Metallic magnetic powders, composite magnetic bodies, and electronic components

Abstract

To provide metal magnetic powders that present a high permeability and a low magnetic loss in a high-frequency region of a giga-hertz band, a composite magnetic body including the metal magnetic powders, and an electronic component.SOLUTION: The present invention relates to metal magnetic powders mainly including Co, the metal magnetic powders including metal nano-particles with average particle diameters (D50) of 1-100 nm. The main phase of each metal nano-particle is hcp-Co and the metal magnetic powders include fcc-Co and / or ε-Co as a sub-phase.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present disclosure relates to a metal magnetic powder containing metal nanoparticles mainly composed of Co, a composite magnetic body, and an electronic component. [Background technology]

[0002] In recent years, the operating frequencies of high-frequency circuits included in various communication devices such as mobile phones and wireless LAN devices have reached the gigahertz band (for example, the 3.7 GHz band (3.6 to 4.2 GHz) and the 4.5 GHz band (4.4 to 4.9 GHz)). Examples of electronic components mounted in such high-frequency circuits include inductors, antennas, and filters for suppressing high-frequency noise. Although air-core coils with non-magnetic cores are generally used for the coils built into such electronic components for high-frequency applications, there is a demand for the development of magnetic materials that can be used in electronic components for high-frequency applications in order to improve the characteristics of electronic components.

[0003] For example, Patent Document 1 discloses a magnetic material made of metal nanoparticles as a magnetic material for high frequencies. Metal nanoparticles can reduce the number of magnetic domains per unit particle compared to metal magnetic particles on the order of micrometers, and can reduce eddy current loss in the high frequency band. However, even with the magnetic material described in Patent Document 1, the magnetic permeability drops dramatically when the operating frequency exceeds 1 GHz (Figure 2 of Patent Document 1), and magnetic loss increases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-303298 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure has been made in consideration of the above-mentioned circumstances, and its purpose is to provide a metal magnetic powder that has high magnetic permeability and low magnetic loss in the high frequency region of the gigahertz band, and a composite magnetic body and electronic component that include the metal magnetic powder. [Means for solving the problem]

[0006] In order to achieve the above object, the metal magnetic powder according to the present disclosure is The main component is Co, Contains metal nanoparticles with an average particle size (D50) of 1 nm or more and 100 nm or less, the primary phase of each of the metal nanoparticles is hcp-Co; The metal magnetic powder contains fcc-Co and / or ε-Co as a subphase.

[0007] The metal magnetic powder of the present disclosure has the above characteristics, and thus can achieve both high magnetic permeability and low magnetic loss in the high frequency region of the gigahertz band.

[0008] The ratio of hcp-Co in the metal magnetic powder is W hcp and the ratio of fcc-Co is W fcc Let the ratio of ε-Co be Wε. Preferably, W hcp / (W hcp +W fcc +Wε) is 70% or more and 99% or less.

[0009] Preferably, the metal nanoparticles have an average particle size (D50) of 1 nm or more and 70 nm or less.

[0010] Preferably, the metal magnetic powder contains Zn, Zn is present on the surface of the nanoparticles and / or inside the nanoparticles.

[0011] The composite magnetic body according to the present disclosure includes the metal magnetic powder and a resin. By including the above-mentioned metal magnetic powder in the composite magnetic body, it is possible to favorably achieve both high magnetic permeability and low magnetic loss in the high frequency region of the gigahertz band.

[0012] Preferably, the composite magnetic body contains Zn.

[0013] The above-described metallic magnetic body and composite magnetic body can be suitably used in electronic components such as inductors, antennas, and filters that are mounted in high-frequency circuits. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing a metal magnetic powder 1 according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a schematic diagram showing a cross section of a composite magnetic body containing the metal magnetic powder 1 shown in FIG. [Figure 3A] FIG. 3A is an example of the X-ray diffraction pattern of metal magnetic powder 1. [Figure 3B] FIG. 3B is an example of the X-ray diffraction pattern of metal magnetic powder 1 containing Zn. [Figure 4] FIG. 4 is a schematic cross-sectional view showing an example of an electronic component including the composite magnetic body 10 shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the present disclosure will be described in detail based on embodiments shown in the drawings.

[0016] (Metal magnetic powder 1) The metal magnetic powder 1 according to this embodiment is composed of nanoparticles 2, and the average particle size of the nanoparticles 2 (i.e., the average particle size of the metal magnetic powder 1) is 1 nm or more and 100 nm or less. The average particle size of the nanoparticles 2 can be calculated by measuring the equivalent circle diameter of each nanoparticle 2 using a transmission electron microscope (TEM). Specifically, the metal magnetic powder 1 is observed with a TEM at a magnification of 500,000 times or more, and the equivalent circle diameter of each nanoparticle 2 included in the observation field is measured using image analysis software. In this case, it is preferable to measure the equivalent circle diameters of at least 500 nanoparticles 2, and a number-based cumulative frequency distribution is obtained based on the measurement results. Then, the equivalent circle diameter at which the cumulative frequency is 50% in the cumulative frequency distribution can be calculated as the average particle size (D50) of the nanoparticles 2.

[0017] The average particle size (D50) of the nanoparticles 2 is preferably 70 nm or less, and more preferably 50 nm or less. The smaller the average particle size of the nanoparticles 2, the more the magnetic loss tan δ of the metal magnetic powder 1 tends to decrease. The shape of the nanoparticles 2 is not particularly limited, but the manufacturing method shown in this embodiment usually produces nanoparticles 2 that are spherical or nearly spherical. In addition, the surface of the nanoparticles 2 may be coated with an oxide film, an insulating film, or the like.

[0018] Metal magnetic powder 1 contains cobalt (Co) as its main component. That is, nanoparticles 2 are Co nanoparticles whose main component is Co. Note that "main component" refers to an element that accounts for 80 wt% or more of metal magnetic powder 1. Metal magnetic powder 1 preferably contains 90 wt% or more of Co, and more preferably contains 93 wt% or more of Co.

[0019] Furthermore, it is preferable that the metal magnetic powder 1 contains at least one amphoteric metal in addition to Co (main component). The amphoteric metal refers to the four elements aluminum (Al), zinc (Zn), tin (Sn), and lead (Pb), and it is more preferable that the metal magnetic powder 1 contains Zn as the amphoteric metal. The content of Co in the metal magnetic powder 1 is expressed as W. Co (wt%), and the content of amphoteric metal is W AM (wt%), WAM / (W Co +W AM ) is preferably 0.001% or more (10 ppm or more) and 10% or less, and more preferably 1% or more and 7% or less. When the metal magnetic powder 1 contains two or more kinds of amphoteric metals, W AM is the sum of the contents of each amphoteric metal.

[0020] Metal magnetic powder 1 may contain other trace elements such as Cl, P, C, Si, N, and O. The total content of other trace elements (elements other than Co and amphoteric metals) in metal magnetic powder 1 is preferably 20 wt% or less.

[0021] Composition of metal magnetic powder 1 (W Co , W AM , W AM / (W Co +W AM ) can be measured by compositional analysis using, for example, inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), energy dispersive X-ray analysis (EDS), or wavelength dispersive X-ray analysis (WDS), with ICP-AES being preferred. In compositional analysis using ICP-AES, a sample containing the metal magnetic powder 1 is first collected in a glove box, and the sample is added to an acid solution such as HNO3 (nitric acid) and heated to dissolve. Compositional analysis using ICP-AES is then performed using this dissolved sample, and the Co and amphoteric metals contained in the sample are quantified.

[0022] The main component of the metal magnetic powder 1 may be identified based on X-ray diffraction analysis, etc. For example, the volume fraction of each element contained in the metal magnetic powder 1 may be calculated by X-ray diffraction analysis, etc., and the element with the highest volume fraction may be identified as the main component of the metal magnetic powder 1.

