JP2020102486A - Composite magnetic material and magnetic core - Google Patents

Abstract

To provide a composite magnetic material and a magnetic core used for a magnetic core having a high relative permeability μr and a low magnetic loss tan δ in a high frequency region of GHz band.SOLUTION: A composite magnetic material includes acicular powder and resin. The acicular powder is mainly composed of Fe or Fe and Co. The average minor axis length in primary particles of the acicular powder is 100 nm or less. In the frequency distribution of the aspect ratio of the primary particles of the acicular powder, the aspect ratio of a first peak having the highest frequency and the aspect ratio of a second peak having the second highest frequency are within a range of 3.0 or more and 10 or less, respectively. The smaller one of (aspect ratio of first peak)/(aspect ratio of second peak) and (aspect ratio of second peak)/(aspect ratio of first peak) is 0.30 or more and 0.80 or less.SELECTED DRAWING: Figure 3

Description

The present invention relates to a composite magnetic material and a magnetic core.

2. Description of the Related Art In recent years, the use frequency band of wireless communication devices such as mobile phones and personal digital assistants has become higher, and the used radio signal frequency is in the GHz band. Therefore, by applying a magnetic material having a relatively large magnetic permeability even in the high frequency region of the GHz band to electronic components used in the high frequency region of the GHz band, the filter characteristics are improved and the antenna size is reduced. Attempts have been made to achieve this. It is also desired to reduce the magnetic loss in the high frequency region. Among them, attempts have been made to increase the aspect ratio of the magnetic material used for the magnetic core.

For example, Patent Document 1 describes a composite material using FeSiAl-based acicular powder and spherical powder. Patent Document 2 describes a composite material using amorphous acicular powder and spherical powder.

However, at present, a magnetic core having a higher relative permeability μr and a lower magnetic loss tan δ is required.

JP, 11-260617, A JP, 2002-105502, A

An object of the present invention is to provide a composite magnetic material and a magnetic core used for a magnetic core having a high relative permeability μr and a low magnetic loss tan δ in a high frequency range of GHz band.

In order to achieve the above object, the composite magnetic material of the present invention,
A composite magnetic material containing acicular powder and resin,
The needle-shaped powder contains Fe or Fe and Co as a main component,
The average minor axis length of the primary particles of the acicular powder is 100 nm or less,
In the frequency distribution of the aspect ratio in the primary particles of the acicular powder, the aspect ratio of the first peak having the highest frequency and the aspect ratio of the second peak having the second highest frequency are within a range of 3.0 or more and 10 or less, respectively. Yes,
The smaller one of (aspect ratio of first peak)/(aspect ratio of second peak) and (aspect ratio of second peak)/(aspect ratio of first peak) is 0.30 or more and 0.80 or less. It is characterized by

The composite magnetic material of the present invention is used for a magnetic core having a high relative permeability μr and a low magnetic loss tan δ in the high frequency region of the GHz band, due to the above-described composition having the average minor axis length and the frequency distribution of the aspect ratio. Becomes

In the acicular powder, the content ratio of Co with respect to the main component is preferably 0 to 40 atom% (not including 0 atom %).

The magnetic core of the present invention includes the above composite magnetic material.

It is drawing which shows the major axis length and the minor axis length in a composite magnetic material. It is an example of a histogram for explaining a procedure for determining a peak. 16 is a histogram showing a frequency distribution of aspect ratios in Example 8.

Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

The magnetic core of the present embodiment is made of a composite magnetic material containing acicular powder and resin.

Then, the acicular powder is made of Fe or a soft magnetic material containing Fe and Co as a main component. The average minor axis length of primary particles of acicular powder is 100 nm or less. When the average minor axis length is 100 nm or less, the magnetic loss (tan δ) of the magnetic core can be reduced. The average minor axis length of the primary particles of the acicular powder has no lower limit. For example, the average minor axis length of primary particles of acicular powder may be 15 nm or more.

The reason why the magnetic loss of the magnetic core increases when the average minor axis length exceeds 100 nm is that double magnetic domains are likely to occur in the primary particles and the eddy current loss increases.

Further, the shape of the acicular powder is not particularly limited. It may be needle-like, pseudo-needle-like, spheroidal or pseudo-spheroidal.

The minor axis length, major axis length and aspect ratio of the primary particles of the acicular powder are calculated by the following method.

