Magnetic body and magnet

Abstract

This magnetic body has magnetic particles (30) comprising: alloy particles (34) containing an FeNi ordered alloy having an L10 ordered structure; and an insulating coating film (35) covering the surfaces of the alloy particles. The magnetic particles individually have a flattened shape in which a major axis (31) and a minor axis (32) shorter than the major axis intersect and in which a flattened surface (30a) along the major axis is wider than a lateral surface (30b) along the minor axis. An axis (33) of easy magnetization of the L10 ordered structure lies along the flattened surface. The insulating coating film has a thickness of 0.5 nanometers or more.

Description

Magnetic material, magnet Cross-reference of related applications

[0001] This application is based on Japanese Patent Application No. 2024-184998, filed in Japan on October 21, 2024, and incorporates the contents of the basic application by reference in whole.

[0002] The disclosures described herein relate to magnetic materials and magnets.

[0003] Patent Document 1 describes L1, which has a degree of order of 0.5 or higher as determined by measurement with an X-ray diffractometer. ０ A magnetic material containing a type of FeNi ordered alloy powder is disclosed.

[0004] Patent No. 6230513

[0005] In magnetic materials or magnetic bodies containing such FeNi ordered alloys, it is preferable to obtain higher coercivity.

[0006] This disclosure relates to L1, which has high coercivity and magnetic flux density. ０ The objective is to provide magnetic materials and magnets, including FeNi ordered alloys with a type-ordered structure.

[0007] The magnetic material in the disclosed embodiment is L1 ０ The magnetic particle comprises alloy particles containing a FeNi ordered alloy with a type ordered structure, and an insulating coating covering the surface of the alloy particles, wherein the magnetic particle, individually, has a flattened shape in which a major axis and a minor axis shorter than the major axis intersect, and the flattened plane along the major axis is wider than the side surface along the minor axis, L1 ０ The magnetization easy axis of the type-ordered structure aligns with the flattened plane, and the thickness of the insulating coating is 0.5 nanometers or more.

[0008] The magnet in the disclosed embodiment is L1 ０ The magnetic material comprises magnetic particles having alloy particles containing a FeNi ordered alloy with a type ordered structure, and an insulating coating covering the surface of the alloy particles, wherein the magnetic particles, individually, have a flattened shape in which a major axis and a minor axis shorter than the major axis intersect, and the flattened plane along the major axis is wider than the side surface along the minor axis, L1 ０ The magnetization easy axis of the type-ordered structure aligns with the flattened plane, and the thickness of the insulating coating is 0.5 nanometers or more.

[0009] As will be explained in detail in the embodiment, this method increases coercivity and magnetic flux density.

[0010] The reference numbers in parentheses above merely indicate the correspondence with the configurations described in the embodiments below, and do not limit the technical scope in any way.

[0011] This is a perspective view of a magnet. This is an enlarged view of region A enclosed by the dashed line in Figure 1. This is a perspective view showing a single magnetic particle. This is a cross-sectional view of a single magnetic particle. This is a schematic diagram showing the unit cell of an FeNi ordered alloy. This is a schematic diagram showing the unit cell of FeNiN. This is a flowchart showing the manufacturing method of an FeNi ordered alloy. This is an SEM image of a magnetic particle. This is an enlarged view of region B shown in Figure 10. This is an enlarged view of region C shown in Figure 10. This is an SEM image of a magnetic particle. This is an enlarged view of region D shown in Figure 13. This is a graph showing the hysteresis curve of a magnet. This is a chart showing the relationship between orientation, volume, and magnetic flux density. This is a chart showing the relationship between thickness and volume.

[0012] This description will explain embodiments for implementing this disclosure with reference to the drawings. In later embodiments, parts corresponding to those described in earlier embodiments may be given the same reference numerals, and redundant explanations may be omitted. If only a part of the configuration is described in each embodiment, the description of the earlier embodiment may be applied to the other parts of the configuration.

[0013] It is possible to combine parts that are explicitly shown to be combinable in each form. In particular, if there are no problems with the combination, it is also possible to partially combine multiple forms with each other, a form with a modified form, and multiple modified forms with each other, even if it is not explicitly shown that they can be combined.

[0014] Furthermore, in the following, the three directions that are orthogonal to each other will be referred to as the X direction, Y direction, and Z direction. The X, Y, and Z directions are linear directions. In the drawings, the term "direction" is omitted, and they are simply shown as X, Y, and Z.

[0015] <First Embodiment> <Magnet> Figure 1 shows a magnet 10. The magnet 10 of this embodiment has six faces. Two of the six faces are aligned in the X direction, two of the remaining four faces are aligned in the Y direction, and the last two faces are aligned in the Z direction. The magnet 10 has a rectangular parallelepiped shape.

[0016] Of course, the shape of the magnet 10 is not particularly limited. For example, the magnet 10 may be arc-shaped. The shape of the magnet 10 can be changed as appropriate depending on the application.

[0017] <Magnetic Material> Figure 2 shows a magnified view of the inside of the magnet 10. A part of the magnet 10 shown in this magnified view is referred to as the magnetic material 20. Figure 2 shows a state in which multiple magnetic particles 30 exist individually within the magnetic material 20.

[0018] <Single Element> The term "single element" above refers to a state in which particles are primary particles that are not aggregated or fixed to each other, and exist independently without being supported by a substrate or other support. The magnetic material 20 includes at least one of the single magnetic particles 30 themselves, a powder as an aggregate of the single magnetic particles 30, granular form of the powder, and a molded mass of the powder.

[0019] <Magnetic Particles> As shown in Figures 3 and 4, the magnetic particles 30 are individually flattened. The magnetic particles 30 have flattened surfaces 30a and side surfaces 30b. The two flattened surfaces 30a are spaced apart and side by side. The side surface 30b is located between the two flattened surfaces 30a. The side surface 30b extends around the direction in which the two flattened surfaces 30a are aligned, forming an annular shape. The side surface 30b connects the two flattened surfaces 30a.