[0023] The main phase of the metal magnetic powder 1, i.e., the main phase of each nanoparticle 2, is hcp-Co. "Hcp-Co" refers to a crystalline phase of Co with a hexagonal close-packed structure, rather than an alloy phase. While chunky Co and micrometer-order Co particles tend to have an hcp structure, when Co is in the form of fine particles of 100 nm or less, the main phase tends to be fcc-Co (face-centered cubic structure) or ε-Co (a type of cubic crystal). In this embodiment, nanoparticles 2 whose main phase is hcp-Co are obtained by a specific manufacturing method described later.

[0024] Furthermore, the metal magnetic powder 1 has an hcp-Co main phase and contains fcc-Co and / or ε-Co as a Co subphase. This Co subphase is mixed within the nanoparticles 2 having hcp-Co as the main phase. In other words, single-phase nanoparticles 2 made of hcp-Co are not mixed with other single-phase nanoparticles made of fcc-Co or ε-Co. Instead, the metal magnetic powder 1 contains nanoparticles 2 having a Co mixed-phase structure (a structure containing a main phase and a subphase within the grain). In the metal magnetic powder 1, all of the nanoparticles 2 may have a mixed-phase structure, or hcp-Co nanoparticles 2 (single-phase nanoparticles 2 without a Co subphase) and nanoparticles 2 with a mixed-phase structure (nanoparticles 2 containing a Co subphase) may be mixed. Of the nanoparticles 2 contained in the metal magnetic powder 1, preferably 80% or more of the nanoparticles 2 by number have a mixed-phase structure.

[0025] By including a Co subphase within the nanoparticles 2 in the metal magnetic powder 1, it is possible to ensure high magnetic permeability in the high frequency band of 1 GHz or higher while reducing magnetic loss compared to conventional methods.

[0026] The term "main phase" refers to a crystalline phase that occupies 50% or more of the metal magnetic powder 1. Specifically, the ratio of hcp-Co in the metal magnetic powder 1 is W hcp , the ratio of fcc-Co is W fcc , the ratio of ε-Co is Wε, W hcp +W fcc +Wε is 100%, and the crystalline phase that occupies 50% or more is the main phase. In other words, 50%≦(W hcp / (W hcp+W fcc If the value of "Wε" satisfies the above formula, the main phase of the metal magnetic powder 1 is determined to be hcp-Co. hcp / (W hcp +W fcc +Wε)" is preferably 70% or more and 99% or less, and more preferably 80% or more and 99% or less. By setting the content ratio of hcp-Co within the above range, it is possible to more suitably achieve both high magnetic permeability and low magnetic loss.

[0027] Metal magnetic powder 1 may contain only either fcc-Co or ε-Co as the Co subphase, or may contain both fcc-Co and ε-Co.

[0028] The crystal structure of the metal magnetic powder 1 (i.e., the crystal structure of the nanoparticles 2) can be analyzed by X-ray diffraction (XRD). (d) shown in FIG. 3A is an example of an XRD pattern of the metal magnetic powder 1. Note that (a) to (c) in FIG. 3A are all XRD patterns recorded in literature or databases such as ICDD, with (a) being the XRD pattern of ε-Co, (b) being the XRD pattern of fcc-Co, and (c) being the XRD pattern of hcp-Co. Also, (e) in FIG. 3A is an example of an XRD pattern of a metal magnetic powder corresponding to a comparative example.

[0029] After obtaining an XRD pattern of metal magnetic powder 1 as shown in Figure 3A(d) by XRD 2θ / θ measurement, profile fitting (peak separation) of the measured XRD pattern is performed using XRD analysis software. The separated diffraction peaks are then compared with a database to identify the crystalline phase contained in metal magnetic powder 1. In the XRD pattern shown in Figure 3A(d), the peaks indicated by "▼" are diffraction peaks derived from hcp-Co, and the peaks indicated by "▽" are diffraction peaks derived from fcc-Co.

[0030] The proportion of the Co crystalline phase can be calculated based on the integrated intensity of the diffraction peaks. Specifically, the diffraction peaks in the XRD pattern (d) are identified by profile fitting, and then the integrated intensity of the identified diffraction peaks is calculated. hcp is the integrated intensity of the diffraction peaks originating from hcp-Co, and W fcc is the integrated intensity of the diffraction peak derived from fcc-Co, and Wε is the integrated intensity of the diffraction peak derived from ε-Co. hcp / (W hcp +W fcc +Wε) can be calculated.

[0031] In the XRD pattern (d) of FIG. 3A, diffraction peaks of hcp-Co and fcc-Co are detected, and the ratio of hcp-Co (W hcp / (W hcp +W fcc +Wε)) is 95.1%, and the ratio of fcc-Co (W fcc / (W hcp +W fcc +Wε)) is 4.9%. That is, in metal magnetic powder 1 of Fig. 3A(d), the main phase is hcp-Co and the subphase is fcc-Co.

[0032] In the XRD pattern (e) of FIG. 3A, which corresponds to a comparative example, diffraction peaks of hcp-Co and fcc-Co are also detected, but the peak intensities around 2θ=43.9° and 51.2° are higher in XRD pattern (e) than in (d). More specifically, in XRD pattern (e), the ratio of hcp-Co (W hcp / (W hcp +W fcc +Wε)) is 38.6%, and the ratio of fcc-Co (W fcc / (W hcp +W fcc +Wε)) is 61.4%. That is, in the metal magnetic powder according to the comparative example in Fig. 3A(e), the main phase is fcc-Co and the subphase is hcp-Co.

[0033] The hcp-Co, which is the main phase of the metal magnetic powder 1, may contain small amounts of amphoteric metals and impurity elements in solid solution. However, it is preferable that the degree of deviation in the lattice constant of the hcp-Co is 0.5% or less. The "degree of deviation in the lattice constant" is expressed by (|d STD -d f |) / d STD (%), d STD is the lattice constant of hcp-Co recorded in the database, d f is the lattice constant of hcp-Co calculated by analyzing the XRD pattern of Metal Magnetic Powder 1. The lattice constant may be measured by electron beam diffraction using a TEM.

[0034] The presence or absence of a mixed-phase structure within the nanoparticles 2 can be confirmed by TEM analysis, such as high-resolution electron microscopy (HREM), electron backscatter diffraction (EBSD), or electron diffraction. For example, when analyzing the crystal structure of each nanoparticle 2 by electron diffraction using a TEM, at least 50 nanoparticles 2 are irradiated with an electron beam, and based on the electron diffraction pattern obtained, it is determined whether each nanoparticle 2 has a single-phase structure or a mixed-phase structure. In this analysis, it is preferable to select nanoparticles 2 that are isolated within the field of view and irradiate them with the electron beam.

[0035] In addition, in analyzing the crystal structure of the metal magnetic powder 1, the crystal structure of the nanoparticles 2 may first be identified by electron diffraction using a TEM, and then the proportion of the Co crystalline phase may be calculated by XRD using the results of the electron diffraction analysis as a reference.

[0036] When the metal magnetic powder 1 contains an amphoteric metal, it is preferable that the amphoteric metal exists as amphoteric metal crystal grains 3 rather than being dissolved in the main phase (hcp-Co) or contained in a compound such as an oxide. In other words, it is preferable that the metal magnetic powder 1 contains amphoteric metal crystal grains 3, and it is particularly preferable that the metal magnetic powder 1 contains Zn crystal grains (3).

[0037] When metal magnetic powder 1 contains crystal grains 3 of an amphoteric metal, not only are diffraction peaks of the Co crystalline phase detected in the XRD pattern of metal magnetic powder 1, but also diffraction peaks of the amphoteric metal are detected. In fact, (e) of FIG. 3B is an example of an XRD pattern of metal magnetic powder 1 containing Zn as the amphoteric metal. Note that (a) to (c) of FIG. 3B, like FIG. 3A, are diffraction peaks of each Co crystalline phase recorded in literature and databases such as ICDD, and (d) of FIG. 3B is a diffraction peak of Zn recorded in the database.

