JPH03257105A - Manufacture of magnetic metal powder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a magnetic material for high-density magnetic recording media.
In more detail, 8. It has an optimal coercive force as a magnetic material for high-density magnetic recording media such as video tapes and commercial metal tapes, has excellent dispersibility and orientation when made into media, and has a high squareness ratio. The present invention relates to a method for producing metal magnetic powder.

[Conventional technology and its problems]

Conventionally, as magnetic powder for magnetic recording media, γ-Fe, 0.
, Co-containing T FezO3, Cr(h, etc.) have been used, but as magnetic recording equipment has become smaller and lighter in recent years, there has been a growing demand for higher performance in magnetic recording media such as magnetic tapes and magnetic disks. It has become to.

Metal magnetic powder, mainly made of iron, has been developed as a magnetic material that meets this demand, and is used in audio metal tapes, 8m video metal tapes, video floppy disks, etc. However, with the recent digitization of audio,
With the development of high-band 8-top video, high-density memory floppies, etc., there is a strong desire for the development of magnetic powder for higher performance magnetic recording media.

- The manufacturing method of the metal magnetic powder mainly composed of iron is to use acicular iron oxyhydroxide or other metals (for example, NZ% Co, Mn, ZnSCr, etc.).

AI, St, B, P, Ca, Mg, B
a, Ti, Zr, etc.), control of magnetic properties,
In this method, the raw material is doped or coated to prevent particles from changing shape due to heat during reduction, and this material is reduced with a reducing gas. Although many proposals have been made regarding this manufacturing method, none satisfy the characteristics desired by recent high-density magnetic recording media, and further improvements are desired.

Higher densities in magnetic recording media are achieved through higher output characteristics and lower noise levels. These characteristics of the magnetic recording medium are closely related to the characteristics of the magnetic material used in the magnetic recording medium, and the following are the characteristics that the magnetic powder for the high-density magnetic recording medium should have.

a.Have an appropriate coercive force (Hc).

b. The saturation magnetic flux density (σS) is large.

The C0 squareness ratio (σr/σS) is large.

d1 Particle size must be small and uniform.

e. Having a dense structure and being easy to disperse.

f. It should be highly weather resistant after being made into a medium.

In order to obtain high output characteristics as a magnetic recording medium, items a, b, c, and e are particularly required for the magnetic material.

The coercive force in item a must be controlled to a value suitable for the purpose of use of the magnetic recording medium, and the main method for this is to control the particle size of iron oxyhydroxide, which is the starting material.

A characteristic of metal magnetic powder is that the saturation magnetic flux density of b is large, but metal magnetic powder in its reduced state is highly active (and when taken out into the atmosphere, it causes a rapid reaction with oxygen. , it changes to α-iron oxide, which has no magnetism.Therefore, before the metal magnetic powder is exposed to the atmosphere, it is treated to form a dense oxide film on the surface of the particles, so that it can be safely handled in the atmosphere. That's what I do.

However, the magnetism of this oxide film is small, and as the ratio of the oxide film to the unit particle light increases, the saturation magnetic flux density becomes small. In particular, when the particles of metal magnetic powder are made finer for the purpose of reducing noise in a magnetic recording medium, the saturation magnetic flux density decreases significantly.

In order to increase the squareness ratio of item C, it is important to increase the acicular ratio (length 1/thickness d) of the raw material iron oxyhydroxide and make the particle sizes uniform. is controlled in consideration of the relationship with the coercive force of item a. Furthermore, in order to improve the squareness ratio, it is important to consider how to prevent particle shape collapse, particle cutting, and sintering during reduction.

For item e, metal magnetic powder particles are desired to have no pores, be dense, and have good surface smoothness.

In order to achieve low noise in a magnetic recording medium, it is important to make the metal magnetic powder fine and increase the number of particles per unit volume of the magnetic recording medium. In other words, "Doyo, Mid-term holiday Journal of the Japanese Society of Applied Magnetics Vol. 1.7, N113, 1
983P 204J [Generally, the tape S/N is
It depends on the particle size, dispersibility, and filling properties of the applied magnetic powder, and the smoothness of the tape surface. It is known that when surface properties and dispersibility are constant, S/N is proportional to the square root of the average number of particles per unit volume.

