阅读说明：本技术 软磁性材料及其制造方法 (Soft magnetic material and method for producing same ) 是由 逸见和宏 高桥亨 吉年规治 牧野彰宏 于 2016-07-27 设计创作，主要内容包括：本公开中涉及的软磁性粉末包含具有多个纳米尺寸的微晶和存在于微晶周围的非晶相的粒子,其中,微晶的平均粒径为30nm以下,非晶相的平均厚度为30nm以下,粒子的截面的短径为r时,在距粒子的表面的深度为0.2r～0.4r的区域,非晶相中的平均Fe浓度低于微晶中的平均Fe浓度。(The soft magnetic powder according to the present disclosure includes particles having a plurality of nano-sized crystallites and an amorphous phase present around the crystallites, wherein when an average particle diameter of the crystallites is 30nm or less, an average thickness of the amorphous phase is 30nm or less, and a short diameter of a cross section of the particles is r, an average Fe concentration in the amorphous phase is lower than an average Fe concentration in the crystallites in a region having a depth of 0.2r to 0.4r from a surface of the particles.)

1. A soft magnetic powder comprising particles having a plurality of crystallites and an amorphous phase present around the crystallites,

wherein the average particle diameter of the fine crystals is 15 to 30nm and the average thickness of the amorphous phase is 3 to 30nm in a region having a depth of 0.2 to 0.4r from the surface of the particle, where r is the minor axis of the cross section of the particle,

wherein when the short diameter of the cross section of the particle is r, the average Fe concentration in the amorphous phase is lower than the average Fe concentration in the microcrystal in the region having a depth of 0.2r to 0.4r from the surface of the particle,

the crystallinity measured by powder X-ray diffraction method is 30% or more.

2. Soft magnetic powder according to claim 1, wherein the amorphous phase has an average thickness of 6 to 30 nm.

3. Soft magnetic powder according to claim 1 or 2, wherein the ratio of the average Fe concentration in the amorphous phase to the average Fe concentration in the crystallites is 0.90 or less in a region having a depth of 0.2r to 0.4r from the surface of the particle.

4. Soft magnetic powder according to claim 1 or 2, wherein the crystallinity as measured by powder X-ray diffraction method is 78% or more.

5. Soft magnetic powder according to claim 1 or 2, wherein the soft magnetic powder comprises a crystalline phase mainly having a body-centered cubic structure.

6. Soft magnetic powder according to claim 1 or 2, wherein,

the average Fe concentration in the microcrystals is 82 at.% to 98 at.%,

the average Fe concentration in the amorphous phase is 69 at.% to 79 at.%.

7. A magnetic core comprising a composite material comprising the soft magnetic powder according to claim 1 or 2 and a resin.

8. The magnetic core according to claim 7, wherein the content of the soft magnetic powder in the composite material is 60 vol% to 90 vol%.

9. A method for manufacturing a magnetic core includes the steps of:

a step of mixing the soft magnetic powder according to claim 1 or 2 with a resin and molding the obtained mixture to obtain a molded article, and

and heating the molded article.

10. A coil component comprising the magnetic core according to claim 7 and a coil conductor wound around the magnetic core.

11. A coil component comprising a magnetic body portion and a coil conductor embedded in the magnetic body portion, wherein the magnetic body portion contains a composite material containing the soft magnetic powder according to claim 1 or 2 and a resin as a main component.

12. The coil component according to claim 11, wherein a content of the soft magnetic powder in the composite material is 60 vol% to 90 vol%.

Technical Field

The present invention relates to a soft magnetic material and a method for producing the same.

Background

Soft magnetic powder having an amorphous structure is widely used for applications such as a magnetic core (core) material for coil components used in electronic devices. As a method for producing a soft magnetic powder, for example, a method for producing an Fe-based soft magnetic alloy is known (patent document 1) which is characterized by forming a thin ribbon-like or powder-like quenched body having an amorphous phase as a main phase by quenching an alloy melt, and crystallizing the quenched body by heat treatment to precipitate crystal grains having an average crystal grain size of at most 50nm and containing bcc-Fe, thereby forming a fine crystal structure, wherein the quenched body is subjected to heat treatment at least 2 times or more to a temperature higher than a crystallization starting temperature and at which a compound phase is not substantially formed. In the method described in patent document 1, when a microcrystalline alloy (nanocrystalline alloy) is produced, the influence of self-heating is reduced by optimizing the conditions of heat treatment at the time of microcrystalline precipitation, and thus a soft magnetic alloy having excellent soft magnetic properties, low loss, and low coercive force is provided.

