Magnetic material and manufacturing method therefor

Abstract

The present disclosure provides a magnetic material comprising a plurality of metal magnetic bodies and a coating layer covering each of the metal magnetic bodies, wherein: the metal magnetic bodies contain at least Fe; the coating layers contain at least one of metal oxides and metal nitrides that contain Si and a first nonmagnetic metal element more susceptible to oxidation than Fe; and the average thickness of the coating layers is 10-153 nm, inclusive.

Description

Magnetic material and method for producing same

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to magnetic materials and methods of making the same.

[0002] Composite magnetic materials are sometimes used as magnetic materials for electronic components such as coil components, etc. These composite magnetic materials include a metal magnetic body containing soft magnetic powder composed of powder particles and a coating layer formed on the surface of the metal magnetic body (see Patent Document 1).

[0003] JP 2013-125887 A

[0004] For example, the magnetic material described in Patent Document 1 includes a metal magnetic body in which a plurality of metal magnetic bodies are bonded without a coating layer and are necking-sintered, thereby enabling high magnetic permeability. However, the inventors of the present application have found that there is room for further improvement in such a magnetic material when prioritizing use in the high frequency range.

[0005] For example, when metal magnetic particles bond together and become coarse, the eddy currents flowing within the metal magnetic particles increase, which can increase eddy current loss in the magnetic material. Generally, the proportion of eddy current loss in the energy loss of a magnetic material increases under high-frequency excitation. Therefore, magnetic materials containing coarse-grained metal magnetic particles may have problems with their high-frequency characteristics due to their high eddy current loss.

[0006] The present disclosure has been made in view of the above-mentioned problems. That is, a main object of the present disclosure is to provide a magnetic material in which coarsening of the metal magnetic body is suppressed, and a method for producing the magnetic material.

[0007] As a result of extensive research into solving the above problems, the inventors of the present application have come up with the invention of a magnetic material and a method for producing the same, which achieve the above-mentioned main object.

[0008] A magnetic material according to one embodiment of the present disclosure comprises a plurality of metal magnetic bodies and a coating layer that coats the metal magnetic bodies, wherein the metal magnetic bodies contain at least Fe, and the coating layer contains at least one of a metal oxide and a metal nitride that contains Si and a first non-magnetic metal element that is more easily oxidized than Fe, and the average thickness of the coating layer is 10 nm or more and 153 nm or less.

[0009] Furthermore, a method for producing a magnetic material according to one embodiment of the present disclosure includes: coating the surfaces of precursor particles with a composite metal alkoxide to form a magnetic material precursor; and sintering the magnetic material precursor, wherein the precursor particles contain at least Fe, and the composite metal alkoxide contains Si and a first non-magnetic metal element that is more easily oxidized than Fe.

[0010] Furthermore, a method for producing a magnetic material according to another embodiment of the present disclosure includes: coating the surface of precursor particles with a Si-containing coating; bringing a liquid in which a metal salt containing a first non-magnetic metal element that is more easily oxidized than Fe into contact with the surface of the Si-containing coating, thereby obtaining a magnetic material precursor; and sintering the magnetic material precursor, wherein the precursor particles contain at least Fe.

[0011] According to the present disclosure, a magnetic material in which coarsening of the metal magnetic body is suppressed, and a method for producing the magnetic material are provided.

[0012] 10 is a partially enlarged cross-sectional view schematically showing the structure of a magnetic material according to the present disclosure. FIG. 11 is a partially enlarged cross-sectional view of part I in FIG. 1. FIG. 12 is a graph showing an example of the results of line analysis of the magnetic material according to the present disclosure. FIG. 13 is a perspective view schematically showing an electronic component including the magnetic material according to the present disclosure. FIG. 14 is a schematic cross-sectional view taken along line a-a in FIG. 4. FIG. 15 is a perspective view schematically showing an electronic component according to another embodiment. FIG. 16 is a schematic cross-sectional view illustrating line analysis of a magnetic material. FIG. 17 is a schematic cross-sectional view illustrating line analysis of a magnetic material. FIG. 18 is a schematic cross-sectional view illustrating line analysis of a magnetic material. FIG. 19 is an enlarged cross-sectional view of part II shown in FIG. 8.

[0013] The following describes specific embodiments of the present invention. The applicant provides the following description and examples to enable those skilled in the art to fully understand the present invention, and it should be noted that these are not intended to limit the subject matter described in the claims. In other words, the present invention is not particularly limited to the preferred embodiments described below, and can be implemented with appropriate modifications within the scope of its intended purpose. For convenience, the present invention may be divided into embodiments and examples, etc., in consideration of ease of explanation or understanding of the main points. However, partial substitution and / or combination of the configurations shown in different embodiments, etc. is possible. In describing such embodiments, redundant explanations of substantially identical matters may be omitted, and only differences may be described. In particular, similar effects resulting from similar configurations may not be mentioned in each embodiment.

[0014] The various numerical ranges referred to herein are intended to include the lower and upper numerical limits themselves unless otherwise specified, and the term "about" means that there may be a variation or difference of a few percent, e.g., ±10%.

[0015] Hereinafter, a magnetic material according to an embodiment of the present disclosure will be described with reference to the drawings. Although the description will be made with reference to the drawings as necessary, the contents shown in the drawings are merely shown as schematic examples for the purpose of understanding the present disclosure, and the appearance, dimensional ratios, etc. may differ from the actual product.

[0016] [Magnetic Material] FIG. 1 is a partially enlarged cross-sectional view schematically showing the structure of the magnetic material of the present disclosure.

[0017] The inventors of the present application have conducted extensive research into a new magnetic material that has a different structure from conventional magnetic materials, as conventional magnetic materials may lead to deterioration of high-frequency characteristics. The magnetic material of the present disclosure will be specifically described below.

[0018] The magnetic material 11 of the present disclosure is a sintered body including a plurality of metal magnetic bodies 11A each having a coating layer 11B. As shown in FIG. 1 , the coating layer 11B can be formed at the boundary between adjacent metal magnetic bodies 11A by arranging the plurality of metal magnetic bodies 11A in close contact with one another. Therefore, the coating layer 11B can also be referred to as an interface phase, grain boundary phase, or intervening phase located between adjacent metal magnetic bodies 11A in a cross-sectional view. Alternatively, as described below, the coating layer 11B can also be referred to as a non-magnetic phase or a low-magnetic phase because it includes a non-magnetic material including a metal oxide and / or a metal nitride.

[0019] The shape of the metal magnetic body 11A is not particularly limited. The metal magnetic body 11A may have various cross-sectional shapes, such as circular, approximately elliptical, polygonal, and / or irregular. For example, the metal magnetic body 11A may be particulate. Note that the "particulate" shape in this specification is not necessarily limited to a perfect sphere, but includes flat, elliptical, or approximately spherical shapes with irregularities on the surface. A metal magnetic body having such a shape may also be referred to as, for example, a "particulate metal magnetic body." The multiple metal magnetic bodies 11A included in the magnetic material 11 may have similar shapes or different shapes from each other.

[0020] In the magnetic material 11 of the present disclosure, the coating layer 11B includes at least one of a metal oxide and a metal nitride formed by oxidizing or nitriding a non-magnetic metal. Note that the coating layer 11B may include an oxide formed by oxidizing a part of the metal magnetic body 11A and / or a nitride formed by nitriding a part of the metal magnetic body 11A.

[0021] When the coating layer 11B has the above-described form, the metal oxide and / or metal nitride contained in the coating layer 11B can contact the metal magnetic body 11A and also covers the surface of the metal magnetic body 11A.

[0022] The above-mentioned metal oxides and metal nitrides are formed by oxidizing or nitriding non-magnetic metals, and therefore can have higher electrical resistivity than magnetic metals. For example, the electrical resistivity of metal oxides and metal nitrides is 1×10 １１ Ω・cm or more 1×10 １６The electrical resistivity of the metallic magnetic material can be 8.9×10 －６ Ω・cm or more 1.76×10 －４ The resistivity of the metal oxides and nitrides may be Ω·cm or less. The metal oxides and nitrides may themselves be non-magnetic.

[0023] Therefore, the coating layer 11B can function as a high-resistance portion having a higher resistance than the metal magnetic body 11A. When the base body of an electronic component includes the magnetic material 11 of the present disclosure, the high-resistance portion can increase the electrical resistance of the path of eddy currents flowing in the magnetic material (corresponding to the sintered body) of the base body, thereby reducing eddy current loss. Since this eddy current loss increases as the current frequency increases, reducing eddy current loss can improve high-frequency characteristics. Therefore, the magnetic material 11 of the present disclosure can be suitable for use at high frequencies (e.g., 10 MHz or higher).

[0024] In order to emphasize the improvement of these characteristics, it is preferable that the coating layer 11B covers 90% or more of the surface perimeter of the metal magnetic body 11A. In other words, the metal magnetic body 11A may be covered by the coating layer 11B over 90% or more of the surface perimeter in a cross-sectional view. This allows the coating layer 11B to function favorably as a high-resistance portion, and a magnetic material with excellent high-frequency characteristics can be provided. Note that, in the surface area of ​​the metal magnetic body 11A where the coating layer 11B is not present, for example, voids or a resin material described below may be present. In other words, voids or resin material may be present partially between adjacent metal magnetic bodies 11A.

[0025] The coating layer 11B may cover the surface of each of the multiple metal magnetic bodies 11A. That is, the multiple metal magnetic bodies 11A may be adjacent to each other via the coating layer 11B that coats each of the multiple metal magnetic bodies 11A. For example, the coating layer 11B that coats one metal magnetic body 11A and the coating layer 11Ba that coats the other metal magnetic body 11Aa may be adjacent to each other (see FIG. 2). Alternatively, one continuous coating layer 11B may be positioned between one metal magnetic body 11A and the adjacent other metal magnetic body 11Aa. In other words, the multiple metal magnetic bodies 11A may share one coating layer 11B. Such a structure can also be interpreted as a structure in which multiple metal magnetic bodies are bonded to each other via the coating layer 11B.

[0026] The metal magnetic body 11A contains at least Fe. For example, the metal magnetic body 11A may be an alloy containing Fe as a main component. Examples of alloys containing Fe include, but are not limited to, Fe-Si alloys, Fe-Al alloys, Fe-Ni alloys, Fe-Co alloys, Fe-Si-Al alloys, Fe-Si-Cr alloys, Fe-based amorphous alloys, and Fe-based nanocrystalline alloys. When a higher saturation magnetic flux density is important, the Fe content in the metal magnetic body 11A may be 95% by weight or more, and more preferably 97% by weight or more. For example, the Fe content in the metal magnetic body 11A may be 99% by weight or more.