Therefore, it is advantageous to have a magnetic powder with a particle size as small as possible and with high filling properties. ” is stated.

However, the miniaturization of metal magnetic powder particles increases the specific surface area, which increases the cohesiveness of the particles and makes dispersion and orientation difficult, and there is a problem that the squareness ratio when used as a medium decreases.

As described above, in order to achieve high density magnetic recording media, there is a demand for finer metal magnetic powders that have excellent dispersibility, a high squareness ratio, and a large saturation magnetic flux density. However, to date, no metal magnetic powder has been produced that satisfies many of these requirements.

[Object of the Invention] The present invention has been made to solve the problems of the prior art as described above. The purpose of this invention is to produce metal magnetic powder that has a high squareness ratio when made into a medium.

[Means to solve the problem]

In the present invention, a ferrous salt aqueous solution is neutralized with an alkali to obtain p)I.
= 10 or more, and by passing an oxygen-containing gas through the suspension to oxidize it, acicular crystals α-F
In a method for producing metal magnetic powder that produces eOOH particles, a water-soluble barium salt is added to the ferrous salt aqueous solution or an alkaline suspension before passing the oxygen-containing gas through the aqueous solution, and then the oxygen-containing gas is introduced into the alkaline suspension. Aeration is performed to generate α-Felon containing barium and having excellent needle-like properties, and then acicular crystal α-FeOOH containing the barium compound is produced.
After depositing a silica compound and/or an aluminum compound on the particle surface with or without depositing a nickel compound and/or cobalt compound, filtration, washing with water, and drying are performed, followed by a non-reducing atmosphere. This is a method for producing metal magnetic powder, which is characterized in that heat treatment is performed in a hydrogen atmosphere, followed by thermal reduction in a temperature range of 300 to 600° C. under a hydrogen stream.

The ferrous salts used in the present invention include ferrous chloride, ferrous nitrate, and ferrous sulfate, with ferrous chloride being preferred. Ferrous nitrate is not economical, and ferrous sulfate may produce barium sulfate microcrystals that may be mixed with the α-FeOOH crystals.

Further, the alkali used in the present invention is KOH1NaO
Alkali hydroxide, K z C02, N a z
Alkali carbonates such as C03, aqueous solutions of NH3, etc.
It is essentially possible to implement the present invention by selecting any of these.

As the water-soluble barium salt used in the method of the present invention, barium chloride, barium nitrate, barium chlorate, barium perchlorate, barium salts of lower carboxylic acids, etc. can be used. The amount of water-soluble barium salt added is preferably 0.2 to 5.0 atomic % based on barium, more preferably 0.
．． It is 3 to 3.0 at%. α-Fe00Fl, which has excellent acicular properties, has no effect when added in an amount of 0.2 atomic%.
is not obtained, and even if more than 5.0 atomic % is added, there is no further effect.

The general method for adding water-soluble barium salt is to mix it with an aqueous ferrous salt solution and neutralize this mixed solution with an alkali.
Various methods can be considered, such as adding it to an alkaline suspension of a neutralized ferrous salt, or adding an excess alkaline suspension of a neutralized fresh water-soluble barium salt to an aqueous ferrous salt solution. However, either method is fine.

