Method for manufacturing magnetic powder, magnetic field-amplifying magnetic material, and ultra high frequency-absorbing magnetic material

Abstract

Provided are: a magnetic powder having outstanding high-frequency characteristics and having low iron loss and outstanding efficiency even when subjected to high frequency waves; a method for manufacturing a magnetic powder having outstanding high-frequency characteristics, and having low deterioration due to eddy currents and outstanding absorption characteristics even when exposed to ultra high frequency waves; a magnetic field-amplifying magnetic material having high frequency magnetic field-amplifying characteristics; and an ultra high frequency-absorbing magnetic material. The present invention relates to a method for manufacturing a magnetic powder, said method including a phosphorus treatment step for obtaining a phosphorus compound and a rare earth-iron-nitrogen magnetic powder by adding an inorganic acid to a slurry containing: a rare-earth-iron-nitrogen magnetic powder that contains R (where R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm; and, if Sm is included, Sm accounts for less than 50 atomic% of the R component as a whole), Fe, and N; water; and a phosphorus-containing substance. The present invention also relates to an ultra high frequency-absorbing magnetic material and a magnetic field-amplifying magnetic material containing a phosphorus compound and a rare earth-iron-nitrogen magnetic powder.

Description

Method for manufacturing magnetic powder, magnetic material for amplifying magnetic field, and magnetic material for absorbing ultra-high frequency waves

[0001] The present disclosure relates to a method for producing magnetic powder, a magnetic material for magnetic field amplification, and a magnetic material for ultra-high frequency absorption.

[0002] In recent years, with the miniaturization and multifunctionality of devices and the increasing speed of computing processes, drive frequencies have become increasingly higher, and the use of high-frequency and ultra-high-frequency devices is steadily expanding. Particularly noteworthy is the development of power devices used in the high-frequency range from 1 MHz to less than 1 GHz. For example, the market for GaN electronic devices is predicted to grow significantly in the future as high-frequency, high-output wireless and power electronics devices. Increasing the frequency of GaN circuits for power electronics requires not only GaN devices but also passive components to be made higher in frequency. For example, GaN wireless power transfer systems handle frequencies exceeding 10 MHz, requiring coils made of magnetic core materials capable of handling high frequencies. However, due to the lack of magnetic core materials with excellent high-frequency characteristics, air-core coils are unavoidable. Even if GaN is used to increase frequency and miniaturize devices, the overall circuit size increases.

[0003] The next area of ​​interest is the development of information infrastructure in the ultra-high frequency range from 1 GHz to 1 THz. There are various needs for high-frequency characteristics of materials that absorb spurious signals and their harmonics in the range of 1 GHz to less than 10 GHz for 5G, 10 GHz to less than 100 GHz for 5G+, and 100 GHz to less than 1 THz for 6G, and this need has been increasing recently. In particular, there are currently no materials that can absorb wide-band ultra-high frequencies above 1 GHz, even above 10 GHz, and there are high hopes for the emergence of ultra-wide frequency band ultra-high frequency absorption materials that can be used widely in the range of 1 GHz to less than 1 THz. One example of a conventional high-frequency magnetic material is a rare earth-iron-nitrogen magnetic material in which the powder surface is coated with a ferrite-based magnetic material (Patent Document 1).

[0004] International Publication No. 2008 / 136391

[0005] However, the material disclosed in Patent Document 1 is not efficient enough to be used as a magnetic field amplification material in the above-mentioned range of 1 MHz to 1 THz, and also has the problem of not having high-frequency characteristics that meet the needs for ultra-wide frequency band absorbers in the ultra-high frequency range.

[0006] The present disclosure aims to provide a magnetic powder with excellent high-frequency characteristics, including low iron loss and excellent efficiency even when subjected to high frequencies, a method for manufacturing a magnetic powder with excellent high-frequency characteristics, including little degradation due to eddy currents and excellent absorption characteristics even when subjected to ultra-high frequencies, and a magnetic material for magnetic field amplification that has high-frequency magnetic field amplification properties.

[0007] A method for producing a magnetic powder according to one embodiment of the present disclosure includes a phosphorus treatment step of adding an inorganic acid to a slurry containing a rare earth-iron-nitrogen-based magnetic powder containing R (where R is a part of rare earth elements and is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R component), Fe, and N, water, and a phosphorus-containing substance, to obtain a phosphorus compound and a rare earth-iron-nitrogen-based magnetic powder.

[0008] Furthermore, the magnetic material for magnetic field amplification and the magnetic material for ultra-high frequency absorption according to one embodiment of the present disclosure include a rare earth-iron-nitrogen magnetic powder containing a phosphorus compound and R (wherein R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, the Sm content is less than 50 atomic % of the total R component), Fe, and N.

[0009] According to the present disclosure, it is possible to provide a magnetic powder having excellent efficiency in the high frequency range, a method for manufacturing a magnetic powder having excellent absorption properties in the ultra-high frequency range, a magnetic material for magnetic field amplification having magnetic field amplification properties, and a magnetic material for ultra-high frequency absorption.

[0010] 1 shows a STEM (scanning transmission electron microscope) image of a cross section of a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder prepared in Example 1. 2 shows a STEM image of a cross section of a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder prepared in Example 2. 3 shows a STEM image of a cross section of a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder prepared in Comparative Example 1. The left-hand image shows a TEM (transmission electron microscope) image of a cross section of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder prepared in Example 1. The two right-hand images are ED (electron diffraction) images of the structure included within the white rectangular frame in the left-hand image. The left-hand image shows a TEM image of a cross section of a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder prepared in Example 2. The two right-hand images are ED images of the structure included within the white rectangular frame in the left-hand image. 4 shows the results of line analysis of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder prepared in Example 1. 1 shows the results of line analysis of the phosphorus compound-coated rare earth-iron-nitrogen magnetic powder produced in Example 2. 2 shows the results of line analysis of the phosphorus compound-coated rare earth-iron-nitrogen magnetic powder produced in Comparative Example 1. 3 shows the frequency dependence of the complex relative permeability of the magnetic materials produced in Examples 3 and 4 and Comparative Example 2. 4 shows the frequency dependence of the complex relative permeability of the magnetic material for ultra-high frequency absorption produced in Example 5.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail. However, the embodiments described below are examples for embodying the technical ideas of the present disclosure, and the present disclosure is not limited to the following. In this specification, the term "process" includes not only an independent process, but also a process that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved. Furthermore, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively.

[0012] In this specification, the term "high frequency" refers to electromagnetic waves having a high frequency, and in this disclosure, unless otherwise specified, particularly refers to electromagnetic waves of 1 MHz or more and less than 1 GHz.

[0013] In this specification, "excellent efficiency" means that at a certain frequency f, the ratio of the real term (μ') to the imaginary term (μ") of the complex relative permeability (μ) of a magnetic material, i.e., the Q factor (quality factor), is large. A magnetic material with such characteristics can amplify electromagnetic waves at frequency f while reducing loss. The ratio of μ" to μ' is called tan δ (= μ" / μ') or the loss factor, and tan δ is equal to the reciprocal of the Q factor. A low tan δ is called "good efficiency," and a high tan δ is called "poor efficiency." A low tan δ is also called "improved tan δ," and a high tan δ is also called "deteriorated tan δ."