[0038] In the XRD pattern (e) of Figure 3B, diffraction peaks of Zn are detected along with diffraction peaks of hcp-Co (the peaks indicated by "○" are diffraction peaks of Zn). In other words, in the metal magnetic powder 1 shown in Figure 3B (e), Zn exists not as a compound such as an oxide, but as metal crystals. In this way, the state of existence of the amphoteric metal can be confirmed by analyzing the XRD pattern.

[0039] Furthermore, when the metal magnetic powder 1 contains an amphoteric metal, the amphoteric metal is preferably present inside the nanoparticles 2 and / or on the surface of the nanoparticles 2. In other words, the metal magnetic powder 1 preferably contains, as crystal grains 3 of the amphoteric metal, crystal grains 3a present inside the nanoparticles 2 and / or crystal grains 3b attached to the surface of the nanoparticles 2. In addition, the particle size of the crystal grains 3 of the amphoteric metal is preferably smaller than the average particle size of the nanoparticles 2. The location of the amphoteric metal can be identified, for example, by mapping analysis using TEM-EDS.

[0040] (Composite magnetic material 10) Next, a composite magnetic body 10 containing the above-described metal magnetic powder 1 will be described with reference to FIG.

[0041] The composite magnetic body 10 contains a metal magnetic powder 1 having the above-described characteristics and a resin 6, and the nanoparticles 2 constituting the metal magnetic powder 1 are dispersed in the resin 6. In other words, the resin 6 is interposed between the nanoparticles 2, insulating adjacent particles. The resin 6 may be any insulating resin material, and its material is not particularly limited. For example, the resin 6 may be a thermosetting resin such as an epoxy resin, a phenolic resin, or a silicone resin, or a thermoplastic resin such as an acrylic resin, polyethylene, or polypropylene, with a thermosetting resin being preferred.

[0042] The area ratio of the metal magnetic powder 1 in the cross section of the composite magnetic body 10 is preferably 10% to 60%, and more preferably 10% to 40%.

[0043] The area proportion of the metal magnetic powder 1 in the cross section of the composite magnetic body 10 can be calculated by observing the cut surface of the composite magnetic body 10 using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and analyzing the cross-sectional image using image analysis software. Specifically, the cross-sectional image of the composite magnetic body 10 is binarized based on contrast to distinguish the metal magnetic powder from other parts, and the proportion of the area occupied by the metal magnetic powder 1 to the entire image (i.e., the area of ​​the observed field of view) is calculated. The area proportion calculated by the above method can be considered as the volume proportion of the nanoparticles 2 contained in the composite magnetic body 10.

[0044] When the metal magnetic powder 1 contains an amphoteric metal, the amphoteric metal preferably exists as crystal grains 3 inside the composite magnetic body 10 as well. More specifically, the crystal grains 3 of the amphoteric metal can exist inside the nanoparticles 2 and on the surface of the nanoparticles 2. In addition, the crystal grains 3 of the amphoteric metal may be dispersed in the resin 6 of the composite magnetic body 10 (crystal grains 3c). It is believed that the crystal grains 3c present in the resin 6 are generated when the crystal grains 3b that were attached to the surface of the nanoparticles 2 peel off from the particle surface during the process of mixing the metal magnetic powder 1 and the resin 6.

[0045] That is, the location of the amphoteric metal in composite magnetic body 10 can be classified into three patterns: A: inside nanoparticles 2, B: on the surface of nanoparticles 2, and C: in resin 6. The amphoteric metal in composite magnetic body 10 may be present in any one of patterns A to C, or in any two of patterns A to C, or in all of locations A to C. The location of the amphoteric metal in composite magnetic body 10 can be identified by performing a mapping analysis using TEM-EDS on a cross section of composite magnetic body 10.

[0046] Even when the metal magnetic powder 1 is contained in the composite magnetic body 10, the average particle size (D50), composition, and crystal structure of the metal magnetic powder 1 can be analyzed by the above-mentioned methods (TEM observation, ICP-AES, XRD, etc.). When analyzing the composition of the metal magnetic powder 1 contained in the composite magnetic body 10 by ICP-AES, XRD, etc., it may be affected by the constituent elements of the resin 6. In such cases, it is necessary to eliminate the effects of elements other than Co and amphoteric metals and to analyze W. AM / (W Co +W AM The main component of the metal magnetic powder 1 may be identified based only on the above.

[0047] Composite magnetic body 10 may contain ceramic particles, metal particles other than nanoparticles 2, etc. Furthermore, the shape and dimensions of composite magnetic body 10 are not particularly limited and may be determined appropriately depending on the application.

[0048] The following describes an example of a method for producing the metal magnetic powder 1 and the composite magnetic body 10. The metal magnetic powder 1 of this embodiment is preferably produced by a gas phase thermal decomposition method or a liquid phase thermal decomposition method involving a disproportionation reaction.

[0049] (Method of manufacturing metal magnetic powder 1 by gas phase pyrolysis method) The thermal decomposition method is a method for producing Co nanoparticles by heating and thermally decomposing a precursor cobalt complex. Typically, the precursor is dispersed in a solvent such as dichlorobenzene or ethylene glycol, and the reaction solution is heated to a high temperature of approximately 180°C to thermally decompose the precursor in the liquid phase (i.e., liquid-phase thermal decomposition method). In this embodiment, the precursor is thermally decomposed in the gas phase in an inert atmosphere without using a solvent (i.e., gas-phase thermal decomposition method). While conventional liquid-phase thermal decomposition methods tend to produce nanoparticles with a main phase of fcc-Co or ε-Co, gas-phase thermal decomposition methods can produce nanoparticles 2 with a main phase of hcp-Co.

[0050] In the gas-phase pyrolysis method, a reaction vessel containing the precursor is placed in an oil bath and heated in an inert atmosphere to pyrolyze the precursor. During this process, the raw materials in the reaction vessel are stirred using a mechanical stirrer or the like. The precursor cobalt complex is octacarbonyldicobalt (Co2(CO)8 or Co4(CO) 12 It is preferable to use Co2(CO)8, and it is more preferable to use Co2(CO)8. As the reaction vessel, for example, a separable flask can be used, and the material of the reaction vessel is not particularly limited. Furthermore, the pyrolysis atmosphere is filled with an inert gas such as Ar gas or N2 gas, and the type of inert gas used is not particularly limited.

[0051] When adding an amphoteric metal to the metal magnetic powder 1, the amphoteric metal raw material is simply charged into a reaction vessel together with the precursor. As the amphoteric metal raw material, it is preferable to use chlorides of amphoteric metals such as ZnCl2, AlCl3, SnCl2, and PbCl2. The ratio of amphoteric metal in the metal magnetic powder 1 (W AM / (W AM +W Co)) can be controlled by the blending ratio of the above raw materials. Furthermore, during the thermal decomposition reaction, a surfactant such as oleic acid or a silane coupling agent may be added. As the silane coupling agent, for example, a silane coupling agent containing an aniline structure and / or a phenyl group is preferably used, and N-phenyl-3-aminopropyltrimethoxysilane is more preferably used.

[0052] When a surfactant is not added, the reaction temperature in the gas-phase pyrolysis method (i.e., the heating temperature of the raw material) can be set to 57°C or higher and 180°C or lower, preferably 57°C or higher and 120°C or lower, and more preferably 57°C or higher and 80°C or lower. On the other hand, when a surfactant is added, the reaction temperature can be set to 52°C or higher and 150°C or lower, preferably 57°C or higher and 120°C or lower, and more preferably 57°C or higher and 80°C or lower. The higher the reaction temperature, the larger the average particle size of the nanoparticles 2 tends to be. When the reaction temperature is low, the average particle size of the nanoparticles 2 tends to be smaller and the proportion of hcp-Co tends to be higher.