[0027] In particular, when the balance between magnetic permeability and saturation magnetic flux density is emphasized, the metal magnetic body 11A is preferably an Fe—Ni alloy. Alternatively, when emphasizing excellent DC bias characteristics due to high saturation magnetic flux density, the metal magnetic body 11A is preferably pure iron. Furthermore, when emphasizing high resistivity and the ability to suppress eddy current loss under high frequency conditions, the metal magnetic body 11A preferably includes an Fe-based amorphous alloy and / or an Fe-based nanocrystalline alloy. Furthermore, when emphasizing low coercivity and the ability to suppress hysteresis loss, it is particularly preferable to include an Fe-based nanocrystalline alloy. In one embodiment, the metal magnetic body 11A may include an amorphous phase containing an Fe-based amorphous alloy. Alternatively, the metal magnetic body 11A may include an amorphous phase and an Fe-based nanocrystalline phase. Such a metal magnetic body 11A may have a structure in which Fe-based nanocrystalline grains are contained in the amorphous phase, for example.

[0028] Here, "pure iron" in this specification means iron containing only Fe element in addition to C element, O element, N element, and / or unavoidable impurity elements. The Fe concentration in the pure iron may be 97.0 wt. % or more for carbonyl iron powder (hard grade), 99.0 wt. % or more for carbonyl iron powder (soft grade), or 99.5 wt. % or more for electrolytic iron powder. The use of such pure iron improves DC bias characteristics.

[0029] The metal oxide and / or metal nitride contained in the coating layer 11B contains a metal element that is more easily oxidized than Fe. Specifically, the coating layer 11B contains at least one of a metal oxide and a metal nitride containing Si and a non-magnetic metal element that is more easily oxidized than Fe. The coating layer 11B may be a single layer. Therefore, Si and a non-magnetic metal element that is more easily oxidized than Fe may coexist in the single layer coating layer 11B. Alternatively, the coating layer 11B may be a composite layer made up of multiple layers. For example, the coating layer 11B may have a layered structure in which a layer containing Si and a layer containing a non-magnetic metal element are stacked on top of each other.

[0030] In this specification, "non-magnetic metal" refers to a metal other than a ferromagnetic metal (e.g., Fe, Ni, Co, etc.). Furthermore, in this specification, "non-magnetic metal element that is more easily oxidized than Fe" refers to a non-magnetic metal element that has a standard electrode potential that is more base than Fe. Examples of non-magnetic metal elements that are more easily oxidized than Fe contained in metal oxides and / or metal nitrides include at least one selected from the group consisting of Zr, Al, Ti, V, Mg, Ca, B, K, Zn, and Mn. In this disclosure, Si, B, and P, which are generally considered to be semimetals, are treated as metallic elements.

[0031] By including a metal oxide and / or metal nitride containing the above-described non-magnetic metal element in the coating layer 11B, the non-magnetic metal element is oxidized preferentially over Fe, thereby effectively suppressing oxidation of Fe contained in the metal magnetic body 11A. This suppresses ionization of Fe in the metal magnetic body 11A, and can suppress bonding (necking) between multiple metal magnetic bodies 11A caused by diffusion of Fe ions. Therefore, the coating layer 11B of the present disclosure can contribute to suppressing coarsening of the metal magnetic body 11A due to necking between multiple metal magnetic bodies 11A. Suppressing coarsening of the metal magnetic body 11A suppresses an increase in eddy current loss, resulting in a magnetic material 11 with better high-frequency characteristics.

[0032] Necking sintering, which is a cause of coarsening of the metal magnetic body 11A, is more likely to occur as the firing temperature increases. According to the present disclosure, a magnetic material that can suitably suppress necking sintering is provided, and therefore it may be possible to subject the magnetic material to higher firing temperatures.

[0033] For example, from the viewpoint of avoiding resource risks, it may be desirable to use Cu as an internal electrode of an electronic component. In this case, a higher firing temperature is required compared to when Ag, which is a common internal electrode, is used. According to the present disclosure, even when using a material that requires such a high firing temperature, it is possible to obtain an electronic component that includes a suitable magnetic material in which necking sintering is suppressed.

[0034] Furthermore, metal oxides and / or metal nitrides containing nonmagnetic metal elements have lower magnetic permeability than Fe. Therefore, the coating layer 11B containing such metal oxides and / or metal nitrides can function as a magnetic gap in the magnetic material 11. This can improve the DC bias characteristics of the magnetic material 11.

[0035] In one embodiment, the metal oxide and / or metal nitride present in the coating layer 11B may contain an additional non-magnetic metal element. For ease of explanation, hereinafter, the non-magnetic metal element contained together with Si will be referred to as the first non-magnetic metal element, and the additional non-magnetic metal element will be referred to as the second non-magnetic metal element. In other words, in the magnetic material 11 of the present disclosure, the coating layer 11B may contain a metal oxide and / or metal nitride containing Si, the first non-magnetic metal element, and the second non-magnetic metal element.

[0036] The second non-magnetic metal element is a non-magnetic metal element different from the first non-magnetic metal element. Examples of the second non-magnetic metal element include at least one selected from the group consisting of Li, Na, Sr, Ba, P, Bi, Sn, Te, Pb, and La. The metal oxide and / or metal nitride contained in the coating layer 11B contains the second non-magnetic metal element as an additional non-magnetic metal element, which can further enhance the effect of suppressing coarsening of the metal magnetic body 11A and the effect of improving the DC bias characteristics by the magnetic gap.

[0037] The present inventors have also newly discovered that further inclusion of a second non-magnetic metal element in coating layer 11B can improve the mechanical strength of magnetic material 11. While not intended to be limited to a particular theory, this is presumed to be because the inclusion of the second non-magnetic metal element lowers the softening point of coating layer 11B, improving the wettability of coating layer 11B to the surface of metal magnetic material 11A and improving the adhesion between metal magnetic material 11A and coating layer 11B.

[0038] A relative ratio R of the sum of Si, the first non-magnetic metal element, and the second non-magnetic metal element contained in the coating layer 11B to the sum of all metal elements contained in the coating layer 11B ｔ(Formula I) may be 50% or more and 100% or less. ｔ [%] = (Si [at %] + α1 [at %] + α2 [at %]) / Sum of all metal elements in coating layer [at %] × 100 (Equation I) (wherein α1 is the first non-magnetic metal element and α2 is the second non-magnetic metal element.)

[0039] Furthermore, the relative ratio R of the first non-magnetic metal element to the total of Si and the first non-magnetic metal element is α１ (Formula II) may be 1% or more and 99% or less, and is preferably, for example, 5% or more and 95% or less, or 30% or more and 95% or less. α１ [%]=α1[at%] / (Si[at%]+α1[at%])×100 (Formula II)

[0040] Furthermore, the relative ratio R of the second non-magnetic metal element to the total of Si, the first non-magnetic metal element, and the second non-magnetic metal element is α２ (Formula III) may be 0% or more and 49% or less, preferably 0% or more and 25% or less, and more preferably 0% or more and 10% or less. α２ [%]=α2[at%] / (Si[at%]+α1[at%]+α2[at%])×100 (Formula III)

[0041] By setting the content of Si, the first non-magnetic metal element, and the second non-magnetic metal element within the above-mentioned ranges, it is possible to further enhance the effect of the coating layer 11B in suppressing the coarsening of the above-mentioned metal magnetic body 11A, and the effect of improving the DC superposition characteristics as a magnetic gap.

[0042] Fig. 2 is a partially enlarged cross-sectional view of part I in Fig. 1. In the cross-sectional view, the average thickness D of the coating layer 11B is 10 nm or more and 153 nm or less. When the average thickness D of the coating layer 11B is within the above range, coarsening of the metal magnetic body 11A is suitably suppressed, and the magnetic material 11 having excellent DC bias characteristics can be provided.

[0043] In this specification, the average thickness D of the coating layer 11B is the average value of the minimum thickness d of the coating layer 11B located between multiple adjacent metal magnetic bodies 11A. For example, when multiple metal magnetic bodies 11A are adjacent to each other and share one coating layer 11B, the thickness d of the coating layer 11B is defined as half the minimum thickness 2d of the coating layer 11B located between the multiple metal magnetic bodies 11A. Note that the thickness d is measured as the minimum thickness d of the coating layer 11B that exists from any metal magnetic body 11A to the metal magnetic body 11Aa closest to that metal magnetic body 11A.

[0044] The thickness d of the coating layer 11B of the magnetic material 11 can be measured by the following method.

[0045] First, the magnetic material 11 is hardened with resin and polished with a polishing device (for example, a Tegramin-25 polishing device manufactured by Struers) to obtain a cross section of the magnetic material. Then, the polished magnetic material is processed by focused ion beam (FIB) processing into a shape suitable for STEM-EDX measurement, and a cleaning process is performed by Ar flat milling. Through these operations, a cross section measurement sample of the magnetic material 11 is obtained.

[0046] Using such a cross-section measurement sample, a cross section of the magnetic material 11 is observed by scanning transmission electron microscope-energy dispersive X-ray (STEM-EDX) measurement, and a STEM image and an element mapping image are obtained. Image analysis software (for example, WinROOF (manufactured by Mitani Corporation)) is used to perform line analysis of the obtained STEM image and element mapping image, and the abundance ratios of Fe, Si, the first non-magnetic metal element, and the second non-magnetic metal element between any two metal magnetic bodies 11A are quantitatively evaluated to determine the thickness 2d of the coating layer 11B located between multiple adjacent metal magnetic bodies 11A.

[0047] Line analysis between metal magnetic bodies is performed by selecting any one metal magnetic body 11A in an STEM image of the magnetic material cross section and performing it on a line corresponding to the shortest distance between that metal magnetic body 11A and the metal magnetic body 11Aa closest to that metal magnetic body 11A via the coating layer 11B.

[0048] In this case, the interface between the metal magnetic body 11A and the coating layer 11B is determined from the plot of the line analysis. Specifically, in the plot of the line analysis obtained by measuring the line along the shortest distance between the plurality of adjacent metal magnetic bodies 11A via one coating layer 11B, the following conditions are met on the plot from the metal magnetic body 11A side to the coating layer 11B side: (a) In the plot of the element of oxygen or nitrogen (when both oxygen and nitrogen are contained, the one detected in the greater amount), the maximum content (at%) of the element is determined as X ｍａｘ When the content of the element is X ｍａｘ and (b) in the plot of the components contained in the coating layer in greater amounts among Si and non-magnetic metal elements, the maximum content (at%) of the component is Y ｍａｘ If the content of the component is Y ｍａｘ The point that satisfies both of the above and above conditions (a) and (b) is determined to be the interface between the metal magnetic material 11A and the coating layer 11B. In other words, among the points on the line analysis plot that satisfy both conditions (a) and (b), the point closest to the metal magnetic material 11A is determined to be the interface between the metal magnetic material 11A and the coating layer 11B.