Disclosure of Invention

When the heat treatment is performed to precipitate the fine crystals as described above, the alloy material itself generates heat, and thus the temperature control during the heat treatment is difficult. If the temperature during the heat treatment is too high due to self-heating, the size of the crystallites (nanocrystals) increases, and as a result, the magnetic properties tend to deteriorate. On the other hand, if the temperature at the time of heat treatment is too low, nanocrystals cannot be formed. According to the studies of the present inventors, it has been found that the influence of self-heating cannot be sufficiently eliminated by the heat treatment conditions described in patent document 1, and it is difficult to form small-sized nanocrystals at high density.

The invention aims to provide a soft magnetic powder having excellent soft magnetic characteristics, in which small-sized nanocrystals are formed at high density, and a method for producing the same.

As a result of intensive studies, the present inventors have found that small-sized nanocrystals can be formed at high density and soft magnetic powder having excellent soft magnetic properties can be obtained by subjecting alloy powder obtained by cooling a molten mother alloy to at least 2 heat treatments and setting the maximum temperature in the 1 st heat treatment and the maximum temperature in the 2 nd heat treatment to appropriate values, and have completed the present invention.

According to the 1 st gist of the present invention, there is provided a soft magnetic powder comprising particles having a plurality of microcrystals and an amorphous phase present around the microcrystals,

the average grain diameter of the crystallites is 30nm or less, the average thickness of the amorphous phase is 30nm or less,

when the minor axis of the cross section of the particle is r, the average Fe concentration in the amorphous phase is lower than the average Fe concentration in the crystallites in a region having a depth of 0.2r to 0.4r from the surface of the particle.

According to the second aspect of the present invention, there is provided a method for producing a soft magnetic powder, comprising the steps of:

a step of cooling the molten master alloy to obtain an alloy powder mainly composed of an amorphous phase;

a step of performing a 1 st heat treatment on the alloy powder; and

a step of performing a 2 nd heat treatment on the alloy powder subjected to the 1 st heat treatment to obtain a soft magnetic powder,

wherein the maximum temperature T1 in the 1 st heat treatment is a temperature at which the Avrami constant is 1.7 or more, the maximum temperature T2 in the 2 nd heat treatment is a temperature lower than T1,

the crystallinity measured by powder X-ray diffraction method is 20% or less in the alloy powder after the 1 st heat treatment and more than 20% in the soft magnetic powder after the 2 nd heat treatment.

According to the 3 rd aspect of the present invention, there is provided a magnetic core formed of a composite material containing the soft magnetic powder and a resin.

According to the 4 th aspect of the present invention, there is provided a method for manufacturing a magnetic core, including the steps of:

a step of mixing the soft magnetic powder and the resin, and molding the obtained mixture to obtain a molded body; and

and a step of heating the molded body.

According to the 5 th aspect of the present invention, there is provided a coil component including the above-described magnetic core and a coil conductor wound around the magnetic core.

According to the gist of the 6 th aspect of the present invention, there is provided a coil component including a magnetic body portion containing a composite material containing the soft magnetic powder and the resin as a main component, and a coil conductor embedded in the magnetic body portion.

The soft magnetic powder of the present invention has excellent soft magnetic characteristics by having the above-described constitution. In addition, the method for producing a soft magnetic powder of the present invention can produce a soft magnetic powder in which small-sized nanocrystals are formed at a high density, and can obtain a soft magnetic powder having excellent soft magnetic characteristics. By using the soft magnetic powder of the present invention as a core material, a coil component having excellent magnetic characteristics can be obtained.

Drawings

Fig. 1 is a diagram schematically showing crystallites and an amorphous phase in a soft magnetic powder according to an embodiment of the present invention.

Fig. 2 is a diagram illustrating an analysis method of an X-ray diffraction pattern.