[0020] The long axis 31 is aligned along the flattened surface 30a, and the short axis 32 is aligned along the side surface 30b. The long axis 31 and the short axis 32 intersect. The short axis 32 is aligned in the direction of the two flattened surfaces 30a. The length of the long axis 31 of the magnetic particle 30 is longer than the length of the short axis 32. The area of ​​the side surface 30b is smaller than that of the flattened surface 30a. Thus, the magnetic particle 30 is flattened on its own. In the magnetic particle 30, the easy magnetization axis 33 is aligned along the flattened surface 30a.

[0021] In the following, for the sake of simplicity, the length of the major axis 31 will be referred to as the major axis length, and the length of the minor axis 32 will be referred to as the minor axis length. The major axis length refers to the longest length in the direction along the flattened plane 30a. The minor axis length refers to the longest length in the direction along the side surface 30b and intersecting the major axis 31.

[0022] As shown in Figure 4, the magnetic particles 30 have alloy particles 34 and an insulating coating 35. The surface of the alloy particles 34 is covered with the insulating coating 35.

[0023] The alloy particle 34 is L1 ０ It contains an FeNi ordered alloy with a type ordered structure. In addition to Fe and Ni, the alloy particles 34 may contain additives such as sulfur or unavoidable impurities. The alloy particles 34 determine the magnetic properties of the magnetic particles 30.

[0024] The alloy particles 34 form the shape of the magnetic particles 30. The alloy particles 34 are flattened in shape. The alloy particles 34 have two main surfaces 34a and an annular surface 34b connecting these two main surfaces 34a.

[0025] As its name suggests, the insulating coating 35 has insulating properties. The thickness of the insulating coating 35 is expected to be uniform. The thickness of the insulating coating 35 covering the main surface 34a is expected to be the same as the thickness of the insulating coating 35 covering the annular surface 34b.

[0026] The flattened surface 30a and side surface 30b of the magnetic particle 30 are formed by an insulating coating 35. However, the shape of the flattened surface 30a is determined by the main surface 34a of the alloy particle 34, and the shape of the side surface 30b is determined by the annular surface 34b of the alloy particle 34. The long axis 31 and the easy magnetization axis 33 are along the main surface 34a, and the short axis 32 intersects the long axis 31 and is along the annular surface 34b. If the magnetic particle 30 does not have an insulating coating 35, the main surface 34a of the alloy particle 34 corresponds to the flattened surface 30a, and the annular surface 34b corresponds to the side surface 30b.

[0027] The insulating film 35 functions to sever the magnetic coupling between the alloy particles 34 contained in a plurality of adjacent magnetic particles 30 located in the vicinity within the magnetic body 20. The magnetic coupling between the plurality of alloy particles 34 is the exchange interaction, which is a quantum mechanical effect occurring between particles of the same kind. The insulating film 35 may also be referred to as a "magnetic severing layer" or a "magnetic severing coating layer".

[0028] <Unit cell> Fig. 5 shows the unit cell of the FeNi regular alloy with the L1 ０ type regular structure as the FeNi superlattice 50. In the FeNi superlattice 50, based on the face-centered cubic lattice, Fe and Ni are arranged in layers in the (001) direction. The FeNi superlattice 50 has an I site 51 located at the end side and an II site 52 located in the middle in the stacking structure of the (001) plane of the face-centered cubic lattice. In Fig. 5, the positions where atoms are arranged at the I site 51 are shown by white circles, and the positions where atoms are arranged at the II site 52 are shown by black circles.

[0029] The a-axis 53 in such a crystal structure is in the (010) direction, and the c-axis 54 is in the (001) direction. The c-axis 54 is the easy magnetization axis 33. In the FeNi superlattice 50 with a regularity of 1.0 described later, only Ni atoms among Fe atoms and Ni atoms exist at the I site 51, and only Fe atoms among Fe atoms and Ni atoms exist at the II site 52.

[0030] The magnetic particles 30 are nanoparticles. The major axis length is 1000 nm or less, several 100 nm or less. The minor axis length is 100 nm or less, several 10 nm or less. "nm" indicates "nanometer". The magnetic particles 30 can also be referred to as magnetic nanoparticles.

[0031] When a plurality of magnetic particles 30 are included in the magnetic body 20, it is presumed that not all of these plurality of magnetic particles 30 necessarily exist alone, and at least a part of them is in a state of being connected to each other. However, even in such a connected state, if there is no fundamental change in the flat shape of the plurality of magnetic particles 30 and the L1 ０ type regular structure, it is presumed that the properties of the plurality of magnetic particles 30 do not become heterogeneous.

[0032] <Regularity> In this embodiment, the magnetic material 20 is manufactured such that the regularity measured by the powder X-ray diffraction method is greater than 0.7, preferably 0.76 or more, and more preferably 0.8 or more. The "regularity" is an index indicating the degree of regularization in the FeNi superlattice 50, as described in Japanese Patent No. 6528865 and the like.

[0033] The regularity is evaluated based on the XRD pattern. Let J be the ratio of the integrated intensity of the superlattice diffraction peak to the integrated intensity of the fundamental diffraction peak in the measured X-ray diffraction pattern. Let K be the ratio of the integrated intensity of the superlattice diffraction peak to the integrated intensity of the fundamental diffraction peak in the FeNi regular alloy with a regularity of "1" estimated from the Rietveld simulation. Then, the regularity is (J / K) ０．５ and is evaluated.

[0034] When the ratio of metal A present at the I site 51 shown in FIG. 5 is x and the ratio of metal B present is 1 - x, the ratio of metal A and metal B present at the I site 51 is A ｘ B １－ｘ and is represented as such. When the ratio of metal B present at the II site 52 is x and the ratio of metal A present is 1 - x, the ratio of metal A and metal B present at the II site 52 is A １－ｘ B ｘ and is represented as such. Letting the regularity be OP, it is represented by OP = 2x - 1. x is a value between 0.5 and 1.0.