[0049] Note that "among Si and non-magnetic metal elements, the component contained in the coating layer in greater amounts" refers to the element among Si and non-magnetic metal elements for which the area enclosed by the plot of each component and the horizontal axis is the largest in a region in which the plot of each component intersects with the plot of Fe on one metal magnetic body side at one end and the plot of Fe on the other metal magnetic body side at the other end. This matter will be explained in more detail with reference to Figure 3.

[0050] 3 is a graph of a line analysis of an exemplary magnetic material. The magnetic material has a coating layer containing Si, Zr as a first non-magnetic metal element, and Na as a second non-magnetic metal element. In the graph shown in FIG. 3, a region S is defined, with one end being the point where the plot of Si intersects with the plot of Fe on one side of the metal magnetic body, and the other end being the point where the plot of Fe intersects with the plot of Fe on the other side of the metal magnetic body. ＳｉThe area surrounded by the plot of Si and the horizontal axis is called A Ｓｉ In addition, a region S is defined as a region S having one end where the plot of Zr intersects with the plot of Fe on one side of the metal magnetic material, and the other end where the plot of Fe intersects with the plot of Fe on the other side of the metal magnetic material. ｍｅｔａｌ The area enclosed by the plot of Zr and the horizontal axis is called A ｍｅｔａｌ Although not shown in the figure, the area A between the intersection points of the plot of Na and the plot of Fe is calculated in the same way. Ｎａ can be calculated. Ｓｉ , A ｍｅｔａｌ , and A Ｎａ In comparison, Zr, which shows the largest plot area, corresponds to "a component contained in a larger amount in the coating layer."

[0051] Using the above-mentioned method, the interface located on the side of any metal magnetic body 11A and the interface located on the side of the metal magnetic body 11Aa closest to that metal magnetic body 11A are determined, and the distance between the interfaces is calculated to obtain the total thickness 2d of the coating layer 11B between adjacent metal magnetic bodies. Half the value d of the total thickness 2d corresponds to the thickness d of the coating layer 11B. Using the same method, the thickness d of the coating layer 11B is measured for each of 10 arbitrary metal magnetic bodies 11A, and the average value of the obtained thicknesses d is defined as the average thickness D of the coating layer 11B.

[0052] In addition, the average circular equivalent diameter of the metal magnetic body 11A may be 0.5 μm to 4 μm, or 0.67 μm to 3.5 μm, in a cross-sectional view. When the average circular equivalent diameter of the metal magnetic body 11A is in the above-mentioned range, eddy current loss is reduced, and the magnetic material 11 having better high-frequency characteristics can be obtained.

[0053] The average equivalent circle diameter of the metal magnetic body 11A can be measured by the following method.

[0054] The magnetic material 11 is hardened with resin, polished with a polishing device (for example, a Tegramin-25 polishing device manufactured by Struers), and then ion milled with an ion milling device (for example, an IM-3000 manufactured by Hitachi High-Technologies Corporation). Thereafter, a field emission scanning electron microscope (for example, an SU8230 manufactured by Hitachi High-Technologies Corporation) is used to obtain SEM images and, if necessary, element mapping images. The imaging magnification may be adjusted within a range of 3,500 to 60,000 times.

[0055] The acquired image is analyzed using image analysis software (for example, WinROOF2021 (manufactured by Mitani Corporation)) to calculate the equivalent circle diameter. In the analysis, the equivalent circle diameters of any 20 metal magnetic bodies per site in any three locations of the magnetic material 11, i.e., a total of 60 metal magnetic bodies, are calculated, and the obtained average value is taken as the average equivalent circle diameter.

[0056] When measuring the equivalent circle diameter from an element body including magnetic material 11, the measurement may be made on a cross section at a position half the length of the element body. When measuring the equivalent circle diameter from an electronic component including the element body, the equivalent circle diameters of 20 metal magnetic bodies may be measured at a total of six locations: three arbitrary locations in a region located above the top surface of the internal coil conductor arranged inside the element body by the thickness of the coil conductor, and three arbitrary locations in a region located below the bottom surface of the internal coil conductor by the thickness of the coil conductor, and the average of the equivalent circle diameters of a total of 120 metal magnetic bodies may be used as the average equivalent circle diameter.

[0057] Furthermore, the magnetic material 11 of the present disclosure may be impregnated with a resin. The resin may be filled so as to fill gaps present between the plurality of metal magnetic bodies 11A contained in the magnetic material 11. In such a structure, the magnetic material 11 contains a resin inside. Specifically, the resin may be present between the plurality of metal magnetic bodies 11A contained in the magnetic material 11.

[0058] According to this structure, the resin is impregnated so as to fill the voids in the magnetic material 11, thereby reducing the volume of the voids contained in the magnetic material 11. This improves the mechanical strength of the magnetic material 11. That is, according to this embodiment, it is possible to obtain a magnetic material that has favorable high-frequency characteristics and excellent mechanical strength. Furthermore, by reducing the voids in the magnetic material 11, it is also possible to prevent moisture and the like from penetrating into the magnetic material 11.

[0059] The resin contained in the magnetic material 11 may be, for example, a thermosetting resin material. Specific examples of the thermosetting resin material include at least one of an epoxy resin and a silicone resin. When emphasis is placed on excellent resin impregnation, it is preferable that the magnetic material be impregnated with an epoxy resin. Furthermore, when emphasis is placed on excellent heat resistance, it is preferable that the magnetic material be impregnated with a silicone resin.

[0060] [Electronic Component] The magnetic material 11 of the present disclosure can be incorporated into an electronic component. Fig. 4 is a perspective view schematically showing an exemplary electronic component including the magnetic material of the present disclosure. Fig. 5 is a schematic cross-sectional view taken along line a-a in Fig. 4.

[0061] 4 and 5 , the electronic component 100 includes an element body 10 including the magnetic material 11 of the present disclosure, a coil conductor 20, and external electrodes 30, 40. The element body 10 includes a sintered body 12 including the magnetic material 11 of the present disclosure. The sintered body 12 itself has at least one magnetic metal sintered layer. As an example, the element body 10 may have a hexahedral structure. An outer layer 60 may be formed to cover the surface of the element body 10 except for the external electrodes 30, 40.

[0062] In the above-mentioned sintered body 12, when metal magnetic layers of the same composition are stacked consecutively, it is difficult to distinguish the boundaries between the metal magnetic layers. Therefore, even if a sintered body has multiple metal magnetic layers stacked, it is treated as a single sintered body if the first insulating layer described below is not located between them. Also, even if multiple metal magnetic layers of different compositions are stacked and these layers can be distinguished, it is treated as a single sintered body as long as the first insulating layer described below is not located between them.

[0063] As an example, the coil conductor 20 may be provided within the element body 10. The coil conductor 20 is made of a conductive material, and may be made of at least one material selected from the group consisting of silver, copper, and aluminum. As an example, the coil conductor 20 may be in the form of a straight wire, as shown in FIG. 4 . Without being limited to this, the coil conductor may have various shapes, such as a wound shape or a meandering shape. For example, the coil conductor may be made of a conductive paste or wire. The external electrodes 30, 40 are provided on the surface of the element body 10. These external electrodes are connected to both ends of the coil conductor 20, respectively, and are arranged to face each other at a distance via the element body 10.

[0064] 4 and 5 , the base body 10 can further include a first insulating layer 13 in addition to the sintered body containing the magnetic material 11. In the present disclosure, a high-resistance portion is provided by the coating layer of the metal magnetic material contained in the magnetic material 11 that constitutes the sintered body of the base body 10, thereby ensuring insulation between the metal magnetic materials. Therefore, even if the first insulating layer is not necessarily used, insulation and eddy current loss can be suppressed, and high-frequency characteristics can be improved.

[0065] The first insulating layer 13 may be continuous in a layer form from one side of the sintered body to the other side in a direction intersecting the stacking direction (the vertical direction in the drawing). In this form, two or more sintered bodies separated by the first insulating layer 13 may be provided.

[0066] In this case, the element body 10 may include two or more sintered bodies and a first insulating layer 13, and adjacent sintered bodies may be stacked with the first insulating layer 13 sandwiched between them.

[0067] Furthermore, it is preferable that the first insulating layer 13 is non-magnetic. This provides a magnetic gap function and makes it possible to improve the DC bias characteristics by reducing the magnetic permeability of the element body 10. However, without being limited to this, the first insulating layer 13 can be an insulating layer that is not non-magnetic but has a low magnetic permeability lower than that of a sintered body. In this case, it is possible to improve the inductance compared to a non-magnetic case.

[0068] Alternatively, the coil conductor 20 may be covered with an insulator. In such a structure, the coil conductor 20 is directly surrounded by the insulator except for the ends connected to the external electrodes 30, 40. The insulator is preferably non-magnetic, so that it can function as a magnetic gap.

[0069] This makes it possible to improve the DC bias characteristics by reducing the magnetic permeability of the element body 10. However, without being limited to this, the insulator can be a low-permeability insulator that is not nonmagnetic and has a magnetic permeability lower than that of the sintered body 12. In this case, it is possible to improve the inductance compared to a nonmagnetic case.

[0070] Two or more of the above-mentioned first insulating layers 13 may be provided, spaced apart from each other. In the embodiment shown in Figures 4 and 5, the base body 10 has four sintered bodies 12. In this case, the coil conductor 20 is disposed between a plurality of first insulating layers 13. Furthermore, when two or more first insulating layers 13 are provided, a layered structure can be formed in which two or more sintered bodies 12 and first insulating layers 13 are alternately stacked. The arrangement of two or more first insulating layers 13 further provides a magnetic gap function, and if each insulating layer 13 has a lower magnetic permeability than the sintered bodies 12, the DC superposition characteristics can be further improved.

[0071] Furthermore, as shown in Figure 4, when the base body 10 has two or more sintered bodies by providing a second insulating layer 50 near the center of the base body in the longitudinal direction, the first external electrode 30 and the second external electrode 40 are arranged on the surfaces of different sintered bodies.

[0072] Specifically, the first external electrode 30 and the second external electrode 40 are respectively disposed on the surfaces of adjacent sintered bodies, with the first external electrode 30 disposed on the surface of the sintered body on one side and the second external electrode 40 disposed on the surface of the sintered body on the other side. In this configuration, the second insulating layer 50 can be disposed between one sintered body on which the first external electrode 30 is disposed and the other sintered body on which the second external electrode 40 is disposed. By disposing the second insulating layer 50 in this manner, it is possible to prevent a short circuit between the first external electrode 30 and the second external electrode 40.

[0073] In one example, the second insulating layer 50 may be a slit-shaped tangible object that extends in a direction intersecting, for example, a direction perpendicular to, the extending direction of the first insulating layer 13. Note that the second insulating layer 50 is not disposed so as to penetrate into and divide the coil conductor located inside the element body 10.

[0074] In the present disclosure, the coil conductor does not necessarily have to be arranged inside the element body, and as shown in Figure 6, the coil conductor 10B may be arranged in a wound state outside the element body 10A.