Detailed Description

Hereinafter, embodiments of the present invention will be described. However, the embodiments described below are for illustrative purposes, and the present invention is not limited to the embodiments described below.

A soft magnetic powder according to an embodiment of the present invention includes particles having a plurality of crystallites and an amorphous phase present around the crystallites. Fig. 1 shows a schematic view of a microcrystalline and amorphous phase contained in a soft magnetic powder. The average particle size of the fine crystals contained in the soft magnetic powder of the present embodiment is 30nm or less. The average particle diameter of the fine crystal may be 2nm or more.

Specifically, the average particle size of the fine crystals can be determined from a Transmission Electron Microscope (TEM) photograph, and can be calculated by measuring the major diameter D L and the minor diameter DS of n (n.gtoreq.5) fine crystals arbitrarily selected in a region having a depth of 0.2r to 0.4r from the surface of the particles, with the minor diameter r being the minor diameter of the cross section of the particles contained in the soft magnetic powder in the TEM photograph of the soft magnetic powder, using the following formula (2).

D＝Σ(DL+DS)/2n (2)

(D: average crystallite diameter)

On the other hand, the average thickness of the amorphous phase contained in the soft magnetic powder of the present embodiment is 30nm or less. The amorphous phase may have an average thickness of 1nm or more. In the present specification, "the thickness of an amorphous phase" means the thickness of an amorphous phase existing between adjacent microcrystals. The average thickness of the amorphous phase can be found from the TEM photograph. Specifically, in a TEM photograph of a soft magnetic powder, the length of a line segment connecting the boundary between a crystalline phase of one crystallite and a peripheral amorphous phase and the boundary between a crystalline phase of a crystallite adjacent to the one crystallite and the peripheral amorphous phase at the shortest distance is measured for n (n.gtoreq.5) crystallites arbitrarily selected in a region having a depth of 0.2r to 0.4r from the surface of the particle, assuming that the minor axis of the cross section of the particle contained in the soft magnetic powder is r. The average value of the lengths of the line segments was taken as the average thickness of the amorphous phase.

When the average particle size of the fine crystals and the average thickness of the amorphous phase contained in the soft magnetic powder are within the above ranges, the soft magnetic powder of the present embodiment contains nano-sized fine crystals at a high density, and thus has high soft magnetic characteristics. Therefore, when the soft magnetic powder of the present embodiment is used as a core material, a coil component having high magnetic characteristics can be obtained. Specifically, the core loss can be reduced, and high magnetic permeability and high saturation magnetic flux density can be achieved.

When the short diameter of the cross section of the particle contained in the soft magnetic powder of the present embodiment is r, the average Fe concentration in the amorphous phase is lower than the average Fe concentration in the microcrystal in the region having a depth of 0.2r to 0.4r from the surface of the particle. The average Fe concentration in the amorphous phase and the crystallites can be determined by combining TEM measurement and energy dispersive X-ray analysis (EDS). Specifically, in a TEM photograph of a soft magnetic powder, assuming that the short diameter of the cross section of a particle contained in the soft magnetic powder is r, for n (n.gtoreq.5) crystallites arbitrarily selected in a region having a depth of 0.2r to 0.4r from the surface of the particle, the Fe concentration at the center of the crystallite is determined by EDS measurement, and the average value thereof is defined as the average Fe concentration in the crystallite. The Fe concentration at the midpoint of a line segment connecting the boundary between the crystalline phase of the above-mentioned crystallite and the peripheral amorphous phase and the boundary between the crystalline phase of the crystallite adjacent to the crystallite and the peripheral amorphous phase at the shortest distance is obtained by EDS measurement, and the average value thereof is defined as the average Fe concentration in the amorphous phase.

In a region having a depth of 0.2r to 0.4r from the surface of the particles contained in the soft magnetic powder, the ratio of the average Fe concentration in the amorphous phase to the average Fe concentration in the crystallites is preferably 0.90 or less. If the ratio of the average Fe concentration is 0.90 or less, the Fe concentration in the fine crystal increases, and as a result, the saturation magnetic flux density increases.