[0014] In this specification, the "magnetic field amplification" property refers to a property in which the real term (μ') of the complex relative magnetic permeability of a magnetic material is greater than 1, which is the real term of the relative magnetic permeability of a vacuum, and the magnetic field in the space in which the magnetic material is placed is increased compared to that in a vacuum (or atmosphere). Good or high magnetic field amplification properties refer to a high μ', and a material with μ' exceeding 2 at a certain frequency f is called a "magnetic field amplification" magnetic material (at frequency f). When simply referring to relative magnetic permeability, this refers collectively to the absolute value of the real term and the absolute value of the imaginary term of the complex relative magnetic permeability. Unless otherwise specified, high relative magnetic permeability refers to a high real term of the relative magnetic permeability.

[0015] In this specification, "ultra-high frequency absorption" properties refer to high frequency properties in the ultra-high frequency range, and are properties in which the imaginary term (μ") of the complex relative permeability of a magnetic material in the ultra-high frequency range is greater than 0, and which attenuate high frequencies entering a space in which the magnetic material is placed. Good or high ultra-high frequency absorption properties at a certain frequency mean that μ" is high at that frequency, and a material with μ" exceeding 0 in the ultra-high frequency range is called an "ultra-high frequency absorbing magnetic material." With regard to magnetic materials for ultra-high frequency absorption only, an increase in μ" is also referred to as "improved μ" and a decrease in μ" is also referred to as "deteriorated μ". Furthermore, the magnetic field amplification properties in the high frequency range and the high frequency absorption properties in the ultra-high frequency range are collectively referred to as "high frequency properties."

[0016] <Method for producing magnetic powder> The method for producing magnetic powder of this embodiment is characterized by including a phosphorus treatment step of adding an inorganic acid to a slurry containing a rare earth-iron-nitrogen based magnetic powder containing R (where R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm is less than 50 atomic % of the total R components), Fe, and N, water, and a phosphorus-containing substance, to obtain a phosphorus compound and a rare earth-iron-nitrogen based magnetic powder.

[0017] [Phosphorus Treatment Step] In the phosphorus treatment step, inorganic acid is added to a slurry containing a rare earth-iron-nitrogen-based magnetic powder containing R, Fe, and N, water, and a phosphorus-containing substance to obtain a phosphorus compound and a rare earth-iron-nitrogen-based magnetic powder. The phosphorus compound and rare earth-iron-nitrogen-based magnetic powder are formed by the precipitation of a phosphorus compound (e.g., iron phosphate, neodymium phosphate, etc.) through a reaction between a metal component (e.g., iron or neodymium) contained in the rare earth-iron-nitrogen-based magnetic powder and a phosphorus component (e.g., phosphoric acid) contained in the phosphorus-containing substance. Furthermore, the phosphorus compound and rare earth-iron-nitrogen-based magnetic powder are preferably formed by coating at least a portion of the surface of the rare earth-iron-nitrogen-based magnetic powder with a phosphorus compound precipitated on the surface of the rare earth-iron-nitrogen-based magnetic powder (such a coating is referred to as a "phosphorus compound coating"; the portion formed by such a coating is referred to as a "phosphorus compound coating portion"). According to this embodiment, adjusting the pH of the slurry by adding an inorganic acid can increase the amount of phosphorus compound precipitated compared to when an inorganic acid is not added. Therefore, a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder having a thick coating (also referred to as film thickness) is obtained, which reduces tan δ and improves magnetic field amplification characteristics. Furthermore, according to this embodiment, by using water as the solvent, phosphorus compounds such as phosphates with smaller particle sizes are precipitated compared to when an organic solvent is used, so dense phosphorus compounds and rare earth-iron-nitrogen-based magnetic powders are obtained, which tend to easily achieve excellent efficiency in the high frequency range and excellent absorption characteristics in the ultra-high frequency range.

[0018] The method for producing a slurry containing a rare earth-iron-nitrogen magnetic powder containing R, Fe, and N, water, and a phosphorus-containing substance is not particularly limited, but for example, it can be obtained by mixing the rare earth-iron-nitrogen magnetic powder with a phosphorus-containing substance solution containing a phosphorus-containing substance using water as a solvent. The content of the rare earth-iron-nitrogen magnetic powder in the slurry is preferably 1% by mass or more and 50% by mass or less, and more preferably 5% by mass or more and 20% by mass or less from the viewpoint of productivity. The content of the phosphorus-containing substance in the slurry is not particularly limited, but it is preferable that the phosphorus-containing substance is phosphoric acid, and the phosphorus-containing substance is a mixture of hydrogen and a phosphoric acid component (PO ４ ) only, the content is ４ The converted amount is, for example, 0.01% by mass or more and 10% by mass or less, and from the viewpoint of the reactivity between the metal component and the phosphoric acid component and productivity, it is preferably 0.05% by mass or more and 5% by mass or less.

[0019] Examples of the phosphorus-containing substance include elemental phosphorus and compositions thereof, phosphate compounds such as orthophosphoric acid, heteropolyacid compounds such as phosphotungstic acid and phosphomolybdic acid, salts of phosphorus-containing acid compounds such as phosphate compounds and heteropolyacid compounds with metal ions or ammonium ions, organic phosphorus compounds such as phosphate esters, phosphite esters and phosphine oxides, and phosphorus-containing metals such as iron phosphide, phosphor bronze, Fe-B-P-Cu and Fe-Nb-B-P alloys.

[0020] When the phosphorus-containing substance is a phosphoric acid compound, the phosphoric acid aqueous solution can be obtained by mixing the phosphoric acid compound with water. Examples of phosphoric acid compounds include phosphate-based compounds such as orthophosphoric acid, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, zinc phosphate, and calcium phosphate; inorganic phosphoric acids such as hypophosphorous acid, hypophosphite, pyrophosphate, and polyphosphoric acid; and organic phosphoric acids. These compounds may be used alone or in combination of two or more. Furthermore, for the purpose of improving the water resistance and corrosion resistance of the coating portion and the magnetic properties of the magnetic powder, additives such as oxoacid salts (e.g., molybdate, tungstate, vanadate, and chromate); oxidizers (e.g., sodium nitrate and sodium nitrite); and chelating agents (e.g., EDTA) can be used. Among the phosphorus-containing substances, from the viewpoint of reaction control and coating amount control, inorganic phosphoric acids such as orthophosphoric acid, pyrophosphoric acid, and polyphosphoric acid, and phosphoric acid compounds such as phosphates of these with Na, Ca, Pb, Zn, Fe, Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, Sm, ammonium, etc. are preferred.

[0021] The concentration of phosphoric acid in the phosphoric acid aqueous solution (PO ４ The concentration (equivalent amount) is preferably 5% by mass or more and 50% by mass or less, and more preferably 10% by mass or more and 30% by mass or less from the viewpoints of the solubility of the phosphate compound, storage stability, and ease of chemical conversion treatment. The pH of the aqueous phosphoric acid solution is preferably 1 or more and 4.5 or less, and more preferably 1.5 or more and 4 or less from the viewpoint of ease of control of the precipitation rate of the phosphate. The pH can be adjusted with dilute hydrochloric acid, dilute sulfuric acid, or the like.

[0022] In the phosphorus treatment step, the slurry is acidified by adding an inorganic acid. The pH is preferably adjusted to 1 to 4.5, more preferably 1.6 to 3.9, and even more preferably 2 to 3. If the pH is less than 1, the rare earth-iron-nitrogen magnetic powder tends to aggregate from locally precipitated large amounts of phosphorus compounds, resulting in a deterioration in tan δ in the high frequency range and a decrease in μ" in the ultra-high frequency range. If the pH is greater than 4.5, the amount of precipitated phosphorus compounds such as phosphates decreases, resulting in a deterioration in tan δ in the high frequency range and a decrease in μ" in the ultra-high frequency range. Examples of inorganic acids that can be added include hydrochloric acid, nitric acid, sulfuric acid, boric acid, and hydrofluoric acid. During the phosphorus treatment step, it is preferable to add an inorganic acid as needed to maintain the pH within the above range. Although inorganic acids are used from the perspective of wastewater treatment, organic acids can be used in combination depending on the purpose. Examples of organic acids include acetic acid, formic acid, and tartaric acid.

