Flattened powder of soft magnetic alloy, compacted powder, and method for producing flattened powder of soft magnetic alloy

Abstract

This invention provides a flattened powder of a soft magnetic alloy with excellent magnetic properties in the high-frequency range. [Solution] The powder contains Si: 6 to 15 atomic percent, B: 6 to 15 atomic percent, Cr: 1 to 5 atomic percent, and optionally one or more elements selected from the group consisting of Co, Ni, Nb, Mo, Cu, Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al, with the remainder being Fe and unavoidable impurities. The content of Co and Ni is 5 atomic percent or less each, the content of Nb, Mo, and Cu is 0.1 atomic percent or less each, the content of Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al is 1 atomic percent or less each, the ratio of powder particle size to powder particle thickness is 30 or more, and Cr microsegregation in the range of formula (1) in the thickness direction from the powder particle surface to 200 nm is within the range of formula (1). 0.1 ≤ σ / C Cr ...(1) σ is the standard deviation in Cr microsegregation measurements, C Cr This refers to the Cr content.

Description

[Technical Field]

[0001] This disclosure relates to flattened powder of a soft magnetic alloy, compacted powder, and a method for producing flattened powder of a soft magnetic alloy. [Background technology]

[0002] Compacted powder made from soft magnetic alloy powder is sometimes used as a magnetic material in inductors and the like. Patent Document 1 discloses a compacted powder made from flattened soft magnetic alloy powder. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-78791 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, the use of power supplies with extremely high switching frequencies of 50 to 150 MHz has been considered. For use in such power supplies, soft magnetic materials with excellent magnetic properties in the high-frequency range are desired.

[0005] The purpose of this disclosure is to provide a flattened powder of a soft magnetic alloy that exhibits excellent magnetic properties in the high-frequency range. [Means for solving the problem]

[0006] A soft magnetic alloy flattened powder according to one embodiment of the present disclosure It contains Si: 6 to 15 atomic percent, B: 6 to 15 atomic percent, and Cr: 1 to 5 atomic percent. It optionally contains one or more elements selected from the group consisting of Co, Ni, Nb, Mo, Cu, Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al. The flattened powder of a soft magnetic alloy, the remainder being Fe and unavoidable impurities, The contents of Co and Ni are each 5 atomic% or less, the contents of Nb, Mo, and Cu are each 0.1 atomic% or less, the contents of Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al are each 1 atomic% or less, the ratio of the powder particle size to the powder particle thickness is 20 or more, a soft magnetic alloy flat powder in which the Cr microsegregation within a range of 200 nm from the powder particle surface along the thickness direction is within the range of formula (1). 0.1 ≦ σ / C [Figure 4] , [Figure 8] , [Figure 7] , [Figure 6] , [Figure 5] , , , , ···(1) where σ is the standard deviation in the Cr microsegregation measurement, and C Cr is the Cr content of the soft magnetic alloy flat powder.

Advantages of the Invention

[0007] According to the present disclosure, it is possible to provide a soft magnetic alloy flat powder having excellent magnetic properties in a high frequency band.

Brief Description of the Drawings

[0008] [Figure 1] It is an X-ray diffraction measurement result of a soft magnetic alloy flat powder according to an embodiment of the present disclosure. [Figure 2] It is a DSC (differential scanning calorimetry) curve of a raw material powder having the composition of the present disclosure. [Figure 3] It is a schematic diagram showing the microstructure of a soft magnetic alloy flat powder according to an embodiment of the present disclosure. [Figure 4] It is a schematic diagram showing the microstructure of a soft magnetic alloy flat powder according to a first comparative form. [Figure 5] It is a schematic diagram showing the microstructure of a soft magnetic alloy flat powder according to a second comparative form. [Figure 6] It is a graph showing the frequency characteristics of a soft magnetic alloy flat powder according to an example. [Figure 7] It is a measurement result of Cr microsegregation measurement of a soft magnetic alloy flat powder according to an example. [Figure 8] It is a measurement result of Cr microsegregation measurement of a soft magnetic alloy flat powder according to a comparative example.