[0053] The reaction time in the gas-phase pyrolysis method is preferably adjusted appropriately depending on the reaction temperature. For example, when the reaction temperature is 150°C to 180°C, the reaction time is preferably 0.01 to 3.5 hours. When the reaction temperature is 100°C or higher but less than 150°C, the reaction time is preferably 0.1 to 10 hours. When the reaction temperature is less than 100°C, the reaction time is preferably 0.25 to 96 hours, more preferably 1 to 50 hours. The longer the reaction time, the larger the average particle size of the nanoparticles 2 tends to be.

[0054] The crystal structure of nanoparticles 2 can be controlled by the type of surfactant and the reaction temperature. For example, when no surfactant is added, the higher the reaction temperature, the more likely it is that fcc-Co will be formed as a subphase. When oleic acid is added as a surfactant, ε-Co will be formed as a subphase, and the proportion of ε-Co tends to increase as the reaction temperature increases. On the other hand, when the silane coupling agent N-phenyl-3-aminopropyltrimethoxysilane is added as a surfactant, both fcc-Co and ε-Co will be formed as subphases, and the proportion of the subphases increases as the reaction temperature increases.

[0055] When adding an amphoteric metal to the metal magnetic powder 1, the amphoteric metal raw material may be added at the start of the reaction or after a predetermined time has elapsed since the start of the reaction. The location of the amphoteric metal can be controlled by the timing of adding the amphoteric metal raw material. Specifically, if the amphoteric metal raw material is added at the start of the reaction, the amphoteric metal is more likely to be present within the particles of the nanoparticles 2. On the other hand, if the amphoteric metal raw material is added during the thermal decomposition reaction, the amphoteric metal will adhere to the surface of the nanoparticles 2, and the more delayed the timing of adding the amphoteric metal raw material, the more the proportion of amphoteric metal present on the surface of the nanoparticles 2 tends to increase. Specifically, if the amphoteric metal raw material is added after 2 / 3 RT or more has elapsed since the start of the reaction, where RT is the final reaction time, the amphoteric metal tends to be present on the surface of the nanoparticles 2 rather than within the particles.

[0056] After allowing the thermal decomposition reaction in the gas phase to continue for the desired time, the reaction vessel is removed from the oil bath and allowed to cool naturally until the product reaches room temperature. After cooling, the generated nanoparticles 2 are washed and collected using a washing solvent. Examples of the washing solvent that can be used include organic solvents such as acetone, dichlorobenzene, or ethanol. To prevent oxidation of the nanoparticles 2, it is preferable to degas the washing solvent beforehand. Alternatively, it is preferable to use an ultra-dehydrated organic solvent with a water content of 10 ppm or less as the washing solvent. A magnet can be used to collect the nanoparticles 2. Through the above steps, a metal magnetic powder 1 is obtained.

[0057] The entire process from weighing the raw materials to cleaning and collecting the nanoparticles is carried out in an inert gas atmosphere such as an Ar atmosphere.

[0058] (Method of manufacturing metal magnetic powder 1 by thermal decomposition in liquid phase accompanied by disproportionation reaction) A disproportionation reaction is a reaction in which two or more molecules of one substance react with each other to produce two or more different substances. When producing metal magnetic powder 1 by liquid-phase pyrolysis accompanied by a disproportionation reaction, it is preferable to use chlorotris(triphenylphosphine)cobalt (CoCl(Ph3P)3) as the precursor (Co raw material). In liquid-phase pyrolysis accompanied by a disproportionation reaction, two compounds, Co(0)(Ph3P)4 and Co(II)Cl2(Ph3P)2, are produced from the precursor, and Co nanoparticles 2 are produced by the decomposition of Co(0)(Ph3P)4. In this production method, as with gas-phase pyrolysis, it is preferable to add an amphoteric metal raw material such as ZnCl2.

[0059] When producing the metal magnetic powder 1 by liquid-phase pyrolysis accompanied by a disproportionation reaction, first, the precursor and amphoteric metal raw materials are weighed so that the metal magnetic powder 1 has the desired composition. Then, the precursor, amphoteric metal raw materials, and solvent are placed in a reaction vessel such as a separable flask, and these raw materials are stirred using a mechanical stirrer or the like. The ratio of the amphoteric metal in the metal magnetic powder 1 (W AM / (W AM +W Co ) can be controlled by the blending ratio of the above raw materials. As the solvent, ethanol, tetrahydrofuran (THF), or oleylamine is preferably used. A surfactant such as oleic acid may also be added.

[0060] The atmosphere in which the nanoparticles 2 are synthesized is preferably an inert gas atmosphere such as an Ar atmosphere or an N2 atmosphere. When ethanol is used as the solvent, the temperature of the reaction solution during stirring (i.e., the reaction temperature) is preferably 25°C (room temperature) or higher and 65°C or lower. On the other hand, when THF or oleylamine is used as the solvent, the reaction temperature can be 10°C or higher and 65°C or lower, and is preferably 25°C (room temperature) or higher and 40°C or lower. The higher the reaction temperature, the larger the average particle size of the nanoparticles 2 tends to be.

[0061] The stirring time (i.e., reaction time) is preferably adjusted depending on the reaction temperature, and is preferably 0.01 to 80 hours, and more preferably 0.1 to 72 hours when the reaction temperature is room temperature. The longer the reaction time, the larger the average particle size of the nanoparticles 2 tends to be.

[0062] When producing the metal magnetic powder 1 by liquid-phase pyrolysis accompanied by a disproportionation reaction, the crystal structure of the nanoparticles 2 can be controlled by the type of solvent and the reaction temperature. For example, the lower the reaction temperature, the higher the ratio of hcp-Co (W hcp / (W hcp +W fcc +Wε)) tends to be higher, and the higher the reaction temperature, the more likely the subphase (fcc-Co and / or ε-Co) is to be formed. When ethanol is used as a solvent, the ratio of hcp-Co is more likely to be higher than when other solvents (THF or oleylamine) are used, and fcc-Co is more likely to be formed as a subphase at reaction temperatures above 25°C. When THF is used as a solvent, a mixed phase structure consisting of a main hcp-Co phase and a subphase fcc-Co is more likely to be obtained. When oleylamine is used as a solvent, a mixed phase structure consisting of a main hcp-Co phase and subphases fcc-Co and ε-Co tends to be obtained. When oleylamine is used and the reaction temperature is set above 40°C, a mixed phase structure consisting of a main hcp-Co phase and a subphase ε-Co is more likely to be obtained.

[0063] In liquid-phase pyrolysis involving a disproportionation reaction, the amphoteric metal raw material may be added at the start of the reaction or after a predetermined time has elapsed since the start of the reaction. The location of the amphoteric metal can be controlled by the timing of adding the amphoteric metal raw material. Specifically, when the amphoteric metal raw material is added at the start of the reaction, the amphoteric metal is more likely to be present inside the nanoparticles 2. On the other hand, when the amphoteric metal raw material is added during the pyrolysis reaction, the amphoteric metal adheres to the surface of the nanoparticles 2, and the more delayed the timing of adding the amphoteric metal raw material, the more the proportion of amphoteric metal present on the surface of the nanoparticles 2 tends to increase. Specifically, when the amphoteric metal raw material is added after 3 / 4 RT or more has elapsed since the start of the reaction, where RT is the final reaction time, the amphoteric metal tends to be present on the surface of the nanoparticles 2 rather than inside the particles.