[0023] The phosphorus treatment step can also be carried out so that the phosphorus content in the magnetic powder obtained is 0.02% by mass or more. The phosphorus content in the magnetic powder obtained in the phosphorus treatment step is preferably 0.05% by mass or more, more preferably 0.15% by mass or more. The phosphorus content in the magnetic powder obtained in the phosphorus treatment step is preferably 4% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. If the phosphorus content is 0.02% by mass or more, the effect of coating with the phosphorus compound tends to be greater, and if it is 4% by mass or less, it tends to be possible to prevent the rare earth-iron-nitrogen magnetic powder from agglomerating with each other starting from the phosphorus compound, resulting in an increase in tan δ in the high frequency range and a decrease in μ" in the ultra-high frequency range. In particular, when producing a magnetic material for magnetic field amplification with excellent efficiency or a magnetic material for ultra-high frequency absorption with excellent absorption properties, the phosphorus content is preferably 0.15% by mass or more and 1% by mass or less. The phosphorus content of the bulk of the entire magnetic powder can be measured using ICP-AES (ICP atomic emission spectroscopy). In addition, the magnetic powder phase and The local phosphorus content of the phosphorus compound coating portion can be measured using STEM-EDX (energy dispersive X-ray analysis). The phosphorus (P) atomic concentration in the phosphorus compound coating portion is preferably 1 atomic % or more, more preferably 5 atomic % or more. The P atomic concentration in the phosphorus compound coating portion may be 25 atomic % or less, and preferably 15 atomic % or less. If the phosphorus content in the phosphorus compound coating portion is less than 1 atomic %, the electrical insulation properties of the phosphorus compound tend to be less effective. If the phosphorus content exceeds 25 atomic %, not only do the real term of the relative magnetic permeability in the high frequency range and the imaginary term of the relative magnetic permeability in the ultrahigh frequency range decrease, but corrosion resistance also tends to decrease.

[0024] The phosphorus treatment step may be carried out so that the phosphorus compound coating portion present on the surface of the resulting magnetic powder has a region (R-high concentration region) in which the rare earth (R) atomic concentration is higher than the R atomic concentration in the rare earth (R)-iron-nitrogen-based magnetic powder that is the base material. The R atomic concentration in the R-high concentration region can be 1.05 times or more, preferably 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.5 times or more, of the R atomic concentration in the rare earth-iron-nitrogen-based magnetic powder. Furthermore, the R atomic concentration in the R-high concentration region can be, for example, 4 times or less of the R atomic concentration in the rare earth-iron-nitrogen-based magnetic powder. Here, the R-high concentration region is a region that includes a layer that shows a P (phosphorus) peak in STEM-EDX line analysis of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder. The thickness of the R-rich region can be, for example, 1 nm or more, preferably 3 nm to 150 nm, more preferably 10 nm to 100 nm, and even more preferably 20 nm to 80 nm. The atomic concentration (atomic %) of each element in the R-rich region can be determined by averaging the atomic concentrations in the phosphorus compound coating portion in STEM-EDX line analysis. The rare earth element (R) may be, for example, Nd, and in that case, the Nd-rich region can be evaluated based on the Nd atomic concentration.

[0025] The pH of the slurry containing the rare earth-iron-nitrogen magnetic powder, water, and phosphorus-containing material is adjusted to a range of 1 to 4.5, preferably for 10 minutes or more, and more preferably for 30 minutes or more in order to reduce the areas where the coating is thin. In the initial stage of pH maintenance, the pH rises quickly, so the intervals between additions of inorganic acid for pH control are short, but as coating progresses, the pH fluctuations gradually slow down, and the intervals between additions of inorganic acid become longer, allowing the reaction endpoint to be determined.

[0026] [Oxidation step after phosphorus treatment] The magnetic powder obtained in the phosphorus treatment step may be subjected to an oxidation treatment, if necessary. By subjecting the magnetic powder to an oxidation treatment, the surface of the rare earth-iron-nitrogen based magnetic powder is oxidized to form an iron oxide layer, improving the oxidation resistance of the magnetic powder. Furthermore, oxidation can suppress undesirable oxidation-reduction reactions, decomposition reactions, and alteration on the surface of the rare earth-iron-nitrogen based magnetic powder particles when the magnetic powder is exposed to high temperatures. As a result, a magnetic material can be obtained that has magnetic field amplification characteristics with a low tan δ in the high frequency range and absorption characteristics with a high μ" in the ultra-high frequency range.

[0027] The oxidation treatment is carried out by heat treating the phosphorus-treated magnetic powder in an oxygen-containing atmosphere. The reaction atmosphere preferably contains oxygen in an inert gas such as nitrogen or argon. The oxygen concentration is preferably 3% to 21%, more preferably 3.5% to 10%. During the oxidation reaction, the gas is preferably exchanged at a flow rate of 2 L / min to 10 L / min per 1 kg of magnetic powder.

[0028] The temperature during the oxidation treatment is preferably 150°C or higher and 330°C or lower, more preferably 150°C or higher and 250°C or lower, and even more preferably 170°C or higher and 230°C or lower. If the temperature is lower than 150°C, the iron oxide layer is not sufficiently formed, and oxidation resistance tends to be reduced. If the temperature exceeds 330°C, the iron oxide layer is excessively formed, and the real term of the relative permeability in the high frequency range and the imaginary term of the relative permeability in the ultrahigh frequency range tend to decrease. The reaction time is preferably 3 hours or higher and 10 hours or lower.

[0029] [Silica Treatment Step] The magnetic powder after phosphorus treatment may be subjected to silica treatment as needed. By forming a silica thin film on the magnetic powder, oxidation resistance can be improved. The silica thin film can be formed, for example, by mixing alkyl silicate, magnetic powder, and an alkaline solution.

[0030] [Silane Coupling Treatment Step] The magnetic powder after silica treatment may be further treated with a silane coupling agent. By subjecting the magnetic powder on which a thin silica film has been formed to a silane coupling treatment, a silane coupling agent film is formed on the thin silica film, improving the magnetic properties of the magnetic powder, as well as improving wettability with resin and the strength of the molded product.The silane coupling agent is not particularly limited and may be selected depending on the type of resin. Examples of the silane coupling agent include 3-aminopropyltriethoxysilane, γ-(2-aminoethyl)aminopropyltrimethoxysilane, γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, N-β-(N-vinylbenzylaminoethyl)-γ-aminopropyltrimethoxysilane hydrochloride, γ-glycidoxypropyltrimethoxysilane, γ-methyl Mercaptopropyltrimethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, vinyltriacetoxysilane, γ-chloropropyltrimethoxysilane, hexamethylenedisilazane, γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, octadecyl[3-(trimethoxysilyl)propyl]ammonium chloride, γ-chloropropylmethyldimethoxysilane, γ-mercaptopropylmethyldimethoxysilane, methyltrichlorosilane, dimethyldichlorosilane, trimethylchlorosilane, vinyl Trichlorosilane, vinyltris(β-methoxyethoxy)silane, vinyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, N-β(aminoethyl)γ-aminopropyltrimethoxysilane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, oleidopropyltriethoxysilane, γ-isocyanatopropyltriethoxysilane Examples of silane coupling agents include silane, polyethoxydimethylsiloxane, polyethoxymethylsiloxane, bis(trimethoxysilylpropyl)amine, bis(3-triethoxysilylpropyl)tetrasulfane, γ-isocyanatepropyltrimethoxysilane, vinylmethyldimethoxysilane, 1,3,5-N-tris(3-trimethoxysilylpropyl)isocyanurate, t-butylcarbamatetrialkoxysilane, and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propaneamine.These silane coupling agents may be used alone or in combination of two or more. The amount of silane coupling agent added is preferably 0.2 parts by mass or more and 0.8 parts by mass or less, and more preferably 0.25 parts by mass or more and 0.6 parts by mass or less, relative to 100 parts by mass of magnetic powder. If the amount is less than 0.2 parts by mass, the effect of the silane coupling agent is small, and if it exceeds 0.8 parts by mass, the magnetic powder tends to aggregate, which reduces the magnetic properties of the magnetic powder and the molded body.

