JPH1097913A - Compound magnetic body, its manufacture and electromagnetic interference restraint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound magnetic body having high real part magnetic permeability by suppressing deterioration of magnetic permeability due to eddy current and further reducing diamagnetic field. SOLUTION: This magnetic body 10 is composed of first and second soft magnetic powders 11 and 12 and organic binder 13. The first soft magnetic powder 11 has a flat shape, the second soft magnetic powder 12 has an arbitrary shape and its size is sufficiently smaller than that of the first soft magnetic powder 11. The total volume of the first soft magnetic powder 11 per unit volume is sufficiently larger than that of the second soft magnetic powder 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite magnetic material having excellent complex magnetic permeability characteristics in a high frequency range and a radio wave absorber as one application example thereof, and more particularly to a high frequency electronic circuit / device. The present invention relates to a composite magnetic material having excellent complex magnetic permeability, which is effective for suppressing electromagnetic interference, which is a problem, a method for manufacturing the same, and an electromagnetic interference suppressor.

[0002]

2. Description of the Related Art In recent years, electronic devices using high frequencies such as digital electronic devices have become widespread. In particular, mobile communication devices using a quasi-microwave band have been remarkably spread.
Accordingly, soft magnetic materials used for inductance components and radio wave absorbers are also required to respond to higher frequencies.

[0003] One of the main factors that hinder the increase in the frequency of soft magnetic materials is eddy current loss. As means for reducing the eddy current, thinning and high electric resistance in consideration of the skin depth are mentioned. Examples thereof include those in which magnetic layers and dielectric layers are alternately laminated, and a representative of the latter is a high electrical resistance Ni-Zn ferrite.

The applications of soft magnetic materials in the quasi-microwave band are mainly the above-mentioned inductance components and radio wave absorbers. The inductance components use the real part permeability μ ′, and the radio wave absorbers use the imaginary part. The permeability μ ″ is used.
However, although a high Q value is often required for the inductance component, the required inductance is extremely small in the quasi-microwave band, so that its use as a magnetic core material is limited.

On the other hand, applications as radio wave absorbers using the imaginary part magnetic permeability μ ″ are expanding with the spread of high frequency devices. For example, mobile communication devices represented by mobile phones are particularly downsized. -The demand for weight reduction is remarkable, and high-density mounting of electronic components is the biggest technical problem.
Therefore, densely mounted electronic components, printed wiring, wiring between modules, and the like are extremely close to each other, and furthermore, the speed of signal processing is also increased, so that electrostatic coupling and / or electromagnetic Coupling causes an increase in line-to-line coupling and interference due to radiated noise, so that a situation that hinders normal operation of the device is not limited.

Conventionally, countermeasures against such electromagnetic interference have been made mainly by providing a conductor shield.

[0007]

However, since the conductor shield is an electromagnetic interference countermeasure that utilizes the reflection of electromagnetic waves due to impedance mismatch with the space, even if a shielding effect is obtained, the conductor shield is not susceptible to unwanted radiation. Electromagnetic coupling due to reflection is promoted, and as a result, secondary electromagnetic interference is often caused. As a countermeasure, it is effective to suppress the unnecessary radiation using the magnetic loss of the magnetic material, that is, the imaginary part magnetic permeability μ ″. That is, a magnetic material having a large magnetic loss is disposed between the conductor shield and the unnecessary radiation source. By doing so, unnecessary radiation can be suppressed.

Here, the thickness d of the magnetic material required for suppression is
Since it is inversely proportional to μ ”in a frequency band satisfying the relationship μ ″> μ ′, it is composed of a thin electromagnetic interference suppressor, that is, a shield body and an absorber, which meets the aforementioned demands for downsizing and weight reduction of electronic devices. To obtain the composite, the imaginary part magnetic permeability μ ”
Requires a magnetic material having a large diameter.

In order to meet such demands, the magnetic material is excellent in high-frequency characteristics of magnetic permeability and functions as a magnetic loss body in a desired frequency range, that is, the value of μ ′ is large in a low frequency range, and In the frequency region of "> μ ', a magnetic material having a large value of μ" was studied.

[0010]

In order to obtain a large magnetic loss in a high frequency region, measures are taken to prevent the magnetic permeability from deteriorating due to an eddy current at a frequency lower than that at which magnetic resonance occurs. Needs to be further reduced.