Embodiments for Carrying Out the Invention

[0009] (Soft magnetic alloy flat powder) First, the soft magnetic alloy flat powder according to an embodiment of the present disclosure will be described. The soft magnetic alloy flat powder according to this embodiment is manufactured for the purpose of obtaining a magnetic material having excellent magnetic properties in a high frequency band. More specifically, for the soft magnetic alloy flat powder according to this embodiment, the real component of the complex relative permeability is μ', the imaginary component of the complex relative permeability is μ'', and the ratio of μ' to μ'' (μ' / μ'') is Q. Both μ' and μ'Q (=μ' 2 / μ'') are soft magnetic materials with high values at a frequency of 100 MHz.

[0010] The soft magnetic alloy flat powder according to this embodiment contains Si: 6 atomic % or more and 15 atomic % or less, B: 6 atomic % or more and 15 atomic % or less, Cr: 1 atomic % or more and 5 atomic % or less, and optionally contains one or more elements selected from the group consisting of Co, Ni, Nb, Mo, Cu, Au, Ti, V, Zr, Hf, Ta, W, C, P, Al, and the balance is an alloy powder of Fe and inevitable impurities. That is, the soft magnetic alloy flat powder according to this embodiment is an Fe-based alloy powder having Fe as a main component and containing Si, B, and Cr as essential components.

[0011] The Fe content of the soft magnetic alloy flat powder according to this embodiment may be 60 atomic % or more and 87 atomic % or less, may be 65 atomic % or more and 85 atomic % or less, or may be 70 atomic % or more and 80 atomic % or less. The Si content of the soft magnetic alloy flat powder may be 7 atomic % or more and 14 atomic % or less, may be 8 atomic % or more and 13 atomic % or less, or may be 9 atomic % or more and 12 atomic % or less. The B content of the soft magnetic alloy flat powder may be 7 atomic % or more and 14 atomic % or less, may be 8 atomic % or more and 13 atomic % or less, or may be 9 atomic % or more and 12 atomic % or less. The Cr content of the soft magnetic alloy flat powder may be 1 atomic % or more and 4.5 atomic % or less, may be 1.5 atomic % or more and 4 atomic % or less, or may be 2 atomic % or more and 3.5 atomic % or less.

[0012] The flattened soft magnetic alloy powder according to this embodiment may contain Co or Ni. Co and Ni are elements that exhibit ferromagnetism in their elemental form, similar to Fe, and good magnetic properties can be obtained even when a portion of Fe is replaced with Co or Ni. In this embodiment, the content of Co and Ni is 5 atomic percent or less each. The total content of Co and Ni may be, for example, 8 atomic percent or less, 5 atomic percent or less, or 3 atomic percent or less.

[0013] The flattened soft magnetic alloy powder according to this embodiment may contain Nb, Mo, or Cu. Nb, Mo, and Cu are elements that promote the formation of nanocrystals. As will be described in detail later, in the flattened soft magnetic alloy powder according to this embodiment, nanocrystals have an effect that hinders the improvement of magnetic properties, so it is preferable to reduce the amount of these elements added. Specifically, in this embodiment, the content of Nb, Mo, and Cu is 0.1 atomic% or less each. It is preferable that the flattened soft magnetic alloy powder according to this embodiment is substantially free of Nb, Mo, and Cu. "Substantially free" means that the elements are not intentionally added, and more specifically, that the content of the elements does not exceed the amount that can be tolerated as an unavoidable impurity.

[0014] The soft magnetic alloy flat powder according to this embodiment may contain Au, Ti, V, Zr, Hf, Ta, W, C, P, or Al. These elements may be added to the soft magnetic alloy flat powder for various purposes, and in small amounts, they will not degrade the properties of the soft magnetic alloy flat powder of this embodiment. In this embodiment, the content of Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al is 1 atomic percent or less each. Furthermore, the total content of Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al may be, for example, 8 atomic percent or less, 5 atomic percent or less, 3 atomic percent or less, or 1 atomic percent or less.