[0064] After stopping the stirring of the reaction solution to terminate the reaction, the generated nanoparticles 2 are washed and collected. When washing the nanoparticles 2, a washing solvent that dissolves unreacted raw materials and intermediate products is used. Specifically, organic solvents such as acetone, dichlorobenzene, or ethanol can be used as the washing solvent. To suppress oxidation of the nanoparticles 2, it is preferable to degas the washing solvent. Alternatively, it is preferable to use an ultra-dehydrated organic solvent with a water content of 10 ppm or less as the washing solvent. A magnet can be used to collect the nanoparticles 2. Through the above steps, a metal magnetic powder 1 is obtained.

[0065] The entire process from weighing the raw materials to cleaning and collecting the nanoparticles is carried out in an inert gas atmosphere such as an Ar atmosphere.

[0066] (Method of manufacturing the composite magnetic body 10) Next, an example of a method for manufacturing the composite magnetic body 10 will be described.

[0067] The composite magnetic body 10 can be manufactured by mixing the metal magnetic powder 1, resin 6, and a solvent and subjecting them to a predetermined dispersion process. The dispersion process is preferably ultrasonic dispersion or media dispersion using a bead mill or the like. The conditions for the dispersion process are not particularly limited; they can be set so that the nanoparticles 2 are evenly dispersed in the resin 6. The solvent added during the dispersion process can be, for example, an organic solvent such as acetone, dichlorobenzene, or ethanol. It is preferable to use a degassed organic solvent or an ultra-dehydrated organic solvent. Various ceramic beads can be used as the media used during the media dispersion process. Among ceramic beads, ZrO2 beads, which have a high specific gravity, are preferred.

[0068] The location of the amphoteric metal in the composite magnetic body 10 may change depending on the dispersion treatment. For example, when ultrasonic dispersion treatment is performed, the amphoteric metal attached to the surface of the nanoparticles 2 is difficult to peel off, but when media dispersion treatment is performed, the amphoteric metal attached to the surface of the nanoparticles 2 is easily peeled off. Therefore, the proportion of the amphoteric metal dispersed in the resin 6 tends to increase as the treatment time of media dispersion is increased.

[0069] The slurry obtained by the above dispersion process is dried in an inert atmosphere such as an Ar atmosphere to volatilize the solvent and obtain a dried body. The dried body is then crushed using a mortar or a dry crusher to obtain granules containing the metal magnetic powder 1 and the resin 6. The granules are then filled into a mold and pressurized to obtain the composite magnetic body 10. When a thermosetting resin is used as the resin 6, it is preferable to subject the composite magnetic body after pressure molding to a hardening treatment. The manufacturing method of the composite magnetic body is not limited to the above pressure molding method. For example, the slurry obtained by the dispersion process may be applied to a PET film and dried to obtain a sheet-like composite magnetic body 10.

[0070] As with the production of the metal magnetic powder 1, the series of steps for obtaining the composite magnetic body 10 are also carried out in an inert atmosphere such as an Ar atmosphere.

[0071] (Summary of the embodiment) The metal magnetic powder 1 of this embodiment is composed of nanoparticles 2 whose main phase is hcp-Co and whose average particle size (D50) is 1 nm to 100 nm (preferably 1 nm to 70 nm). The metal magnetic powder 1 also contains fcc-Co and / or ε-Co as a subphase. By including nanoparticles 2 with a mixed phase structure in the metal magnetic powder 1, it is possible to ensure high magnetic permeability in the high frequency band of 1 GHz or more while reducing magnetic loss compared to conventional methods. Furthermore, by including metal magnetic powder 1 having the above characteristics in the composite magnetic body 10, it is possible to preferably achieve both high magnetic permeability and low magnetic loss in the high frequency band.

[0072] In the metal magnetic powder 1 and the composite magnetic body 10, W hcp / (W hcp +W fcc +Wε) is 70% or more and 99% or less. When the ratio of the main phase hcp-Co satisfies the above requirement, it is possible to more suitably achieve both high magnetic permeability and low magnetic loss in the high frequency band.

[0073] Furthermore, the metal magnetic powder 1 and the composite magnetic body 10 contain crystals of an amphoteric metal (preferably Zn crystals). By adding an amphoteric metal to the metal magnetic powder 1 composed of nanoparticles 2 having a Co mixed phase structure, magnetic loss can be further reduced.

[0074] Both the metal magnetic powder 1 and the composite magnetic body 10 can be applied to various electronic components such as inductors, transformers, choke coils, filters, and antennas, and are particularly suitable for use in electronic components for high-frequency circuits with operating frequencies of 1 GHz or higher (more preferably 1 GHz to 10 GHz).

[0075] An example of an electronic component containing the metal magnetic powder 1 (or composite magnetic body 10) is an inductor 100 as shown in FIG. 4. The inductor 100 has an element body made of the composite magnetic body 10 of this embodiment, with a coil portion 50 embedded inside the element body. A pair of external electrodes 60, 80 are formed on the end faces of the element body, and each of the external electrodes 60, 80 is electrically connected to the lead portions 50a, 50b of the coil portion 50, respectively. Electronic components such as the inductor 100 have excellent high-frequency characteristics because they contain the metal magnetic powder 1 (composite magnetic body 10) of this embodiment.

[0076] Although the embodiments of the present disclosure have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the gist of the present disclosure. [Example]

[0077] The present disclosure will be described in more detail below based on specific examples, although the present invention is not limited to the following examples.

[0078] (Experiment 1) In Experiment 1, metal magnetic powders according to Samples A1 to A18 were produced by a gas-phase pyrolysis method. Specifically, the precursor Co2(CO)8 was placed in a separable flask, and the precursor was stirred using a mechanical stirrer while being heated to 57°C. An oil bath was used to heat the separable flask, but no solvent was added to the separable flask, and the precursor was pyrolyzed in the gas phase. The atmosphere used during this was an Ar atmosphere, and the reaction time for each sample was set to the value shown in Table 1.

[0079] For samples A1 to A6, the precursor was pyrolyzed without adding a surfactant, for samples A7 to A12, oleic acid was added as a surfactant during pyrolysis, and for samples A13 to A18, the silane coupling agent N-phenyl-3-aminopropyltrimethoxysilane was added as a surfactant during pyrolysis.

[0080] After synthesizing the nanoparticles by pyrolysis, the separable flask was left standing at room temperature, and the nanoparticles were allowed to cool naturally to room temperature. After cooling, the nanoparticles were washed with ultra-dehydrated acetone and collected using a magnet. The entire process, from weighing the raw materials to washing and collection, was carried out in an Ar atmosphere. Through the above steps, metal magnetic powders relating to samples A1 to A18 were obtained.

[0081] Next, the above-mentioned metal magnetic powder was used to manufacture a composite magnetic body, which was manufactured by the same method for manufacturing the composite magnetic body for Samples A1 to A18.

[0082] First, metal magnetic powder was weighed out so that the nanoparticle content in the composite magnetic body was 10 vol%. The weighed metal magnetic powder was then mixed with epoxy resin and acetone as a solvent, and the mixture was subjected to ultrasonic dispersion treatment. The ultrasonic dispersion treatment time was 10 min, and the dispersion obtained by the ultrasonic dispersion treatment was dried in an Ar atmosphere at 50°C to obtain a dried body. The dried body was then crushed in a mortar, and the resulting granules were filled into a mold and pressed to obtain a composite magnetic body. Each composite magnetic body sample had a toroidal shape with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 1 mm. The series of processes for producing the composite magnetic body were carried out in an Ar atmosphere.

[0083] The composite magnetic bodies of the respective samples in Experiment 1 were evaluated as follows.

[0084] Average particle size of nanoparticles The nanoparticles produced in each sample in Experiment 1 were observed at a magnification of 500,000 times using a TEM (JEOL Ltd.: JEM-2100F). The circle-equivalent diameters of 500 nanoparticles were measured using image analysis software, and the average particle size (D50) was calculated.

