (1) the fine structure of the magnetic powder changes due to the coating or surface treatment, and the magnetic properties are changed. Characteristics deteriorate,
(2) In order to sufficiently exert the coating effect, the oxide film must be thickened, and the volume ratio of the magnet is reduced, and the magnetic characteristics are significantly reduced. (3) The process of coating and surface treatment is complicated However, problems such as inefficiency were pointed out.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to improve corrosion resistance and weather resistance without deteriorating magnetic properties and to increase the thickness of an oxidation-resistant coating on the surface of a magnetic powder in view of the above-mentioned problems of the prior art. Rare earth magnetic powder capable of easily and efficiently producing bonded magnets and the like and capable of reducing deterioration over time in a practical environment, and a method for producing the same, and a magnet using the same. Is to do.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, when the particle surface of the rare earth magnetic powder is substantially covered with an aluminum oxide film, the deterioration with time is remarkable. The inventors have found that reduced magnetic powder can be obtained, and have completed the present invention.

That is, according to the first aspect of the present invention, one or more kinds selected from rare earth elements and Fe, C
one or two selected from the group consisting of o, Ni and Mn
A rare earth magnetic powder comprising an alloy or an intermetallic compound containing at least one or more transition metal elements, wherein at least 80% or more of the particle surface of the magnetic powder is covered with an aluminum oxide film. A magnetic powder is provided.

Further, according to the second aspect of the present invention, the first aspect
In the invention, a rare earth magnetic powder is provided, wherein the thickness of the aluminum oxide film covering the particle surface of the rare earth magnetic powder is 5 to 500 nm.

According to the third aspect of the present invention, the first aspect is provided.
In the invention, the average particle size of the rare earth magnetic powder is 1 to
A rare earth magnetic powder having a thickness of 10 μm is provided.

According to the fourth aspect of the present invention, the first aspect is provided.
The present invention provides a rare earth magnetic powder, wherein the rare earth element is either Sm or Nd.

Further, according to a fifth aspect of the present invention, in the first aspect, the content of the rare earth element is from 20 to 50.
The rare earth magnetic powder is provided by weight.

On the other hand, according to the sixth aspect of the present invention, the first aspect
Or, in the second invention, 1 selected from rare earth elements
A rare earth magnetic powder made of an alloy or an intermetallic compound containing one or more kinds of transition metal elements and one or more kinds of transition metal elements selected from the group consisting of Fe, Co, Ni and Mn; Is added and mixed, water is added thereto, and the mixture is hydrolyzed and heated, whereby the surface of the particles of the magnetic powder is covered with an aluminum oxide film, thereby providing a method for producing a rare earth magnetic powder.

According to a seventh aspect of the present invention, the sixth aspect is provided
The present invention provides a method for producing a rare earth magnetic powder, wherein 0.1 to 30 parts by weight of aluminum alkoxide is added to 100 parts by weight of the rare earth magnetic powder.

Further, according to the eighth invention of the present invention, the sixth invention
In the invention, water is added to a mixture of the rare earth magnetic powder and the aluminum alkoxide in an amount of 0.1 to 1 of a stoichiometric amount required for hydrolysis of the aluminum alkoxide.
The present invention provides a method for producing a rare earth magnetic powder, which is added by a factor of 00.

On the other hand, according to the ninth aspect of the present invention, the first
According to the second aspect of the present invention, there is provided a magnet formed by molding a rare earth magnetic powder by at least one molding method selected from an injection molding method, a compression molding method, an extrusion molding method, and a rolling molding method.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a rare earth magnetic powder of the present invention,
The manufacturing method and the magnet using the same will be described in detail.

1. Rare earth magnetic powder The rare earth magnetic powder targeted in the present invention is one or more elements selected from rare earth elements in the composition and one selected from the group consisting of Fe, Co, Ni and Mn. Rare earth magnetic powder composed of an alloy or an intermetallic compound containing one or more kinds of elements.

The average particle size of the rare earth magnetic powder is 1 to 50.
It needs to be μm. Preferred average particle size is 2 to
It is 30 μm, more preferably 3 to 10 μm. 1μ
If the particle size is less than 50 μm, the activity of the magnet is increased, and problems such as ignition are likely to occur. Cannot be shut off satisfactorily.

The rare earth elements include La, Ce, Gd,
Any one of Tb, Dy, Ho, Er, Sm, Nd, Pr and Y is used, or two or more are used in combination. Preferred rare earth elements are either Sm or Nd.
The content of the rare earth element is 20 to 50% by weight, particularly preferably 30 to 40% by weight.