[0015] In addition to the elements specifically mentioned above, the flattened powder of the soft magnetic alloy according to this embodiment may contain unavoidable impurities. Unavoidable impurities refer to any element that is not intentionally added. The acceptable amount of unavoidable impurities varies depending on the type of element and should be understood appropriately based on the common technical knowledge in this field.

[0016] The aspect ratio of the flattened soft magnetic alloy powder to the powder particle thickness is 20 or more. An aspect ratio of 20 or more means that the powder is sufficiently flattened. The aspect ratio may be 25 or more, 30 or more, 35 or more, or 40 or more. Increasing the aspect ratio reduces the demagnetizing coefficient of the flattened soft magnetic alloy powder, and increases the real component μ' of the complex relative permeability. There is no particular upper limit, but the aspect ratio may be, for example, 100 or less.

[0017] The powder particle thickness of soft magnetic alloy flattened powder refers to the length of the particle along its short axis. Specifically, a compact containing soft magnetic alloy flattened powder (described later) is prepared, embedded in resin, and the resulting cross-section is observed using a scanning electron microscope (SEM). The length of the particle along its short axis is then calculated as the powder particle thickness. This process is repeated for multiple powder particles (e.g., 10 to 60 particles) to calculate the powder particle thickness, and the average value is taken as the powder particle thickness of the flattened powder.

[0018] The particle size of flattened powder refers to the length of the particles along their long axis. The particle size can be measured, for example, using a method similar to that used to measure the powder particle thickness described above.

[0019] In the flattened soft magnetic alloy powder according to this embodiment, Cr segregation occurs at least on the surface of the powder particles. Specifically, Cr microsegregation in the range of 200 nm from the surface of the powder particles along the thickness direction is within the range of equation (1). 0.1 ≤ σ / C Cr ...(1) Here, σ is the standard deviation (unit: atomic %) in Cr microsegregation measurements, and C Cr This represents the Cr content (unit: atomic %) of the flattened powder of the soft magnetic alloy.

[0020] Details of the Cr microsegregation measurement are described below. The Cr microsegregation measurement in this disclosure is performed using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray analyzer (EDX). Specifically, a thin section sample including a cross-section of a flattened powder particle is prepared, and line analysis is performed at a predetermined pitch (e.g., 5 nm) from the powder particle surface along the direction perpendicular to the surface up to 200 nm to obtain a profile of the Cr composition (atomic %). The standard deviation σ of the Cr composition is obtained from the Cr composition at each measurement point. The standard deviation σ may be the average value of the standard deviations of the Cr composition obtained from line analysis at multiple locations (e.g., three or more locations). In cases where the powder particle thickness is less than 200 nm, the above parameters may be calculated using the results of line analysis performed within the measurable range, but even in that case, a range of at least 100 nm or more should be measured.

[0021] σ / C Cr A value of 0.1 or higher indicates that Cr segregation is occurring in the flattened powder of the soft magnetic alloy. As will be explained in detail later, Cr segregation improves the μ'Q of the flattened powder of the soft magnetic alloy. σ / C Cr The value of may be 0.3 or greater, or 0.5 or greater. There is no particular upper limit, but σ / C Cr For example, it may be 2 or less.

[0022] The powder particle thickness of the soft magnetic alloy flattened powder according to this embodiment may be, for example, 0.1 μm or more and 5 μm or less. A powder particle thickness within this range makes it easier to achieve a high aspect ratio. The powder particle size of the soft magnetic alloy flattened powder may be, for example, 10 μm or more and 100 μm or less.

[0023] The average crystal grain size of the flattened soft magnetic alloy powder according to this embodiment may be 5 nm or more and 100 nm or less.