[0031] After the phosphorus treatment step, oxidation step, silica treatment step, or silane coupling treatment step, the magnetic powder can be filtered, dehydrated, and dried by conventional methods.

[0032] The rare earth-iron-nitrogen magnetic powder used in the manufacturing method of this embodiment contains R (where R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm is less than 50 atomic % of the entire R component), Fe, and N. R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, with Nd, Y, Ce, Pr, Gd, and Dy being preferred from the viewpoint of achieving a stable raw material supply and a high relative magnetic permeability, and Nd, Y, Ce, and Pr being more preferred from the viewpoint of cost. Here, when Sm is contained, the content of Sm is less than 50 atomic % of the entire R component, and more preferably less than 20 atomic %. In particular, when the content of Nd or Pr is 50 atomic % or more of the total R component, a magnetic material with a higher relative magnetic permeability and a magnetic material with a lower tan δ can be obtained. Furthermore, from the perspective of balancing oxidation resistance and cost, the content of Nd or Pr is preferably 70 atomic % or more, and a rare earth-iron-nitrogen magnetic powder made of NdFeN with a Nd content of 100 atomic % is particularly preferred because it is an abundant resource, has a large absolute value of the magnetocrystalline anisotropy field (an index showing the magnitude of magnetic anisotropy), and has high absorption performance at ultra-high frequencies.

[0033] The content of Fe in the rare earth-iron-nitrogen magnetic powder is preferably 40 atomic % or more and 87 atomic % or less, and more preferably 50 atomic % or more and 85 atomic % or less.

[0034] The rare earth-iron-nitrogen magnetic powder used in the manufacturing method of this embodiment is Th ２ Zn １７ It has a crystal structure of the type R ｘ Fe １００－ｘ－ｙ N ｙ (where R is at least one element selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R components), iron (Fe), and nitrogen (N). Here, it is preferable that x is 3 or more and 30 or less, y is 10 or more and 30 or less, and the remainder is mainly Fe.

[0035] In addition, without carrying out the silica treatment step and / or the silane coupling treatment step, or after carrying out these treatment steps, isopropyl triisostearoyl titanate, isopropyl tri(N-aminoethyl-aminoethyl) titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraisopropyl titanate, tetrabutyl titanate, tetraoctyl bis(ditridecyl phosphite) titanate, isopropyl trioctanoyl titanate, isopropyl tridodecyl benzenesulfonate, The magnetic powder can be surface-treated using a titanium-based coupling agent such as phenyl titanate, isopropyl tri(dioctyl phosphate) titanate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyl dimethacryl isostearoyl titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(ditridecyl phosphite) titanate, or isopropyl tricumyl phenyl titanate, or an aluminum-based, zirconium-based, chromium-based, iron-based, or tin-based coupling agent such as acetoalkoxyaluminum diisopropylate. When the powder that has undergone this treatment is used as a bonded magnetic material, the affinity with the added resin is improved, the isolated dispersion of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder becomes more pronounced, and electrical insulation between the powder particles is achieved, resulting in excellent efficiency in the high frequency range and excellent absorption characteristics in the ultra-high frequency range.

[0036] There are no particular limitations on the methods for producing the rare earth-iron-nitrogen magnetic powder, and these methods will be described in detail below.

[0037] <<Solid-Phase Method>> The method for producing rare earth-iron-nitrogen magnetic powder by the solid-phase method includes the steps of mixing R oxide powder, Fe raw material, and Ca powder (mixing step), reducing the resulting mixture (reduction step), and nitriding the alloy particles obtained in the reduction step (nitriding step).

[0038] [Mixing step] In the mixing step, the Fe raw material may be not only metallic Fe but also Fe ２ O ３ and / or Fe ３ O ４ It is also possible to use Fe ２ O ３ and / or Fe ３ O ４ When using the content (metallic Fe, Fe ２ O ３ and / or Fe ３ O ４ Fe relative to the total moles of Fe contained in ２ O ３ and / or Fe ３ O ４ The total moles of Fe contained in the granular Ca oxide is preferably 30 atomic % or less. The heat of reaction generated when these iron oxides are reduced by Ca allows the reaction to proceed uniformly as a whole, leading to savings in external energy and improved yield. The amount of granular Ca to be mixed must be sufficient to reduce the oxides of the R oxide and the metal oxides to be selectively mixed. The amount of granular Ca to be mixed is preferably 30 atomic % or less. ２ O ３ and / or Fe ３ O ４ The amount may be 0.5 to 3 times, preferably 1 to 2 times the equivalent of the oxygen atoms contained therein.

[0039] [Reduction Step] The mixed powder obtained in the mixing step is placed in a heating container capable of being evacuated. After evacuating the heating container, the mixture is heated at 600°C to 1300°C, preferably 700°C to 1200°C, and more preferably 800°C to 1100°C while passing argon gas through the container. If the heating temperature is less than 600°C, the reduction reaction of the oxides does not proceed. If the heating temperature exceeds 1300°C, the rare earth and Fe may melt and form a mass. Furthermore, if the heating temperature is 700°C or higher, the reduction time can be shortened, which tends to improve productivity. If the heating temperature is 1200°C or lower, the scattering of Ca can be reduced, which tends to further reduce variation during reduction. From the viewpoint of carrying out the reduction reaction more uniformly, the heat treatment time may be 4 hours or less, preferably less than 120 minutes, more preferably less than 90 minutes, and preferably 10 minutes or more, more preferably 30 minutes or more. Here, in addition to metallic Fe, Fe may be added to the mixed powder. ２ O ３ and / or Fe ３ O ４ When an appropriate amount of Fe is contained, self-heating occurs during the temperature rise, and the reaction proceeds efficiently and uniformly. On the other hand, when Fe is contained in an amount exceeding 30 atomic % relative to metallic Fe in terms of elemental Fe, as in the above-mentioned mixing process, ２ O ３ and / or Fe ３ O ４ If the rare earth-iron-nitrogen magnetic powder is mixed with the powder, it may explode or scatter due to the extremely high heat generated. In addition, the particle size of the resulting rare earth-iron-nitrogen magnetic powder can be controlled by controlling the reduction temperature. Generally, the higher the reduction temperature, the larger the powder particle size.