[0035] <FeNiN> There is FeNiN as a precursor material for the FeNi regular alloy. In FIG. 6, the unit cell of FeNiN is shown as the FeNiN lattice 60. The crystal structure including this unit cell can be identified from the XRD diffraction pattern. XRD is an abbreviation for X-ray diffraction.

[0036] The FeNiN lattice 60 has III sites 61, IV sites 62, and V sites 63. The III sites 61 correspond to the I sites 51 in the FeNi superlattice 50. The IV sites 62 correspond to the II sites 52 in the FeNi superlattice 50. The V sites 63 are located in the middle between two adjacent III sites 61 in the stacking direction. In FeNiN 50, it is expected that Ni atoms are present at the III sites 61, Fe atoms are present at the IV sites 62, and N atoms are present at the V sites 63.

[0037] <Method for manufacturing magnetic material> Next, a method for manufacturing the magnetic particles 30 will be outlined based on FIG. 7.

[0038] In step S10, FeNiN, which is a precursor material of the FeNi ordered alloy, is synthesized. In freshly synthesized FeNiN, many FeNiN particles are aggregated or adhered.

[0039] In step S20, FeNiN is coarsely pulverized. By doing so, FeNiN particles smaller in size than FeNiN are obtained.

[0040] In step S30, mechanical forces such as mechanical shear force are applied to the FeNiN particles. By doing so, the shape of the FeNiN particles is flattened. At this point, there is a particle size distribution among the plurality of flattened FeNiN particles obtained.

[0041] In step S40, flattened FeNiN particles within a desired particle size range are selected from among the plurality of flattened FeNiN particles having a particle size distribution. The flattened FeNiN particles are classified.

[0042] In step S50, the surfaces of the classified flattened FeNiN particles are coated with a constituent material of the insulating film 35. The constituent material of the insulating film 35 is silica or the like.

[0043] In step S60, the flattened FeNiN particles coated with the constituent material of the insulating film 35 are heat-treated (annealed). By doing so, defects that may have occurred in the flattened FeNiN particles due to the treatments such as coarse pulverization and flattening performed so far are repaired.

[0044] In step S70, the heat-treated flattened FeNiN particles are subjected to a denitrification treatment. This removes nitrogen from the flattened FeNiN particles, thereby producing flattened magnetic particles 30.

[0045] Next, the method for manufacturing the magnetic particles 30 shown in Figure 7 will be described in detail.

[0046] <FeNiN Synthesis> For the synthesis of FeNiN, a precursor material, techniques described in, for example, Japanese Patent Publication No. 6230513 and Japanese Patent Publication No. 6627818 can be used.

[0047] Specifically, FeNiN is synthesized by nitriding FeNi disorder alloy powder produced by methods such as thermal plasma, flame spray, or coprecipitation. FeNiN can also be obtained by reduction and nitriding of FeNi oxide. The FeNi oxide used in the reduction process may contain Fe oxide or Ni oxide, or an oxide containing both Fe and Ni.

[0048] The Fe oxide is not particularly limited, but for example, FeO, Fe ２ O ３ Fe ３ O ４ These include, among others. Fe oxides include oxides obtained by oxidizing raw materials such as metallic iron, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron bromide, iron sulfate, iron nitrate, iron phosphate, and iron oxalate.

[0049] Ni oxides are not particularly limited, but examples include NiO. Ni oxides include oxides obtained by oxidizing raw materials such as metallic nickel, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel bromide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate.

[0050] An oxide containing Fe and Ni can be produced by carrying out the following precipitation and oxidation steps. In the precipitation step, a solution containing Fe and Ni is mixed with a precipitating agent to obtain a precipitate containing Fe and Ni. Next, in the oxidation step, the precipitate is heat-treated to obtain an oxide containing Fe and Ni. According to the above production method, it is easy to control the average particle size and particle size distribution of the obtained oxide containing Fe and Ni, and the distribution of Fe and Ni in the oxide containing Fe and Ni tends to be uniform.

[0051] The Fe and Ni raw materials are not limited as long as they can be dissolved in an acidic solution. Examples of Fe raw materials include metallic iron, iron oxide, iron hydroxide, iron carbonate, iron chloride, iron iodide, iron sulfate, iron nitrate, iron phosphate, and iron oxalate. Examples of Ni raw materials include metallic nickel, nickel oxide, nickel hydroxide, nickel carbonate, nickel chloride, nickel iodide, nickel sulfate, nickel nitrate, nickel phosphate, and nickel oxalate. Examples of acidic solutions include sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid. The concentration of the solution containing Fe and Ni can be appropriately adjusted within the range in which the Fe and Ni raw materials are substantially soluble in the acidic solution.

[0052] To react a solution containing Fe and Ni with a precipitating agent, the precipitating agent may be added to the solution containing Fe and Ni, or the solution containing Fe and Ni may be added to the precipitating agent. The solution containing Fe and Ni referred to here only needs to be a solution containing Fe and Ni when reacting with the precipitating agent; the Fe and Ni raw materials may be prepared as separate solutions, and each solution may be added to react with the precipitating agent. Even when the Fe and Ni raw materials are prepared as separate solutions, the range can be adjusted as appropriate so that each raw material is substantially soluble in the acidic solution.

[0053] The precipitating agent mentioned above is not limited to any agent that reacts with a solution containing Fe and Ni to produce a precipitate. Examples of precipitating agents include alkaline solutions such as oxalic acid, sodium hydroxide aqueous solution, sodium bicarbonate aqueous solution, potassium hydroxide aqueous solution, and lithium hydroxide aqueous solution. Alternatively, a precipitate can be obtained by blowing carbon dioxide into a solution containing Fe and Ni. The precipitates produced may include oxalates, carbonates, and hydroxides.

[0054] To give a specific example, FeNiN can be obtained by firing iron nickel oxalate powder in air, hydrogen reduction, and nitriding.