[0085] Crystal structure analysis First, during TEM observation, 50 isolated nanoparticles within the field of view were irradiated with an electron beam to obtain electron diffraction patterns. Then, based on the obtained electron diffraction patterns, it was determined whether each nanoparticle had a single-phase structure or a mixed-phase structure. In each of Samples A1 to A18 in Experiment 1, it was confirmed that the nanoparticles had a mixed-phase structure.

[0086] In addition, the XRD pattern of the composite magnetic material was obtained by 2θ / θ measurement using an XRD device (Rigaku Corporation: Smart Lab). The obtained XRD pattern was then analyzed using X-ray analysis integrated software (SmartLab Studio II) to determine the ratio of hcp-Co, fcc-Co, and ε-Co (W hcp , W fcc , and Wε) were calculated. In this analysis, the ratio of each Co crystalline phase was calculated with the total of hcp-Co, fcc-Co, and ε-Co being 100%.

[0087] Evaluation of magnetic properties The real part of the complex permeability (i.e., permeability μ' (unitless)) and the imaginary part μ" at 5 GHz were measured using the coaxial S-parameter method with a network analyzer (Agilent Technologies: HP8753D). The magnetic loss tangent delta (unitless) at 5 GHz was then calculated as μ" / μ'. The permeability μ' and magnetic loss tangent delta also vary depending on the nanoparticle content in the composite magnetic material. When the nanoparticle content in the composite magnetic material is 10 vol%, as in the samples in Experiment 1, samples with a permeability μ' of 1.15 or more and a magnetic loss tangent delta of 0.100 or less were judged to be "good."

[0088] The evaluation results of each sample in Experiment 1 are shown in Table 1. [Table 1]

[0089] As shown in Table 1, when the reaction temperature (pyrolysis temperature) was set at 57°C, samples (Examples) with a reaction time ranging from 1 to 96 hours produced nanoparticles with an average particle size (D50) of 1 to 100 nm and a mixed-phase structure. Samples A6, A12, and A18 (Comparative Examples) with a reaction time of 120 hours produced nanoparticles with a mixed-phase structure, but the average particle size (D50) of the nanoparticles was greater than 100 nm. Comparative Examples A6, A12, and A18 failed to meet the evaluation criteria for both permeability and magnetic loss. On the other hand, Examples (Samples A1 to A5, A7 to A11, and A13 to A17) with an average particle size (D50) ranging from 1 to 100 nm exhibited improved permeability and magnetic loss characteristics compared to the Comparative Examples, and excellent magnetic properties were obtained at 5 GHz.

[0090] In the examples shown in Table 1, the smaller the average particle size, the more the magnetic loss could be reduced. In other words, it was found that for nanoparticles with a mixed phase structure in which the main phase is hcp-Co, the average particle size is preferably 72 nm or less, and more preferably 52 nm or less.

[0091] Furthermore, the evaluation results shown in Table 1 indicate that the addition of a surfactant changes the crystalline structure of Co nanoparticles. Specifically, when no surfactant was added (samples A1 to A6), fcc-Co was formed as a subphase, and the proportion of hcp-Co, the main phase, was higher than when a surfactant was added. On the other hand, when oleic acid was added as a surfactant (samples A7 to A12), ε-Co was formed as a subphase, and when N-phenyl-3-aminopropyltrimethoxysilane was added as a surfactant (samples A13 to A18), both fcc-Co and ε-Co were formed as subphases.

[0092] (Experiment 2) In Experiment 2, the reaction temperature during pyrolysis was changed to produce metal magnetic powders under the conditions shown in Tables 2 to 4. For each of Samples B1 to B28 (and A1 to A6 in Experiment 1) shown in Table 2, the precursor Co2(CO)8 was pyrolyzed in the gas phase to obtain metal magnetic powder without adding a surfactant. On the other hand, for each of Samples C1 to C28 (and A7 to A12 in Experiment 1) shown in Table 3, oleic acid was added to produce Co metal magnetic powders, and for Samples D1 to D28 (and A13 to A18 in Experiment 1) shown in Table 4, the silane coupling agent N-phenyl-3-aminopropyltrimethoxysilane was added to produce metal magnetic powders.

[0093] The manufacturing conditions other than the reaction temperature and reaction time were the same as in Experiment 1, and the metal magnetic powder and composite magnetic body for each sample of Experiment 2 were manufactured. The evaluation results of each sample of Experiment 2 are shown in Tables 2 to 4.

[0094] [Table 2] [Table 3] [Table 4]

[0095] The evaluation results in Tables 2 to 4 show that the higher the reaction temperature during gas-phase pyrolysis, the more easily subphases are generated, and the lower the proportion of hcp-Co. In other words, the lower the reaction temperature during gas-phase pyrolysis, the higher the proportion of hcp-Co.

[0096] In the samples B1 to B6 (comparative examples) shown in Table 2, metal magnetic powders containing no subphases were obtained by pyrolyzing the precursor at 52°C without adding a surfactant. Although the magnetic loss of these samples B1 to B6 was 0.100 or less, the magnetic permeability was lower than 1.15 (reference value), failing to meet the evaluation criteria for magnetic properties. Under conditions without using a surfactant, when the reaction temperature was set between 57°C and 180°C, a mixed-phase structure containing a hcp-Co main phase (a crystalline phase accounting for 50% or more of the nanoparticles) and an fcc-Co subphase was obtained. Furthermore, among the samples containing nanoparticles with a mixed-phase structure, the examples (samples A1 to A5 and samples B7 to B28) with an average particle size (D50) in the range of 1 nm to 100 nm were able to achieve both high permeability and low magnetic loss at 5 GHz.

[0097] For samples C25 to C28 (comparative examples) shown in Table 3, oleic acid was added and the precursor was pyrolyzed at a high temperature of 180°C to obtain metal magnetic powders with ε-Co as the main phase. Samples C25 to C28, which have ε-Co as the main phase, achieved high permeability at 5 GHz, but had magnetic loss greater than 0.100, failing to meet the evaluation criteria for magnetic properties. When oleic acid was added, a mixed-phase structure containing a hcp-Co main phase and an ε-Co subphase was obtained by setting the reaction temperature between 52°C and 150°C. Furthermore, among the samples containing nanoparticles with a mixed-phase structure, examples (samples C1 to C5, A7 to A11, and C7 to C24) with an average particle size (D50) in the range of 1 nm to 100 nm achieved both high permeability and low magnetic loss at 5 GHz.

[0098] Furthermore, for samples D25 to D28 shown in Table 4, N-phenyl-3-aminopropyltrimethoxysilane was added and the precursor was pyrolyzed at a high temperature of 180°C to obtain metal magnetic powders with a hcp-Co ratio of less than 50%. Although samples D25 to D28 achieved high permeability at 5 GHz, their magnetic loss was greater than 0.100, failing to meet the evaluation criteria for magnetic properties. When N-phenyl-3-aminopropyltrimethoxysilane was added, a mixed-phase structure containing a hcp-Co main phase and fcc-Co and ε-Co subphases was obtained by setting the reaction temperature between 52°C and 150°C. Furthermore, among the samples containing nanoparticles with a mixed-phase structure, examples with an average particle size (D50) between 1 nm and 100 nm (samples D1 to D5, A13 to A17, and D7 to D24) achieved both high permeability and low magnetic loss at 5 GHz.

[0099] From the results of Tables 2 to 4 above, it was found that Co nanoparticles having an average particle size (D50) in the range of 1 nm to 100 nm, containing a main phase of hcp-Co and a subphase of fcc-Co and / or ε-Co, can achieve both high permeability and low magnetic loss in the high frequency band. In the examples shown in Tables 2 to 4, the higher the proportion of the main phase hcp-Co, the lower the magnetic loss tends to be, and the higher the proportion of the subphase, the higher the permeability tends to be. The proportion of hcp-Co in the metal magnetic powder (W hcp / (W hcp +W fcc +Wε) is preferably 68% or more and 99% or less, and more preferably 80% or more and 99% or less.