The higher the crystallinity of the soft magnetic powder, the more improved the soft magnetic characteristics, and thus is preferable. The crystallinity of the soft magnetic powder is preferably greater than 20%, more preferably 30% or more. If the crystallinity of the soft magnetic powder is 30% or more, the soft magnetic properties can be further improved. The crystallinity of the soft magnetic powder can be measured by a powder X-ray diffraction method in accordance with the method described below. Fig. 2 is a schematic diagram illustrating a method of analyzing an X-ray diffraction pattern. In fig. 2, a crystal peak indicating a body-centered cubic structure is denoted by P, a crystal peak indicating a low symmetry (lowy symmetry) crystal structure is denoted by P2, and a halo (halo) region indicating amorphousness is denoted by H. The crystallinity can be calculated based on the X-ray diffraction spectrum of the soft magnetic powder by using the following formula (3).

X＝{Ic/(Ic+Ic’+Ia)}×100 (3)

(X: crystallinity, Ic: area of crystal peak region of body-centered cubic structure, Ic': area of crystal peak region of low symmetry (lowy symmetry) crystal structure, Ia: area of amorphous halo region)

The crystal peak P indicating the body-centered cubic structure is a peak having a diffraction angle 2 θ from the 110 plane of Fe in the range of 44.5 ° to 45.5 °.

The soft magnetic powder preferably contains a crystal phase mainly having a body-centered cubic structure. The soft magnetic properties are further improved if the crystalline phase has predominantly a body-centered cubic structure. Whether or not the crystal phase mainly has a body-centered cubic structure can be evaluated by a powder X-ray diffraction method. In the X-ray diffraction spectrum, the peak area ratio Y of a crystal peak indicating a crystal structure with low symmetry can be represented by the following formula (4).

Y＝{Ic’/(Ic+Ic’+Ia)}×100 (4)

When the value of Y is 1 or less, the crystal phase is considered to have mainly a body-centered cubic structure.

In one example, the particles contained in the soft magnetic powder preferably contain Fe of the general formula_aSi_bB_cP_dCu_eM_fC_gCr_hThe alloy composition shown. Wherein a, b, c, d, e, f, g and h respectively satisfy 71.0 ≦ (a + f + g + h) 81.0, 0.14 ≦ b/c 5, 0 ≦ d ≦ 14, 0 ≦ e ≦ 1.4, d ≦ 0.8(a + f + g + h) -50, e ≦ -0.1(a + d + f + g + h) +10, 0 ≦ f ≦ 12, 0 ≦ g ≦ 8, 0 ≦ h ≦ 10, and a + b + c + d + e + f + g + h 100, and M is at least 1 element of Ni and Co. When the particles contained in the soft magnetic powder contain the alloy composition having the above composition, an amorphous phase can be stably formed, and the soft magnetic characteristics are further improved.

In the above alloy composition, it is preferable that a part of Fe is substituted by at least 1 element of Ni and Co (i.e., 0 < f.ltoreq.12 in the above general formula). By replacing a part of Fe with Ni and/or Co, the magnetic properties can be further improved.

In the alloy composition, it is preferable that a part of Fe is substituted by C (that is, 0 < g.ltoreq.8 in the above formula). By replacing a part of Fe with C, an amorphous phase is easily formed. Further, since the same magnetic properties can be obtained even when a part of Fe is replaced with C, the raw material cost can be reduced by replacing a part of Fe with inexpensive C.

In the alloy composition, it is preferable that a part of Fe is replaced by Cr (that is, 0 < h.ltoreq.10 in the above formula). Cr tends to be more easily oxidized than Fe. Therefore, in the case where a part of Fe is replaced with Cr, Cr is preferentially oxidized, so that oxidation of Fe can be suppressed, thereby suppressing deterioration of magnetic properties.

In another example, the particles contained in the soft magnetic powder preferably contain Fe of the general formula_a’Si_b’B_c’P_d’Cu_e’M’_f’The alloy composition shown. Wherein a ', b', c ', d', e 'and f' respectively satisfy 81 ≦ (a '+ f') 86, 2 ≦ b '8, 6 ≦ c' 10, 2 ≦ d '5, 0.4 ≦ e' 1.4, 0.08 ≦ e '/d' 0.8, and 0 ≦ f '3, and M' is at least 1 element of Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Co, Ni, Al, Mn, Ag, Zn, Sn, As, Sb, Bi, Y, N, O, and rare earth elements. When the particles contained in the soft magnetic powder contain the alloy composition having the above composition, an amorphous phase can be stably formed, and the soft magnetic characteristics are further improved.