[0055] <Coarse Grinding> For coarse grinding of FeNiN, general grinding methods such as ball milling can be used.

[0056] <Flattening> Flattening of FeNiN particles is not particularly limited, but can be achieved, for example, by applying mechanical shear force to the FeNiN particles. Specifically, a wet bead mill is performed on a slurry containing FeNiN particles. In this way, mechanical shear force is applied to the FeNiN particles, and their shape can be flattened.

[0057] The slurry containing the FeNiN particles described above can be prepared by dispersing coarsely ground FeNiN particles in a solvent containing a surfactant. A surfactant that provides good coating properties for the FeNiN particles can be used. Examples of surfactants include nitrogen-containing surfactants such as oleylamine and trioctylamine, and sulfur-containing surfactants such as octanthiol and triazinedithiol. Polymeric surfactants such as polyvinyl alcohol, polyacrylic acid, polyethyleneimine, and polyvinylpyrrolidone can also be used. As a solvent, a liquid that allows for stable dispersion of the surfactant-coated FeNiN particles can be used. Examples of solvents include pure water, alcohols such as ethanol and isopropyl alcohol, and nonpolar solvents such as toluene and cyclohexane.

[0058] As an example, a slurry containing 5% by weight of FeNiN particles in ethanol is introduced into a bead mill apparatus together with zirconia media with a diameter of 0.1 mm and processed at 600 rpm for 30 minutes. This process yields a slurry containing flattened FeNiN particles. The bead mill apparatus used is a planetary ball mill, PL-7, manufactured by Fritsch.

[0059] <Classification> The slurry containing flattened FeNiN particles is centrifuged. This allows for particle size classification. For example, centrifugation is performed in the following order: 500G for 10 min, 4000G for 10 min, and 4000G for 120 min. This allows the flattened FeNiN particles with larger particle sizes to settle first. These particles are then collected. To obtain high coercivity, small-particle flattened FeNiN particles are extracted. This coercivity is evaluated as the strength of the magnetic field when a magnetic field is applied to the magnetic particles 30 and the magnetization direction of the FeNi ordered alloy is switched by the influence of the magnetic field.

[0060] <Coating> As described above, the insulating film 35 plays a role in disrupting the magnetic bonds between multiple magnetic particles 30 located in close proximity within the magnetic material 20. For this reason, the constituent material of the insulating film 35 must be non-magnetic. Furthermore, the constituent material of the insulating film 35 must be a substance that can be subjected to heat treatment and denitrification treatment, and that does not react with the alloy particles 34.

[0061] Examples of constituent materials for the insulating coating 35 that satisfy the above requirements include oxides of Group III-VII and Group XIII-XVI elements, such as silica, titania, zirconia, yttria, and alumina. In addition, insulating materials such as nitride films can also be used as constituent materials for the insulating coating 35. The thickness of the insulating coating 35 is 1 nm or more.

[0062] In this example, the classified flattened FeNiN particles were coated with silica (silica coating). When silica is used as the insulating film 35 in this way, the powdered flattened FeNiN particles are mixed with a solvent of water or ethanol to which tetraethoxysilane has been added, and then an aqueous ammonia solution is poured in. As a result, silica is produced by the hydrolysis and condensation of tetraethoxysilane. The flattened FeNiN particles are covered with silica. The flattened FeNiN particles are coated with the insulating film 35.

[0063] As explained above, the coating treatment on the flattened FeNiN particles is performed before the heat treatment and denitrification. This suppresses the sintering of the flattened FeNiN particles during the subsequent heat treatment and denitrification. In addition, it suppresses the bonding of the alloy particles 34 contained in the magnetic material 20 during the molding of the magnet 10. This suppresses the deterioration of the magnetic properties of the magnet 10.

[0064] <Heat Treatment> The heat treatment performed on the flattened FeNiN particles is carried out, for example, in an ammonia gas environment. Specifically, as an example, the flattened FeNiN particles are placed in an electric furnace capable of introducing ammonia gas. The ambient temperature is set to 300 to 450°C, and the treatment time is set to 4 to 48 hours. This arranges the atomic structure of the flattened FeNiN particles.

[0065] Flattened FeNiN particles contain sulfur as an impurity or additive. After grinding, the stabilizing effect of sulfur on the FeNiN particles weakens, making them more susceptible to decomposition at high temperatures. Therefore, the optimal heat treatment conditions vary depending on the amount of sulfur present in the flattened FeNiN particles and their particle size. The temperature for this heat treatment should preferably be lower than the nitriding temperature used in the FeNiN synthesis process.

[0066] <Denitrification> Flattened FeNiN particles, whose atomic arrangement has been aligned by heat treatment, are subjected to denitrification treatment. This denitrification treatment removes nitrogen from the flattened FeNiN particles. At the same time, the atomic arrangement is corrected. Flattened FeNi particles with a regular atomic arrangement and increased coercivity are produced. Alloy particles 34 containing an FeNi ordered alloy, covered with an insulating coating 35, are produced.

[0067] The denitrification treatment can be carried out using the apparatus and method described in Japanese Patent Publication No. 6230513 and Japanese Patent Publication No. 6627818. Specifically, the denitrification treatment can be carried out, for example, by heat treatment under a hydrogen atmosphere. The hydrogen flow rate can be, for example, 0.01 to 10 liters / min per 1 g of flattened FeNiN particles. Preferably, the hydrogen flow rate can be 0.1 to 5 liters / min. The heat treatment temperature can be, for example, 100 to 400°C. Preferably, the heat treatment temperature can be 200 to 350°C. The heat treatment time can be, for example, 1 to 24 hours. Preferably, the heat treatment time can be 2 to 10 hours.

[0068] <Long axis length and short axis length> The method for measuring the long axis length and short axis length of the magnetic particle 30 is described below. The length can be measured using image analysis software.