As one of the effective countermeasures against eddy current, a laminated structure in which magnetic layers and dielectric layers are alternately laminated has been proposed, and some of them have been put to practical use. The feature of the composite magnetic material having this laminated structure is that the thickness of the magnetic material layer is equal to or less than the skin depth determined by electric resistance, magnetic permeability and frequency.

However, there is a problem that the magnetic permeability of the laminated magnetic material is deteriorated because a displacement current flows through the dielectric layer. Here, since the displacement current depends on the size of the laminated magnetic material (that is, the size in the direction orthogonal to the laminating direction), the influence is eliminated by subdividing the laminated magnetic material into a column structure. It becomes possible. It is not easy to realize such a laminated magnetic material by a so-called thin film forming process such as sputtering, but practical application is facilitated by applying a soft magnetic material powder to the magnetic material layer.

That is, the soft magnetic material powder corresponding to the magnetic material layer has a flat shape whose thickness is smaller than the skin depth, and the soft magnetic material powder has a demagnetizing coefficient Nd of approximately 1 for the powder. Composite magnetic material with extremely small eddy current loss by providing a dielectric layer obtained by oxidizing the surface of the soft magnetic material powder as equivalent to a dielectric layer. I hoped I could get my body.

The magnitude of the demagnetizing field of the composite magnetic material is determined by the demagnetizing field coefficient Nd of the flat soft magnetic powder and the arrangement of the flat soft magnetic powder in the composite magnetic material. It is determined by the filling amount of the soft magnetic material powder and the like, and is reduced by arranging the flat soft magnetic material powder in the in-plane direction of the composite magnetic material with a high degree of orientation.

However, since the soft magnetic powder usually has a distribution in shape and size, the degree of orientation is improved due to steric hindrance of the powder and insufficient affinity with an organic binder. It was extremely difficult. In fact, when a cross section of the composite magnetic material composed of the flat soft magnetic material powder and the organic binder in a direction perpendicular to the easy axis of magnetization is observed with an electron microscope, the gap between the flat soft magnetic material powders indicates There was a region (air layer) where no agent was present, and it was confirmed that the region was a useless space that did not function magnetically or mechanically.

Therefore, the present inventors pay attention to this space, and fill a soft magnetic material powder having a size sufficiently smaller than the flat soft magnetic material powder into the organic binder in or near the space. This is expected to further reduce the demagnetizing field of the composite magnetic material, and furthermore, by specifying the thickness of the soft magnetic material powder and providing a dielectric layer on the surface of the soft magnetic material powder, eddy current loss The present inventors have found that it is possible to provide an inferior conductive composite magnetic material which has less inconsistency and is less likely to cause impedance mismatch with a space.

According to the present invention, there is provided a composite magnetic material comprising first and second soft magnetic material powders and an organic binder, wherein the first soft magnetic material powder has a flat shape. 2 soft magnetic material powder has an arbitrary shape, the size is sufficiently smaller than the first soft magnetic material powder, and the first soft magnetic material powder per unit volume of the composite magnetic material. A composite magnetic material whose total volume is sufficiently larger than the total volume per unit volume of the second soft magnetic material powder is obtained.

According to the present invention, the first soft magnetic powder has a BET specific surface area of 0.1 to ³ m ² / g, and the second soft magnetic powder has a BET specific surface area. 5m
A composite magnetic material having a ratio of ² / g or more is obtained.

Further, according to the present invention, there can be obtained a composite magnetic material in which the average thickness of the first soft magnetic material powder is smaller than the skin depth δ at the operating frequency of the composite magnetic material.

Further, according to the present invention, the first soft magnetic material powder is a composite magnetic material which is oriented and arranged in the composite magnetic material.

Further, according to the present invention, a composite magnetic material having an oxide layer on at least the surface of the first soft magnetic material powder can be obtained.

Further, according to the present invention, the soft magnetic material powder having an oxide layer on at least the surface thereof can be treated with an oxygen-containing mixed gas by a gas phase slow acid method or a liquid phase slow acid method. Is obtained by subjecting the magnetic composite to an oxidation treatment.