Next, a method for producing a soft magnetic powder according to an embodiment of the present invention will be described. The method for producing a soft magnetic powder according to the present embodiment includes the steps of: a step of cooling the molten master alloy to obtain an alloy powder mainly composed of an amorphous phase; a step of performing a 1 st heat treatment on the alloy powder; and a step of performing a 2 nd heat treatment on the alloy powder subjected to the 1 st heat treatment to obtain a soft magnetic powder. Hereinafter, each step will be described in detail.

First, a molten mother alloy is cooled to obtain an alloy powder mainly composed of an amorphous phase. The master alloy can be prepared by weighing raw materials of Fe, Si, Fe-B alloy, Fe-P alloy, Cu, Ni, Co, C, Cr, etc. to have a predetermined alloy composition, heating to a melting point or higher to melt the raw materials, and then cooling the melt. In one example, the master alloy preferably has the general formula Fe_aSi_bB_cP_dCu_eM_fC_gCr_hComposition of the representation. Wherein a, b, c, d, e, f, g and h respectively satisfy 71.0 ≦ (a + f + g + h) 81.0, 0.14 ≦ b/c 5, 0 ≦ d ≦ 14, 0 ≦ e ≦ 1.4, d ≦ 0.8(a + f + g + h) -50, e ≦ -0.1(a + d + f + g + h) +10, 0 ≦ f ≦ 12, 0 ≦ g ≦ 8, 0 ≦ h ≦ 10, and a + b + c + d + e + f + g + h 100, and M is at least 1 element of Ni and Co. By having the above composition, the master alloy can stably form an amorphous phase, and a soft magnetic powder having higher soft magnetic characteristics can be obtained. The master alloy having the above composition is suitable for use in the case where a melt of the master alloy is pulverized by a high-pressure gas stream in the production of an alloy powder described later.

In another example, the master alloy preferably has the general formula Fe_a’Si_b’B_c’P_d’Cu_e’M’_f’Composition of the representation. Wherein a ', b', c ', d', e 'and f' respectively satisfy 81 ≦ (a '+ f') or less 86, 2 ≦ b 'or less 8, 6 ≦ c' or less 10, 2 ≦ d 'or less 5, 0.4 ≦ e' or less 1.4, 0.08 ≦ e '/d' or less 0.8, and 0 ≦ f 'or less 3, and M' is at least 1 element of Ti, Zr, Hf, Nb, Ta, Mo, W, Cr, Co, Ni, Al, Mn, Ag, Zn, Sn, As, Sb, Bi, Y, N, O, and rare earth elements. By having the above composition, the master alloy can stably form an amorphous phase, and a soft magnetic powder having higher soft magnetic characteristics can be obtained. The master alloy having the above composition is suitable for use in the case where a melt of the master alloy is pulverized by a high-pressure water stream or the case where a melt of the master alloy is pulverized by a high-pressure water stream and cooled by water in the production of alloy powder described later.

The molten master alloy is cooled to obtain an alloy powder mainly composed of an amorphous phase. The alloy powder can be produced, for example, by pulverizing a melt of the master alloy with a high-pressure water stream or a high-pressure gas stream and cooling the pulverized product. That is, the alloy powder can be formed by blowing high-pressure water or high-pressure gas to the melt of the master alloy. The high-pressure gas is a gas having a pressure of 1MPa to 10 MPa. Specifically, the powder is pulverized to a size of about 3cm to facilitate melting of the master alloy, and then put into a crucible of an atomizing device such as a gas atomizing device, and high-frequency induction heating is performed to melt the master alloy to obtain a melt. The inside of the atomizing device is preferably set to an inert atmosphere such as an argon atmosphere. Next, a jet fluid (i.e., a high-pressure water stream or a high-pressure gas stream) is jetted to the melt to pulverize the melt, and the melt is cooled (quenched), thereby obtaining an alloy powder mainly composed of an amorphous phase. As the ejection fluid, for example, argon gas, nitrogen gas, or the like can be used. The cooling may be performed using a cooling medium such as water or gas. It is preferable to use a gas (for example, an inert gas such as argon or nitrogen) as the cooling medium.