[0075] For example, as shown in FIG. 7, a toroidal ring core 200 can be provided, which includes a ring-shaped element body 210 containing the magnetic material of the present disclosure and a coil conductor 220 wound around the element body.

[0076] [Method of Manufacturing Electronic Component] As an example, a method of manufacturing the inductor shown in FIGS. 4 and 5 will be described below.

[0077] (Magnetic Material Precursor Preparation Step) First, a metal magnetic material containing Fe is prepared.

[0078] As the material for the metallic magnetic body, for example, precursor particles (also referred to as "particulate material") such as an Fe-containing alloy, pure iron, and / or an Fe-based nanocrystalline alloy are used. From the viewpoint of high frequency compatibility, it is preferable to use precursor particles with a D50 particle size of 10.0 μm or less. Furthermore, when emphasis is placed on reducing the risk of ignition, it is more preferable to use particles with a D50 particle size of 0.10 μm or more, and from the viewpoint of handleability, it is even more preferable to use particles with a D50 particle size of 0.50 μm or more, or 0.67 μm or more.

[0079] In this specification, the "D50 particle size" corresponds to the particle size at the point where the cumulative value reaches 50% on a cumulative curve obtained by calculating the particle size distribution on a volume basis and setting the total volume to 100%. The D50 particle size can be measured using a laser diffraction dry particle size distribution analyzer (e.g., HELOS (H3190) & RODOS (manufactured by Sympatec)).

[0080] In one embodiment, a sol-gel process is then used to prepare a slurry by mixing a metal alkoxide containing Si, a metal alkoxide containing a first non-magnetic metal element, a solvent (water and / or alcohol, etc.), and precursor particles, and the metal alkoxide is hydrolyzed in the slurry. The slurry is then dried to obtain precursor particles whose surfaces are covered with a coating film containing Si and the first non-magnetic metal element, which is more easily oxidized than Fe. At this time, a second or third or more coating films may be formed using a metal alkoxide containing a non-magnetic metal element different from the first non-magnetic metal element used to form the coating film. Subsequent firing results in a magnetic material in which a coating layer containing a metal oxide and / or metal nitride is formed on the surface of the metal magnetic body.

[0081] Metal alkoxides are represented by the chemical formula M(OR)x (M: non-magnetic metal element, OR: alkoxy group, x: a value determined by the valence of M). The metal species M constituting the metal alkoxide is Si and a first non-magnetic metal element (e.g., at least one selected from the group consisting of Zr, Al, Ti, V, Mg, Ca, B, K, Zn, and Mn). Furthermore, as the second non-magnetic metal element, a further non-magnetic metal element different from the first non-magnetic metal element (e.g., at least one selected from the group consisting of Li, Na, Sr, Ba, P, Bi, Sn, Te, Pb, and La) may also be used.

[0082] The inclusion of Si and non-magnetic metal elements in the coating film suppresses the diffusion of Fe ions during firing of the magnetic material, thereby suppressing necking sintering of the metal magnetic material and preventing coarsening of the metal magnetic material, thereby suppressing an increase in eddy current loss and enabling the production of a magnetic material with excellent high-frequency characteristics.

[0083] Furthermore, a metal alkoxide containing a second non-magnetic metal element may be used to form a coating film further containing the second non-magnetic metal element. The inclusion of the second non-magnetic metal element lowers the softening point of the coating layer, improves the wettability of the coating layer to the surface of the metal magnetic body, and increases the strength of the resulting magnetic material or the base body containing the magnetic material.

[0084] The alkoxy group OR constituting the metal alkoxide is not particularly limited, and may be, for example, an alkoxy group having 10 or less carbon atoms, particularly 5 or less, and more particularly 3 or less. The smaller the carbon number, the more easily the hydrolysis reaction can proceed. The alkoxy group is preferably at least one selected from the group consisting of, for example, a methoxy group, an ethoxy group, a propoxy group, and a butoxy group.

[0085] Specifically, the metal alkoxide is preferably at least one selected from the group consisting of methoxide, ethoxide, n-propoxide, isopropoxide, n-butoxide, isobutoxide, and t-butoxide containing each metal.

[0086] The slurry containing the precursor particles and the metal alkoxide may contain a water-soluble polymer, such as at least one selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, hydroxypropyl cellulose, poly(2-methyl-2-oxazoline), polyethyleneimine, polyacrylic acid, and carboxymethyl cellulose.

[0087] The formation of the coating film is not necessarily limited to the above-mentioned sol-gel method in which a single metal alkoxide containing a single metal is used multiple times to form a coating film containing multiple non-magnetic metal elements. For example, the coating film may be formed by a sol-gel method using a composite metal alkoxide containing multiple metals. Such a composite metal alkoxide may be, for example, a compound represented by the following chemical formula (Formula IV): M １ OM ２ (OR １ ) ｘ１ (OR ２ ) ｘ２ (Formula IV) (wherein, M １ is Si, and M ２ is the first non-magnetic metal element, and OR １ and OR ２ are each an alkoxy group, and x1 is M １ is a value determined by the valence of M ２The alkoxide may be a double alkoxide represented by the formula (wherein the valence of the alkoxide is determined by the valence of the metal element), or a composite metal alkoxide containing two or more of Si, a first non-magnetic metal element, and a second non-magnetic metal element.

[0088] Alternatively, a coating film containing Si may be formed by a sol-gel method, followed by adding a metal salt containing the first non-magnetic metal element and / or the second non-magnetic metal element to the slurry. Briefly, the surface of precursor particles may be coated with a Si-containing coating, and then a liquid containing a metal salt containing the first non-magnetic metal element and / or the second non-magnetic metal element may be brought into contact with the surface of the Si-containing coating to form the non-magnetic metal element-containing coating. For example, a liquid containing a metal salt containing the first non-magnetic metal element and / or the second non-magnetic metal element may be applied to the surface of the Si-containing coating to form the non-magnetic metal element-containing coating. Alternatively, a non-magnetic metal element-containing coating may be formed on the surface of the Si-containing coating by adding precursor particles having a Si-containing coating to a liquid containing a metal salt containing the first non-magnetic metal element and / or the second non-magnetic metal element and mixing the liquid.

[0089] Alternatively, precursor particles containing the first and / or second non-magnetic metal element may be prepared, and a Si-containing coating film containing Si may be formed on the precursor particles. Then, when the precursor particles having the Si-containing coating film are fired, the first and / or second non-magnetic metal element contained in the precursor particles may be diffused and penetrated into the Si-containing coating film during firing, thereby causing the coating layer to contain the first and / or second non-magnetic metal element.

[0090] Furthermore, a metal nitride component may be applied to the surface of the precursor particles. Alternatively, a non-magnetic metal nitride component may be applied to the surface of the precursor particles in advance by mechanofusion or the like, without forming a coating film containing an element that is more easily oxidized than Fe. Even in this case, the sintered metal nitride component remains in the coating layer and has high electrical resistivity. Naturally, metal oxides and metal nitrides of non-magnetic metals are non-magnetic.

[0091] (Preparation of magnetic material paste) After preparing the magnetic material precursor described above, the magnetic material precursor is mixed with a varnish (e.g., ethyl cellulose, polyvinyl butyral, and / or polyvinyl alcohol), a solvent (e.g., terpineol), etc. in a mixer, and then a dispersion process is performed in a roll mill to obtain a magnetic material paste.

[0092] (Insulator Paste Preparation Process) Non-magnetic insulator particles with a D50 particle size of about 0.1 μm to about 0.5 μm, varnish (a mixture of ethyl cellulose and terpineol), a solvent (terpineol), and optional additives were mixed in a stirrer, and then dispersed in a three-roll mill to obtain a non-magnetic insulator paste. The non-magnetic insulator particles may be composed of, for example, alumina, silica, crystallized glass, or a mixture of a dielectric material such as calcium zirconate, strontium zirconate, or barium zirconate with borosilicate glass for adjusting the sintering temperature.

[0093] (Preparation of Coil Conductor Paste) Conductive particles, varnish, and a solvent (e.g., terpineol) are mixed in a mixer. The mixture is then dispersed in a roll mill to obtain a coil conductor paste. The conductive particles can be copper particles and / or silver particles.

[0094] (Process for Producing Unfired Mother Laminate) After preparing each paste, a magnetic material layer of a predetermined thickness is formed using the magnetic material paste, for example, by screen printing, and then dried. After drying, slit grooves of a predetermined width are formed by laser processing, and the above-mentioned insulating paste is filled into these slit grooves by screen printing or the like, and then dried to form an insulating paste layer corresponding to the second insulating layer 50 (see FIG. 4). Note that the slit grooves are not limited to post-processing by laser processing, and may also be patterned in advance using a screen printing plate or the like.

[0095] After filling the slit grooves with insulating paste and drying it, an insulating layer of a predetermined thickness is formed on the magnetic material layer using the above insulating paste by screen printing and then dried (this will later become the first insulating layer 13 (see Figures 4 and 5)). The insulating paste used to form the insulating layer may be of a different type from the insulating paste filled into the slit grooves.

[0096] Next, a coil conductor having a desired shape (for example, a straight shape, a coil shape, a meander shape, etc.) is formed on the dried insulator paste by screen printing using a coil conductor paste.

[0097] After the coil conductor is formed, magnetic material layers of the same thickness as the coil conductor are formed on the left and right sides of the coil conductor using magnetic material paste, and then dried. After drying, slit grooves of a predetermined width are formed by laser processing, and the above-mentioned insulating paste is filled into these slit grooves by screen printing or the like, and then dried to form an insulating paste layer corresponding to the second insulating layer 50 (see FIG. 4).

[0098] An insulating layer of a predetermined thickness is formed thereon by screen printing using the above insulating paste, and then dried to form an insulating paste layer corresponding to first insulating layer 13 (see FIGS. 4 and 5). The insulating paste used to form the insulating layer may be of a different type from the insulating paste filled into the slit grooves.

[0099] The magnetic material paste is then used to form a magnetic material layer of a predetermined thickness by screen printing, followed by drying. After drying, slit grooves of a predetermined width are formed by laser processing, and the insulating paste is then filled into the slit grooves by screen printing or the like, followed by drying to form an insulating paste layer corresponding to the second insulating layer 50.

[0100] The above has been an example of a method for manufacturing the inductor shown in FIGS. 4 and 5, but by repeatedly forming magnetic material layers and, optionally, insulating layers, various types of unsintered laminates can be obtained.

[0101] In addition, when manufacturing an electronic component having a higher L value, the number of insulating layers may be reduced or eliminated. This makes it possible to adjust the balance between the L value and the DC bias characteristics of the electronic component. In addition, although the above embodiment shows a case in which screen-printed layers formed using a screen printing method are laminated, the present invention is not limited to this, and the electronic component may be manufactured by separately preparing sheets and laminating the sheets.