First, the needle-like powder 1 for measuring the major axis length, the minor axis length and the aspect ratio is photographed as a two-dimensional image using SEM or TEM. On the photographed two-dimensional image, an ellipse 1a circumscribing the needle-shaped powder 1 is drawn as shown in FIG. 1, and the length of the major axis L1 of the ellipse 1a is the major axis length and the minor axis L2 is the minor axis. The axial length. The aspect ratio is L1/L2.

The composite magnetic material according to the present embodiment has the first peak with the highest frequency and the second peak with the second highest frequency in the frequency distribution of the aspect ratio in the primary particles of the acicular powder. That is, the frequency distribution of the aspect ratio of primary particles of acicular powder has at least two peaks.

The aspect ratio of the first peak and the aspect ratio of the second peak are in the range of 3 or more and 10 or less, respectively. The presence of two high-frequency peaks in the range of the aspect ratio of 3.0 or more and 10 or less makes it easier to increase the filling rate described later as compared with the case where only one peak exists. Then, the relative permeability μr can be improved.

When the aspect ratio of the first peak or the second peak exceeds 10, the effect of improving the relative magnetic permeability μr cannot be obtained.

Further, the smaller one of (aspect ratio of first peak)/(aspect ratio of second peak) and (aspect ratio of second peak)/(aspect ratio of first peak) is 0.30 or more and 0.80 or less. Is. That is, the aspect ratio of the first peak and the second peak needs to be open to some extent. Since the aspect ratio is open to some extent between the first peak and the second peak, it becomes easy to increase the filling rate and easily improve the relative magnetic permeability μr.

Hereinafter, the smaller one of (aspect ratio of first peak)/(aspect ratio of second peak) and (aspect ratio of second peak)/(aspect ratio of first peak) is simply referred to as “aspect ratio ratio”. May be called.

The smaller the aspect ratio, the higher the filling rate. On the other hand, if the aspect ratio is too large, it becomes difficult to increase the filling rate and it becomes difficult to improve the relative permeability μr.

Hereinafter, a method of determining a peak in the frequency distribution of the aspect ratio will be described with reference to the drawings.

First, the aspect ratio of 500 or more acicular powder primary particles is measured. Next, as shown in FIG. 2, a histogram is created with the width of each class set to 0.25.

Next, it is assumed that a class having a higher frequency than the frequency of any of the adjacent classes is detected and that the median value of the classes having a higher frequency than any of the adjacent classes has a provisional peak.

When two or more classes adjacent to each other have the same frequency, these two or more classes are regarded as a single class group. The frequency of the class group is the same as the frequency of each class composing the class group. Then, it is assumed that the median value of the class group having a higher frequency than any of the adjacent classes has a temporary peak.

Then, the temporary peaks are sorted in descending order of frequency.

Next, the frequency of the next adjacent class from the class (class group) having the temporary peak is examined. When the frequencies of the two classes next to each other are lower than the frequency of the class (class group) having the temporary peak, the temporary peak is officially set as the peak. Then, each peak is a first peak, a second peak,...

The procedure for determining the first peak, the second peak,... In the histogram of FIG. 2 will be described below.

First, the provisional peak in the histogram of FIG. 2 is determined. In the histogram of FIG. 2, there are provisional peaks A to I. In addition, each provisional peak has a high frequency in the order of ABC.

Then, it is checked whether or not each provisional peak is officially a peak.

The frequency of the class having the provisional peak A is higher than the frequency of any two classes next to each other. Therefore, the tentative peak A becomes the first peak.

The frequency of the class having the tentative peak B is lower than the frequency of the class next to two in the negative aspect ratio (class having the tentative peak A). Therefore, the provisional peak B is not the second peak.

The frequency of the class having the tentative peak C is lower than the frequency of the class next to two in the positive direction of the aspect ratio (class having the tentative peak A). Therefore, the provisional peak C is not the second peak.

The frequency of the class group having the provisional peak D is higher than the frequency of any two adjacent classes. Therefore, the provisional peak D is the second peak.

The frequency of the class having the tentative peak E is lower than the frequency of the class next to two in the positive direction of the aspect ratio (class included in the class group having the tentative peak D). Therefore, the provisional peak E is not the third peak.

The frequency of the class having the provisional peak F is lower than the frequency of the next two classes in the negative aspect ratio (classes included in the class group having the provisional peak D). Therefore, the provisional peak F is not the third peak.

The frequency of the class having the tentative peak G is lower than the frequency of the class next to two in the negative aspect ratio (class having the tentative peak F). Therefore, the provisional peak G is not the third peak.