By blowing oxidizing gas into an alkaline suspension of ferrous salt in the presence of barium ions, α
-Fe00Fl is obtained, and the particle size can be controlled by the amount of water-soluble barium salt added, the temperature of the suspension, the oxygen concentration in the blown gas, and the blown amount. In addition, a reduction accelerator or a magnetic property control agent, an anti-sintering agent during reduction, and an additive for improving oxidation stability (for example, Ni, Co, Zn, etc.) may be added to the suspension.
Cu, Mn, CrS Al, Zr, B
, Ca, Mg, Ti, etc.) in an appropriate combination to obtain acicular α-Fe001 containing these metal compounds. Crystal α-Fe
When depositing a nickel compound and/or a cobalt compound on the surface of OOH, chlorides and nitrates are suitable as the types of nickel and cobalt compounds to be added.
Sulfates containing sulfate groups should be avoided because they react with barium ions to produce barium sulfate crystals that are insoluble in water. The method of deposition is to drop an aqueous solution of a nickel compound and/or cobalt compound to a suspension of acicular crystal α-FeOOH containing a barium compound, stir thoroughly, and then drop an alkali to adjust the pH of the suspension. 7 to 9, or by reversing the order of dropping, or by adding an aqueous solution of a nickel compound and/or cobalt compound to a suspension of acicular α-Felon containing a barium compound. Alkali was added dropwise at the same time to adjust the pH of the suspension to 7-7.
It is possible to carry out the present invention by any method, such as a method in which the amount is continuously deposited while keeping the amount constant within the range of 9. The amount of the nickel compound and/or cobalt compound to be deposited is 0.3 to 30 at%, respectively, based on iron.
A preferable range is 0.5 to 20 atomic %, and a more preferable range is 0.5 to 20 atomic %. Both nickel and cobalt act as reduction accelerators and as magnetic property control agents.If the amount added is too small, the reduction reaction will be difficult to proceed, and if the amount is too large, the saturation magnetic flux will decrease for nickel. Desired magnetic properties cannot be obtained due to a decrease in density and a decrease in coercive force. In particular, a decrease in saturation magnetic flux density is a major negative factor for manufacturing high-output magnetic recording media.

In the case of cobalt, assuming that it is alloyed with iron, the saturation magnetic flux density will theoretically increase up to 30 at. There is a problem with economic efficiency.

Next, regarding the deposition of a silica compound and/or an aluminum compound, any silica compound or aluminum compound used in the present invention can be used as long as it is water-soluble or colloidal. Examples of compounds preferably used include aluminum chloride, aluminum nitrate, water glass, colloidal silica, sodium aluminate, and alumina sol.

The deposition method is to add a silica compound and/or an aluminum compound to a barium-containing α-Fe0OH suspension that has been treated with a nickel compound and/or a cobalt compound (or has not been subjected to a deposition treatment). If the added compound is acidic, add alkali, or if alkaline, add acid (e.g., hydrochloric acid,
Nitric acid, etc.) may be added dropwise to neutralize the suspension so that the pH thereof falls within the range of 7 to 9, and then the suspension may be deposited.

When applying both a silica compound and an aluminum compound, there are two methods: applying the two types of compounds in an overlapping manner, or mixing the two types of compounds and applying them at the same time. There is no problem in implementing the present invention.

The amount of silica compound and aluminum compound to be deposited is
The preferable range is 0.5 to 20 atom %, and more preferably 1.0 to 15 atom %, based on iron.

The deposition of silica compounds and/or aluminum compounds is
The purpose is to prevent sintering of particles during reduction, and if the amount is too small, there will be no sintering prevention effect, and if it is too large, silica and aluminum will not have magnetism, so the amount added should be adjusted accordingly. The magnetism is proportionally diluted and the saturation magnetic flux density decreases. In addition, reduction becomes extremely difficult, probably because a refractory substance is formed between these sintering inhibitors and iron.

After the above deposition treatment is completed, the treated product is filtered, thoroughly washed and dried.Then, heat treatment is performed in a non-reducing atmosphere, for example, in air or in an inert gas such as nitrogen. This heat treatment causes a dehydration reaction of α-FeOOH to produce α-FezO.

It changes into an oxide mainly composed of , which has the effect of preventing particles from deforming during reduction. The temperature of the heat treatment is preferably 500 to 850°C; if the temperature is low, the heat treatment has no effect, and if it is too high, the shape of the particles will change during the heat treatment, and the properties of the metal magnetic powder will deteriorate. do.