[0069] The shapes of the multiple magnetic particles 30 visible in the image captured by the scanning electron microscope (SEM image) are varied. From these, we select the magnetic particles 30 for which it is easy to determine the longest length on the flattened plane 30a. For example, we select particles whose flattened plane 30a has an elliptical shape, making it easy to determine the major axis length, and we do not select particles whose flattened plane 30a has a U-shape or J-shape, making it difficult to determine the major axis length. We select, for example, 100 such magnetic particles 30. Then, we measure the longest length on the flattened plane 30a of these particles and calculate the average value. In this way, the major axis length (average particle size) can be determined. The standard deviation of the measured values ​​for the major axis lengths of the 100 magnetic particles 30 can be evaluated as the measurement error of the major axis length.

[0070] From among several magnetic particles 30 with varying shapes displayed in the SEM image, a magnetic particle 30 is selected that makes it easy to determine the longest thickness between two flattened surfaces 30a on its side surface 30b. Similarly to the long axis length, for example, 100 magnetic particles 30 that make it easy to determine the longest thickness between two flattened surfaces 30a are selected. Then, the longest thickness on their side surface 30b is measured, and the average value is calculated. In this way, the short axis length can be determined. The standard deviation of the measured thicknesses of the 100 magnetic particles 30 can be evaluated as the thickness measurement error.

[0071] Of course, there is no upper limit to the number of magnetic particles 30 suitable for measuring the long axis length and short axis length. However, from the perspective of minimizing measurement errors, it is preferable to select at least 30 magnetic particles 30.

[0072] As described above, magnetic particles 30 suitable for measuring the long axis length and short axis length are selected. Therefore, the magnetic particles 30 used to measure the long axis length and the magnetic particles 30 used to measure the short axis length are different, meaning the objects of measurement for the long axis length and short axis length are different. However, as described above, 100 magnetic particles 30 are selected for each measurement of the long axis length and short axis length. The average values ​​of the long axis length and short axis length are calculated. Therefore, although the objects of measurement for the long axis length and short axis length are different, it is considered that the influence of the difference in measurement objects on the calculated long axis length and short axis length is small.

[0073] More precisely, when actually measuring the major and minor axis lengths as described above, it is better to measure the major and minor axis lengths of the flattened FeNiN particles before denitrification, rather than the major and minor axis lengths of the magnetic particles 30 after denitrification. The reason for this is as follows.

[0074] As shown in the manufacturing method in Figure 7, the coating treatment in step S50 is performed before the denitrification treatment in step S70. Therefore, in the magnetic particles 30 obtained by denitrification, the outer surface of the alloy particles 34 is covered with an insulating film 35. The insulating film 35 is electrically insulating. Therefore, it becomes difficult to obtain a clear SEM image due to charge-up. As a result, it becomes difficult to measure the long axis length and short axis length of the magnetic particles 30. For this reason, it is preferable to measure the long axis length and short axis length of the flattened FeNiN particles before they are covered with the insulating film 35, rather than the long axis length and short axis length of the magnetic particles 30.

[0075] Furthermore, it is presumed that the size of the alloy particles 34 of the magnetic particles 30 shrinks to some extent due to the denitrification treatment compared to the flattened FeNiN particles. It is presumed that the lattice constant decreases by about 10% due to the change from the FeNiN lattice 60 to the FeNi superlattice 50. However, this change in size is within the range of the measurement error (standard deviation) mentioned above. In addition, it is presumed that the particle shape and size distribution do not change much before and after denitrification. The thickness of the insulating coating 35 is also within the range of the measurement error. For these reasons, the major axis length and minor axis length based on the measurement results from the SEM image of the flattened FeNiN particles can be considered as the major axis length and minor axis length of the magnetic particles 30. In the magnetic particles 30 of Examples 1 to 3 described later, their major axis length and minor axis length are considered to be the major axis length and minor axis length based on the measurement results from the SEM image of the flattened FeNiN particles.

[0076] <Evaluation of Examples> In the classification process of step S40, magnetic particles 30 of Example 1 were produced by centrifugal separation under the conditions of 500 G and 10 min. In the classification process of step S40, magnetic particles 30 of Example 2 were produced by centrifugal separation under the conditions of 4000 G and 10 min. In the classification process of step S40, magnetic particles 30 of Example 3 were produced by centrifugal separation under the conditions of 4000 G and 120 min. It was confirmed that the shape of the magnetic particles 30 of Examples 1 to 3 was flattened.

[0077] In contrast, the nanoparticles of Comparative Example 1 were produced by omitting steps S30, S40, and S50 from the manufacturing method described in Figure 7. The shape of the nanoparticles of Comparative Example 1 was not flattened.

[0078] The major axis length and minor axis length of the magnetic particles 30 in the above-described example, and the particle size of Comparative Example 1 were measured. Furthermore, their orderliness and coercivity were measured. Although Comparative Example 1 is not flattened, the method for measuring the major axis length and minor axis length of the magnetic particles 30 can be used to measure its length.

[0079] The measured length of the long axis of the magnetic particle 30 in Example 1 was 640 nm, with a measurement error (standard deviation) of 205 nm. The measured length of the short axis was 49 nm, with a measurement error of 15 nm. The degree of order was 0.80, with a measurement error of 0.04. The coercivity was 160 kA / m.

[0080] The measured length of the long axis of the magnetic particle 30 in Example 2 was 221 nm, with a measurement error of 82 nm. The measured length of the short axis was 33 nm, with a measurement error of 8 nm. The orderliness was 0.81, with a measurement error of 0.04. The coercivity was 220 kA / m.

[0081] The measured length of the long axis of the magnetic particle 30 in Example 3 was 96 nm, with a measurement error of 40 nm. The measured length of the short axis was 20 nm, with a measurement error of 4 nm. The orderliness was 0.89, with a measurement error of 0.05. The coercivity was 380 kA / m.

[0082] Furthermore, the particle size of the nanoparticles in Comparative Example 1 was 182 nm, with a measurement error of 64 nm. The orderliness was 0.63, with a measurement error of 0.03. The coercivity was 120 kA / m.