[0102] (Single-Piece Process of Unfired Mother Laminate and Firing Process) The unfired mother laminate is cut into individual pieces using a dicer or the like, and then the individual pieces are degreased in a firing furnace in a nitrogen atmosphere. ２ : 3% / N ２ By firing the material in a 97% reducing atmosphere at a temperature of 550°C to 1050°C for a predetermined time (for example, 1 hour), a fired laminate of magnetic material and insulating layers with a high-resistance coating layer inside can be obtained. By firing, the multiple metal magnetic bodies are bonded to each other via the coating layer.

[0103] The resulting coating layer in the magnetic material contains oxides or nitrides of non-magnetic metal elements (Si and the first non-magnetic metal element) that are more easily oxidized than Fe. The nitrides are formed by oxidizing the non-magnetic metal elements in a furnace at a pressure of 1 kPa under H ２ : 3% / N ２ : Firing in a 97% reducing atmosphere, N in the reducing gas ２ The non-magnetic metal element can be contained in the coating layer by reacting with the non-magnetic metal element.

[0104] Furthermore, although the above is based on the premise that a non-magnetic insulating layer is formed, by performing an operation such as extending the holding time at the maximum temperature during the firing, it is possible to diffuse and infiltrate the metal magnetic material component from the metal magnetic material layer into the non-magnetic insulating layer, thereby obtaining a low magnetic permeability insulating layer with some magnetic properties.

[0105] (Resin Impregnation Step) Optionally, the fired laminate may be impregnated with a resin material. Specifically, the fired laminate may be immersed in a liquid resin material to fill the voids contained within the fired laminate. This further improves the strength of the fired laminate.

[0106] The resin material to be impregnated may be a thermosetting resin, and specific examples of the thermosetting resin include epoxy resin and silicone resin.

[0107] (Formation of External Electrodes) The outer surface of the fired laminate may then be coated with an insulating resin or the like. In this case, the coating on the portion where the external electrodes are to be connected may be removed using a laser or the like before the external electrodes are installed. At this time, if a coating is provided on the coil conductor, the coating on the coil conductor may also be removed. After the coating is removed, a plating process is performed to form external electrodes connected to the coil conductor, thereby finally obtaining the electronic component of the present disclosure. The material of the external electrodes may be, for example, at least one selected from the group consisting of copper, nickel, and tin.

[0108] In the above-described manufacturing method, metal magnetic particles containing an Fe component are used as the starting material, but the method is not necessarily limited to this. Any method can be applied that can cause a metal magnetic particle containing an Fe component to be present in the magnetic material obtained after firing.

[0109] For example, a metal magnetic material containing an Fe component may be produced by using oxide particles containing an Fe component as precursor particles, which are starting materials, and reducing the oxide particles during firing. Examples of such precursor particles include metal oxides such as ferrite, iron titanate, iron silicate, and iron phosphate. For example, it is particularly preferable to use precursor particles containing iron oxide and reduce them during firing to produce pure iron.

[0110] Alternatively, a mixture of Fe-containing metal magnetic precursor particles and Fe-containing metal oxide particles may be used as the precursor particles. In this method, some unreduced oxide may remain in the sintered magnetic material. In either case, using metal oxide particles as the starting material offers significant advantages, such as improved handling safety and lower material costs.

[0111] Alternatively, Fe-based amorphous alloy particles may be used as precursor particles, and an Fe-based nanocrystalline alloy may be crystallized by firing. Specifically, by firing a magnetic material precursor containing Fe-based amorphous alloy particles as precursor particles, the amorphous phase is crystallized, and an Fe-based nanocrystalline phase can be crystallized. This allows for the production of a magnetic material containing alloy particles containing an Fe-based nanocrystalline phase as a metal magnetic material. Such a metal magnetic material can also be considered as an Fe-based nanocrystalline alloy-containing particle. In the metal magnetic material of the magnetic material produced in this manner, an amorphous phase remains as an uncrystallized portion of the Fe-based amorphous alloy particles. In other words, the metal magnetic material contained in the magnetic material obtained after firing may contain both an amorphous phase and an Fe-based nanocrystalline phase. The presence of an amorphous phase in the metal magnetic material makes it possible to improve the resistivity.

[0112] [Method for manufacturing a sintered toroidal ring core] The present disclosure also provides a method for manufacturing a toroidal ring core as an electronic component having an element body 210 including the magnetic material of the present disclosure and a coil conductor 220 wound around the element body (see FIG. 7).

[0113] (Preparation process for green ring) When manufacturing a toroidal ring core, a magnetic material precursor and a magnetic material paste are prepared in the same manner as in the manufacturing method of the electronic component described above. Then, a magnetic material layer of a predetermined thickness is formed using the magnetic material paste by, for example, a screen printing method, and dried. This is then punched into a ring shape to produce a green ring.

[0114] (Firing process of unfired ring) The unfired ring is degreased in a nitrogen atmosphere in a firing furnace, and then ２ : 3% / N ２ : Sintering is performed in a 97% reducing atmosphere at a temperature of 550°C to 1050°C for a predetermined time (e.g., 1 hour). This results in a toroidal ring core with a high-resistance coating layer inside. By sintering, multiple metal magnetic bodies are bonded to each other via the coating layer. By winding a coil conductor around the resulting toroidal ring core, an electronic component such as that shown in Figure 7 can be obtained.

[0115] Although the embodiments of the present invention have been described above, they are merely typical examples. Those skilled in the art will readily understand that the present invention is not limited to these, and that various modifications are possible within the scope of the present invention.

[0116] Note that one embodiment of the present disclosure as described above includes the following preferred aspects. <1> A magnetic material comprising a plurality of metal magnetic bodies and a coating layer coating the metal magnetic bodies, wherein the metal magnetic bodies contain at least Fe, and the coating layer contains at least one of a metal oxide and a metal nitride containing Si and a first non-magnetic metal element that is more easily oxidized than Fe, and the average thickness of the coating layer is 10 nm or more and 153 nm or less. <2> The magnetic material according to <1>, wherein the first non-magnetic metal element is at least one selected from the group consisting of Zr, Al, Ti, V, Mg, Ca, B, K, Zn, and Mn. <3> A relative ratio R of the first non-magnetic metal element to the total of Si and the first non-magnetic metal element, represented by the following formula I, α１ <1> or <2>, wherein R is 5% or more and 95% or less. α１[%] = α1 [at %] / (Si [at %] + α1 [at %]) × 100 (Formula I) (wherein α1 is a first non-magnetic metal element.) <4> The magnetic material according to <1> to <3>, wherein at least one of the metal oxide and the metal nitride further contains a second non-magnetic metal element different from the first non-magnetic metal element. <5> The magnetic material according to <4>, wherein the second non-magnetic metal element is at least one selected from the group consisting of Li, Na, Sr, Ba, P, Bi, Sn, Te, Pb, and La. <6> The magnetic material according to any one of <1> to <5>, wherein the metal magnetic body contains 99.0 wt % or more of Fe. <7> The magnetic material according to any one of <1> to <5>, wherein the metal magnetic body contains 97.0 wt % or more of Fe. <8> The magnetic material according to any one of <1> to <7>, wherein the metal magnetic body contains an amorphous phase. <9> The magnetic material according to <8>, wherein the metal magnetic body contains an Fe-based nanocrystalline phase. <10> The magnetic material according to any one of <1> to <9>, wherein the metal magnetic body has an equivalent circle diameter of 0.67 μm or more and 3.50 μm or less in a cross-sectional view. <11> The magnetic material according to any one of <1> to <10>, further comprising a resin interposed between the metal magnetic bodies. <12> The magnetic material according to <11>, wherein the resin is at least one selected from the group consisting of epoxy-based resins and silicone-based resins. <13> An electronic component comprising an element body including the magnetic material according to any one of <1> to <12> and a coil conductor. <14> A method for producing a magnetic material, comprising: coating the surfaces of precursor particles with a composite metal alkoxide to form a magnetic material precursor; and sintering the magnetic material precursor, wherein the precursor particles contain at least Fe, and the composite metal alkoxide contains Si and a non-magnetic metal element that is more easily oxidized than Fe. <15> A method for producing a magnetic material, comprising: coating the surface of precursor particles with a Si-containing coating; contacting the surface of the Si-containing coating with a solution of a metal salt containing a first non-magnetic metal element that is more easily oxidized than Fe to obtain a magnetic material precursor; and sintering the magnetic material precursor, wherein the precursor particles contain at least Fe. <16> The production method according to <14> or <15>, wherein the first non-magnetic metal element is at least one selected from the group consisting of Zr, Al, Ti, V, Mg, Ca, B, K, Zn, and Mn.<17> The method according to any one of <14> to <16>, wherein the composite metal alkoxide or the metal salt further contains a second non-magnetic metal element different from the first non-magnetic metal element. <18> The method according to <17>, wherein the second non-magnetic metal element is at least one selected from the group consisting of Li, Na, Sr, Ba, P, Bi, Sn, Te, Pb, and La. <19> The method according to any one of <14> to <18>, wherein the precursor particles contain oxide particles containing Fe element, and the sintering comprises reducing the metal oxide particles. <20> The method according to <19>, wherein the metal oxide particles are iron oxide particles. <21> The method according to any one of <14> to <18>, wherein the precursor particles contain an Fe-based amorphous alloy, and the sintering comprises crystallizing an Fe-based nanocrystalline alloy from the Fe-based amorphous alloy.

[0117] The above effects are merely examples, and the present invention is not limited to the above, and additional effects may also be provided.

[0118] Examples related to the present disclosure will be described below.

[0119] [Example A] <Production of Samples of Examples 1 to 4 and Comparative Examples 1 to 3> (Preparation of Magnetic Material Precursor) Pure iron particles (carbonyl iron powder (soft grade), Fe concentration 99.1 wt%) with a D50 particle size of 8.82 μm were used as the precursor particles, which are the starting material for the metal magnetic body.

[0120] Next, a coating film was formed on the precursor particles by a sol-gel method. Specifically, the precursor particles and Si alkoxide (Si(OEt) ４ ) and water to prepare a slurry, and the Si alkoxide was hydrolyzed in this slurry. The slurry was then dried to obtain a magnetic material precursor containing precursor particles whose surfaces were covered with a coating film containing Si. This magnetic material precursor was used as Comparative Example 1.

[0121] In Examples 1 to 4 and Comparative Examples 2 and 3, the magnetic material precursor was introduced into a liquid in which Al metal salt (Al nitrate) was dissolved in water, and a magnetic material precursor was obtained whose surface was covered with a coating film containing Si and Al. The cross-section of the obtained magnetic material precursor was observed using the following method. First, the magnetic material precursor was solidified with resin and polished with a polishing device (polishing device Tegramin-25 (manufactured by Struers)) to obtain a cross-section. The polished magnetic material was then processed by FIB processing into a shape suitable for STEM-EDX measurement, and a cleaning process was performed using Ar flat milling. The cross-section of the magnetic material precursor after the cleaning process was observed using STEM-EDX measurement, and STEM images and element mapping images were obtained. It was found that the coating film was a single layer, with Si and Al coexisting within the coating film.