Next, the alloy powder is subjected to the 1 st heat treatment. The 1 st heat treatment may be performed using a heating device such as an infrared heating device. The atmosphere in the heating device is preferably an inert gas atmosphere such as helium. As another method, the atmosphere in the heating apparatus may be a mixed gas atmosphere in which hydrogen gas is added to helium gas. By adding hydrogen gas, the metal element can be suppressed from being oxidized at the time of heat treatment. Hydrogen gas may be added in an amount of about 3% in terms of partial pressure.

By heat-treating the alloy powder mainly composed of an amorphous phase, microcrystals are formed in the alloy powder. If the size of the crystallite is too large, the magnetic properties are degraded. Therefore, it is preferable to form nano-sized fine crystallites with high density. In order to form nano-sized fine crystallites at high density, it is necessary to appropriately control the heat treatment temperature. However, since the alloy powder itself generates heat during heat treatment, it is difficult to control the heat treatment temperature. If the heat treatment temperature is too high due to self-heating, the size of the fine crystal increases and the magnetic properties deteriorate. On the other hand, if the heat treatment temperature is lowered, microcrystals cannot be formed. The present inventors have found that nano-sized fine crystallites can be formed at high density by setting the maximum temperature T1 in the 1 st heat treatment to a temperature at which the aversion constant is 1.7 or more and setting the maximum temperature T in the 2 nd heat treatment, which will be described later, to a temperature lower than T1. The Abirami constant is a parameter indicating the form of crystallization. The smaller the Abrah constant, the more difficult the crystallization proceeds, and the larger the Abrah constant, the more easy the crystallization proceeds. When the crystallinity is the same value, the larger the Abbe's number, the more densely the fine crystallites can be formed. The efrah constant of the alloy powder can be determined by Differential Scanning Calorimetry (DSC) in the following order. Isothermal DSC measurement of the alloy powder was performed 2 times in an argon atmosphere using a differential scanning calorimeter (temperature increase rate 400 ℃/min, isothermal holding measurement time 60 min). Since the alloy powder was completely crystallized in the 1 st measurement, no exothermic reaction due to self-heating occurred in the 2 nd measurement. The amount of heat generated by the alloy powder sample was calculated from the difference between the DSC curve obtained from the 1 st measurement and the DSC curve obtained from the 2 nd measurement, using the DSC curve obtained from the 2 nd measurement as a background. The cumulative amount of heat generated from the start of isothermal measurement is determined as a function of time t. The total heating value is defined as the cumulative heating value in 60 minutes. The maximum eframy constant at each temperature was calculated from the following equation (5).

N＝d{ln(-ln(1-x))}/d{ln(t-τ)} (5)

(x: crystallization reaction ratio (cumulative calorific value/total calorific value), t: isothermal holding time (sec), τ: incubation time (sec) (time when x is 0.01))

The maximum value of the above-obtained eframy constants was defined as an eframy constant at each temperature.

The maximum temperature T1 in the 1 st heat treatment was set to a temperature at which the alfummer constant was 1.7 or more. By setting the 1 st heat treatment temperature in this way, nano-sized fine crystallites can be formed at high density.

The crystallinity of the alloy powder after the 1 st heat treatment measured by a powder X-ray diffraction method is 20% or less. The self-heating of the alloy powder in the 1 st heat treatment can be suppressed by the low value of the crystallinity after the 1 st heat treatment of 20% or less. The crystallinity can be calculated by the powder X-ray diffraction method using the above formula (3).

The 1 st heat treatment is preferably performed for a time period from a time period in which the crystallization reaction ratio is 0.01 or more to a time period in which the crystallization reaction ratio is 0.4 or less. If the time of the 1 st heat treatment is within the above range, the crystallinity of the alloy powder after the 1 st heat treatment can be easily made an appropriate value.

Next, the alloy powder subjected to the 1 st heat treatment is subjected to the 2 nd heat treatment to obtain a soft magnetic powder. The 2 nd heat treatment may be performed by using a heating device such as an infrared heating device. The 1 st heat treatment and the 2 nd heat treatment may be continuously performed in the same heating apparatus, or may be performed separately using different heating apparatuses. In the 2 nd heat treatment, the atmosphere in the heating apparatus is preferably an inert gas atmosphere such as argon.