The transition metal elements include Fe, Co, Ni
And one or more selected from the group consisting of Mn and Mn, and may further contain any of Cr, V and Cu. Particularly preferred transition metal elements are either Fe or Co. A magnetic force is generated by alloying the rare earth element and the transition metal element or by forming an intermetallic compound with an element containing any of Zr, Ga, Si, C, N or B. The content ratio of the rare earth element to the transition metal element is 1 to 5: 9 to 5, particularly 2 to 4: 8, by weight.
To 6 are preferable.

The greatest feature of the present invention is that at least 80% or more of the surface of the rare earth magnetic particles is covered with an aluminum oxide film. The coated state is obtained by cutting the particles of the magnetic powder, observing the cross section with a transmission electron microscope, measuring the outer periphery (full length) of the particle surface, and the portion (coated length) covered with the aluminum oxide film, The ratio is calculated (hereinafter, this will be referred to as coverage). Sample particles can be placed at any location (approximately the center is optimal)
Using FIB (focused ion beam)
For example, it is processed into a flake shape having a thickness of about 0.1 μm. When a plurality of particles form an aggregate, the periphery of the primary particles constituting the aggregate is measured with a transmission electron microscope, and the average value is defined as the coverage.

In the present invention, in order to impart corrosion resistance and weather resistance to the rare earth magnetic powder, it is necessary that the coverage of the magnetic powder with the aluminum oxide film is 80% or more. The coverage is preferably 83% or more, particularly 90% or more, and it is desirable that the magnetic powder be substantially completely covered.
If the coverage is less than 80%, the surface of the particles is not sufficiently covered, so that moisture, oxygen and the like cannot be blocked. There is a problem that deterioration is increased. on the other hand,
When the coverage exceeds 97%, the corrosion resistance and weather resistance are sufficiently ensured, but the aluminum oxide film becomes too thick, which may cause a decrease in magnetic properties.

The aluminum oxide film covering the surface of the rare earth magnetic powder has a thickness of 5 to 500 nm. It is desirable that the thickness be 5 to 250 nm, particularly 5 to 100 nm. When the thickness is less than 5 nm, the improvement in corrosion resistance and weather resistance is not remarkable. On the other hand, when the thickness exceeds 500 nm, the volume ratio of the magnet is reduced, and the magnetic properties are significantly reduced.
The rare earth magnetic powder of the present invention is characterized in that the surface of the particles is covered with the aluminum oxide film with the above-mentioned thickness, so that cracks, cracks and the like hardly occur during storage or use in a practical environment.

2. Method for producing rare earth magnetic powder The rare earth magnetic powder of the present invention is obtained by adding an aluminum alkoxide to the magnetic powder as a raw material, mixing and hydrolyzing with water, and coating the particle surface of the magnetic powder with an aluminum oxide film. To manufacture.

The rare earth magnetic powder used as a raw material is SmCo
, NdFeB and SmFeN magnetic powders. These magnetic powders are pulverized magnetic powder,
It is classified into isotropic magnetic powder by liquid quenching method and anisotropic magnetic powder by hydrogen treatment. The method for obtaining the rare-earth magnetic powder is not particularly limited, but if it is an SmFeN-based powder, an SmFe alloy (Sm:
25% by weight) under an inert gas atmosphere such as argon or nitrogen at 1000 to 1200 ° C. for 20 to 30 hours, pulverize to 20 to 60 μm, and then under an inert gas atmosphere for 60 to 80 hours at 400 to 400 μm. Heat-treated at 500 ° C,
It can be obtained by grinding this.

The aluminum alkoxide is not particularly limited, and known compounds such as aluminum ethoxide, aluminum isopropylate, aluminum isopropylate monosecondary butyrate and aluminum secondary butylate can be used. Among them, aluminum isopropylate and aluminum isopropylate monosecondary butyrate are preferred from the viewpoints of reaction rate, ease of handling, and the like. The aluminum alkoxide is conveniently used as an alcohol (eg, ethanol, isopropanol, butanol, etc.) solution.