[0040] [Nitridation step] The mixture is cooled in argon gas to a temperature range of preferably 250°C to 800°C, more preferably 300°C to 600°C. To suppress decomposition of the nitriding reaction product and increase the reaction efficiency in the subsequent nitridation step, the mixture is further cooled to a temperature range of 400°C to 550°C. The heating vessel is then evacuated again, and nitrogen gas is introduced. The gas introduced is not limited to nitrogen, but may also be a gas containing nitrogen atoms, such as ammonia. The mixture may be heated for 4 hours or more while passing nitrogen gas through it at a pressure equal to or higher than atmospheric pressure, and preferably heated for 10 hours to 40 hours, after which the heating is stopped and the mixture is allowed to cool.

[0041] The product obtained after the nitriding step may contain by-produced CaO, unreacted metallic calcium, etc. in addition to the rare earth-iron-nitrogen magnetic powder, and may be in the form of a composite sintered mass. In this case, the product is put into ion-exchanged water as a water washing step to remove calcium oxide (CaO) and other calcium-containing components from the product and convert them into calcium hydroxide (Ca(OH) ２ ) can be separated from the magnetic particles as a suspension. This water washing step may involve several cycles of stirring in water, leaving the particles to stand, and removing the supernatant. Furthermore, residual calcium hydroxide may be thoroughly removed by washing the magnetic particles with acetic acid or the like. Because the remaining unreacted Ca becomes calcium nitride (CaN), which makes removal easier, it is preferable to perform the water washing step after heat treatment in a nitrogen atmosphere. The rare earth-iron-nitrogen magnetic powder obtained in this way tends to have a sharper particle size distribution.

[0042] <<Precipitation Method>> A method for producing rare earth-iron-nitrogen based magnetic powder by the precipitation method includes the steps of: mixing a solution containing R and Fe with a precipitant to obtain a precipitate containing R and Fe (precipitation step); firing the precipitate to obtain an oxide containing R and Fe (oxidation step); heat-treating the oxide in an atmosphere containing a reducing gas to obtain a partial oxide (pretreatment step); reducing the partial oxide (reduction step); and nitriding the alloy particles obtained in the reduction step (nitridation step).

[0043] [Precipitation Step] In the precipitation step, an R raw material and an Fe raw material are dissolved in a strongly acidic solution to prepare a solution containing R and Fe. The R raw material and the Fe raw material are not limited as long as they can be dissolved in a strongly acidic solution. For example, in terms of ease of availability, R oxide is used as the R raw material and iron sulfate (FeSO 4 ) is used as the Fe raw material. ４ The concentration of the solution containing R and Fe can be appropriately adjusted within a range in which the R raw material and the Fe raw material are substantially dissolved in the acidic solution. As the acidic solution, sulfuric acid can be used in view of solubility.

[0044] An insoluble precipitate containing R and Fe is obtained by reacting a solution containing R and Fe with a precipitant. Here, the solution containing R and Fe is sufficient as long as it becomes a solution containing R and Fe upon reaction with the precipitant. For example, a raw material containing R and a raw material containing Fe may be prepared as separate solutions, and each solution may be added dropwise to react with the precipitant. Even when prepared as separate solutions, the concentrations of each raw material are appropriately adjusted so that they are substantially soluble in the acidic solution. The precipitant is not limited as long as it is an alkaline solution that reacts with the solution containing R and Fe to produce a precipitate, and examples thereof include ammonia water and caustic soda, with caustic soda being preferred.

[0045] After separating the precipitate, it is preferable to remove the solvent from the separated material in order to prevent the precipitate from redissolving in the remaining solvent during the heat treatment in the subsequent oxidation step, which may result in aggregation of the precipitate when the solvent evaporates, or changes in particle size distribution, powder particle size, etc. Specific examples of the method for removing the solvent include, when water is used as the solvent, drying in an oven at 70°C or higher and 200°C or lower for 5 hours to 12 hours.

[0046] The precipitation step may be followed by a step of separating and washing the resulting precipitate. The washing step may be appropriately carried out until the conductivity of the supernatant solution becomes 5 mS / m or less. The step of separating the precipitate may involve, for example, adding a solvent (preferably water) to the resulting precipitate and mixing, followed by filtration, decantation, or the like.

[0047] [Oxidation Step] The oxidation step is a step in which the precipitate formed in the precipitation step is fired to obtain an oxide containing R and Fe. For example, the precipitate can be converted to an oxide by heat treatment. When the precipitate is heat-treated, it must be performed in the presence of oxygen, for example, in an air atmosphere. Furthermore, since it must be performed in the presence of oxygen, it is preferable that the non-metallic portion of the precipitate contains oxygen atoms. The heat treatment temperature in the oxidation step (hereinafter referred to as the oxidation temperature) is not particularly limited, but is preferably 700°C or higher and 1300°C or lower, and more preferably 900°C or higher and 1200°C or lower. Temperatures below 700°C result in insufficient oxidation, while temperatures above 1300°C tend to result in the desired shape, average particle size, and particle size distribution of the rare earth-iron-nitrogen-based magnetic powder. The heat treatment time is also not particularly limited, but may be 0.5 hours or higher and 4 hours or lower, and preferably 1 hour or higher and 3 hours or lower.

[0048] [Pretreatment Step] The pretreatment step is a step in which an oxide containing R and Fe is heat-treated in an atmosphere containing a reducing gas to obtain a partial oxide in which part of the oxide is reduced.

[0049] [Reduction Step] The reduction step involves heating the partial oxide in the presence of a reducing agent at a temperature of 600°C to 1300°C, preferably 700°C to 1200°C, and more preferably 800°C to 1100°C. At a heating temperature below 600°C, the reduction reaction of the oxide does not proceed. At a heating temperature above 1300°C, R and Fe may melt and form clumps. Furthermore, a heating temperature of 700°C or higher tends to shorten the reduction time, improving productivity. A temperature of 1200°C or lower tends to reduce the scattering of the reducing agent, Ca, and further reduce variation during reduction. Controlling the reduction temperature allows for control of the particle size of the rare earth-iron-nitrogen magnetic powder; generally, the higher the reduction temperature, the larger the powder particle size. The heat treatment time is preferably less than 120 minutes, more preferably less than 90 minutes, from the viewpoint of conducting the reduction reaction more uniformly. The heat treatment time is preferably 10 minutes or more, more preferably 30 minutes or more.

[0050] [Nitriding Process] The nitriding process is a process for obtaining anisotropic magnetic particles by nitriding the alloy particles obtained in the reducing process. Since the particulate precipitate obtained in the precipitation process is used, porous aggregate alloy particles are obtained in the reducing process. This allows for immediate nitriding by heat treatment in a nitrogen atmosphere without pulverization, thereby enabling uniform nitriding.

[0051] The heat treatment temperature in the nitriding treatment of the alloy particles (hereinafter referred to as the nitriding temperature) is preferably 250°C or higher and 800°C or lower, more preferably 300°C or higher and 600°C or lower. Furthermore, in order to suppress decomposition of the nitriding reaction product in the subsequent nitriding step and increase the reaction efficiency, the temperature is particularly preferably 400°C or higher and 550°C or lower, and the atmosphere is replaced with a nitrogen atmosphere within this temperature range. The heat treatment time may be set so that the nitriding of the alloy particles is sufficiently uniform. For example, the alloy particles may be heated for 4 hours or longer while passing nitrogen gas at a pressure higher than atmospheric pressure, and preferably heated for 10 hours to 40 hours, after which the heating is stopped and the alloy particles are allowed to cool.