Next, the treated product is charged into a reduction reactor and reduced by a conventional method at a temperature range of 300 to 600"C under a hydrogen stream. However, if the reduction temperature is too low, the reaction time becomes long and it is not economical. In addition, if the temperature is high, the reaction time will be shortened, but the metal magnetic powder will sinter, lowering the coercive force and squareness ratio, and further increasing the noise level when used as a medium. Put it away.

After reduction, the reduction reactor is cooled, and the metal magnetic powder is stabilized by a conventional method such as flowing a mixed gas of nitrogen and air, and then taken out of the system.

As described above, the metal magnetic powder of the present invention having good acicularity, excellent dispersibility, and a good squareness ratio is produced.

〔Example〕 Next, the present invention will be explained using examples.

Example-1 Contains 1.0 atomic% of barium based on iron,
Barium chloride (BaC12-2tt2on 146.6g
Ferrous chloride obtained by adding 0.6 mol/j2
100 N of aqueous solution was prepared in advance in the reactor, and 200 N of 1.8 mol/f NaOH aqueous solution was prepared in advance! Nitrogen gas was flowed into the solution and added while stirring to perform a reaction to form an alkaline suspension.

The suspension was bubbled with air at a rate of 1001/min for 7 hours at a temperature of 50°C to form acicular α-Fe containing barium.
Got OOH.

This product was filtered and washed with water in a conventional manner to obtain a wet cake (this was referred to as raw material A).

As a result of electron microscopy, this barium-containing acicular α-FeOOH particle has excellent acicularity with an average long axis of 0.55 μ■ and an average acicular ratio (long axis/short axis) of 28. there were. Also, the specific surface area value of this product according to the BET method is 68
rd/g. The added barium was detected in α-Fe00)1 by fluorescent X-ray analysis, and it was confirmed that barium was dissolved in solid solution in the needle-like α-FeOOtl.

500 g of acicular α-FeOOH containing this barium
(purity equivalent) was added to 1001 distilled water and well dispersed. To this was added a separately prepared aqueous solution in which 0.28 mol each of nickel chloride and cobalt chloride were dissolved in distilled water, and the mixture was stirred for 30 minutes. Then, a 2N NaOH aqueous solution was added dropwise over 1 hour to neutralize to p)l=8, and stirring was continued for 1 hour. Next, an aqueous solution of 0.34 mol of aluminum chloride dissolved in distilled water of 21 was added and stirred well, and to this was added an aqueous solution of 0.11 mol of water glass (calculated as silica) dissolved in distilled water of 21 for 1 hour. It dripped. After this,
2N Na0f (aqueous solution) was added dropwise until the pH of the suspension reached 8, and stirring was continued for 1 hour. After the adhesion treatment, α-FeOOH was filtered, washed with water, and dried to form nickel and cobalt compounds and aluminum. And silica compound-coated α-FeOOH was obtained.

Next, the deposited α-FeOOH was heated for 2 hours in an electric furnace at 650°C.
The heat treated product was then reduced in a hydrogen gas stream at a temperature of 460° C. for 5 hours.

After the reduction was completed, the gas in the reaction system was changed to nitrogen gas, and after cooling to room temperature, air was gradually introduced to stabilize the reduced product to obtain metal magnetic powder. The metal magnetic powder was subjected to a maximum magnetic field of 10K using a sample vibrating magnetometer (VSM manufactured by Toei Kogyo).
When magnetically measured with G, coercive force (He) = 16030
e, saturation magnetic flux density (σ5) = 137. Oes+u/g
, squareness ratio (or/σs) = 0.525. The BET value was 56.5rd/g. Furthermore, when the particle morphology of the metal magnetic powder was observed using a transmission electron microscope (TEM), it was found that the particles had excellent acicular properties without sintering.