The frequency of the class having the provisional peak H is higher than the frequency of any two classes next to each other. Therefore, the provisional peak H is the third peak.

The frequency of the class having the provisional peak I is higher than that of any two adjacent classes. Therefore, the provisional peak I is the fourth peak.

From the above, in the histogram of FIG. 2, there are four peaks from the first peak to the fourth peak. The aspect ratio of the first peak is 2.125, the aspect ratio of the second peak is 4.25, the aspect ratio of the third peak is 6.875, and the aspect ratio of the fourth peak is 8.125.

Further, the aspect ratio is 2.125/4.25=0.5.

Further, the acicular powder contains Fe or Fe and Co as a main component. Here, containing as a main component means that the content ratio of Fe or Fe and Co with respect to the whole acicular powder is 50 atom% or more.

Further, the content of Co with respect to the total content of Fe and Co which are the main components is preferably 0 to 40 atom (not including 0 atom %), and more preferably 15 to 25 atom %. When the acicular powder contains Fe and Co as the main components, the effect of increasing the relative magnetic permeability μr is further increased.

Further, the acicular powder includes elements other than the main components, such as V, Cr, Mn, Cu, Zn, Ni, Mg, Ca, Sr, Ba, rare earth elements, Ti, Zr, Hf, Nb, Ta, Zn, Al. , Ga and Si may be contained, and particularly Al, Si and/or Ni may be contained in order to improve the oxidation resistance. The content of other elements is not particularly limited, but it is preferably 5% by mass or less in total with respect to the entire acicular powder.

The acicular powder may be covered with an oxide layer. There is no particular limitation on the type of oxide constituting the oxide layer and the thickness of the oxide layer. For example, it may be an oxide containing one or more non-magnetic metals selected from Mg, Ca, Sr, Ba, rare earth elements, Ti, Zr, Hf, Nb, Ta, Zn, Al, Ga and Si. The thickness of the oxide layer may be, for example, 1.0 nm or more and 10.0 nm or less, or 1.0 nm or more and 5.0 nm or less. By coating the acicular powder with the oxide layer, it becomes easier to prevent the acicular powder from being oxidized.

The acicular powder is further coated with resin. That is, the composite magnetic material according to this embodiment has a resin. The type of resin is not particularly limited. For example, epoxy resin, phenol resin, and acrylic resin are exemplified. By coating with a resin, it is possible to improve the insulating property, suppress the generation of an eddy current between the powders that suppress the magnetization rotation described later, and easily improve the relative permeability μr greatly.

It is considered that the reason why the relative magnetic permeability μr of the magnetic core containing the acicular powder having the above-mentioned first peak and second peak in the frequency distribution of the aspect ratio is improved particularly in the high frequency region is as follows.

In particular, the magnitude of the magnetization developed in the high frequency region is considered to strongly depend on the magnitude of the displacement of the precession movement of the magnetization inside the acicular powder. The larger the displacement of the precession movement, the larger the generated magnetization and the higher the magnetic permeability.

Here, when acicular powder having a large shape anisotropy, that is, acicular powder having a large aspect ratio is used, the single magnetic domain structure is more likely to self-assemble due to the demagnetizing field when an external magnetic field is applied.

As a result, when acicular powder having a frequency distribution of the aspect ratio of only one peak is used, the larger the aspect ratio at the peak, the more the precession of magnetization is suppressed, and the relative permeability μr tends to be low. However, since the internal structure is uniform due to self-organization, the effective magnetization increases and the frequency characteristic becomes higher.

On the other hand, the smaller the aspect ratio at the peak, the more the precession motion of the magnetization increases, and the relative permeability μr tends to increase. However, since the self-organization is difficult and the internal texture is non-uniform, the effective magnetization is reduced and the frequency characteristic is lowered.

Here, when the frequency distribution of the aspect ratio has two peaks with high frequency and the aspect ratio is 0.80 or less, the acicular powder with a large aspect ratio preferentially self-assembles. At this time, an exchange interaction occurs between the acicular powders, and the acicular powders with a small aspect ratio are likely to self-assemble in the same direction as the acicular powders with a large aspect ratio. Therefore, the internal structure of the needle-shaped powder having a small aspect ratio is made uniform by using the self-organization of the needle-shaped powder having a large aspect ratio as a starting point, and the effective magnetization is increased. Then, the frequency characteristic is increased in frequency.