[0083] As shown above, the order of the nanoparticles in Comparative Example 1 could not exceed 0.7. In contrast, the order of the magnetic particles 30 in Examples 1 to 3 exceeded 0.7. The expected range of possible values ​​for the order is 0.76 or higher and 0.94 or lower. In Comparative Example 1, the coercivity was 120 kA / m, while in Examples 1 to 3, the coercivity was 160 to 380 kA / m.

[0084] Furthermore, the degree of regularity tended to increase as the minor axis length decreased. It is expected that a degree of regularity of 0.7 or higher can be achieved by setting the minor axis length to 100 nm or less, or to a few tens of nm or less. A possible range for minor axis lengths that yield a degree of regularity of 0.76 or higher is a few nanometers or more, and 50 nm or less.

[0085] Furthermore, the shorter the major axis length, the greater the coercivity tended to be. A range of major axis lengths that yield good coercivity is considered to be between several tens of nanometers and 350 nm. If the particles are too small, the orientation may decrease, and from this perspective as well, the aforementioned ranges for both the minor and major axis lengths are preferable.

[0086] As shown above, it was confirmed that Examples 1 to 3 showed improved regularity and greater coercivity compared to Comparative Example 1.

[0087] When diffraction spots were observed in flattened FeNiN particles using electron diffraction, diffraction spots indicating the presence of the c-axis 54 within the flattened plane were observed. Furthermore, it was found that some flattened FeNiN particles had a structure in which multiple regions with different c-axis orientations were arranged along the long axis. This orientation of the c-axis 54 is similar in the FeNi ordered alloy after denitrification.

[0088] Furthermore, a correlation was observed where the azimuthal distribution became smaller as the length of the major axis decreased. It is thought that as the length of the major axis decreased, the distribution in the c-axis direction narrowed, the degree of regularity increased, and the coercivity increased.

[0089] In Comparative Example 2, the nanoparticles produced by performing steps S30 and S40 of the manufacturing method described in Figure 7 after step S70 were flattened in shape. However, although the shape of Comparative Example 2 was flattened, the orderliness and coercivity were lower than those of Comparative Example 1.

[0090] Specifically, the measured length of the long axis of the nanoparticles in Comparative Example 2 was 245 nm, with a measurement error of 101 nm. The measured length of the short axis was 38 nm, with a measurement error of 8 nm. The orderness was 0.30, with a measurement error of 0.02. The coercivity was 25 kA / m.

[0091] Furthermore, analysis of the electron diffraction pattern of Comparative Example 2 revealed that while a diffraction pattern typical of polycrystalline particles was observed, no spots corresponding to {001} or {002}, which appear when the c-axis 54 is located within a flattened plane, were observed. Therefore, it was confirmed that Comparative Example 2 is polycrystalline and does not have a specific crystal orientation direction.

[0092] <Insulating Coating> As described above, in Examples 1 to 3, a coating treatment is performed in step S50. Therefore, as shown in Figures 8 to 12, the surface of the alloy particles 34 is covered with an insulating coating 35. The alloy particles 34 are darker than the insulating coating 35.

[0093] Figure 9, an enlarged view of the SEM image shown in Figure 8, shows that the thickness of the insulating coating 35 is 3.2 nm. In the SEM image shown in Figure 10, the thickness of the insulating coating 35 is 3.5 nm. Furthermore, in Figure 12, an enlarged view of the SEM image shown in Figure 11, the thickness of the insulating coating 35 is 5.0 nm.

[0094] To verify the effect of the insulating coating 35, the nanoparticles of Comparative Example 3 were manufactured by omitting the coating treatment in step S50 from the manufacturing method described in Figure 7. Other processing conditions, such as the classification conditions, were the same as those of Example 3.

[0095] The order of the nanoparticles in Comparative Example 3 was 0.75, and the measurement error was 0.04. The coercivity was 180 kA / m. In Comparative Example 3, contact occurred between multiple adjacent alloy particles 34. In contrast, in the magnetic particles 30 of Example 3, which underwent a coating treatment, an insulating film 35 was interposed between multiple adjacent alloy particles 34, resulting in an order of 0.89 and a measurement error of 0.05. The coercivity was 380 kA / m.

[0096] Example 3 exhibits higher order and coercivity than Comparative Example 3. This is presumed to be because, as described above, the coating treatment is performed before the heat treatment and denitrification, which suppresses contact and sintering between particles during the heat treatment and denitrification, thereby maintaining the independence of the alloy particles 34. Furthermore, it is presumed that the insulating film 35 provides a magnetic separation effect between adjacent alloy particles 34, resulting in high coercivity.

[0097] In order to achieve the aforementioned effect, the thickness of the insulating film 35 needs to be adjusted. The thickness of the insulating film 35 needs to be greater than half the magnetic coupling distance between two adjacent alloy particles 34 in the vicinity. This magnetic coupling distance is approximately 1 nm. In order to achieve the aforementioned effect, the thickness of the insulating film 35 needs to be greater than 0.5 nm.

[0098] The thickness of the insulating film 35 in this embodiment is approximately 1.0 nm, or a few nm. This thickness of the insulating film 35 represents the average thickness of the insulating film 35 covering a single alloy particle 34. As shown in Figures 8 to 12, the thickness of the insulating film 35 can be measured from SEM images. Select an alloy particle 34 in which there are regions where the particles do not overlap in a plan view of the SEM image. Measure the thickness of the insulating film 35 covering the selected alloy particle 34. Measure the thickness of the insulating film 35 covering different alloy particles 34. Measure the thinnest part of the insulating film 35 covering a single alloy particle 34. The average of these thickness measurements is approximately 1.0 nm for the insulating film 35 in this embodiment. For example, if the thickness of the insulating film 35 is measured at 100 locations, the standard deviation of these measurements can be evaluated as the measurement error of the insulating film 35 thickness. Of course, the number of measurements of the insulating film 35 thickness is not particularly limited.