[0100] (Experiment 3) In Experiment 3, in order to evaluate in more detail the influence of the mixed phase structure of Co nanoparticles on the magnetic properties, composite magnetic bodies according to Samples H1 to H8 corresponding to comparative examples were produced.

[0101] Sample H1 (comparative example) For sample H1, the metal magnetic powder was produced by liquid-phase thermal decomposition. First, the precursor Co2(CO)8 and the solvent dichlorobenzene were placed in a separable flask to obtain a reaction solution. The separable flask was then placed in an oil bath and heated to 180°C, and the reaction solution was stirred with a mechanical stirrer. In other words, Co nanoparticles were produced by thermally decomposing Co2(CO)8 in dichlorobenzene heated to 180°C.

[0102] After stirring the reaction solution for 0.5 hours, the separable flask was left standing at room temperature, and the resulting nanoparticles were allowed to cool naturally to room temperature. After cooling, the nanoparticles were washed with ultra-dehydrated acetone and collected using a magnet. Through these steps, a metal magnetic powder according to Sample H1 (Comparative Example) was obtained. The entire process, from weighing the raw materials to washing and collection, was carried out under an Ar atmosphere.

[0103] When the crystalline structure of the nanoparticles was confirmed by TEM electron diffraction, it was found that single-phase nanoparticles made of ε-Co were obtained in sample H1. For sample H1, a composite magnetic body was manufactured using this metal magnetic powder under the same conditions as in experiment 1.

[0104] Samples H2 to H4 (comparative examples) For samples H2 to H4, a composite magnetic body was produced by mixing the metal magnetic powder of sample B2 (comparative example) having a single-phase structure of hcp-Co (hereinafter referred to as B2 powder) with the metal magnetic powder of sample H1 (comparative example) having a single-phase structure of ε-Co (hereinafter referred to as H1 powder). The compounding ratio of B2 powder to H1 powder was controlled so that the proportion of Co crystalline phase in the mixed powder was the value shown in Table 5. The manufacturing conditions for the composite magnetic bodies of samples H2 to H4 were the same as those in Experiment 1, except that mixed powders were used.

[0105] Sample H5 (comparison example) For sample H5, when manufacturing metal magnetic powder by liquid-phase pyrolysis, Co2(CO)8 was used as the precursor, tetralin (1,2,3,4-tetrahydronaphthalene) was used as the solvent, and polyvinylpyrrolidone (Poly(N-vinyl-2-pyrrolidone)) was used as the surfactant, and the reaction temperature was set to 200°C. All other manufacturing conditions were the same as for sample H1. When the crystalline structure of the nanoparticles was confirmed by TEM electron diffraction, it was found that single-phase nanoparticles made of fcc-Co were obtained for sample H5. For sample H5, a composite magnetic body was manufactured using this metal magnetic powder under the same conditions as in experiment 1.

[0106] Samples H6 to H8 (comparison examples) For samples H6 to H8, composite magnetic bodies were produced by mixing B2 powder, which has a single-phase structure of hcp-Co, with the metal magnetic powder of sample H5, which has a single-phase structure of fcc-Co (hereinafter referred to as H5 powder). The compounding ratio of B2 powder to H5 powder was controlled so that the proportion of Co crystalline phase in the mixed powder was the value shown in Table 5. The manufacturing conditions for the composite magnetic bodies of samples H6 to H8 were the same as those in Experiment 1, except that mixed powders were used.

[0107] The evaluation results of Experiment 3 are shown in Table 5. Table 5 also shows the evaluation results of Samples A2, B2, B13, and B22 from Experiments 1 and 2.

[0108] [Table 5]

[0109] As shown in Table 5, when a single-phase metal magnetic powder was mixed, increasing the compounding ratio of B2 powder made of hcp-Co reduced the magnetic loss to 0.080 or less, but the magnetic permeability was low at less than 1.15, failing to meet the magnetic permeability evaluation criteria (Samples H2 and H6). On the other hand, increasing the compounding ratio of H1 powder made of ε-Co or H5 powder made of fcc-Co increased the magnetic permeability to 1.15 or more, but the magnetic loss exceeded 0.100, failing to meet the magnetic loss evaluation criteria (Samples H3-4, H7-8). Thus, the samples mixed with a single-phase metal magnetic powder were unable to achieve both high permeability and low magnetic loss.

[0110] In contrast, in the examples having a mixed phase structure (samples A2, B13, and B22), the magnetic permeability was 1.15 or more and the magnetic loss was 0.100 or less. The results of Experiments 1 to 3 showed that nanoparticles having a main phase of hcp-Co and a mixed phase structure containing fcc-Co and / or ε-Co can favorably achieve both high magnetic permeability and low magnetic loss in the high frequency band.

[0111] (Experiment 4) In Experiment 4, ZnCl2 was added as a raw material for the amphoteric metal, and metal magnetic powders according to Samples E1 to E6 were produced by a gas-phase thermal decomposition method. ZnCl2 was added at the start of the reaction, and the amount of ZnCl2 added was determined based on the ratio of Zn in each sample (W AM / (W Co +W AM )) were controlled to the values ​​shown in Table 6. In Experiment 4, the reaction temperature was set to 57°C and the reaction time to 3 hours so that the average particle size (D50) of the nanoparticles would be 20±2 nm. The manufacturing conditions other than those mentioned above were the same as in Experiment 1, and the magnetic properties of the composite magnetic bodies of Samples E1 to E6 were evaluated. The evaluation results of Experiment 4 are shown in Table 6.

[0112] [Table 6]

[0113] As shown in Table 6, samples E1 to E6, which contained Zn as an amphoteric metal, also achieved both high permeability and low magnetic loss at 5 GHz. Zn diffraction peaks were detected in the XRD patterns of samples E1 to E6, confirming that Zn was present as metal crystals.

[0114] (Experiment 5) In Experiment 5, metal magnetic powders for each sample were manufactured under the conditions shown in Table 7. Specifically, in Experiment 5, ZnCl2 was added at the start of the reaction, and the reaction temperature was varied to manufacture multiple metal magnetic powders with different Co crystalline phase ratios. The reaction time was set to a predetermined time depending on the reaction temperature so that the average particle size (D50) of the nanoparticles in each sample was 20±2 nm. The manufacturing conditions other than those mentioned above were the same as in Experiment 1, and the magnetic properties of the composite magnetic bodies for each sample were measured. The evaluation results of Experiment 5 are shown in Table 7.

[0115] [Table 7]

[0116] In Experiment 2, where Zn was not added, magnetic loss tended to increase as the ratio of the subphase increased, but in the examples of Experiment 5 shown in Table 7, the addition of Zn tended to reduce magnetic loss more than in Experiment 2 (Tables 2 to 4). This result shows that the addition of an amphoteric metal can further reduce magnetic loss in the high frequency band. Furthermore, in each example of Experiment 5, XRD analysis confirmed that Zn was present as metal crystals.

[0117] (Experiment 6) In Experiment 6, metal magnetic powders for each sample were produced under the conditions shown in Table 8. Specifically, in Experiment 6, ZnCl2 was added at the start of the reaction, and the reaction time was varied to produce multiple metal magnetic powders with different average particle sizes. The reaction temperature for each sample was set to 57°C. All other production conditions were the same as in Experiment 1, and the magnetic properties of the composite magnetic bodies for each sample were measured. The evaluation results of Experiment 6 are shown in Table 8.

[0118] [Table 8]

[0119] In Experiment 1, where Zn was not added, magnetic loss tended to increase as the average particle size of the nanoparticles increased, but in the examples of Experiment 6 shown in Table 8, the addition of Zn tended to reduce magnetic loss more than in Experiment 1 (Table 1). This result shows that the addition of an amphoteric metal can further reduce magnetic loss in the high frequency band. Furthermore, in each example of Experiment 6, XRD analysis confirmed that Zn was present as metal crystals.