Conversely, needle-like powder with a small aspect ratio has increased precession. At this time, an exchange interaction occurs between the needle-shaped powders, and the precession movement of the needle-shaped powders having a large aspect ratio easily increases. Therefore, the precession movement of the needle-shaped powder having a large aspect ratio also increases, starting from the precession movement of the needle-shaped powder having a small aspect ratio. Then, the relative magnetic permeability μr increases.

From the above, when the frequency distribution of the aspect ratio has two peaks with high frequency, the aspect ratio of each peak is 3.0 or more and 10 or less, and the aspect ratio is 0.80 or less, Higher frequency characteristics and an increase in relative permeability μr are achieved at the same time.

When the aspect ratio of the frequently-used peak exceeds 10, the density of the magnetic core manufactured by using the magnetic powder decreases, and the relative permeability μr decreases. When the aspect ratio of a high-frequency peak is less than 3.0, the magnetic loss tan δ becomes high especially in a high frequency region of 3 GHz or higher.

The magnetic core according to this embodiment may include the above-mentioned composite magnetic material. The type of magnetic core is not particularly limited and may be, for example, a dust core. Further, for example, a dust core in which a coil is embedded may include the above composite magnetic material.

Further, the content ratio of the acicular powder to the entire magnetic core (hereinafter, also referred to as filling rate) is preferably 25 vol% or more. By making the filling rate sufficiently high, the relative magnetic permeability μr can be sufficiently improved.

Here, the method of calculating the filling rate is not particularly limited. For example, the following method may be mentioned.

First, the cross section obtained by cutting the magnetic core is polished to prepare an observation surface. Next, the observation surface is observed with an electron microscope (SEM). At this time, the observed image may be binarized by removing noise. Then, the area ratio of the acicular powder to the area of the entire observation surface is calculated. Then, in the present embodiment, the area ratio and the filling rate are regarded as equal, and the area rate is set as the filling rate.

Further, in calculating the filling rate, the observation surface has a size including the acicular powder in total of 1000 particles or more. It should be noted that the observation surface may be plural, and may have a size including 1000 particles or more in total.

Hereinafter, the method for manufacturing the composite magnetic material and the magnetic core according to the present embodiment will be described, but the method for manufacturing the composite magnetic material and the magnetic core according to the present embodiment is not limited to the following method.

First, needle-like powder made of a soft magnetic material whose main component is Fe or Fe and Co is prepared. Here, for example, by preparing a plurality of types of acicular powders having different average aspect ratios, acicular powders having a predetermined aspect ratio frequency distribution can be included in the finally obtained composite magnetic material. The method for producing the acicular powder is not particularly limited, and a usual method in this technical field can be used. For example, it may be produced by a known method of heating and reducing a raw material powder made of a compound such as α-FeOOH, FeO or CoO. By controlling the content of Fe, Co and/or other elements in the raw material powder, the composition of the obtained acicular powder can be controlled.

Here, by controlling the average minor axis length and the average aspect ratio of the raw material powder, the average minor axis length, the average major axis length and the average aspect ratio of the needle-shaped powder can be controlled. The method of controlling the average minor axis length, the average major axis length, and the average aspect ratio of the acicular powder is not limited to the above method.

Further, as a case of coating the non-magnetic metal oxide layer on the acicular powder, a method of heating the raw material powder after the non-magnetic metal is contained therein is exemplified. The method of incorporating the non-magnetic metal into the raw material powder is not particularly limited. For example, there is a method of mixing the raw material powder and a solution containing a non-metal element, adjusting the pH, filtering and drying. Further, the thickness of the oxide layer can be controlled by controlling the concentration, pH, mixing time, etc. of the solution containing the non-metal element.

The needle-like powder can be coated with the resin by mixing the needle-like powder obtained by heating and reducing by the above method with the resin. The method for coating the resin is not particularly limited. For example, the resin can be coated by adding a solution containing 20 to 60% by volume of the resin to 100% by volume of the acicular powder, mixing and drying the solution.

Then, a plurality of types of acicular powders having different average aspect ratios are mixed at a predetermined ratio to obtain the composite magnetic material according to this embodiment. When two types of acicular powders having different aspect ratios are mixed, the average aspect ratio of each acicular powder is the aspect ratio of the first peak or the second peak in the frequency distribution of the finally obtained aspect ratio. It is easy to agree with.

The method for producing the magnetic core from the above composite magnetic material is not particularly limited, and the usual method according to this embodiment can be used.