[0099] Furthermore, the thicker the insulating coating 35, the more the ratio of alloy particles 34 to insulating coating 35 in a single magnetic particle 30 becomes unbalanced, resulting in a decrease in the amount of alloy particles 34 contained in the magnetic material 20. As a result, there is a risk that the magnetic force of the magnetic material 20 and the magnet 10 will decrease. To avoid such problems, the volume fraction of alloy particles 34 in a single magnetic particle 30 is larger than that of the insulating coating 35.

[0100] The magnitude of the magnetic flux density emitted from the magnet 10 is determined by the product of the magnetic flux density emitted from the magnetic particles 30, the volume ratio of the alloy particles 34 contained in the magnetic particles 30, and the degree of orientation of the multiple magnetic particles 30 in the magnet 10. In the following, let B0 be the magnitude of the magnetic flux density emitted from the magnet 10. Let B1 be the magnetic flux density emitted from the magnetic particles 30. Let V1 be the volume ratio of the alloy particles 34 contained in the magnetic particles 30. Let O be the degree of orientation of the multiple magnetic particles 30 in the magnet 10. Then, B0 can be expressed as B1 × V1 × O.

[0101] Figure 13 shows the hysteresis curve of a magnet 10 in which magnetic particles 30 having an insulating coating 35 within the above thickness range are magnetically oriented. The maximum value of the external magnetic field is approximately 3T. The magnetic flux density output from the magnet 10 when the external magnetic field is at its maximum value is the saturation magnetic flux density Bs. The magnetic flux density output from the magnet 10 when the external magnetic field is gradually reduced to zero corresponds to the residual magnetic flux density Br. If the magnetic particles 30 are magnetically oriented completely randomly on the magnet 10, Br / Bs is expected to be 0.5. This Br / Bs corresponds to the orientation degree O mentioned above.

[0102] L1 ０ The magnetic flux density of alloy particles 34 containing a FeNi ordered alloy with a type ordered structure is approximately 1.6T. Therefore, when manufacturing a magnet 10 with, for example, B0 = 1.0T, the following equations must hold: For example, B0 = 1.6 × 0.625 × 1.0 or B0 = 1.6 × 1.0 × 0.625 must hold. 0.625 < V1 < 1.0 and 0.625 < O < 1.0 must also hold.

[0103] Figure 14 shows the values ​​of magnetic flux B0 output from the magnet 10 when the orientation degree O and magnetic particle susceptibility V are varied. In Figure 14, the hatched values ​​indicate that B0 = 1.0T or greater.

[0104] Figure 15 shows a table with values ​​for the thickness T of the insulating coating 35, the volume V0 of the magnetic particles 30, the volume ratio V1 of the alloy particles 34, and the volume ratio V2 of the insulating coating 35. Here, the alloy particles 34 are defined as cylinders with a major axis length of 150 nm and a minor axis length of 30 nm. In Figure 2, L is 150 nm and S is 30 nm.

[0105] As shown in Figure 15, when the thickness T is 10 nm or less, the volume fraction V1 of the alloy particles 34 is greater than the volume fraction V2 of the insulating film 35. Therefore, according to these calculations, in order for the amount of alloy particles 34 contained in the magnetic material 20 to be greater than the amount of insulating film 35, it is desirable that the average thickness of the insulating film 35 be approximately 10 nm or less.

[0106] As shown in Figures 8 to 12, the thickness of the insulating film 35 is not uniform in all locations. Due to manufacturing tolerances, the thickness is not the same everywhere. However, the above-mentioned 10 nm or less can be adopted as an indicator for setting a manufacturing target thickness for the insulating film 35, including these manufacturing tolerances. This figure of 10 nm or less is a useful indicator when considering the industrial use of the magnetic particles 30 of this disclosure.

[0107] <Effects> As explained above, the thickness of the insulating film 35 in this embodiment is approximately 1.0 nm. The thickness of the insulating film 35 is greater than half the magnetic bonding distance between two adjacent alloy particles 34 in the vicinity. Furthermore, the upper limit of the average thickness of the insulating film 35 is determined such that the volume fraction of the alloy particles 34 is greater than that of the insulating film 35. Theoretically, it is desirable that the thickness of the insulating film 35 be greater than 0.5 nm and less than or equal to 10 nm. Taking into account manufacturing variations in the thickness of the insulating film 35, it is desirable that the average thickness of the insulating film 35 be 1.0 nm or more.

[0108] Within the desired thickness range described above, the insulating film 35 functions to disrupt the magnetic coupling between multiple magnetic particles 30. Furthermore, when the thickness of the insulating film 35 approaches 10 nm, the insulating film 35 also functions to effectively disrupt the magnetic interaction between multiple adjacent magnetic particles 30 in the vicinity. The magnetic interaction between multiple magnetic particles 30 refers to the significant inhibition of the behavior of individual magnetic particles 30 due to the mutual influence caused by the magnetic field formed by the multiple magnetic particles 30. When the magnetic interaction between multiple magnetic particles 30 is disrupted by the insulating film 35, the disruption of the orientation of the multiple magnetic particles 30 is suppressed when manufacturing the magnet 10 by oriented the multiple magnetic particles 30.

[0109] As described above, the volume fraction of the alloy particles 34 is larger than that of the insulating coating 35. As a result, the coercivity and magnetic flux density of the magnet 10 are increased.

[0110] Flattened particles have a smaller surface area per unit volume than needle-shaped particles. Therefore, the amount of insulating film 35 covering the alloy particles 34 is reduced. Consequently, flattened alloy particles 34 are more advantageous than needle-shaped nanoparticles for achieving a high packing efficiency of the magnetic material during filling. The density of alloy particles 34 contained in the magnet 10 can be increased. As a result, the magnetic flux density and coercivity of the magnet 10 increase.