Next, the metal magnetic powder was dispersed in a solution containing a vinyl chloride-vinyl acetate copolymer resin, together with a dispersant, a lubricant, and an abrasive, and a urethane elastomer was added thereto for thorough dispersion. After adding a crosslinking agent to the dispersed paint and mixing thoroughly, a 14μ Akebono PE coating was applied using a gravure coater.
Apply it on the T-film and apply it 2 times while the magnetic paint is not dry.
Magnetic field orientation treatment was performed using a 500 Gauss magnet, and after drying, supercalender treatment was performed and slits were made to a width of 81 mm to produce an 8 mm video tape. When the magnetic properties of the tape were measured by VSM at a maximum magnetic field of 10 KG, Hc = 15700e, Br = 3420 G, B
m=3931 G, Br/B+++=0.87, and the squareness ratio was extremely good.

Example-2 Acicular crystal α-F containing barium produced in Example-1
eOOH (raw material A) 500g (purity equivalent) to 10
02 distilled water (dispersed).To this, 1 mol each of nickel chloride and cobalt chloride prepared separately was added.
An aqueous solution of 1 dissolved in distilled water was added and stirred for 30 minutes.Next, a 2N NaOH aqueous solution was added dropwise over 1 hour to neutralize to pH=8, and stirring was continued for 1 hour.Next, in terms of silica An aqueous solution of 0.26 mol of water glass dissolved in 21 distilled water was added and thoroughly stirred, and 2N HCl
An aqueous solution was added dropwise and neutralized to pH=8 in 1 hour, and a silica compound was deposited. After neutralization, stirring was continued for 1 hour, and the adhered α-Felon was filtered, washed with water,
After drying, α-FeOOH coated with a nickel compound, a cobalt compound, and a silica compound was obtained.

Next, the deposited α-FeOOH was heated for 2 hours in an electric furnace at 600°C.
The heat treated product was then reduced in a hydrogen gas stream at a temperature of 450° C. for 5 hours.

After the reduction was completed, the mixture was stabilized in the same manner as in Example 1, and a metal magnetic powder was obtained. The magnetic properties of the metal magnetic powder are Hc-163
50e, as =139. Oemu 7g.

σr/as=0.530. BET value is 5
It was 4.2nf/g. The magnetic properties when made into a tape as in Example-1 are: Hc=15900e, Br=
3551G.

Bm=4105 G, Br/Bm=0.865, and the squareness ratio was the same as in Example-1.

Example 3 Using the raw material A produced in Example 1, 0.5 at. An aqueous solution in which aluminum was dissolved in distilled water in Step 21 was added and thoroughly stirred. A 2N NaOH aqueous solution was added dropwise to this over 1 hour to give p)I=8.5, and stirring was continued for 1 hour. Thereafter, it was filtered, washed with water, dried, heat treated in an electric furnace at 700''C for 2 hours, and reduced under a hydrogen stream at 440C for 5 hours. It was stabilized in the same manner as in Example 1, and a metal magnetic powder was obtained. The magnetic properties of the metal magnetic powder are Hc=15450e, -as
=128. Oemu 7g, er/tys
=0.524. BET value is 53.8rrf/g
Met. The magnetic properties when made into a tape as in Example-1 are: Hc=15300e, Br=3381G,
Bm=3900 G, Br/Bm=0°867, and like Example L2, the squareness ratio was extremely good.

Example-4 Barium chloride (BaC
1t ・2H2O) 73.3g and nickel chloride (N
100 jI of an aqueous solution of 0.6 mol/Il of ferrous chloride obtained by adding 214 g of iC1g ・68tO)
! was added to a 1.8 mol/2 NaOH aqueous solution 2001 prepared in advance in a reactor while flowing nitrogen gas and stirring to perform a reaction for producing an alkaline suspension. The suspension was subjected to ioo z per minute at a temperature of 45°C.
Air was passed through the solution for 6 hours to obtain needle-shaped α-FeOOH containing barium and nickel. This material was separated by filtration and washed with water to obtain a wet cake (this is referred to as raw material B).
. This acicular crystal α-FeO containing barium and nickel
As a result of electron microscopic observation, the average value of the long axis of OH particles was 0.4.
It had excellent acicularity with a diameter of 9μ and an average acicularity ratio (major axis/minor axis) of 23. Further, the specific surface area value of this product by BET method was 63 nf/g.