Furthermore, according to the present invention, the first and the second
Consisting of a soft magnetic material powder and the organic binder, and
A composite magnetic material having poor electrical conductivity can be obtained.

Further, according to the present invention, in the method for producing a composite magnetic material comprising a soft magnetic material powder and an organic binder, the soft magnetic material powder is processed into a flat shape to obtain a first soft magnetic material powder, The soft magnetic material powder is processed into an arbitrary shape having a size sufficiently smaller than the first soft magnetic material powder to form a second soft magnetic material powder, and at least a surface of the first soft magnetic material powder is A method for producing a composite magnetic body in which an oxide layer is formed with an oxygen-containing gas by a gas phase slow acid method or a liquid phase slow acid method is obtained.

Further, according to the present invention, there is obtained an electromagnetic interference suppressor having the composite magnetic material as a constituent element, and further having an electroconductive material layer.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a metal soft magnetic material such as an iron aluminum silicon alloy (Sendust), an iron nickel alloy (Permalloy), or an amorphous alloy having a high high-frequency magnetic permeability is used as a raw material. I can do it.

According to the present invention, in the case of the first soft magnetic powder, these raw materials are flattened by pulverization, stretching, tearing or the like, so that the thickness is equal to or less than the skin depth, and the powder is not crushed. In order to make the magnetic field coefficient Nd approximately 1, the aspect ratio of the powder needs to be approximately 10 or more. Here, the skin depth δ is given by the following equation.

Δ = (ρ / πμf) ^{1/2 In the above} equation, ρ is a specific resistance, μ is a magnetic permeability, and f is a frequency. Therefore, the value of the skin depth δ varies depending on the target frequency. However, in order to obtain a desired skin depth and an aspect ratio, it is one of the simplest means to specify the average particle size of the starting coarse raw material powder. One. Typical milling means that can be used for the milling, stretching and tearing operations include a ball mill, an attritor, a pin mill, and the like. There is no limitation on the grinding means as long as the ratio can be obtained.

Also, in the present invention, the first soft magnetic powder is used so that the electrical isolation between the individual magnetic powders, that is, the nonconductivity of the composite magnetic material can be ensured even when the magnetic powder is highly filled. The body powder needs to have a dielectric layer formed on its surface. The dielectric layer is a metal oxide layer composed of oxygen and constituent elements obtained by oxidizing the surface of the metal magnetic powder. For example, in the case of an iron aluminum silicon alloy (Sendust), the dielectric layer is mainly made of AlO _x And SiO _X.

As an example of the means for oxidizing the surface of the metal powder, in particular, for those having relatively small powder size and high activity, the partial pressure of oxygen in a hydrocarbon organic solvent or an inert gas atmosphere is used. It is preferred from the viewpoint of controllability, stability, and safety that the oxidation treatment is performed by a gradual acid method in a liquid phase or a gradual acid method in a gas phase in which a nitrogen-oxygen mixed gas is introduced.

In the present invention, the second soft magnetic powder used together with the first soft magnetic powder is a metal magnetic powder similar to the first soft magnetic powder or an oxide magnetic powder. Any of the above may be used, but whether or not to perform a slow acid treatment for surface oxidation when using the metal magnetic powder is optional.

The size of the particles of the first and second soft magnetic powders is such that the first soft magnetic powder is sufficiently larger than the second soft magnetic powder, It is necessary that the total volume of the body powder per unit volume of the composite magnetic material be sufficiently smaller than the total volume of the first soft magnetic material powder. In other words, the second soft magnetic material powder may have a size and a total amount that can be present so as to fill the gaps of the first soft magnetic material powder, that is, the voids in the composite magnetic material. Specifically, the first soft magnetic material powder has a BET specific surface area of 0.1.
1 to 3 (m ² / g) and the BE of the second soft magnetic material powder
The T specific surface area is preferably 5 (m ² / g) or more.

The organic binder used as one component of the present invention includes polyester resin, polyethylene resin, polyvinyl chloride resin, polyvinyl butyral resin, polyurethane resin, cellulose resin, ABS resin, nitrile-butadiene rubber. Styrene-butadiene rubber, epoxy resin, phenol resin, amide resin, imide resin, and copolymers thereof.

The means for obtaining the composite magnetic material by kneading and dispersing the constituent elements of the present invention described above is not particularly limited, and a preferred method may be selected based on the properties of the binder used and the ease of the process. Good.