[0052] The product obtained after the nitriding step may contain, in addition to the rare earth-iron-nitrogen magnetic powder, by-product CaO, unreacted metallic calcium, and the like, in the form of a composite sintered mass. In this case, a water-washing step may be performed in which the product is placed in ion-exchanged water to separate calcium oxide (CaO) and other calcium-containing components from the magnetic particles as a calcium hydroxide (Ca(OH)2) suspension. This water-washing step may involve several cycles of stirring in water, leaving the product to stand, and removing the supernatant. Furthermore, residual calcium hydroxide may be thoroughly removed by washing the magnetic particles with acetic acid or the like. Because the remaining unreacted Ca becomes calcium nitride (CaN), which makes removal easier, it is preferable to perform the water-washing step after heat treatment in a nitrogen atmosphere. The rare earth-iron-nitrogen magnetic powder obtained in this way tends to have a sharper particle size distribution.

[0053] <Phosphorus Compound Coated Rare Earth-Iron-Nitrogen-Based Magnetic Powder> The magnetic powder of this embodiment is characterized by containing a phosphorus compound, R (where R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R component), Fe, and N. The rare earth-iron-nitrogen-based magnetic powder and phosphorus content of this embodiment are as described in the phosphorus treatment step above. Because the rare earth-iron-nitrogen-based magnetic powder is a nitride, it has higher electrical resistance and superior corrosion resistance than metal materials.

[0054] The average particle size of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder is preferably 0.1 μm or more and 100 μm or less. As a magnetic material for magnetic field amplification, a range of 1 μm or more and 100 μm or less is preferred. As a magnetic material for ultra-high frequency absorption, a range of 0.1 μm or more and 10 μm or less is preferred. A more preferred particle size range is 3 μm or more and 100 μm or less for magnetic material for magnetic field amplification, as described below, and 0.1 μm or more and 3 μm or less for magnetic material for ultra-high frequency absorption. If the particle size is less than 1 μm, the filling amount of magnetic powder in the compact decreases, resulting in a decrease in the real term of the relative magnetic permeability in the high frequency range and the imaginary term of the relative magnetic permeability in the ultra-high frequency range. If the particle size is 0.1 μm or less, the specific surface area increases further, resulting in a decrease in the volume fraction of the magnetic body portion with a high real term of the relative magnetic permeability in the high frequency range and the imaginary term of the relative magnetic permeability in the ultra-high frequency range. As a result, the properties of the magnetic material tend to be extremely poor. If the particle size exceeds 10 μm, the μ" of the molded body tends to decrease, and if the particle size exceeds 100 μm, this tendency becomes even more pronounced. Here, the average particle size refers to the median diameter measured under dry conditions using a laser diffraction particle size distribution measuring device. In other words, the average particle size of the magnetic powder of the present disclosure is represented by D50, and D50 is the particle size at which the integrated value of the particle size distribution on a volume basis of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder is 50%.

[0055] When the particle size of rare earth-iron-nitrogen magnetic powder becomes large, eddy currents begin to occur within the particles at low frequencies due to the skin effect, and the larger the particle size, the lower the real term of the relative permeability begins to decrease in the low frequency region. Therefore, by reducing the particle size of the magnetic powder, the magnetic field amplification characteristics and ultra-high frequency absorption characteristics tend to be maintained high up to high frequencies. For example, Nd ２ Fe １７ N ３ At this frequency, the particle size r (m) of the magnetic powder and the real term of the relative permeability begin to decrease. ０ The relationship between the frequency and the frequency (Hz) is f ０ = 1 THz, 3 μm, then f ０ = 1 GHz, 100 μm, then f ０ = 1 MHz. Therefore, a rare earth-iron-nitrogen-based magnetic powder with an upper particle size value around this range is preferable as the magnetic field amplification material of the present disclosure. On the other hand, as the particle size becomes smaller, the filling rate of the compact cannot be achieved and the surface area increases. For example, if the thickness of the phosphorus compound coating portion is 10 nm and the particle size of the powder is 0.1 μm, the relative permeability will only decrease by about 50%, but if the particle size is 0.05 μm, the relative permeability will be about 6%. Therefore, the lower limit of the powder particle size of the magnetic powder of the present disclosure will be around 0.1 μm, regardless of frequency. Due to the above trade-off, it is preferable to set a particle size range that is more suitable for the target frequency band of the magnetic material.

[0056] The phosphorus compound-coated rare earth-iron-nitrogen magnetic powder preferably has a heat generation onset temperature in DSC of 145°C or higher, more preferably 170°C or higher. The heat generation onset temperature in DSC is a comprehensive evaluation of the density, thickness, oxidation resistance, etc. of the phosphorus compound, and when it is 145°C or higher, excellent efficiency in the high frequency range and excellent ultra-high frequency absorption characteristics in the ultra-high frequency range are obtained. The heat generation onset temperature in DSC can be measured under the conditions described in the Examples.

[0057] The carbon content of the phosphorus compound-coated rare earth-iron-nitrogen magnetic powder is preferably 1000 ppm by mass or less, more preferably 800 ppm by mass or less, even more preferably 500 ppm by mass or less, and particularly preferably 420 ppm by mass or less. The carbon content indicates the amount of organic impurities in the phosphorus compound. If the carbon content exceeds 1000 ppm by mass, when the magnetic powder is exposed to high temperatures, the organic impurities decompose, creating voids in the phosphorus compound, which tends to reduce efficiency, reduce magnetic field amplification characteristics in the high frequency range, and reduce ultra-high frequency absorption characteristics. In particular, to obtain excellent efficiency in the high frequency range and excellent ultra-high frequency absorption characteristics in the ultra-high frequency range, it is preferable to set the carbon content to 0 ppm by mass or more and 800 ppm by mass or less. Here, the carbon content can be measured by the TOC method.

[0058] When the surface of a rare earth-iron-nitrogen based magnetic powder is coated with a phosphorus compound, the thickness of the coating is preferably 10 nm or more and 200 nm or less, and more preferably 12 nm or more and 100 nm or less, from the viewpoint of improving the tan δ of the magnetic material in the high frequency range and μ" in the ultrahigh frequency range. The thickness of the coating can be measured by performing composition analysis on a cross section of the rare earth-iron-nitrogen based magnetic powder coated with the phosphorus compound using a TEM (transmission electron microscope), STEM or FE-SEM observation image by line analysis or area analysis using EDX (energy dispersive X-ray analysis), or further by point analysis with a sufficient number of measurement points. When measuring by line analysis or the like, for example, the range in which the atomic concentration of phosphorus (P) is observed to be 1 atomic % or more may be regarded as the phosphorus compound coating. A typical example of the ideal powder microstructure of this embodiment having excellent high frequency characteristics is a structure in which the phosphorus compound coating completely covers the surface of the rare earth-iron-nitrogen based magnetic powder (surface coverage rate 100%). In this case, it is possible to completely maintain the electrical insulation state of adjacent magnetic particles. It is known that this structure has the effect of reducing iron loss due to eddy currents that cross between grains by the phosphorus compound coating, further improving tan δ in the high frequency range and providing a magnetic material for magnetic field amplification with higher efficiency. In addition, the influence of eddy currents can be reduced up to the ultra-high frequency range, making it possible to provide a magnetic material for ultra-high frequency absorption that maintains higher ultra-high frequency absorption characteristics. It is not necessary for the phosphorus compound coating to completely cover the surface of the rare earth-iron-nitrogen magnetic powder, and a surface coverage rate of 10% or more will be sufficient to reduce eddy currents to a certain extent. This effect can be expected. A surface coverage of 50% or more is desirable, and more preferably 80% or more is desirable. When the surface coverage is 10% or more but less than 80%, it is preferable that the free phosphorus compound is present between the magnetic powder particles. The surface coverage of the phosphorus compound coating of the magnetic powder can be estimated by observing the cross section of the powder using a TEM, STEM, or FE-SEM equipped with EDX, and the ratio of the length of the contact portion of the phosphorus-containing coating to the entire perimeter of the observed surface of the rare earth-iron-nitrogen-based magnetic powder is defined as the "surface coverage." In this case, it is preferable to measure the cross sections of 20 to 50 magnetic powders from the images observed using the above method and use the average value as the surface coverage.