When barium and nickel in this α-FeOOFI were analyzed using fluorescent light, both elements were detected, confirming that barium and nickel were dissolved in the acicular α-Felon.

Next, 0.28 mol of cobalt (using cobalt chloride) was deposited on the α-FeOOH in the same manner as in Example 1, and then 0.26 mol of silica (using water glass) was deposited, and the mixture was filtered. , washed with water, dried, and heat-treated at 600°C for 2 hours in an electric furnace. The heat-treated product was heated at 450° under a hydrogen stream.
The mixture was reduced at a temperature of C for 5 hours. After the reduction was completed, it was stabilized in the same manner as in Example-1 to obtain metal magnetic powder. The magnetic properties of the metal magnetic powder are Hc=16470e, as=1
34. Oemu/g, tyr/ets =0.5
31, and the BET value was 52°0rrf/g.

The magnetic properties of the tape manufactured by the same method as Example-1 are as follows:
Flc=16040e, Br=3476, G,
Bn+=4018 G, Br/Bm=0.865, and the squareness ratio was excellent.

Example-5 To the acicular α-Fe00tl (raw material B) containing barium and nickel compounds produced in Example-4, 1.8 atom% of a silica compound and 9.0 atom of an aluminum compound were added to the iron. % was deposited on the silica compound in order of the aluminum compound by a neutralization method. After filtration, washing, and drying,
Heat treated in an electric furnace at 650°C for 2 hours and heated under a hydrogen stream for 47 hours.
Reduction was performed at 0°C for 5 hours.

Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

In addition, the raw material α-FeO used in the following Examples and Comparative Examples
The production conditions of OH, the specific surface area value of the product determined by the BET method, the average long axis dimension, and the average axial ratio are summarized in Table 1. Similarly, the type and amount of the metal compound added for adhesion in each Example and Comparative Example, heat treatment conditions, and reduction conditions are summarized in Table 2.

Example-6 Using the same method as Example-1, barium equivalent to 3
．． Acicular α-Fe containing 0 at% barium compound
OOH was produced (this product was designated as raw material C).

This raw material C was coated with 15 at% nickel compound and 4.7 at% silica compound based on iron, filtered, washed with water, dried, and then heat treated in an electric furnace at 600°C for 2 hours, followed by hydrogen gas flow. The mixture was reduced at 440°C for 5 hours. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

Example-7 A nickel compound of 3.0 atomic % with respect to iron and a cobalt compound of 12.0 atomic % with respect to iron were deposited on raw material C,
Furthermore, in the same manner as in Example-1, a silica compound was added at 2.0 atomic % based on iron, and an aluminum compound was added at 6.0 atomic % based on iron.
Atomic % deposited.

The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

Example-8 A cobalt compound of 3.0 atomic % based on iron was deposited on raw material C, and a mixed aqueous solution of water glass and sodium aluminate was added to the deposited α-FeOOH suspension and stirred thoroughly.
A 2N HCI aqueous solution was added dropwise thereto to adjust the pH to 8.0, and a silica compound was deposited at 2.0 atomic % and an aluminum compound was deposited at 5.0 atomic % based on iron. The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

Comparative Example-1 Contains 3.0 atomic% of nickel based on iron,
Ferrous chloride 0.6 mol/! obtained by adding 214 g of nickel chloride (NiC1□ 6HzO)! An aqueous solution of 100 j2 was prepared in advance in the reactor.
Nitrogen gas was flowed into 200 f of an 8 mol/l NaOH aqueous solution and added with stirring to perform a reaction to form an alkaline suspension. 1 min per minute at a temperature of 45°C to the suspension.
By blowing air at 00 ffi for 6 hours, acicular α-FeOOH containing a nickel compound was obtained (this was used as a raw material).

Next, the acicular crystal α-FeO containing this nickel compound is
A cobalt compound was deposited on the surface of the OH in an amount of 5.0 atomic % based on iron in the same manner as in the example, and then a silica compound was deposited on the surface of OH at 4.7 atomic % based on iron. The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

This product can be compared with Example 4 in terms of the metal composition of the metal magnetic powder, and the squareness ratio of the tape is not a bad value. However, it is inferior to the example.