The first in the kneaded and dispersed magnetic mixture
Means for orienting and arranging the particles of the soft magnetic material powder include a method using shear stress and a method using magnetic field orientation.
Either method may be used.

FIG. 1 is a cross-sectional view of a composite magnetic material obtained according to the present invention.
The composite magnetic body 10 in which the second soft magnetic body powder 12 exists so as to fill the gap between the soft magnetic body powders 11 is obtained.

FIG. 2 is a cross-sectional view of an electromagnetic interference suppressor obtained by the present invention. An electromagnetic interference suppressor 20 having a conductive layer 14 made of a conductive material formed on one surface side of a composite magnetic body 10 is shown in FIG. can get.

[0038]

Next, an experiment was conducted to verify the effect of the present invention, and the embodiment will be described below in detail.

First, an iron-aluminum-silicon alloy powder prepared by a water atomizing method is prepared, and ground by using an attritor. Further, a nitrogen-oxygen mixture having a partial pressure of oxygen of 35% in a hydrocarbon organic solvent is used. The mixture was stirred for 8 hours while introducing a gas and subjected to a slow acid treatment in a liquid phase to obtain a flat magnetic powder sample as a first soft magnetic material powder. As a result of surface analysis of the powder obtained here, formation of a metal oxide was clearly confirmed, and the presence of an oxide film on the surface of the sample powder was recognized.

In verifying the effects of the present invention, a composite magnetic material described below was prepared, and the μ-f characteristics and the effect of suppressing electromagnetic interference were examined.

For the measurement of the μ-f characteristic, a composite magnetic material sample processed into a toroidal shape was used. This was inserted into a test fixture forming a one-turn coil, and μ ′ and μ ″ were determined by measuring the impedance.

On the other hand, the effect of suppressing the electromagnetic interference was verified by the evaluation system shown in FIG. 3, and as the electromagnetic interference suppressor sample 20, the conductor layer 14 having a thickness of 2 m lined with a copper plate was used.
A composite magnetic body 10 having a side length of 20 cm and a length of 20 cm was used.
Here, the loop diameter is 1.5 for the wave source element and the receiving element.
mm micro-loop antennas 21 and 22 are used, a sweep generator (electromagnetic field wave source oscillator) 23 is used as a signal source connected to the receiving element, and a network analyzer (electromagnetic field intensity measuring device) is used to measure the coupling level. ) 24 was used.

[Testing Sample 1] A soft magnetic paste having the following composition was prepared, formed into a film by the doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours for testing. Sample 1 was obtained.

When the obtained verification sample 1 was analyzed using a scanning electron microscope, the arrangement direction of the flat soft magnetic particles was in the plane of the sample film.

Flat soft magnetic material (Fe—Al—Si alloy) fine powder A: 95 parts by weight Average particle size: φ20 μm × 0.3 μm ^t Fine powder of arbitrary shape soft magnetic material (Fe—Al—Si alloy) B: 5 parts by weight Average particle size: φ0.25 μm Polyurethane resin: 8 parts by weight Curing agent (isocyanate compound): 2 parts by weight Solvent (mixture of cyclohexanone and toluene): 40 parts by weight [verification] Sample 2] A soft magnetic paste having the following composition was prepared, formed into a film by the doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a sample 2 for verification. .

When the obtained verification sample 2 was analyzed using a scanning electron microscope, the arrangement direction of the flat soft magnetic particles was in the in-plane direction of the sample film.

Flat soft magnetic material (Fe-Al-Si alloy) fine powder A: 95 parts by weight Average particle diameter: φ20 μm × 0.3 μm ^t Soft magnetic material (carbonyl iron) fine powder C: Arbitrary shape 5 parts by weight Average particle size: φ0.3 μm Polyurethane resin 8 parts by weight Curing agent (isocyanate compound) 2 parts by weight Solvent (mixture of cyclohexanone and toluene) 40 parts by weight [Sample 3 for verification] A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain a verification sample 3.

When the obtained verification sample 3 was analyzed using a scanning electron microscope, the arrangement direction of the flat soft magnetic particles was in the in-plane direction of the sample film.