[0024] The crystals of the flattened soft magnetic alloy powder according to this embodiment include at least a bcc phase of Fe and a compound phase. Figure 1 shows the results of X-ray diffraction (XRD) measurement of the flattened soft magnetic alloy powder according to this embodiment. In the X-ray diffraction peaks, the ratio of the peak intensity I2 of the compound phase to the peak intensity I1 of the bcc phase of Fe (I2 / I1) may be 0.02 or more and 0.15 or less. Here, the peak intensity I1 of the bcc phase is the intensity of the peak appearing at 2θ = 44.8° ± 0.2° in powder X-ray diffraction measurement using CuKα rays (λ = 0.15418 nm) as the X-ray source, and the peak intensity I2 of the compound phase is the intensity of the peak appearing at 2θ = 43.1° ± 0.2° in the same measurement. In this disclosure, the peak intensity is based on the height from the baseline, not the peak area.

[0025] (Method for manufacturing flattened powder of soft magnetic alloy) Next, a method for producing flattened soft magnetic alloy powder according to this embodiment will be described. First, a raw material powder having the desired composition is prepared. The raw material powder is amorphous and is produced, for example, by atomization. Next, the raw material powder is flattened using a flattening device such as a bead mill and processed into a shape in which the ratio of powder particle size to powder particle thickness (aspect ratio) is 20 or more. The aspect ratio of the raw material powder can be adjusted as appropriate, for example, by changing the flattening treatment time.

[0026] Next, the flattened raw material powder is heat-treated to crystallize it. By heat-treating the amorphous raw material powder, crystals containing the Fe bcc phase and a compound phase are formed. The heat treatment temperature is adjusted according to the crystal precipitation temperature. Figure 2 is a DSC (Differential Scanning Calorimetry) curve of an example of a raw material powder having the composition of this disclosure. In Figure 2, the horizontal axis represents the heat treatment temperature, the vertical axis represents the heat flow, and the upward-pointing peak represents exothermic reaction. As shown in Figure 2, two peaks, P1 and P2, are typically observed in the DSC curve of a raw material powder having the composition of this disclosure. Of the two peaks, peak P1 at a lower crystallization temperature Tx1 corresponds to the precipitation of the bcc phase due to the crystallization of Fe, and peak P2 at a higher crystallization temperature Tx2 corresponds to the precipitation of the compound phase due to the crystallization of elements other than Fe. In this disclosure, the crystallization temperatures Tx1 and Tx2 are the temperatures at the intersection of the baseline in the DSC curve and the tangent line passing through the inflection point on the low-temperature side of the corresponding peak. If multiple peaks are superimposed as shown in Figure 2, the crystallization temperature is calculated for each peak after peak separation. In this embodiment, heat treatment is performed under conditions that cause precipitation of the compound phase in order to improve the magnetic properties. Specifically, the raw material powder is heat-treated at a temperature of Tx2-100°C or higher and Tx2+150°C or lower, with the compound precipitation temperature Tx2 as the reference. If the heat treatment temperature is Tx2-100°C or higher, precipitation of the compound phase occurs, reducing μ'' and improving μ'Q. If the heat treatment temperature is Tx2+150°C or lower, the rise of μ'' in the frequency characteristics can be kept sufficiently on the high-frequency side, thus avoiding an increase in μ'' and the resulting decrease in μ'Q. Specifically, the heat treatment temperature may be 500°C or higher and 700°C or 550°C or higher and 650°C or lower.

[0027] The heat treatment time is not particularly limited and can be, for example, between 1 hour and 12 hours. The heat treatment atmosphere is preferably an inert atmosphere such as a nitrogen atmosphere.

[0028] The order of flattening and heat treatment described above can be reversed. That is, the raw material powder may be heat-treated to crystallize it, and then flattened using a bead mill or the like.