The magnet powder is added to an alcohol solution of aluminum alkoxide, mixed and stirred for a certain time. After the mixture forms a uniform solution, a certain amount of water is added to the magnetic powder, stirring is continued, and the powder is heated and dried in an inert gas or in a vacuum. The aluminum alkoxide is added in an amount of 0.1 to 30 parts by weight, preferably 0.2 to 20 parts by weight, based on 100 parts by weight of the rare earth magnetic powder, depending on the type of the aluminum alkoxide. . If the amount is less than 0.1 part by weight, the coverage is 80%.
% Or less, and the effect of improving corrosion resistance and weather resistance is insufficient.
If the amount exceeds 0 parts by weight, the magnetic properties are greatly reduced.

Water is added to a mixture of the rare earth magnetic powder and the aluminum alkoxide solution at a stoichiometric amount of 0.1 to 10 which is required for the hydrolysis of the aluminum alkoxide.
0 times, preferably 0.3 to 80 times, more preferably 0.1 times.
Add 5 to 40 times. The theoretical amount of water corresponds to 0.001 to 100 parts by weight of water with respect to 100 parts by weight of the magnetic powder. Even if water is added less than 0.1 times the theoretical amount, the aluminum oxide film on the magnetic powder is thin and the coverage does not reach 80%, so that desired corrosion resistance and weather resistance cannot be obtained. Further, when the amount of water exceeds 100 times the theoretical amount, the ratio of aluminum oxide isolated and unevenly distributed as particles on the surface of the magnetic particles increases,
It is difficult to form a good coating.

The stirring time is such that the rare earth magnetic powder and the aluminum alkoxide can be sufficiently uniformly mixed, and is usually 1 to 60 minutes, preferably 3 to 10 minutes. The same applies to the hydrolysis. The stirrer is not particularly limited,
For example, mixers such as ribbon blenders, tumblers, Nauter mixers, Henschel mixers, super mixers, planetary mixers, and kneaders such as Banbury mixers, kneaders, rolls, kneader ruders, single screw extruders, and twin screw extruders. Just use it.

After confirming that the particle surface of the magnetic powder was covered with the aluminum oxide film, finally, 100 to 300
The magnetic powder is dried until the alcohol, water and the like are volatilized and evaporated from the magnetic powder to be substantially removed. In this case, it is effective to perform the treatment in an atmosphere of an inert gas such as nitrogen or argon or in a vacuum as described above.

3. Magnets Rare earth magnetic powders whose particle surfaces are covered with an aluminum oxide film are suitable materials for the production of various magnets, especially for the production of bonded magnets. The magnetic powder is mixed with a thermoplastic resin, a thermosetting resin, or rubber, and the mixture is molded by at least one molding method selected from an injection molding method, a compression molding method, an extrusion molding method, or a roll molding method. You. As the thermoplastic resin, nylon, polyethylene terephthalate, polyethylene or polyphenylene sulfide, etc., as the thermosetting resin, epoxy, unsaturated polyester or bismaleimide / triazine, etc., as the rubber, nitrile rubber, synthetic rubber such as butyl rubber, etc. Can be The resin composition of the rare earth magnetic powder can contain a diluent, a modifying agent, a lubricant, and the like, if necessary, so that a magnet product suitable for the intended use can be obtained.

The rare-earth magnetic powder is mixed with a thermoplastic resin or rubber and molded by an injection molding method or a rolling molding method. The rare-earth magnetic powder is mixed with a thermosetting resin and compressed and molded. For example, a bonded magnet (also called a flexible rubber magnet) can be manufactured. In a bonded magnet, the surface of the magnetic powder may be treated in advance using a coupling agent. In the present invention, such a coupling treatment can be performed.

[0034]

EXAMPLES Hereinafter, the specific structure of the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. In addition, the measurement in the Example and the comparative example was based on the following method.

[1. Coverage by aluminum oxide film]
The particles of the rare earth magnetic powder coated with the aluminum oxide film are cut by an ion beam (FIB), and observed by a transmission electron microscope. The coated portion (coating length) was measured, and the coverage of the aluminum oxide film was calculated from these values.

[2. Evaluation of Magnetic Properties] Rare earth magnetic powders were used as samples, and magnetic properties were measured at room temperature using a thiophy-type self-recording magnetometer. After keeping this sample in a constant temperature and humidity chamber of 80 ° C. and 90% RH for 24 hours, the magnetic properties were measured at room temperature in the same manner.