[0111] In the magnetic particle 30 described above, which has a flattened shape with a long axis 31 and a short axis 32, and whose easy magnetization axis 33 is aligned with the flattened plane 30a along the long axis 31, the easy magnetization axis 33 is oriented inward towards the flattened plane 30a. As a result, it is less susceptible to the influence of the demagnetizing field, and it is possible to increase the coercivity.

[0112] The magnetic particles 30 have the characteristics described above even when they are in a standalone state and not supported by a substrate or other support. Therefore, it is easy to form a magnet 10 using these magnetic particles 30.

[0113] The direction of crystalline magnetic anisotropy and the direction of shape magnetic anisotropy can be made parallel, resulting in a high angle ratio. Therefore, superior magnetic properties can be obtained compared to spherical particles.

[0114] <Variations> The disclosure of this specification is not limited to the exemplary embodiments. The disclosure includes the exemplary embodiments and modifications made by those skilled in the art based on those exemplary embodiments. The disclosure is not limited to combinations of parts and elements shown in the embodiments, but can be implemented in various modifications. The disclosure can be implemented in a variety of combinations. The disclosure may have parts that can be added to the embodiments. The disclosure includes embodiments in which parts and elements have been omitted. The disclosure includes substitutions of parts, substitutions of elements, combinations of parts, or combinations of elements between one embodiment and another. The technical scope of the disclosure is not limited to the descriptions of embodiments. The technical scope of the disclosure is indicated by the description of the claims. The technical scope of the disclosure should be understood to include the description of the claims and equivalents, and all modifications within the claims.

[0115] The applications of the magnetic particles 30 are not limited to the manufacture of magnets 10, but can also be applied to the manufacture of magnetic recording media, etc. Individual magnetic particles 30, powder which is an aggregate of such particles, and molded bodies in the form of such powder can all be the subject of claims under this disclosure. The flattening of the magnetic particles 30 can be successfully performed, and is not limited to the ball mill or bead mill used in the examples. Furthermore, the expression "orderliness measured by powder X-ray diffraction" does not necessarily mean that the orderliness is directly measured by powder X-ray diffraction, but includes the orderliness that can be calculated using various patterns, waveforms, values, etc. measured by powder X-ray diffraction. For this reason, "orderliness measured by powder X-ray diffraction" can also be rephrased as "orderliness that can be determined by measurement by powder X-ray diffraction."

[0116] <Disclosure of Technical Ideas> This specification discloses a plurality of technical ideas described in a plurality of items listed below. Some items may be described in a multiple dependent form that alternatively cites a preceding item in a subsequent item. Further, some items may be described in a multiple dependent form that cites another multiple dependent form item. The items described in these multiple dependent forms define a plurality of technical ideas.

[0117] <Technical Idea 1> L1 ０ Magnetic particles (30) comprising alloy particles (34) of a FeNi regular alloy having a L1 type regular structure, and an insulating film (35) covering the surface of the alloy particles, wherein the magnetic particles are in a flat shape where the long axis (31) intersects with the short axis (32) shorter than the long axis and the flat plane (30a) along the long axis is wider than the side surface (30b) along the short axis, and the ０ magnetization easy axis (33) of the L1 type regular structure is along the flat plane, and the thickness of the insulating film is 0.5 nanometers or more.

[0118] <Technical Idea 2> The magnetic body according to Technical Idea 1, wherein the thickness of the insulating film is 1 nanometer or more.

[0119] <Technical Idea 3> The magnetic body according to Technical Idea 1 or Technical Idea 2, wherein in the magnetic particles, the volume fraction of the alloy particles is larger than that of the insulating film.

[0120] <Technical Idea 4> The magnetic body according to any one of Technical Ideas 1 to 3, wherein the length of the long axis is 1000 nanometers or less, the length of the short axis is 100 nanometers or less, and the thickness of the insulating film is 10 nanometers or less.

[0121] <Technical Idea 5> L1 ０The magnetic material includes a magnetic particle (30) comprising alloy particles (34) containing a FeNi ordered alloy with a type ordered structure, and an insulating coating (35) covering the surface of the alloy particles, wherein the magnetic particle, individually, has a flattened shape in which a long axis (31) and a short axis (32) shorter than the long axis intersect, and the flattened plane (30a) along the long axis is wider than the side surface (30b) along the short axis, and the L1 ０ A magnet in which the magnetization easy axis (33) of the type-ordered structure is aligned with the flattened plane, and the thickness of the insulating coating is 0.5 nanometers or more.

Claims

1. L1 ０ The magnetic particle (30) comprises alloy particles (34) containing a FeNi ordered alloy with a type ordered structure, and an insulating coating (35) covering the surface of the alloy particles, wherein the magnetic particle, individually, has a flattened shape in which a long axis (31) and a short axis (32) shorter than the long axis intersect, and the flattened plane (30a) along the long axis is wider than the side surface (30b) along the short axis, and the L1 ０ A magnetic material in which the magnetization easy axis (33) of the type ordered structure is aligned with the flattened plane, and the thickness of the insulating coating is 0.5 nanometers or more.

2. The magnetic material according to claim 1, wherein the thickness of the insulating coating is 1 nanometer or more.

3. The magnetic material according to claim 2, wherein the alloy particles have a larger volume fraction than the insulating film in the magnetic particles.

4. The magnetic material according to any one of claims 1 to 3, wherein the length of the major axis is 1,000 nanometers or less, the length of the minor axis is 100 nanometers or less, and the thickness of the insulating coating is 10 nanometers or less.

5. L1 ０ The magnetic material includes a magnetic particle (30) comprising alloy particles (34) containing a FeNi ordered alloy with a type ordered structure, and an insulating coating (35) covering the surface of the alloy particles, wherein the magnetic particle, individually, has a flattened shape in which a long axis (31) and a short axis (32) shorter than the long axis intersect, and the flattened plane (30a) along the long axis is wider than the side surface (30b) along the short axis, and the L1 ０ A magnet in which the magnetization easy axis (33) of the type-ordered structure is aligned with the flattened plane, and the thickness of the insulating coating is 0.5 nanometers or more.

Images