For example, a magnetic core made of a green compact can be manufactured by filling a mold with the above composite magnetic material and pressurizing it.

The use of the magnetic core according to this embodiment is not particularly limited. For example, coil components, LC filters, antennas, etc. may be mentioned.

Next, the present invention will be described in more detail based on specific examples, but the present invention is not limited to the following examples.

First, needle-like powder was produced. The acicular powder was produced by a known method of heating and reducing a powder of α-FeOOH in H ₂ .

At this time, a plurality of acicular powders of α-FeOOH having different average aspect ratios were prepared. A needle-like powder was finally obtained from a needle-like powder of α-FeOOH. By controlling the minor axis length, major axis length and average aspect ratio of the acicular powder of α-FeOOH at this time, the needle shape having the minor axis length, major axis length and average aspect ratio shown in each table is obtained. Got the powder.

Furthermore, by controlling the Co content in the powder made of α-FeOOH, the composition of the acicular powder was controlled to the composition shown in each table. The composition shown in each table is the atomic number ratio.

A resin was added to the acicular powder obtained by the above method. Further, the needle-shaped powder 1 and the needle-shaped powder 2 shown in each table were mixed at the volume ratio shown in each table. A composite magnetic material was obtained by kneading at 95° C. using a mixing roll and continuing kneading while gradually cooling to 70° C. and stopping kneading at 70° C. or less and rapidly cooling to room temperature. The resin used was JER806:Mitsubishi Chemical, which is an epoxy resin.

Next, the obtained composite magnetic material was put into a mold heated to 100° C., and molded at a molding pressure of 980 MPa. The obtained molded body was heat-cured at 180° C. and then cut out to obtain magnetic cores of Examples and Comparative Examples shown in each table. The shape of the magnetic core was a rectangular parallelepiped measuring 1 mm×1 mm×100 mm.

The relative permeability μr and the magnetic loss tan δ of Examples and Comparative Examples were measured at a frequency of 1.0 GHz and a frequency of 3.5 GHz. The relative magnetic permeability μr and the magnetic loss tan δ were measured by a perturbation method using a network analyzer (HP8753D manufactured by Agilent Technologies, Inc.) and a cavity resonator (manufactured by Kanto Electronics Application Development Co., Ltd.). The results are shown in each table. The magnetic loss tan δ was set to 0.005 or less when the frequency was 1.0 GHz. When the frequency was 3.5 GHz, 0.015 or less was considered good.

In addition, of the two types of acicular powders included in each example, each table describes how much the relative permeability μr changed, based on a comparative example using only acicular powders having a small average aspect ratio. did. The amount of change in relative permeability μr when the frequency was 1.0 GHz was Δμ1, and the amount of change in relative permeability μr when the frequency was 3.5 GHz was Δμ2.

Further, 700 aspect ratios of primary particles of acicular powder contained in the obtained magnetic core were measured to create a histogram. Then, the presence or absence of the second peak, whether the average minor axis length is 100 nm or less, and whether the aspect ratio of the first peak and the aspect ratio of the second peak are 3.0 or more and 10 or less, respectively, are evaluated. Further, the aspect ratio was calculated. The results are shown in each table. In addition, the histogram of Example 8 was illustrated in FIG.

Tables 1 and 2 show the results of Example 1 in which needle powder having an average aspect ratio of 3.0 and needle powder having an average aspect ratio of 5.0 were mixed in the case where the needle powder consisted of iron only. It was Moreover, the result of the comparative example 1 using only the acicular powder of average aspect ratio 3.0 and the comparative example 2 using only the acicular powder of average aspect ratio 5.0 was shown.

From Table 1 and Table 2, in Example 1 in which the frequency distribution of the aspect ratio is the predetermined frequency distribution and the average minor axis length is also within the predetermined range, the frequency distribution of the aspect ratio does not have the second peak. The relative magnetic permeability μr was improved as compared with Examples 1 and Comparative Example 2.

In Table 3 and Table 4, in the case where the needle-shaped powder is an alloy of iron and cobalt, the needle-shaped powder having the average aspect ratio of 3.0 is added to the needle-shaped powder having the average aspect ratio of 4.1 to 9.9. The results of mixed Examples 2 to 12 are shown. Further, the results of Comparative Example 9 in which needle-like powder having an average aspect ratio of 3.0 is mixed with needle-like powder having an average aspect ratio of 3.0 are shown. Furthermore, the results of Comparative Examples 3 to 8 using only one kind of acicular powder are shown.