Flat soft magnetic material (Fe—Ni alloy) fine powder D: 95 parts by weight Average particle size: φ30 μm × 0.4 μm ^t Soft powder of arbitrary shape (α-Fe ₃ O ₄ alloy) fine powder 5 parts by weight Average particle size: 0.4 μm Polyurethane resin 8 parts by weight Curing agent (isocyanate compound) 2 parts by weight Solvent (mixture of cyclohexanone and toluene) 40 parts by weight [Comparative sample 4] A soft magnetic paste having the following composition was prepared, formed into a film by a doctor blade method, subjected to hot pressing, and then cured at 85 ° C. for 24 hours to obtain Comparative Sample 4.

When the obtained comparative sample 4 was analyzed using a scanning electron microscope, it was found that the arrangement was almost isotropic.

Substantially spherical soft magnetic material (Fe—Al—Si alloy) fine powder E: 95 parts by weight Average particle diameter: φ15 μm Polyurethane resin: 8 parts by weight Curing agent (isocyanate compound): 2 parts by weight Solvent (mixture of cyclohexanone and toluene) ... 40 parts by weight [Comparative sample 5] A soft magnetic paste having the following composition was prepared, formed into a film by the doctor blade method, and subjected to hot pressing. Curing was performed at 24 ° C. for 24 hours to obtain Comparative Sample 5.

When the obtained comparative sample 5 was analyzed using a scanning electron microscope, the particle arrangement direction was in the sample film plane.

Flat soft magnetic material (Fe—Al—Si alloy) fine powder A: 95 parts by weight Average particle size: φ20 μm × 0.3 μm ^t polyurethane resin: 8 parts by weight Hardener (isocyanate compound) 2 parts by weight Solvent (mixture of cyclohexanone and toluene) 40 parts by weight Real part permeability μ 'and magnetic resonance frequency f of each sample obtained
r is shown in Table 1 below.

[0054]

[Table 1]

FIG. 4 shows the μ-f characteristics of the verification sample 1 which is the verification example of the present invention and the comparison samples 4 and 5 which are the comparative examples. The sample for verification 1 which is the example of (1) shows the largest value.

Referring to Table 1 in conjunction with FIG.
The difference in the real part permeability μ ′ of the verification sample composed of two soft magnetic powders was smaller than that of the comparative sample 4 using the substantially spherical raw magnetic powder or the comparative sample 5 composed of only the flat magnetic powder. It is obvious.

From these results, it can be seen that the first soft magnetic powder having a flat shape and a dielectric layer on its surface, and the second soft magnetic powder having an arbitrary shape and a size sufficiently smaller than the first soft magnetic powder.
It is evident that the composite magnetic material comprising the soft magnetic powder of the above exhibits high magnetic permeability characteristics in a high frequency range.

Next, Table 2 below shows the results of comparison of the surface resistance, the value of μ ″, and the effect of suppressing electromagnetic interference between the verification sample 2 and the comparison sample 5.

[0059]

[Table 2]

Here, the surface resistance is ASTM-D-257.
The value of μ ″ is a value obtained by the one-turn coil method as in the case of μ ′, and the value of the electromagnetic interference suppression effect is:
This is the signal attenuation when the copper plate is used as a reference (0 dB).

The following effects are apparent from Table 2 above.

That is, both the verification sample and the comparative sample of the present invention have a surface resistance of 10 ⁷ to 10 ⁸ Ω, and the use of a magnetic powder having at least an oxidized surface makes it possible to produce a composite magnetic material. It can be made to be non-conductive, and can suppress surface reflection of electromagnetic waves due to impedance mismatch as seen in conductors and bulk metallic magnetic materials.

Further, the sample for verification of the present invention shows a good effect of suppressing electromagnetic interference, and it can be understood that the increase of μ ″ value according to the present invention is effective for suppressing electromagnetic interference.

[0064]

As described above, according to the present invention, in a composite magnetic material comprising a soft magnetic material powder and an organic binder,
Since it has a configuration that can suppress the deterioration of the magnetic permeability characteristic due to the eddy current and a configuration that reduces the demagnetizing field, a high magnetic permeability characteristic can be realized, and an excellent effect of suppressing electromagnetic interference appears.