In the heat treatment 2, crystallites grow, and a soft magnetic powder having a desired crystallinity can be obtained. In order to suppress self-heating of the alloy powder in the 2 nd heat treatment, the maximum temperature T2 in the 2 nd heat treatment is set to a temperature lower than T1.

The 2 nd heat treatment is preferably performed for a period of 1 minute to 120 minutes, and more preferably for a period of 5 minutes to 60 minutes. When the time of the 2 nd heat treatment is within the above range, a soft magnetic powder in which fine crystallites having a nanometer size are formed at a high density can be obtained, and the soft magnetic properties are further improved.

The crystallinity of the soft magnetic powder after the 2 nd heat treatment as measured by a powder X-ray diffraction method is more than 20%. If the crystallinity of the soft magnetic powder is within the above range, a soft magnetic powder having excellent soft magnetic characteristics can be obtained.

Next, a magnetic core according to an embodiment of the present invention will be described. The magnetic core of the present embodiment is formed of a composite material containing the soft magnetic powder of the present invention and a resin. As the resin, for example, an epoxy resin, a phenol resin, a silicone resin, or the like can be used. The content of the soft magnetic powder in the composite material is preferably 60 vol% to 90 vol%. If the content of the soft magnetic powder is within the above range, a magnetic core having excellent magnetic characteristics is obtained. The size and shape of the magnetic core are not particularly limited, and may be appropriately set according to the intended use. The magnetic core may be, for example, a toroidal core having an outer diameter of 13mm, an inner diameter of 8mm, and a thickness of 2.5 mm.

Next, a method for manufacturing a magnetic core according to an embodiment of the present invention will be described. The method for manufacturing a magnetic core according to the present embodiment includes the steps of: a step of mixing the soft magnetic powder of the present invention with a resin such as an epoxy resin, a phenol resin, or a silicone resin, and molding the obtained mixture to obtain a molded body; and a step of heating the molded article. The molded article can be obtained, for example, by pressure molding a mixture containing a soft magnetic powder and a resin at a pressure of about 100 MPa. The size and shape of the molded body are not particularly limited, and may be appropriately set according to the desired size and shape of the magnetic core. The heating temperature of the molded article can be appropriately set according to the kind of the resin used, and the like.

Next, a coil component according to an embodiment of the present invention will be described. The coil component of the present embodiment includes the magnetic core of the present invention and a coil conductor wound around the magnetic core. The coil conductor may be formed by winding a metal wire such as a copper wire coated with enamel around the magnetic core. The coil component of the present embodiment uses the soft magnetic powder of the present invention as a core material, and therefore has excellent magnetic properties.

Next, a coil component according to another embodiment of the present invention will be described. The coil component of the present embodiment includes a magnetic body portion and a coil conductor embedded in the magnetic body portion, and the magnetic body component includes a composite material containing the soft magnetic powder of the present invention and a resin such as an epoxy resin, a phenol resin, or a silicone resin as a main component. The coil component of the present embodiment uses the soft magnetic powder of the present invention as a core material, and therefore has excellent magnetic properties. The content of the soft magnetic powder in the composite material is preferably 60 vol% to 90 vol%. If the content of the soft magnetic powder is within the above range, the magnetic properties of the coil component can be further improved. The coil component of the present embodiment can be manufactured, for example, in the following procedure. First, a plurality of sheets of composite material are formed. Then, a coil conductor is disposed between the sheets. The coil component is obtained by hot-pressing sheets with the coil conductors disposed therebetween. In addition, a stator core of a motor can be formed using the soft magnetic powder of the present invention. The motor is provided with: the stator includes a coil member having a coil conductor wound around armature teeth, a rotor rotatably disposed inside the coil member, and a stator core having a plurality of armature teeth arranged at equal intervals on the same circumference. Since the soft magnetic powder of the present invention has a high saturation magnetic flux density and low magnetic loss, a high-quality motor with low power loss can be obtained by forming a stator core from the soft magnetic powder of the present invention.