[0059] The phosphorus compound coating portion present on the surface of the rare earth-iron-nitrogen-based magnetic powder may have a region (R-high concentration region) in which the rare earth (R) atomic concentration is higher than the R atomic concentration in the rare earth-iron-nitrogen-based magnetic powder as the base material. The R atomic concentration in the R-high concentration region can be 1.05 times or more, preferably 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.5 times or more, of the R atomic concentration in the rare earth-iron-nitrogen-based magnetic powder. Furthermore, the R atomic concentration in the R-high concentration region can be, for example, 4 times or less of the R atomic concentration in the rare earth-iron-nitrogen-based magnetic powder. Here, the R-high concentration region is a region including a layer that shows the maximum P (phosphorus) peak in STEM-EDX line analysis of the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder. The thickness of the R-rich region can be, for example, 1 nm or more, preferably 3 nm to 150 nm, more preferably 10 nm to 100 nm, and even more preferably 20 nm to 80 nm. When the R atomic concentration in the R-rich region is within the above-mentioned range relative to the R atomic concentration in the base material, the electrical resistivity tends to be high and the relative permeability tends to be high. The atomic concentration (atomic %) of each element in the R-rich region is determined by averaging the atomic concentrations in the phosphorus compound coating portion in STEM-EDX line analysis. The rare earth element may be, for example, Nd, and in that case, the Nd-rich region can be evaluated based on the Nd atomic concentration.

[0060] The R atom concentration in the R-rich region may be 0.3 times or more, and preferably 1 time or more, the Fe atom concentration in the R-high concentration region. The R atom concentration in the R-high concentration region is preferably 20 times or less the Fe atom concentration in the R-high concentration region. When the relationship between the R atom concentration and the Fe atom concentration in the R-high concentration region is within the above-mentioned range, the Fe atom concentration near the surface of the rare earth-iron-nitrogen-based magnetic powder tends to be lower, and water resistance tends to be further improved.

[0061] The atomic concentration ratio R / Fe of R to Fe in the R-high concentration region may be 0.3 or more, preferably 0.5 or more, more preferably 1 or more, and even more preferably 2 or more. The R / Fe in the R-high concentration region may be 100 or less, or even 10 or less. Furthermore, the R / Fe in the R-high concentration region may have a higher value than the R / Fe in the rare earth-iron-nitrogen-based magnetic powder matrix. The R / Fe in the R-high concentration region may be 1 or more times the R / Fe in the rare earth-iron-nitrogen-based magnetic powder matrix, preferably 1.5 or more times, more preferably 2 or more times, and even more preferably 5 or more times. When the R / Fe in the R-high concentration region is within the above-mentioned range, the Fe atomic concentration near the surface of the rare earth-iron-nitrogen-based magnetic powder tends to be lower, further improving water resistance.

[0062] The rare earth-iron-nitrogen magnetic powder is Th ２ Zn １７ Type or Th ２ Ni １７ It has a crystal structure of the type R ｘ Fe １００－ｘ－ｙ N ｙ (where R is at least one element selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R component), iron (Fe), and nitrogen (N). Here, it is preferable that x is 3 or more and 30 or less, y is 10 or more and 30 or less, and the remainder is mainly Fe. This magnetic powder is a powder that exhibits ferromagnetism.

[0063] Examples of phosphorus compounds contained in phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powders include inorganic phosphoric acids such as orthophosphoric acid, pyrophosphoric acid, and polyphosphoric acid, as well as phosphates of these compounds with Na, Ca, Pb, Zn, Fe, R, and ammonium (these metal elements and atomic groups are referred to as M components in this disclosure and may be simply referred to as M), as well as "phosphorus-containing amorphous compounds" and "phosphorus-containing nanocrystalline compounds" containing at least one element selected from R, Fe, M, and N and P and / or phosphorus-containing substances. Among these, phosphates, "phosphorus-containing amorphous compounds," and "phosphorus-containing nanocrystalline compounds" are preferred in terms of achieving a dense surface coating for rare earth-iron-nitrogen-based magnetic powders. The inclusion of a "phosphorus-containing nanocrystalline compound" further improves thermal stability, so the high-frequency characteristics of the magnetic powder tend not to deteriorate even after high heat is applied after the phosphorus treatment, kneading process, and heat curing process, and also contributes to the high thermal stability of the final molded product. Here, nanocrystals refer to fine crystals of 1 nm or more but less than 1 μm, and phosphorus compounds containing fine crystals less than 1 nm are considered to be amorphous compounds. The crystallinity of the phosphorus compound coating and the diameter of the fine crystals in the phosphorus compound coating can be confirmed by lattice image observation using the TEM method or analysis using an ED (electron diffraction) device attached to the TEM device. The content of the phosphorus compound in the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder is preferably 0.5% by mass or more but less than 4.5% by mass, more preferably 0.55% by mass or more but less than 2.5% by mass, and most preferably 0.75% by mass or more but less than 2% by mass. If the content exceeds 4.5% by mass, the rare earth-iron-nitrogen-based magnetic powder tends to aggregate, reducing the relative permeability and deteriorating tan δ in the high-frequency range. If the content is less than 0.5% by mass, the electrical insulation effect of the phosphorus compound coating decreases, similarly reducing the relative permeability and deteriorating tan δ in the high-frequency range. The phosphorus content in the phosphorus compound-coated rare earth-iron-nitrogen based magnetic powder can be 0.02% by mass or more. The phosphorus content in the phosphorus compound-coated rare earth-iron-nitrogen based magnetic powder is preferably 0.05% by mass or more, and more preferably 0.15% by mass or more. The phosphorus content in the phosphorus compound-coated rare earth-iron-nitrogen based magnetic powder is preferably 4% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less.

[0064] The phosphorus compound preferably coats at least a portion of the surface of the rare earth-iron-nitrogen magnetic powder, in order to prevent a decrease in efficiency due to eddy currents, i.e., an increase in tan δ. A surface coverage of 10% or more in the magnetic powder is effective in reducing eddy currents to a certain extent, but a surface coverage of 50% or more, and more preferably 80% or more, is desirable. A surface coverage of less than 10% is not sufficient to prevent eddy currents from occurring between particles, resulting in a large tan δ, which is undesirable. Rare earth-iron-nitrogen magnetic powders with a 100% coverage due to the phosphorus compound coating have an extremely small tan δ, and can achieve a tan δ of 0.01 or less at 1 MHz, depending on the composition, crystal structure, and powder particle size of the magnetic powder.

[0065] It is preferable that the phosphorus compound coats at least a portion of the surface of the rare earth-iron-nitrogen based magnetic powder, in order to prevent a decrease in relative permeability, particularly a decrease in μ" due to eddy currents, i.e., to prevent a deterioration in ultra-high frequency absorption characteristics. A surface coating rate of 10% or more is effective in reducing eddy currents to a certain extent, but a surface coating rate of 50% or more, and more preferably 80% or more, is desired. A surface coating rate of less than 10% is not preferable because it is not possible to sufficiently block eddy currents that occur between particles, and μ" decreases due to the skin effect. A rare earth-iron-nitrogen based magnetic powder that has a 100% coverage rate due to the phosphorus compound coating portion shows extremely small decreases in relative permeability due to eddy currents, and can achieve a μ" of 1 or more at 1 GHz, depending on the composition, crystal structure, and powder particle size of the magnetic powder, etc.