[0029] (Magnetic properties of flattened powder of soft magnetic alloy) The flattened soft magnetic alloy powder according to this embodiment can achieve both high μ' and μ'Q. Specifically, it can achieve excellent magnetic properties such as μ'≧18 and μ'Q≧400, preferably μ'≧20 and μ'Q≧400, at a frequency of 100MHz. The main reason for obtaining such excellent frequency characteristics is that the flattened soft magnetic alloy powder according to this embodiment contains Cr. The reason why excellent magnetic properties can be obtained by adding Cr will be explained below, along with the expected mechanism.

[0030] Figures 3 to 5 schematically show the assumed microstructures 1, 1A, and 1B of the soft magnetic alloy flattened powder, respectively. Figure 3 shows the soft magnetic alloy flattened powder according to this embodiment, Figure 4 shows the soft magnetic alloy flattened powder according to the first comparative form, and Figure 5 shows the soft magnetic alloy flattened powder according to the second comparative form. This embodiment, the first comparative form, and the second comparative form each have different compositions. This embodiment has the composition described above, including Fe, Si, B, and Cr. The first comparative form has a composition that does not include Cr. The second comparative form has a composition in which the content of Nb, Mo, or Cu is greater than 0.1 atomic percent.

[0031] A common feature of each form is that each flattened soft magnetic alloy powder is manufactured by heat treatment at around the crystallization temperature Tx2 of the compound phase, resulting in numerous crystal grains 2 precipitated in the compound phase, as shown in Figures 3 to 5. In the microstructure, there are magnetic domains, which are regions where the direction of magnetization is aligned, and domain walls 3, which are the boundaries between adjacent magnetic domains. Typically, one domain wall 3 is formed for each crystal grain 2, and the domain wall 3 is pinned to the crystal grain boundary 21. When the external magnetic field changes, the pinned domain wall 3 moves within the domain wall movement range 31, indicated by the dashed line, thereby changing the direction and magnitude of magnetization. Each form shown in Figures 3 to 5 exhibits different behavior of the domain walls 3 due to differences in composition, and therefore shows different magnetic properties. Note that in each figure, only the domain wall 3 of one crystal grain 2 is depicted, and the domain walls 3 of other crystal grains 2 are omitted. Note that while Figures 3 to 5 only depict the crystal grains 2 of the compound phase for explanatory purposes, the actual microstructure may also include crystal grains of the Fe bcc phase.

[0032] The details of the microstructure of each form will now be explained. As mentioned above, in the microstructure 1 of this embodiment shown in Figure 3, segregation of Cr occurs. The segregated Cr (reference numeral 4) is thought to exist in such a way as to divide the crystal grains 2 of the compound phase, as shown in Figure 3. In the microstructure 1 of Figure 3, where the crystal grains 2 are divided by the segregated Cr4, magnetic domain walls 3 are formed in each region surrounded by the segregated Cr4 and the crystal grain boundaries 21. That is, by dividing the crystal grains 2 with segregated Cr4, multiple magnetic domain walls 3 are formed within a single crystal grain 2, and the magnetic domains are subdivided. For example, as shown in Figure 3, four magnetic domains can be formed within a single crystal grain 2: the first magnetic domain 61, the second magnetic domain 62, the third magnetic domain 63, and the fourth magnetic domain 64.

[0033] On the other hand, the first comparative form shown in Figure 4 does not contain Cr, so in its microstructure 1A, fragmentation of the compound phase crystal grains 2 does not occur, and one magnetic domain wall 3 is formed for each crystal grain 2, resulting in the formation of two magnetic domains, the first magnetic domain 61 and the second magnetic domain 62. As can be seen from the comparison between Figure 3 and Figure 4, in this embodiment shown in Figure 3, segregation of Cr occurs, and it can be considered that the crystal grain size is smaller compared to the first comparative form in Figure 4.