[0122] The above-described coating film formation procedure was repeated one more time in producing the magnetic material of Example 4. In Comparative Example 3, the above-described coating film formation procedure was repeated two more times.

[0123] The thickness of the coating film on the precursor particles contained in the magnetic material precursor before firing was measured from an STEM image and was in the range of about 14 nm to about 308 nm. Note that, since the thickness of the coating film increases as the concentration of the metal alkoxide in the slurry increases, in Comparative Example 2 and Examples 1 to 3, the thickness of the coating film was adjusted by the concentration of the metal alkoxide.

[0124] (Forming of green rings) The above-mentioned magnetic material precursor, varnish (a mixture of ethyl cellulose and terpineol), and solvent (terpineol) were mixed in a stirrer. Then, a dispersion process was performed in a roll mill to obtain a magnetic material paste. Using the obtained magnetic material paste, a magnetic material layer of a predetermined thickness was formed by screen printing and dried. This was punched into a ring shape to produce a green ring.

[0125] (Firing of Unfired Rings) Unfired rings were placed in a firing furnace in a nitrogen atmosphere (N ２ After degreasing with 100%), ２ : 3% / N ２The resultant was fired at 1000°C for 120 minutes in a 97% reducing atmosphere. The firing formed a magnetic material including a plurality of metal magnetic bodies having a high-resistivity coating layer containing Si and Al as a first non-magnetic metal element.

[0126] (Resin Impregnation) The magnetic material obtained after firing was immersed in a silicone resin (KR-242A (manufactured by Shin-Etsu Chemical Co., Ltd.)) to fill the voids present inside the toroidal ring core. The silicone resin was then cured by heating at 200°C, and a toroidal ring core containing the magnetic material was obtained.

[0127] <Preparation of Samples of Examples 5 to 9 and Comparative Examples 4 to 5> (Preparation of Magnetic Material Precursor) For the precursor particles, which are the starting material for the metal magnetic body, Fe-Ni alloy (Fe: 55 at %, Ni: 45 at %) particles with a D50 particle size of 0.80 μm were prepared. Note that these precursor particles were prepared by a wet synthesis method, and Na derived from the reducing agent used during synthesis was contained within the particles.

[0128] Next, the precursor particles and Si alkoxide (Si(OEt) ４ The silicon alkoxide was hydrolyzed in the slurry, and the slurry was then dried to obtain a magnetic material precursor containing precursor particles whose surfaces were covered with a coating film containing silicon.

[0129] In preparing the magnetic materials of Examples 5 to 9 and Comparative Examples 4 and 5, Zr alkoxide (Zr(OBu) ４ The Si alkoxide and Zr alkoxide were hydrolyzed in the composite alkoxide slurry, which was then dried to obtain a magnetic material precursor containing precursor particles whose surfaces were covered with a coating film containing Si and Zr as a first non-magnetic metal element.

[0130] The above-described coating film formation procedure was repeated once more in the preparation of the magnetic material of Example 9. In Comparative Example 5, the above-described coating film formation procedure was repeated two more times.

[0131] The thickness of the coating film on the precursor particles contained in the magnetic material precursor before firing was in the range of 12 nm to 293 nm.

[0132] (Forming of green rings) The above-mentioned magnetic material precursor, varnish (a mixture of ethyl cellulose and terpineol), and solvent (terpineol) were mixed in a stirrer. Then, a dispersion process was performed in a roll mill to obtain a magnetic material paste. Using the obtained magnetic material paste, a magnetic material layer of a predetermined thickness was formed by screen printing and dried. This was punched into a ring shape to produce a green ring.

[0133] (Firing of Unfired Rings) Unfired rings were placed in a firing furnace in a nitrogen atmosphere (N ２ After degreasing with 100%), ２ : 3% / N ２ The material was fired at 800°C for 60 minutes in a 97% reducing atmosphere. Sintering was possible at a relatively low firing temperature. This is presumably because the Na contained in the precursor particles diffused into the coating film as a second non-magnetic metal element, thereby lowering the softening point of the coating film. The firing yielded a magnetic material containing multiple metal magnetic bodies with a high-resistance coating layer. The coating layer contained Si, Zr as the first non-magnetic metal element, and Na as the second non-magnetic metal element, due to the Na contained in the precursor particles diffusing into the coating film.

[0134] (Resin Impregnation) The magnetic material obtained after firing was immersed in epoxy resin to fill the voids present inside the toroidal ring core. The epoxy resin was then cured by heating at 100°C to obtain the final toroidal ring core.

[0135] <Evaluation Method> The obtained toroidal ring cores of the examples and comparative examples were evaluated for the average equivalent circle diameter, the average thickness of the coating layer, the presence or absence of defects in the coating film, and the sinterability. The specific evaluation methods are as follows.

[0136] (Method for measuring the average equivalent circle diameter) Each of the obtained toroidal ring cores was resin-hardened, polished with a polishing machine Tegramin-25 (manufactured by Struers), and subjected to ion milling with an ion milling machine IM-3000 (manufactured by Hitachi High-Technologies Corporation). SEM images and element mapping images were then obtained using a field emission scanning electron microscope SU8230 (manufactured by Hitachi High-Technologies Corporation). The imaging magnification was adjusted in the range of 3,500 to 60,000 times.

[0137] The acquired images were analyzed using image analysis software WinROOF2021 (manufactured by Mitani Corporation) to calculate the equivalent circle diameter. For the analysis, the equivalent circle diameters were calculated for 20 metal magnetic bodies at each of three arbitrary locations near halfway along the thickness direction of the toroidal ring core, that is, for a total of 60 metal magnetic bodies at the three locations. The average equivalent circle diameter was calculated from the average of the calculated equivalent circle diameters.

[0138] (Method for measuring the average thickness D of the coating layer) Each of the obtained toroidal ring cores was hardened with resin and polished to a position halfway along the length of the toroidal ring core using a polishing machine Tegramin-25 (manufactured by Struers). After that, it was processed by FIB (focused ion beam) processing into a shape suitable for the subsequent STEM-EDX measurement, and finally, a cleaning process was performed by Ar flat milling to obtain a processed sample.

[0139] Using the obtained processed sample, the cross section of the toroidal ring core was observed by STEM-EDX measurement, and STEM images and element mapping images were obtained. Line analysis of the obtained STEM images and element mapping images was performed using image analysis software, and the thickness of the coating layer was determined by quantitatively evaluating the abundance ratio of Si, the first non-magnetic metal element (Zr or Al), and the second non-magnetic metal element (Na) in the coating layer between Fe and the metal magnetic material. The line analysis was performed at the position of the smallest distance between any one metal magnetic material in the SEM image of the cross section of the toroidal ring core and the metal magnetic material closest to the selected metal magnetic material via the coating layer. In this case, the interface between the coating layer and the metal magnetic body was determined as the point where the plot of each component of Si and the first non-magnetic metal element intersects with the plot of Fe contained in one metal magnetic body as one end point, and the point where the plot of Fe contained in the other metal magnetic body intersects with the plot of Fe contained in the other metal magnetic body as the other end point.The area enclosed by the plot of each component and the horizontal axis was determined as the point where the area exceeded 1% of the maximum value in the plot of the element where the area exceeded 35% of the maximum value in the plot of oxygen.The distance between the determined interfaces was obtained as the total thickness 2d of the coating layer existing between the two metal magnetic bodies.Half of the obtained total thickness 2d was determined as the coating layer thickness d.

[0140] The coating layer thickness d was measured for any 10 metallic magnetic bodies, and the average value of the thicknesses d was taken as the average thickness D.

[0141] (Method for determining the presence or absence of defects in the coating film (before firing)) After the coating film was formed, the magnetic material precursor containing the precursor particles was hardened with resin and polished using a polishing machine Tegramin-25 (manufactured by Struers). After that, it was processed by FIB (focused ion beam) processing into a shape suitable for STEM-EDX measurement, and finally, a cleaning process was performed by Ar flat milling to obtain a processed sample.

[0142] Using the obtained processed samples, the cross-sections of the precursor particles were observed by STEM-EDX measurement, and STEM images and elemental mapping images were obtained. The imaging magnification was adjusted in the range of 3,500 to 60,000 times. The presence or absence of coating film defects was determined for 20 random precursor particles from STEM images and elemental mapping images obtained using image analysis software. Specifically, the presence or absence of discontinuities in the coating film due to the presence of voids or peeling (cracks) in the coating film was used as the criterion for evaluation (criterion 1). In Table 1, the presence of discontinuities in the coating film or peeling (cracks) in the coating film was evaluated as ×, and the absence of discontinuities in the coating film or peeling (cracks) in the coating film was evaluated as 〇. Note that for precursor particles that were evaluated as × in terms of the coating film, the precursor particles were not properly coated before firing, and therefore the sinterability of the fired metal magnetic body, as described below, was not evaluated.

[0143] (Method for Determining Sinterability) The sinterability of the magnetic material was determined by evaluating the degree of coarsening of the metal magnetic body after sintering. As described above, excessively coarsened metal magnetic body increases eddy current loss, so it is preferable that magnetic materials used under high frequency conditions contain metal magnetic body in which coarsening is suppressed. The degree of coarsening of the metal magnetic body was evaluated by measuring the coverage rate of the metal magnetic body, which will be described in detail below. For example, when the metal magnetic body coarsens, a structure in which multiple metal magnetic bodies are connected is formed, and the coverage rate of the metal magnetic body decreases. In other words, the higher the coverage rate of the metal magnetic body contained in the magnetic material, the more suppressed is the coarsening of the metal magnetic body in the magnetic material. Below, the method for determining sinterability will be described using the measurement of the toroidal ring core of Example 5 as an example.

[0144] Using the STEM image and EDX image acquired when measuring the average thickness of the coating layer described above, the judgment criterion (criterion 2) was whether or not 80% or more of any 20 independent metal magnetic particles present in the image were surrounded by the coating layer. In this case, an independent metal magnetic particle was one that could be determined from the STEM image and EDX image to be clearly separated and not overlapping with other metal magnetic particles.

[0145] The metal magnetic body surrounded by the coating layer is defined as a metal magnetic body whose proportion of the periphery covered by the coating layer (coverage) is 90% or more. The coverage was calculated as follows.