Example 1 SmFe having an average particle size of about 4 μm
Using N magnetic powder as a raw material, an alcohol solution (isopropanol) of 10% by weight of aluminum isopropylate was quantified and mixed with the magnetic powder so that the amount of aluminum isopropylate in the solution was 3 parts by weight with respect to the magnetic powder. Minutes. The SmFeN magnetic powder used as a raw material was added to an SmFe (Sm: 25% by weight) alloy cast by high frequency melting at 1100 ° C. in an argon gas atmosphere.
Heat treatment was performed for 4 hours, and after pulverizing to 20 to 60 μm, heat treatment was performed at 480 ° C. for 72 hours in a nitrogen gas atmosphere, and the pulverized SmFeN powder was used. After stirring, water was added at a ratio of 1 part by weight to 100 parts by weight of the magnetic powder, and the mixture was further stirred for 5 minutes, and then dried at 150 ° C. in nitrogen. The particle cross section of the obtained sample was observed with a transmission electron microscope, the state of coverage with the aluminum oxide film was measured, and the coverage was calculated. Further, the change in the magnetic properties of the sample was measured. Table 1 shows the results.
Shown in

(Embodiment 2) The same Sm as shown in Embodiment 1
An alcohol solution of 10% by weight of aluminum isopropylate was quantified and mixed with the FeN magnetic powder so that the amount of aluminum isopropylate in the solution was 0.3 parts by weight with respect to 100 parts by weight of the magnetic powder, and stirred with a mixer for 5 minutes. did. Thereafter, 0.01 parts by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes and dried at 150 ° C. in nitrogen.
The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured. Table 1 shows the results.

(Embodiment 3) The same Sm as shown in Embodiment 1
For the FeN magnetic powder, an alcohol solution of 10% by weight of aluminum isopropylate was used.
The mixture was quantified and mixed so as to be parts by weight, and the mixture was stirred with a mixer for 5 minutes. Thereafter, 80 parts by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes and dried at 150 ° C. in nitrogen. The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured. Table 1 shows the results.

Comparative Example 1 The same Sm as shown in Example 1
For the FeN magnetic powder, an alcohol solution of 10% by weight of aluminum isopropylate was used, and the aluminum isopropylate in the solution was added in an amount of 0.1% to 100 parts by weight of the magnetic powder.
The mixture was quantified and mixed so as to be 1 part by weight, and stirred with a mixer for 5 minutes. Then, 0.003 parts by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes and dried at 150 ° C. in nitrogen. The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured. Table 1 shows the results.

(Comparative Example 2) The same Sm as shown in Example 1
For the FeN magnetic powder, an alcohol solution of 10% by weight of aluminum isopropylate was used.
The mixture was quantified and mixed so as to be parts by weight, and the mixture was stirred with a mixer for 5 minutes. Thereafter, 200 parts by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes and dried at 150 ° C. in nitrogen.
The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured. Table 1 shows the results. This is an example in which the aluminum oxide film is too thick, and indicates that the magnetization is reduced in the initial characteristics.

Comparative Example 3 The same Sm as shown in Example 1 was used.
The FeN magnetic powder was stabilized by gradually oxidizing it at 80 ° C. for 1 hour in a 1% oxygen concentration. The resulting sample was not observed with a transmission electron microscope because it was not covered with an aluminum oxide film. The change in the magnetic properties of the sample was measured, and the results are shown in Table 1.

(Embodiment 4) The same Sm as shown in Embodiment 1
Alcohol solution of 10 wt% aluminum isopropylate monosecondary butyrate was used for FeN magnetic powder, aluminum isopropylate in the solution was quantified and mixed so as to be 3 parts by weight with respect to 100 parts by weight of magnetic powder, and mixed with a mixer. Stir for 5 minutes. Thereafter, 1 part by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes and dried at 150 ° C. in nitrogen. The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured.
Table 1 shows the results.

Example 5 SmCo having an average particle size of about 8 μm
_{5 Using a} magnetic powder as a raw material, an alcohol solution of 10% by weight of aluminum isopropylate was used, and aluminum isopropylate in the solution was quantified and mixed so as to be 2 parts by weight with respect to 100 parts by weight of the magnetic powder. Stirred. The SmCo ₅ magnetic powder as a raw material was obtained by pulverizing an SmCo ₅ (Sm: 34% by weight) alloy cast by high frequency melting to ₅ to 10 μm. After stirring, 2 parts by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes, and then dried at 150 ° C. in nitrogen. The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured.
Table 1 shows the results.

(Comparative Example 4) The same Sm as shown in Example 5
The Co ₅ magnetic powder was kept in a thermo-hygrostat at 80 ° C. and 90% RH for 24 hours without coating the aluminum oxide film on the Co ₅ magnetic powder, and the change in magnetic properties before and after the holding was measured. Table 1 shows the results.