[0034] Here, Snoek's formula regarding the movement of magnetic walls pinned at grain boundaries is as shown in the following formula (2). [Number] In the above formula, μ' is the relative permeability, f r is the magnetic resonance frequency, D m is the average crystal grain size, M s is the saturation magnetization. According to the above Snoek's formula, when the saturation magnetization is the same, the smaller the average crystal grain size D m , the larger the magnetic resonance frequency f r . As the magnetic resonance frequency f r increases, the rise of μ'' in the frequency characteristics shifts to the high-frequency side, so μ'' at 100 MHz becomes smaller. Therefore, in the present embodiment shown in FIG. 3, due to the segregation of Cr, the apparent crystal grain size becomes smaller compared to the first comparative form in FIG. 4, so μ'' becomes smaller and μ'Q is considered to become larger.

[0035] Subsequently, the microstructure 1B of the second comparative form shown in FIG. 5 will be described. The second comparative form has a composition containing Nb, Mo, or Cu. Nb, Mo, and Cu are all elements having the effect of promoting the formation of nanocrystals. Therefore, as shown in FIG. 5, precipitation of nanocrystals 5 can be seen in the microstructure 1B of the second comparative form. In the second comparative form as well, magnetic walls 3 are formed in the crystal grains 2 divided by segregated Cr4. The nanocrystals 5 have the effect of inhibiting the movement of the magnetic walls 3. Therefore, in the second comparative form shown in FIG. 5, the movement of the magnetic walls 3 within the crystal grains 2 is inhibited, so μ'', which is the loss component of the complex relative permeability, becomes larger. As a result, it is considered that μ'Q becomes smaller compared to the present embodiment shown in FIG. 3.

[0036] As explained above, according to this embodiment shown in Figure 3, the grain size can be considered to have decreased due to Cr segregation, and since the composition has Nb, Mo, and Cu content of 0.1 atomic percent or less each, nanocrystals that inhibit magnetic domain wall movement are not formed, so it is thought that a high μ'Q can be obtained in the high-frequency region such as 100 MHz.

[0037] In particular, it has been conventionally believed that the formation of nanocrystals contributes to the improvement of magnetic properties, and Fe-based nanocrystalline soft magnetic materials containing elements such as Nb, Mo, and Cu have been extensively studied. However, contrary to such conventionally known techniques, it has been found that excellent magnetic properties can be obtained in the flattened powder of the soft magnetic alloy according to this embodiment by employing a composition that does not allow for the formation of nanocrystals.

[0038] (Compacted powder) This disclosure also relates to compacts containing flattened soft magnetic alloy powder. Specifically, a compact according to one embodiment of this disclosure comprises a binder resin and flattened soft magnetic alloy powder according to one embodiment of this disclosure.

[0039] A known method can be used to manufacture the compacted body; for example, it can be formed by pressurizing and heat-treating a mixture of a binder resin and a soft magnetic alloy flat powder. The compacted body according to this embodiment can be used as a compacted magnetic core, and more specifically, it can be used in an ultra-small special power supply used directly beneath a processor. The shape of the compacted body is not particularly limited and may be, for example, toroidal.

[0040] Various thermosetting resins can be used as the binder resin included in the compacted powder. From the viewpoint of heat resistance, epoxy resin is preferred as the binder resin.

[0041] The soft magnetic alloy flat powder, compacted powder, and method for producing the soft magnetic alloy flat powder have been described above with reference to specific embodiments. However, the present disclosure is not limited to these examples, and the configuration can be modified as appropriate without contradicting the purpose of the invention, and such embodiments are also included in the scope of the present disclosure. [Examples]

[0042] Next, the soft magnetic alloy flat powder of this disclosure will be further described with reference to examples, but this disclosure is not limited to these specifically shown examples.

[0043] [Sample preparation] (Example 1) Fe 75.3 Si 11.4 B 11 Cr 2.3 An amorphous raw material powder having the above composition was flattened using a bead mill to obtain a flattened powder with an average particle size of 30 μm and an aspect ratio of 39. The flattened powder thus obtained was heat-treated at 550°C in a nitrogen atmosphere to obtain the soft magnetic alloy flattened powder of Example 1.