Comparative Example-2 Each compound of nickel, cobalt, silica, and aluminum was added to the surface of the raw material in the same manner as in Example-1 at a rate of 2.0.5.0.2.0.6.0 relative to the iron. Atomic % deposited. The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

Although this product was comparable to Example 1 in terms of the metal composition of the metal magnetic powder, the squareness ratio of the tape was inferior.

Comparative Example-3 Nickel, cobalt, and silica compounds were applied to the surface of the raw material in the same manner as in Example-2 at a rate of 5.0.8.0.
4.7 atomic percent was deposited. The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

Although this product was comparable to Example 2 in terms of the metal composition of the metal magnetic powder, the squareness ratio of the tape was inferior.

Comparative Example-4 Ferrous chloride obtained by adding nickel chloride and zinc chloride to iron so as to contain 3.0 atomic % in terms of nickel and 2.5 atomic % in terms of zinc. A 5 mol/l aqueous solution 1001 was prepared in advance in the reactor 1,
Nitrogen gas was flowed into 200 f of an 8 mol/l aqueous Mail solution and added while stirring to perform a reaction for producing an alkaline suspension.

100 per minute at a temperature of 45°C. air of 6
After aeration for a period of time, acicular α-FeOOH containing nickel and zinc compounds was obtained. This material is filtered out using the usual method.
A wet cake was obtained by washing with water (this is referred to as raw material E).

Acicular α-Fe containing this nickel and zinc compound
When OOH was observed under an electron microscope, it was found to be bundles of very fine particles.

The average major axis length of these bundled particles was about 0.44 μm, and although the short axis length could not be measured because they were bundled particles, they were particles with good acicularity. Further, the specific surface area determined by the BET method was 70.0 ffl/g, indicating that the particles were fine.

Next, a cobalt compound of 5.0 atomic % and a silica compound of 4.7 atomic % based on iron were deposited on the α-FeOOH surface. The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.

This product can be compared with Example 4 in terms of the metal composition of the metal magnetic powder, and although it shows a good squareness ratio due to the effect of zinc, it is not as good as the numerical value of Example.

Comparative Example-5 Raw material E contains 1.8 at% silica compound based on iron,
9.0 atomic % aluminum compound was deposited in the same manner as in Example-5. The following treatments were carried out under the conditions shown in Table 2. Table 3 shows the magnetic properties of the obtained metal magnetic powder, the specific surface area value determined by the BET method, and the magnetic properties when made into a tape.
It was shown to.

Although this product could be compared with Example 5 in terms of the metal composition of the metal magnetic powder, the squareness ratio of the tape was not as good as that in Example-5.

〔Effect of the invention〕

As is clear from the Examples and Comparative Examples, the metal magnetic powder produced by the method of the present invention is fine, but has excellent dispersibility and orientation, and has an extremely excellent squareness ratio when made into a tape. be.

Claims (1)

[Claims] 1. Neutralize the ferrous salt aqueous solution with an alkali to obtain an alkaline suspension with a pH of 10 or more, and generate acicular α-FeOOH particles by passing an oxygen-containing gas through the suspension to oxidize it. In the method for producing metal magnetic powder, a water-soluble barium salt is added to the ferrous salt aqueous solution or the alkaline suspension before passing the oxygen-containing gas,
Next, oxygen-containing gas is passed through to generate α-FeOOH containing barium and having excellent needle-like properties, and then a nickel compound and/or a cobalt compound is applied to the surface of the acicular α-FeOOH particles containing the barium compound. After depositing a silica compound and/or an aluminum compound thereon with or without deposition, filtration, washing with water, and drying are performed, followed by heat treatment in a non-reducing atmosphere, followed by heat treatment under a hydrogen stream. A method for producing metal magnetic powder, characterized by carrying out thermal reduction in a temperature range of 300 to 600°C.