In particular, the second soft magnetic powder of an arbitrary shape whose size is sufficiently smaller than that of the first soft magnetic powder having a flat shape is dispersed in the composite magnetic material. Thereby, the demagnetizing field of the composite magnetic body is reduced, and as a result, the magnetic permeability is improved. Incidentally, the demagnetizing field H in the hard axis direction
The ratio Dr (= Hde / H) between dd and the demagnetizing field Hde in the easy axis direction.
Regarding dd), the value of Dr when the shape of the sample to be measured is a cube is about 5 to 6 in the conventional example, but is improved to about 7 in the present invention. And 300
The real part permeability μ 'at MHZ is 16
On the other hand, it is about 19 in the present invention. Here, it goes without saying that the imaginary part magnetic permeability μ ″, which is a magnetic loss term, also increases as the real part magnetic permeability μ ′ increases.

That is, according to the present invention, it is possible to obtain a thin electromagnetic interference suppressor that is effective for suppressing electromagnetic wave interference inside high-frequency electronic devices such as mobile communication devices.

The composite magnetic body and the electromagnetic interference suppressor according to the present invention can be easily imparted with flexibility as can be seen from the constituent elements, so that they can cope with complicated shapes and withstand severe vibration resistance. It is possible to respond to impact demand.

[Brief description of the drawings]

FIG. 1 is a sectional view of a composite magnetic body according to the present invention.

FIG. 2 is a sectional view of an electromagnetic interference suppressor according to the present invention.

FIG. 3 is a schematic diagram showing an evaluation system used for evaluating characteristics of the electromagnetic interference suppressor according to the present invention.

FIG. 4 is a diagram illustrating μ-f characteristics of a verification sample 1 as a verification example of the present invention and comparative samples 4 and 5 as comparative examples.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Composite magnetic material 11 1st soft magnetic material powder 12 2nd soft magnetic material powder 13 Organic binder 14 Conductive layer 20 Electromagnetic interference suppressor 21, 22 Loop antenna 23 Sweep generator 24 Network analyzer

Claims (9)

[Claims] 1. A composite magnetic material comprising first and second soft magnetic powders and an organic binder, wherein the first soft magnetic powder has a flat shape and the second soft magnetic powder The body powder has an arbitrary shape, the size thereof is sufficiently smaller than that of the first soft magnetic body powder, and the total volume of the first soft magnetic body powder per unit volume of the composite magnetic body is: A composite magnetic material, which is sufficiently larger than a total volume per unit volume of the second soft magnetic material powder. 2. The composite magnetic material according to claim 1, wherein
The first soft magnetic material powder has a BET specific surface area of 0.1 to
3 m ² / g, and the second soft magnetic powder is BET
A composite magnetic material having a specific surface area of 5 m ² / g or more. 3. The composite magnetic material according to claim 1, wherein the average thickness of the first soft magnetic material powder is a skin depth δ at an operating frequency of the composite magnetic material.
A composite magnetic material characterized by being smaller than the composite magnetic material. 4. The composite magnetic material according to claim 1, wherein the first soft magnetic material powder is oriented and arranged in the composite magnetic material. Composite magnetic material. 5. The composite magnetic material according to claim 1, wherein the first soft magnetic material powder has an oxide layer at least on a surface thereof. . 6. The composite magnetic material according to claim 5, wherein
The soft magnetic material powder having an oxide layer on at least the surface thereof is obtained by oxidizing the surface thereof with an oxygen-containing mixed gas by a gas phase slow acid method or a liquid phase slow acid method. A magnetic composite. 7. The composite magnetic material according to claim 5, wherein the first and second soft magnetic powders are:
A composite magnetic material comprising the organic binder and being electrically non-conductive. 8. A method for producing a composite magnetic material comprising a soft magnetic material powder and an organic binder, wherein the soft magnetic material powder is processed into a flat shape to obtain a first soft magnetic material powder, and the soft magnetic material powder is The second soft magnetic material powder is processed into an arbitrary shape having a size sufficiently smaller than the first soft magnetic material powder, and the first soft magnetic material powder is processed.
Forming an oxide layer on at least the surface of the soft magnetic material powder with an oxygen-containing gas by a gas phase slow acid method or a liquid phase slow acid method. 9. An electromagnetic interference suppressor having the composite magnetic material according to claim 1 as a component thereof, further comprising a conductive material layer. Suppressor.