Example 6 Commercially available Nd-based powder MQP-B
(Magnequench International Co., Ltd.) A 10% by weight aluminum isopropylate alcohol solution was added to magnetic powder (Nd: 30% by weight, Fe: 69% by weight, B: 1% by weight, average particle size: 50 μm) in the solution. Aluminum isopropylate was quantified and mixed so as to be 3 parts by weight with respect to 100 parts by weight of the magnetic powder, and stirred for 5 minutes with a mixer. Thereafter, 1 part by weight of water was added to the magnetic powder, and the mixture was further stirred for 5 minutes and dried at 150 ° C. in nitrogen.
The particle cross section of the obtained sample was observed with a transmission electron microscope, and the covering state of the aluminum oxide film was measured. Further, the change in the magnetic properties of the sample was measured. Table 1 shows the results.

(Comparative Example 5) Nd same as that shown in Example 6
A magnetic powder was used, and the aluminum oxide film was not coated thereon. The magnetic powder was kept in a thermo-hygrostat at 80 ° C. and 90% RH for 24 hours, and the change in magnetic properties before and after the holding was measured. Table 1 shows the results.

From the above results, when at least 80% or more of the surface of the particles of the rare earth magnetic powder is covered with the aluminum oxide film as in the embodiment, corrosion resistance and weather resistance are exhibited and the magnetic characteristics are not deteriorated. When the coating with the aluminum oxide film is insufficient or the film is too thick as in the comparative example, the magnetic properties are deteriorated. From this, it is understood that according to the present invention, it is possible to produce a rare earth magnetic powder whose performance does not deteriorate even in a practical environment.

[0049]

[Table 1]

[0050]

According to the present invention, one or more selected from rare earth elements and one or more transition metal elements selected from the group consisting of Fe, Co, Ni and Mn are used. In a rare earth magnetic powder comprising an alloy or an intermetallic compound containing, the surface of particles of the magnetic powder is substantially covered with an aluminum oxide film so that the magnetic properties of the rare earth magnetic powder are not reduced, and the corrosion resistance and weather resistance are improved. Means for improvement can be provided. For this reason, deterioration over time in a practical environment such as a bonded magnet using a rare earth magnetic powder can be suppressed, and its industrial value is extremely large.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K018 BA05 BA18 BC04 BC28 BC32 BD01 5E040 AA03 CA01 HB17 NN00

Claims (9)

[Claims] 1. An alloy or metal containing one or more selected from rare earth elements and one or more transition metal elements selected from the group consisting of Fe, Co, Ni and Mn. A rare earth magnetic powder comprising a rare earth magnetic powder comprising an intermetallic compound, wherein at least 80% or more of the particle surface of the magnetic powder is covered with an aluminum oxide film. 2. The rare earth magnetic powder according to claim 1, wherein the thickness of the aluminum oxide film covering the particle surface of the rare earth magnetic powder is 5 to 500 nm. 3. The rare earth magnetic powder has an average particle size of 1 to 5
2. The rare earth magnetic powder according to claim 1, wherein the thickness is 0 μm. 4. The rare earth magnetic powder according to claim 1, wherein the rare earth element is one of Sm and Nd. 5. The rare earth magnetic powder according to claim 1, wherein the content of the rare earth element is 20 to 50% by weight. 6. An alloy or metal containing one or more selected from rare earth elements and one or more transition metal elements selected from the group consisting of Fe, Co, Ni and Mn. An aluminum alkoxide is added to a rare earth magnetic powder composed of an intermetallic compound, mixed, water is added thereto, and the mixture is hydrolyzed, followed by heating to cover the particle surface of the magnetic powder with an aluminum oxide film. Item 3. The method for producing a rare earth magnetic powder according to Item 1 or 2. 7. The method for producing a rare earth magnetic powder according to claim 6, wherein the aluminum alkoxide is added in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the rare earth magnetic powder. 8. Water is added to a mixture of the rare earth magnetic powder and the aluminum alkoxide in an amount of 0.1 to 10 of a theoretical amount required for hydrolysis of the aluminum alkoxide.
The method for producing a rare earth magnetic powder according to claim 6, wherein the rare earth magnetic powder is added 0 times. 9. A magnet obtained by molding the rare earth magnetic powder according to claim 1 or 2 by at least one molding method selected from an injection molding method, a compression molding method, an extrusion molding method, and a rolling molding method. .