[0044] (Examples 2-5) Examples 2 to 4 were obtained using the same manufacturing conditions as in Example 1, except that the heat treatment temperatures were set to 650°C, 750°C, and 450°C, respectively. The flat powder before heat treatment was used as Example 5.

[0045] (Examples 6 and 7) The flattened powders of Examples 6 and 7 were obtained under the same manufacturing conditions as in Example 1, except that the flattening treatment conditions were changed to set the aspect ratios of the flattened powders to 28 and 10, respectively.

[0046] For each of Examples 1 to 7, the flattened soft magnetic alloy powder was mixed with epoxy resin to form a slurry, and the slurry was molded into a sheet-like preform using the doctor blade method. The thickness of the preform was 200 μm. By stacking a predetermined number of preforms and applying a hot press (300°C), evaluation samples containing the flattened soft magnetic alloy powders of Examples 1 to 7 were obtained. The thickness of each evaluation sample was 0.5 mm.

[0047] [analysis] (Frequency characteristics) The frequency characteristics of the complex relative permeability of each sample were measured using a BH analyzer. Table 1 shows the real component μ' and μ'Q of the complex relative permeability at a frequency of 100 MHz. Figure 6 shows the frequency characteristics of the real component μ' and imaginary component μ'' of the complex relative permeability of the samples in Example 1 and Example 5 in the range of 10 MHz to 1 GHz. Figure 6 shows the magnetic resonance frequency f identified from the frequency characteristics. r The frequency at which μ' is maximized is also shown.

[0048] (Cr microsegregation measurement) Microsegregation measurements of Cr were performed on the flattened powders of soft magnetic alloys in Examples 1, 5, and 6. Specifically, thin sections containing the cross-section of the flattened powder were prepared, and line analysis was performed using a TEM equipped with EDX at a predetermined pitch (e.g., 5 nm) from the surface along the direction perpendicular to the surface up to 200 nm. The standard deviation was then determined from the obtained Cr composition (atomic %). Measurements were performed at three locations, and the average of the standard deviations obtained from each location was defined as the standard deviation σ. The obtained standard deviation σ was used to determine the Cr composition ratio C Cr (Value divided by 2.3 atomic%) σ / C Cr This is shown in Table 1. Furthermore, the line analysis results for Example 1 and Example 5 are shown in Figures 7 and 8, respectively.

[0049] [Table 1]

[0050] Examples 1, 2, and 6 are examples, while Examples 3 through 5 and 7 are comparative examples. Blank spaces in Table 1 indicate that the corresponding measurement was not performed. As shown in Table 1, in Examples 1, 2, and 6, μ'≧18 and μ'Q≧400 at 100MHz, demonstrating excellent magnetic properties in the high-frequency range.

[0051] According to the frequency characteristics shown in Figure 6, in Example 1, where heat treatment was performed at 550°C, the magnetic resonance frequency f is higher compared to Example 5, where no heat treatment was performed. rThe peak is on the high-frequency side, and the rise time of μ'' is also shifted to the high-frequency side. As a result, at 100MHz, in Example 5, μ'' is large and the value of μ'Q is small, but in Example 1, μ'' is small while μ' remains constant, and μ'Q is improved.

[0052] According to the line analysis shown in Figures 7 and 8, in Example 5, which was not heat-treated, the Cr composition is almost constant regardless of the position in the thickness direction, whereas in Example 1, which was heat-treated at 550°C, there is a mixture of areas with high and low Cr content. Therefore, it can be seen that heat treatment causes Cr segregation.

[0053] In Example 3, where the heat treatment temperature was 450°C, μ' became smaller, while μ'' at 100 MHz was relatively large, resulting in a small μ'Q. This is thought to be due to the low heat treatment temperature preventing sufficient crystallization of the compound phase. In Example 4, where the heat treatment temperature was 750°C, μ'' at 100 MHz became larger, resulting in a small μ'Q. From Example 4, it can be seen that the desired magnetic properties cannot be obtained if the heat treatment temperature is too high.