[0146] (1) The metal magnetic body was divided into 10 areas at equal intervals radially, with the center of gravity of the metal magnetic body as the center. (2) For each divided area, a line analysis was performed from the metal magnetic body to be measured to a metal magnetic body adjacent to the metal magnetic body to be measured via a coating layer. Hereinafter, for convenience of explanation, the metal magnetic body to be measured will be referred to as the target metal magnetic body 11A, and the metal magnetic body adjacent to the metal magnetic body to be measured 11A will be referred to as the adjacent metal magnetic body 11Aa. As shown in Figures 8 to 10, the line analysis was performed by drawing a line L along a normal to the outermost edge from the intersection P of the center of gravity G of the target metal magnetic body 11A, which intersects with the outermost edge of the target metal magnetic body 11A, and the center line C extends radially to bisect the divided area 112. ｓｔ -L ｅｎ The above was carried out. Here, "the outermost edge of the metal magnetic body" means the outer edge of the target metal magnetic body that is closer to the adjacent metal magnetic body 11Aa among the outer edges of the target metal magnetic body. For example, when the center line C of the divided area 112 has multiple intersections with the outer edge of the target metal magnetic body 11A (see Figures 10 and 11), the "intersection P with the outermost edge of the metal magnetic body" refers to the intersection that is closer to the adjacent metal magnetic body. Such intersection P can also be interpreted as an intersection that is farther from the center of gravity G of the target metal magnetic body. Starting point L of line analysis ｓｔ is an arbitrary point within the target metal magnetic body 11A, and the end point L ｅｎwas an arbitrary point within the adjacent metal magnetic body 11Aa. (3) From the results of the line analysis, the interface between the coating layer and the metal magnetic body was determined in the same manner as in measuring the average thickness of the coating layer. If a measurement point where the total content of Si, non-magnetic metal elements, O (oxygen), and N (nitrogen) was 70 at% existed between the interface between the target metal magnetic body and the coating layer and the interface between the adjacent metal magnetic body and the coating layer, that divided area was determined to be an area covered by the coating layer (hereinafter also referred to as a "coated area"). Note that if the line analysis results showed that the content of N (nitrogen) or O (oxygen) was below the lower detection limit (0.5 at%), the divided area where a measurement point where the total content of other elements constituting the coating layer (Si, non-magnetic metal elements, and O (oxygen) or N (nitrogen)) was 70 at% existed was determined to be a covered area. (4) Measurements (2) and (3) were performed for each divided area, and the coverage rate of the target metal magnetic body was calculated according to the following formula (V). Coverage (%) = Number of "covered areas" / 10 (Number of divided areas) × 100 (Formula V)

[0147] Toroidal ring cores in which 80% or more of the metal magnetic material had a coverage rate of 90% or more (i.e., 90% or more of the divided areas were covered) were judged to be "good products" (◯) with "little coarsening." On the other hand, toroidal ring cores in which all of the measured metal magnetic material had a coverage rate of less than 90% were judged to be "significantly coarsened" (×), and toroidal ring cores in which the proportion of metal magnetic material with a coverage rate of 90% or more was less than 80% were judged to be "coarsened" (△).

[0148] In the present disclosure, a magnetic material in which a coating film is suitably formed and in which coarsening of the metal magnetic material is suppressed is evaluated as a magnetic material with excellent high-frequency characteristics. Specifically, a toroidal ring core that is evaluated as ◯ in both the above-mentioned Criterion 1 and Criterion 2 is judged to have passed the overall evaluation and is indicated as "pass" in Table 1. On the other hand, a toroidal ring core that is evaluated as × or △ in at least one of Criterion 1 and Criterion 2 is judged to have failed and is indicated as "fail" in Table 1. The evaluation results are shown in Table 1 below.

[0149]

[0150] As shown in Table 1, in Comparative Example 1, which did not contain the first non-magnetic metal element in addition to Si, significant coarsening due to necking sintering of multiple metal magnetic materials was observed. Furthermore, in the magnetic materials of Comparative Examples 2 and 4, which contained Si and the first non-magnetic metal element but had an excessively small average thickness D of the coating layer, the thickness of the coating film was insufficient, and coarsening due to necking sintering was observed. Furthermore, in the magnetic materials of Comparative Examples 3 and 5, which had an excessively large average thickness D of the coating layer, cracks were observed in the coating film when the precursor particles were observed before firing. This is thought to be due to distortion occurring at the interface between the precursor particles and the coating layer as the surface smoothness of the precursor particles was impaired with each increase in the number of treatments used to form the coating film.

[0151] On the other hand, it was confirmed that the toroidal ring cores of Examples 1 to 9 contained magnetic materials in which coarsening due to necking was suitably suppressed. This is presumably because the magnetic materials were provided with a coating layer containing Si, which is more easily oxidized than Fe, and the first non-magnetic metal element Zr or Al, which suppressed the diffusion of Fe ions during firing and thus suppressed necking sintering.

[0152] Furthermore, it was found that the magnetic materials of Examples 1 to 9, in which the average thickness D of the coating layer was within an appropriate range, had formed coating films that were free of defects and could suitably suppress the diffusion of Fe ions. From the above, it was found that by providing a coating layer that contains Si, which is more easily oxidized than Fe, and the first non-magnetic metal element, and that has an appropriate average thickness, it is possible to suitably suppress the coarsening of the metal magnetic material, suppress eddy current loss, and obtain a magnetic material with excellent high-frequency characteristics.

[0153] Tables 2 and 3 also show the relative contents of Si, the first non-magnetic metal element, and the second non-magnetic metal element in the coating layer, obtained from the results of line analysis performed on the magnetic materials of Examples 1 to 4 and 5 to 9. The contents are based on the values ​​obtained from the results of line analysis within the range of coating layer thickness 2d, determined in accordance with the method for measuring the thickness of the coating layer. The contents shown in Tables 2 and 3 are the average values ​​of the contents obtained for 10 random metal magnetic particles. Tables 2 and 3 also show the results of calculating the average equivalent circle diameter of the metal magnetic particles contained in the magnetic material of each Example.

[0154]

[0155]

[0156] The results in Tables 2 and 3 show that when the contents of Si, the first non-magnetic metal element, and the second non-magnetic metal element are changed, providing a coating layer containing Si and the first non-magnetic metal element at various contents suppresses the occurrence of defects in the coating film and the coarsening of the metal magnetic material. Furthermore, since the provision of the coating layer suppresses the coarsening of the metal magnetic material, a magnetic material containing small-sized metal magnetic material with an equivalent circle diameter in the range of 0.67 μm to 3.5 μm was obtained.

[0157] In addition, similar evaluations were also performed on magnetic materials having coating films containing, instead of Zr or Al, other non-magnetic metal elements (e.g., Ti) that are more easily oxidized than Fe as the first non-magnetic metal element. As a result, it was confirmed that, as in Examples 1 to 9, the effects of suppressing the occurrence of defects in the coating film and suppressing the coarsening of the metal magnetic material were achieved.

[0158] In addition, similar evaluations were performed on magnetic materials having coating films containing, instead of Na, another non-magnetic metal element (e.g., Li) that is more easily oxidized than Fe as the second non-magnetic metal element. As a result, it was confirmed that, as in Examples 6 to 9, the effects of suppressing the occurrence of defects in the coating film and suppressing the coarsening of the metal magnetic material were achieved.

[0159] [Example B] In Example B, a magnetic material was produced using carbonyl iron powder (soft grade) having a smaller particle size than that of Example A as precursor particles, and the metal magnetic material contained in the obtained magnetic material was evaluated.

[0160] <Preparation of Sample of Example 10> (Preparation of Magnetic Material Precursor) Pure iron particles (carbonyl iron powder (soft grade), Fe concentration 99.2 wt %) with a D50 particle size of 3.07 μm were used as precursor particles, which are the starting material of the metal magnetic material.

[0161] A coating film was formed on the precursor particles by the same method as in Example 5. Specifically, Ca alkoxide (Ca(OEt) ４ ) and polyvinylpyrrolidone (Pitzcol manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a water-soluble polymer were further added to prepare a composite alkoxide slurry, and the Si alkoxide and Ca alkoxide were hydrolyzed in this slurry. The slurry was then dried to obtain a magnetic material precursor containing precursor particles whose surfaces were covered with a coating film containing Si and Ca as the first non-magnetic metal element.

[0162] (Firing of green rings) The H ２ : 3% / N ２ : By firing at 650°C for 60 minutes in a 97% reducing atmosphere, a magnetic material including a plurality of metal magnetic bodies having a coating layer containing Si and a first non-magnetic metal element (Ca) was formed.

[0163] <Preparation of Sample of Example 11> Zn alkoxide (Zn(OEt) ２ A magnetic material containing a plurality of metal magnetic bodies having a coating layer containing Si and a first non-magnetic metal element (Zn) was formed in the same manner as in Example 10, except that a magnetic material containing a plurality of metal magnetic bodies having a coating layer containing Si and a first non-magnetic metal element (Zn) was formed in place of polyvinylpyrrolidone, and a polyamideimide (HPC-1000-28, manufactured by Resonac Co., Ltd.) which is a mixture with ion-exchanged water was used instead of polyvinylpyrrolidone.

[0164] <Preparation of Sample of Example 12> Instead of Ca alkoxide, Al alkoxide (Al(OPr) ３A magnetic material containing a plurality of metal magnetic bodies having a coating layer containing Si and a first non-magnetic metal element (Al) was formed in the same manner as in Example 10, except that a magnetic material containing a plurality of metal magnetic bodies having a coating layer containing Si and a first non-magnetic metal element (Al) was formed in place of polyvinylpyrrolidone, and a polyamideimide (HPC-1000-28, manufactured by Resonac Co., Ltd.) which is a mixture with ion-exchanged water was used instead of polyvinylpyrrolidone.

[0165] (Evaluation of Metallic Magnetic Material) The magnetic material precursor before firing and the toroidal ring core after firing were evaluated in the same manner as in Example A. The evaluation results are shown in Table 4 below.

[0166]

[0167] It was confirmed that the toroidal ring cores of Examples 10 to 12 contained magnetic materials in which coarsening due to necking was suitably suppressed. This is presumably because the magnetic materials were provided with a coating layer containing Si, which is more easily oxidized than Fe, and the first non-magnetic metal element Ca, Zn, or Al, which suppressed the diffusion of Fe ions during firing and suppressed necking sintering.

[0168] Furthermore, it was confirmed that a coating film that was free of defects and capable of suitably suppressing the diffusion of Fe ions was formed in the magnetic materials of Examples 10 to 12. From the above, it was found that the magnetic materials of Examples 10 to 12, like Examples 1 to 9, were magnetic materials in which the coarsening of the metal magnetic body was suitably suppressed, eddy current loss was suppressed, and the magnetic materials had excellent high-frequency characteristics.

[0169] Table 5 also shows the relative contents of Si and the first non-magnetic metal element α1 in the coating layer obtained from the results of line analysis performed on the magnetic materials of Examples 10 to 12. The contents correspond to the values ​​obtained from the results of line analysis within the range of coating layer thickness 2d determined in accordance with the method for measuring the thickness of the coating layer. The contents shown in Table 5 are the average values ​​of the contents obtained for 10 random metal magnetic bodies. Table 5 also shows the results of calculating the average equivalent circle diameter of the metal magnetic bodies contained in the magnetic material of each example.