From Table 3 and Table 4, in Examples 2 to 12 in which the frequency distribution of the aspect ratio is the predetermined frequency distribution and the average minor axis length is also within the predetermined range, the frequency distribution of the aspect ratio has the second peak. The relative magnetic permeability μr was improved as compared with Comparative Examples 3 to 8 which were not provided.

Furthermore, even if it had the second peak, Comparative Example 9 in which the aspect ratio of the second peak was larger than 10.0 did not improve the relative magnetic permeability μr as compared with Comparative Example 3.

In Tables 5 and 6, in the case where the needle-shaped powder is an alloy of iron and cobalt, the needle-shaped powder having an average aspect ratio of 4.1 is the needle-shaped powder having an average aspect ratio of 5.1 to 9.9. The results of mixed Examples 13 to 15 are shown. Further, the results of Comparative Example 11 in which the needle-shaped powder having the average aspect ratio of 4.1 and the needle-shaped powder having the average aspect ratio of 12.2 are mixed are shown. Furthermore, the results of Comparative Examples 4 to 8 using only one kind of acicular powder are shown.

From Table 5 and Table 6, in Examples 13 to 15 in which the frequency distribution of the aspect ratio is the predetermined frequency distribution and the average minor axis length is also within the predetermined range, the frequency distribution of the aspect ratio has the second peak. The relative magnetic permeability μr was improved as compared with Comparative Examples 4 to 8 which were not provided.

Furthermore, even if it had the second peak, in Comparative Example 11 in which the aspect ratio of the second peak was larger than 10.0, the relative magnetic permeability μr was not improved as compared with Comparative Example 4.

In Tables 7 and 8, when the needle-shaped powder is an alloy of iron and cobalt, needle-shaped powder having an average aspect ratio of 7.3 was mixed with needle-shaped powder having an average aspect ratio of 9.9. The results of Example 16 are shown. Further, the results of Comparative Example 12 in which the needle-shaped powder having the average aspect ratio of 7.3 and the needle-shaped powder having the average aspect ratio of 12.2 are mixed are shown. Further, the results of Comparative Examples 6 to 8 using only one kind of acicular powder are shown.

From Table 7 and Table 8, in Example 16 in which the frequency distribution of the aspect ratio is the predetermined frequency distribution and the average minor axis length is also within the predetermined range, the frequency distribution of the aspect ratio does not have the second peak. The relative permeability μr was improved as compared with Examples 6 to 8.

Further, even if it had the second peak, Comparative Example 12 in which the aspect ratio of the second peak was larger than 10.0 did not improve the relative magnetic permeability μr as compared with Comparative Example 6.

In Table 9 and Table 10, Example 17 and Comparative Examples 13 and 14 using needle-shaped powders having a longer average minor axis length than the needle-shaped powders described in Tables 1 to 8 are shown.

From Table 9 and Table 10, in Example 17 in which the frequency distribution of the aspect ratio is the predetermined frequency distribution and the average minor axis length is also within the predetermined range, the frequency distribution of the aspect ratio does not have the second peak. Compared to Examples 13 and 14, the relative magnetic permeability μr was improved.

Tables 11 and 12 show Comparative Examples 15 to 17 using needle-shaped powders having a longer average short axis length than the needle-shaped powders shown in Tables 9 and 10.

From Table 11 and Table 12, Comparative Examples 15 to 17 in which the average minor axis length was too long resulted in too large magnetic loss tan δ regardless of the frequency distribution of the aspect ratio.

1... Needle-like powder 1a... (Occlusion with needle-like powder) Ellipse

Claims (3)

A composite magnetic material containing acicular powder and resin,
The needle-shaped powder contains Fe or Fe and Co as a main component,
The average minor axis length of the primary particles of the acicular powder is 100 nm or less,
In the frequency distribution of the aspect ratio in the primary particles of the acicular powder, the aspect ratio of the first peak having the highest frequency and the aspect ratio of the second peak having the second highest frequency are within a range of 3.0 or more and 10 or less, respectively. Yes,
The smaller one of (aspect ratio of first peak)/(aspect ratio of second peak) and (aspect ratio of second peak)/(aspect ratio of first peak) is 0.30 or more and 0.80 or less. A composite magnetic material characterized in that The composite magnetic material according to claim 1, wherein in the acicular powder, the content ratio of Co with respect to the main component is 0 to 40 atom% (not including 0 atom %). A magnetic core comprising the composite magnetic material according to claim 1.

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