[0054] In Examples 1, 2, and 6, where the aspect ratio was 20 or higher, μ' was 18 or higher. In particular, in Examples 1 and 2, where the aspect ratio was 30 or higher, μ' was 20 or higher, which was good. On the other hand, in Example 7, where the aspect ratio was less than 20, μ' was low, below 18. It is thought that the smaller aspect ratio resulted in a larger demagnetizing coefficient, leading to a decrease in μ'.

[0055] From the above, it can be seen that in order to obtain excellent magnetic properties that satisfy μ'≧18 and μ'Q≧400 at 100MHz, it is necessary to appropriately control Cr segregation and aspect ratio in a flattened powder of a soft magnetic alloy having a predetermined composition. [Explanation of Symbols]

[0056] 1, 1A, 1B Microstructure 2 crystal grains 21. Grain boundaries 3 Domain wall 31. Range of movement of magnetic domain walls 4. Segregated Cr 5 nanocrystals 61 First magnetic domain 62 Second magnetic domain 63 Third magnetic domain 64. The fourth magnetic domain

Claims

1. It contains Si: 6 atomic percent to 15 atomic percent, B: 6 atomic percent to 15 atomic percent, and Cr: 1 atomic percent to 5 atomic percent. It contains one or more elements arbitrarily selected from the group consisting of Co, Ni, Nb, Mo, Cu, Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al. The flattened powder of a soft magnetic alloy, the remainder being Fe and unavoidable impurities, The Co and Ni content is 5 atomic percent or less, The content of Nb, Mo, and Cu is 0.1 atomic percent or less for each component. The content of Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al is each 1 atomic percent or less. The ratio of powder particle size to powder particle thickness is 20 or more. A flattened soft magnetic alloy powder in which Cr microsegregation in the range of formula (1) is present in the thickness direction, within a range of 200 nm from the surface of the powder particles. 0.1≦σ / C Ｃｒ ・・・(1) Here, σ is the standard deviation in Cr microsegregation measurements, C Ｃｒ This is the Cr content of the flattened soft magnetic alloy powder.

2. The soft magnetic alloy flat powder according to claim 1, wherein the powder particle thickness is 0.1 μm or more and 5 μm or less.

3. The soft magnetic alloy flat powder according to claim 1 or 2, wherein the powder particle size is 10 μm or more and 100 μm or less.

4. The flattened soft magnetic alloy powder according to claim 1 or 2, wherein the average crystal grain size is 5 nm or more and 100 nm or less.

5. A compacted powder comprising a binder resin and the flattened soft magnetic alloy powder described in claim 1 or 2.

6. It contains Si: 6 atomic percent to 15 atomic percent, B: 6 atomic percent to 15 atomic percent, and Cr: 1 atomic percent to 5 atomic percent. It contains one or more elements arbitrarily selected from the group consisting of Co, Ni, Nb, Mo, Cu, Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al. A method for producing flattened powder of a soft magnetic alloy, the remainder being Fe and unavoidable impurities, The Co and Ni content is 5 atomic percent or less, The content of Nb, Mo, and Cu is 0.1 atomic percent or less for each component. The content of Au, Ti, V, Zr, Hf, Ta, W, C, P, and Al is each 1 atomic percent or less. A step of flattening the raw material powder having the above composition and processing it into a shape in which the ratio of powder particle size to powder particle thickness is 30 or more, A method for producing flattened powder of a soft magnetic alloy, comprising the step of heat-treating the raw material powder at a temperature of Tx2-100°C or higher and Tx2+150°C or lower, where Tx2 is the compound deposition temperature.

7. A method for producing flattened soft magnetic alloy powder according to claim 6, wherein the heat treatment temperature in the heat treatment is 500°C or more and 700°C or less.

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