[0170]

[0171] From the results in Table 5, it was found that in Examples 10 to 12, which had different contents of Si and the first non-magnetic metal element, the effects of suppressing the occurrence of defects in the coating film and suppressing the coarsening of the metal magnetic body were obtained, similar to the magnetic materials of Examples 1 to 9. Furthermore, since the provision of the coating layer suppresses the coarsening of the metal magnetic body, a magnetic material containing metal magnetic bodies with a small equivalent circle diameter was obtained.

[0172] Example C Furthermore, in Example C, a magnetic material was produced using iron oxide particles as precursor particles, and the metal magnetic material contained in the obtained magnetic material was evaluated.

[0173] (Preparation of Magnetic Material Precursor) A toroidal ring core was produced in the same manner as in Example 5, except that iron oxide particles were used as precursor particles. As the iron oxide particles, iron oxide particles (Fe) having a D50 particle size of 1.27 μm were used. ２ O ３ : hematite) was used.

[0174] (Evaluation of Metallic Magnetic Material) The coercivity of the unsintered ring before sintering and the toroidal ring core obtained after sintering was measured using an automatic coercivity meter K-HC1000 (manufactured by Tohoku Special Steel Co., Ltd.). As a result, the coercivity of the unsintered ring was 32 A / m, while the coercivity of the toroidal ring core after sintering was 1320 A / m, confirming an increase in coercivity due to sintering. This indicated that the iron oxide particles, which have a low coercivity, had a high coercivity after sintering. In other words, it was shown that the iron oxide particles were reduced to ferromagnetic metallic Fe by sintering.

[0175] The resulting toroidal ring core was then resin-hardened, polished using a Tegramin-25 polishing machine (manufactured by Struers), and subjected to ion milling using an IM-3000 ion milling machine (manufactured by Hitachi High-Technologies Corporation). SEM images, and optionally elemental mapping images, were then obtained using a field-emission scanning electron microscope SU8230 (manufactured by Hitachi High-Technologies Corporation). The imaging magnification was 20,000x. As a result, Fe was detected in each of the metallic magnetic particles contained within the field of view, while oxygen was below the lower detection limit (1 at%). These results confirmed that the non-magnetic iron oxide used as the precursor particles was reduced to ferromagnetic metallic Fe after firing.

[0176] Furthermore, the magnetic material precursor before firing and the toroidal ring core after firing were evaluated using the same method as in Example A, and the results are shown in Table 6. As shown in the table, no defects were observed in the coating film in the magnetic material precursor of Example B. Furthermore, in the toroidal ring core after firing, the average circular equivalent diameter of the metal magnetic material was 1.05 μm. Furthermore, since the proportion of metal magnetic material with a coverage rate of 90% or more by the coating layer was 80% or more, it was recognized that the degree of coarsening of the metal magnetic material due to necking, etc. was also suppressed.

[0177]

[0178] From the above, it was confirmed that the toroidal ring core obtained using iron oxide as precursor particles satisfied the criteria 1 and 2 described in Example A. Therefore, according to the present disclosure, it was confirmed that even when a magnetic metal oxide is used as the precursor particle as the starting material, a magnetic material with excellent high-frequency characteristics can be obtained, similar to when magnetic metal precursor particles are used.

[0179] Example D Furthermore, in Example D, a magnetic material was produced using Fe-based nanocrystalline alloy particles as precursor particles, and the metallic magnetic material contained in the obtained magnetic material was evaluated.

[0180] (Preparation of Magnetic Material Precursor) As precursor particles, Fe-based nanocrystalline alloy particles (Fe) of standard FINEMET® composition with a D50 particle size of 2.23 μm were used. ７４ Si １５ B ７ Nb ３ Cu １ (Fe: 74 at%, Si: 15 at%, B: 7 at%, Nb: 3 at%, Cu: 1 at%) was used.

[0181] The precursor particles were placed in a liquid in which K metal salt was dissolved in a solvent (ethanol), to obtain a magnetic material precursor whose surface was covered with a coating film containing Si and K. In other words, the magnetic material of this example contained K as a non-magnetic metal element. Then, a green ring was molded in the same manner as in Example 1.

[0182] The unsintered powder compact is placed in a sintering furnace in a nitrogen atmosphere (N ２ After degreasing with 100%), ２ : 3% / N ２ The mixture was fired at 570°C for 60 minutes in a 97% reducing atmosphere. The firing yielded a magnetic material including a plurality of metal magnetic bodies having a high-resistivity coating layer containing Si and K as a first non-magnetic metal element.

[0183] <Evaluation of Core Loss> The core loss per unit volume of the obtained toroidal ring core was measured. For the measurement, a network analyzer (8753E, manufactured by HP), an RF power amplifier (A009K401-4444R), a stabilized power supply (PWR800L, manufactured by Kikusui Electronics Co., Ltd.), and a stabilized power supply controller (PIA4830, manufactured by Kikusui Electronics Co., Ltd.) were used. The measurement was carried out under the conditions of a DC bias current Idc of 1 A, a maximum magnetic flux density of 2 mT, and a frequency of 15 MHz. As a result of the measurement, the core loss of the toroidal ring core of this Example C was 140 kW / m ３ It was.

[0184] Furthermore, as a reference sample, the core loss of a toroidal ring core produced by the same process as above using pure iron particles as precursor particles was also measured. The pure iron particles used were pure iron particles (carbonyl iron powder (soft grade), Fe content: 99.1 wt%) with a D50 particle size of 1.59 μm. When the core loss was measured under the same conditions as in Example C, the core loss of this reference sample was 170 kW / m ３ From this result, it was found that when Fe-based nanocrystalline alloy particles were used as precursor particles, a magnetic material that was more suitable in terms of core loss could be obtained.

[0185] Furthermore, the magnetic material precursor before sintering and the toroidal ring core after sintering were evaluated using the same method as in Example A, and the results are shown in Table 7. As a result of the evaluation, no defects were found in the coating film in the magnetic material precursor. Furthermore, in the toroidal ring core after sintering, the average circular equivalent diameter of the metal magnetic material was 1.87 μm. Furthermore, since the proportion of metal magnetic material with a coverage rate of 90% or more by the coating layer was 80% or more, it was recognized that the degree of coarsening of the metal magnetic material due to necking, etc. was also suppressed.

[0186]

[0187] From the above, it was confirmed that the toroidal ring core obtained using an Fe-based nanocrystalline alloy as precursor particles satisfied the criteria 1 and 2 described in Example A. Therefore, according to the present disclosure, it was confirmed that by using Fe-based nanocrystalline alloy particles as precursor particles, a magnetic material with excellent high-frequency characteristics that is more suitable in terms of core loss can be obtained.

[0188] REFERENCE SIGNS LIST 100 Electronic component 10 Base body 11A Metal magnetic body 11B Coating layer 11 Magnetic material 13 First insulating layer 20 Coil conductor 30, 40 External electrode 50 Second insulating layer 60 Outer layer 200 Electronic component 210 Base body 220 Coil conductor

Claims

1. A magnetic material comprising a plurality of metal magnetic bodies and a coating layer coating the metal magnetic bodies, wherein the metal magnetic bodies contain at least Fe, and the coating layer contains at least one of a metal oxide and a metal nitride containing Si and a first non-magnetic metal element that is more easily oxidized than Fe, and the average thickness of the coating layer is 10 nm or more and 153 nm or less.

2. The magnetic material according to claim 1, wherein the first non-magnetic metal element is at least one selected from the group consisting of Zr, Al, Ti, V, Mg, Ca, B, K, Zn, and Mn.

3. A relative ratio R of the first non-magnetic metal element to the sum of Si and the first non-magnetic metal element, as represented by the following formula I: α１ The magnetic material according to claim 1 or 2, wherein R is 5% or more and 95% or less. α１ [%]=α1[at %] / (Si[at %]+α1[at %])×100 (Equation I) (wherein α1 is the first non-magnetic metal element.) 4. A magnetic material according to any one of claims 1 to 3, wherein at least one of the metal oxide and the metal nitride further contains a second non-magnetic metal element different from the first non-magnetic metal element.

5. The magnetic material according to claim 4, wherein the second non-magnetic metal element is at least one selected from the group consisting of Li, Na, Sr, Ba, P, Bi, Sn, Te, Pb, and La.

6. The magnetic material according to any one of claims 1 to 5, wherein the metallic magnetic body contains 99.0% by weight or more of Fe.

7. The magnetic material according to any one of claims 1 to 5, wherein the metallic magnetic body contains 97.0% by weight or more of Fe.

8. The magnetic material according to any one of claims 1 to 7, wherein the metallic magnetic substance contains an amorphous phase.

9. The magnetic material according to claim 8, wherein the metallic magnetic body comprises an Fe-based nanocrystalline phase.

10. The magnetic material according to any one of claims 1 to 9, wherein the metal magnetic substance has an equivalent circle diameter of 0.67 μm or more and 3.50 μm or less in cross section.

11. The magnetic material according to any one of claims 1 to 10, further comprising a resin interposed between the metal magnetic particles.

12. The magnetic material according to claim 11, wherein the resin is at least one selected from the group consisting of epoxy resins and silicone resins.

13. An electronic component comprising an element body containing the magnetic material according to any one of claims 1 to 12 and a coil conductor.

14. A method for producing a magnetic material, comprising: coating the surfaces of precursor particles with a composite metal alkoxide to form a magnetic material precursor; and sintering the magnetic material precursor, wherein the precursor particles contain at least Fe, and the composite metal alkoxide contains Si and a first non-magnetic metal element that is more easily oxidized than Fe.

15. A method for producing a magnetic material, comprising: coating the surface of precursor particles with a Si-containing coating; contacting the surface of the Si-containing coating with a liquid in which a metal salt containing a first non-magnetic metal element that is more easily oxidized than Fe is dissolved, thereby forming a non-magnetic metal element-containing coating, thereby obtaining a magnetic material precursor; and sintering the magnetic material precursor.

16. The method according to claim 14 or 15, wherein the first non-magnetic metal element is at least one selected from the group consisting of Zr, Al, Ti, V, Mg, Ca, B, K, Zn, and Mn.

17. The method according to any one of claims 14 to 16, wherein the composite metal alkoxide or the metal salt further contains a second non-magnetic metal element different from the first non-magnetic metal element.

18. The method according to claim 17, wherein the second non-magnetic metal element is at least one selected from the group consisting of Li, Na, Sr, Ba, P, Bi, Sn, Te, Pb, and La.

19. The method according to any one of claims 14 to 18, wherein the precursor particles include oxide particles containing elemental Fe, and the sintering step includes reducing the oxide particles.

20. The method of claim 19, wherein the oxide particles are iron oxide particles.

21. The method according to any one of claims 14 to 18, wherein the precursor particles include an Fe-based amorphous alloy, and the sintering step includes crystallizing an Fe-based nanocrystalline alloy from the Fe-based amorphous alloy.

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