[0120] (Experiment 7) Samples A21 and A22 (Examples) For samples A21 and A22, metal magnetic powder was produced under the same conditions as sample A2 in Experiment 1, and then composite magnetic bodies were produced by media dispersion using a bead mill. ZrO2 beads with a diameter of 0.2 mm were used for media dispersion. The media dispersion treatment time for sample A21 was 10 minutes, and the media dispersion treatment time for sample A22 was 30 minutes. All other manufacturing conditions were the same as in Experiment 1.

[0121] Samples E11 to E15 (Examples) For samples E11 to E15, ZnCl2 was added after a predetermined time had elapsed since the start of the reaction. For each of samples E11 to E15, the reaction temperature was set to 57°C and the reaction time was set to 3 hours. For samples E11, E13, and E14, ZnCl2 was added 1 hour after the start of the reaction, and the reaction was continued for another 2 hours. For samples E12 and E15, ZnCl2 was added 2 hours after the start of the reaction, and the reaction was continued for another 1 hour.

[0122] Furthermore, for samples E11 and E12, composite magnetic bodies were manufactured by ultrasonic dispersion in the same manner as in Experiment 1 (i.e., the same as for sample E5). On the other hand, for samples E13 to E15, composite magnetic bodies were manufactured by media dispersion using a bead mill. The processing time for media dispersion for sample E13 was 10 minutes, and the processing time for samples E14 and E15 was 30 minutes. The manufacturing conditions other than those mentioned above were the same as in Experiment 1.

[0123] The evaluation results of each example of Experiment 7 are shown in Table 9. In Experiment 7, a cross section of the composite magnetic body was analyzed by mapping analysis using TEM-EDS to identify the location of Zn. In the "Location of Zn Detection" section of Table 9, the location where an amphoteric metal was detected is marked with "Y", and the location where an amphoteric metal was not detected is marked with "-". In each example of Experiment 7, a Zn diffraction peak was detected in the XRD pattern, indicating that Zn was present as metal crystal grains.

[0124] [Table 9]

[0125] The results shown in Table 9 indicate that the location of the amphoteric metal (Zn) can be controlled by adjusting the timing of adding the amphoteric metal raw material (ZnCl2) and the conditions of the dispersion process. It was also confirmed that even when the location of the amphoteric metal is changed, it is possible to achieve both high magnetic permeability and low magnetic loss in the high frequency band.

[0126] (Experiment 8) In Experiment 8, a metal magnetic powder was produced under the same conditions as Sample B23 in Experiment 2, and then the metal magnetic powder was subjected to a gradual oxidation treatment to obtain metal magnetic powders according to Samples B29 and B30. The conditions for the gradual oxidation treatment were as follows: the content of Co relative to 100 wt% of the metal magnetic powder (W Co ) was controlled to the value shown in Table 10. Note that, because the gradual oxidation treatment oxidized a portion of the Co contained in the metal magnetic powder, the metal magnetic powders of samples B29 and B30 contained oxygen (O) in addition to Co (main component).

[0127] For samples B29 and B30 in Experiment 8, composite magnetic bodies were manufactured under the same conditions as sample B23 (i.e., the conditions described in Experiment 1), and their magnetic properties were measured. The evaluation results of Experiment 8 are shown in Table 10. The Co contents shown in Table 10 were calculated by analyzing the XRD patterns of the composite magnetic bodies using integrated X-ray analysis software.

[0128] [Table 10]

[0129] As shown in Table 10, the same effect as that of sample B23 was confirmed in samples B29 and B30, in which the Co content was changed by gradual oxidation treatment, and at 5 GHz, high magnetic permeability was maintained while magnetic loss was reduced compared to the conventional (comparative) sample.

[0130] (Experiment 9) In Experiment 9, metal magnetic powder was produced under the same conditions as sample A2 in Experiment 1, and then the compounding ratio of the metal magnetic powder in the composite magnetic body was changed to produce composite magnetic bodies according to samples A201 to A205. The compounding ratio of the metal magnetic powder in each of samples A201 to A205 was controlled so that the content of nanoparticles in the composite magnetic body would be the value shown in Table 11. The production conditions other than the compounding ratio of the metal magnetic powder were the same as those for sample A2.

[0131] Furthermore, in Experiment 9, composite magnetic bodies according to Samples C261 to C265 were manufactured as comparative examples. For each of Samples C261 to C265, a metal magnetic powder having an ε-Co main phase was manufactured under the same conditions as Sample C26 (Comparative Example) in Experiment 2. The compounding ratio of the metal magnetic powder was then adjusted to obtain a composite magnetic body so that the content of nanoparticles in the composite magnetic body would be the value shown in Table 11. The manufacturing conditions other than the compounding ratio of the metal magnetic powder were the same as those for Sample C26.

[0132] In Experiment 9, the cross section of the manufactured composite magnetic body was observed by TEM, and the area ratio of the metal magnetic powder (nanoparticles) contained in the composite magnetic body was measured. As a result, it was confirmed that the area ratio of nanoparticles in each sample in Experiment 9 matched the target value (vol%) shown in Table 11.

[0133] Generally, increasing the content (filling rate) of magnetic powder in a composite magnetic body increases the magnetic permeability, but the magnetic loss characteristics tend to decrease (i.e., magnetic loss increases). In Experiment 9, taking into account the changes in magnetic properties due to increases or decreases in the filling rate, we decided to set criteria for magnetic properties for each nanoparticle content rate. Specifically, in Experiment 9, samples that met the following requirements were judged to be "good." Nanoparticle content 10vol%: 1.15≦μ´, tanδ≦0.100 Nanoparticle content 20vol%: 1.30≦μ´, tanδ≦0.150 Nanoparticle content 30vol%: 1.45≦μ´, tanδ≦0.200 Nanoparticle content 40vol%: 1.60≦μ´, tanδ≦0.250 Nanoparticle content 50vol%: 1.75≦μ´, tanδ≦0.300 Nanoparticle content 60vol%: 1.90≦μ´, tanδ≦0.350 The evaluation results of Experiment 9 are shown in Table 11.

[0134] [Table 11]

[0135] The results shown in Table 11 show that even in the examples (samples A201 to A205) in which the nanoparticle content in the composite magnetic body was changed, high magnetic permeability μ' was maintained while reducing magnetic loss more than the corresponding comparative examples (samples C261 to C265). [Explanation of symbols]

[0136] 1 … Metal magnetic powder 2... nanoparticles 3,3a,3b,3c … Crystal grains of amphoteric metals 10 … Composite magnetic material 6...resin 100... inductor 50... Coil section 60,80 … external electrode

Claims

1. A metal magnetic powder containing Co as a main component, The metal magnetic powder contains metal nanoparticles having an average particle size (D50) of 1 nm or more and 100 nm or less, the primary phase of each of the metal nanoparticles is hcp-Co; The metal magnetic powder contains fcc-Co and / or ε-Co as a subphase.

2. The proportion of hcp-Co in the metal magnetic powder is W hcp The ratio of fcc-Co is W fcc and the ratio of ε-Co is Wε. W hcp / (W hcp +W fcc 2. The metal magnetic powder according to claim 1, wherein the value of Wε is 70% or more and 99% or less.

3. 3. The metal magnetic powder according to claim 1, wherein the metal nanoparticles have an average particle size (D50) of 1 nm or more and 70 nm or less.

4. The metal magnetic powder contains Zn, 3. The metal magnetic powder according to claim 1, wherein Zn is present on the surface of the nanoparticles and / or inside the nanoparticles.

5. A composite magnetic body comprising the metal magnetic powder according to claim 1 and a resin.

6. The composite magnetic body according to claim 5 , which contains Zn.

7. An electronic component comprising the metal magnetic powder according to claim 1 or 2.

8. An electronic component comprising the composite magnetic body according to claim 5 or 6.

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