[0066] A surface coverage of 10% or more has some effect in reducing eddy currents, but a surface coverage of 50% or more is preferable, and more preferably 80% or more is desirable. In the high frequency range below 1 GHz, a surface coverage of less than 10% cannot sufficiently block eddy currents that occur between particles, and tan δ tends to be large. A rare earth-iron-nitrogen magnetic powder with a 100% coverage due to the phosphorus compound coating has an extremely small tan δ, and although it depends on the composition, crystal structure, and powder particle size of the magnetic powder, it can achieve a tan δ of 0.01 or less at 1 MHz.

[0067] The magnetic anisotropy of the rare earth-iron-nitrogen magnetic powder of this embodiment exhibits in-plane magnetocrystalline anisotropy, which has the property that the magnetic moment is more likely to orient in the c-plane direction than in the c-axis direction. It is extremely important that the magnetic powder of this embodiment has this property in order to maintain the real term μ' of high relative permeability in the high frequency range, and further to express the imaginary term μ" of high relative permeability in the ultra-high frequency range. The absolute value of the negative magnetocrystalline anisotropy energy in the magnetic powder of this embodiment is very large, and furthermore, since the magnetic powder having this in-plane magnetocrystalline anisotropy is contained in a non-oriented state, its natural resonance frequency is distributed widely in the range of 1 GHz to 1 THz. Therefore, below 1 GHz, there is no increase in μ" and no decrease in μ' due to natural resonance, and in the range of 1 GHz to 1 THz, there is a wide band A high μ" is achieved due to natural resonance. In particular, in the magnetic powder of this embodiment, the surface of the ferromagnetic powder is coated with the phosphorus compound contained in the magnetic powder, and the phosphorus compound is present between the magnetic powder particles, thereby suppressing the generation of eddy currents between the particles. Furthermore, when the magnetic powder has a specific average particle size, the generation of eddy currents within the particles is also suppressed, so the inherent high-frequency characteristics of the magnetic powder are less likely to deteriorate due to eddy currents, and tend to be further improved in the 1 MHz to 1 THz range. There is no known "magnetic field amplification material" created using a material design concept that covers such a wide frequency band in one go. Furthermore, there is no known "ultra-high frequency absorption material" that functions seamlessly in an "ultra-wide frequency band" using the same design concept.

[0068] <Magnetic Material for Magnetic Field Amplification> The magnetic material for magnetic field amplification of this embodiment is characterized by containing a rare earth-iron-nitrogen magnetic powder containing a phosphorus compound and R (R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the entire R component), Fe, and N.

[0069] The magnetic material for magnetic field amplification of this embodiment contains a rare earth-iron-nitrogen-based magnetic powder and a phosphorus compound, and has a high relative permeability of μ ' of 2 or more in the range of 1 MHz to less than 1 GHz for magnetic field amplification, and a region where tanδ is 0.2 or less in the range of 1 MHz to less than 1 GHz, and may also have excellent efficiency. The magnetic material for magnetic field amplification of this embodiment is not particularly limited as long as it contains a rare earth-iron-nitrogen-based magnetic powder containing a phosphorus compound and R (R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm is less than 50 atomic % of the total R component), Fe, and N, but for example, the magnetic powder of the above-mentioned embodiment can be used.

[0070] The rare earth-iron-nitrogen magnetic powder preferably has a particle size of 1 μm or more and 100 μm or less. The reason for this is as described above: when powder larger than 100 μm is used as a magnetic material for amplifying a magnetic field at 1 MHz or higher, the relative permeability tends to decrease due to the skin effect. Furthermore, when using powders of 7 μm or larger as a magnetic material for amplifying a magnetic field, a large pressure of 0.5 GPa or more is usually applied to increase the volume fraction. This causes large eddy current losses due to contact between the powder particles, significantly reducing the real term of the relative permeability. Therefore, it is extremely important that a fine, moderately soft substance such as a phosphorus compound, which is not as hard as ferrite or transition metal oxides but not too soft like resin, covers the rare earth-iron-nitrogen magnetic powder or is interposed between the particles, in order to prevent deterioration of the inherent properties of the magnetic powder, such as the relative permeability. In other words, the inclusion of a phosphorus compound is an essential requirement for the method for producing a magnetic material for amplifying a magnetic field of this embodiment, which achieves high density and high relative permeability by applying large pressure, and for the magnetic material for amplifying a magnetic field produced thereby.

[0071] Magnetic materials for magnetic field amplification are preferably used at frequencies of 1 MHz or higher but lower than 1 GHz, but are also used as magnetic materials for ultra-high frequency absorption at frequencies above 1 GHz. Therefore, depending on the composition and particle size distribution of the rare earth-iron-nitrogen-based magnetic powder, the imaginary term of the relative permeability may begin to increase in the frequency range of 0.5 GHz or higher but lower than 1 GHz. The magnetic material for magnetic field amplification of this embodiment may be used in the range of 1 MHz or higher but lower than 0.5 GHz, and is preferably used in the range of 1 MHz or higher but lower than 0.1 GHz. When used as a magnetic field amplification material within the above range, powders of 3 μm or higher but lower than 100 μm can be used without using a fine pulverizing device such as a jet mill, and magnetic field orientation, which reduces throughput, is unnecessary, which is preferable from the perspective of balancing cost and properties.

[0072] More specific applications of the magnetic material for magnetic field amplification include wireless power supply coils, magnetic field amplification materials for RFID (Radio Frequency Identification) tags, transformers, inductors, and reactors for high-frequency circuits exceeding 20 MHz, etc. For example, the magnetic material can be used as a magnetic field amplification magnetic material by forming a thin sheet and attaching it to the back surface of an antenna or a transmitter / receiver to concentrate magnetic flux within the sheet due to its magnetic field amplification properties, or by inserting it into a cylindrical or rectangular coil, or by winding a conductor around a donut-shaped or yoke-equipped magnetic core to improve the real term of the relative magnetic permeability of the coil.

[0073] The magnetic material for magnetic field amplification of this embodiment is characterized by a high real term of relative permeability even in the high frequency region. For example, the real term of relative permeability at a frequency of 1 MHz or more and 20 MHz or less is preferably 3 or more, more preferably 4 or more. Furthermore, the real term of relative permeability at a frequency greater than 20 MHz and less than 1 GHz is preferably 2 or more, more preferably 3 or more. Furthermore, the magnetic material for magnetic field amplification of this embodiment can have a real term μ' of relative permeability at a frequency of, for example, 20 MHz of 3.2 or more, preferably 3.5 or more, more preferably 4 or more, and even more preferably 4.5 or more. The magnetic material for magnetic field amplification of this embodiment can have a real term μ' of relative permeability at a frequency of 20 MHz of, for example, 200 or less, and may even be 100 or less.

[0074] The magnetic material for magnetic field amplification of this embodiment preferably has a Q value (μ' / μ") at 20 MHz of 3 or more, more preferably 3.5 or more, and even more preferably 4 or more. The Q value at 20 MHz may be 10,000 or less. If the Q value at 20 MHz is within the above range, it is preferable to use it at frequencies around this range (for example, 10 MHz to 30 MHz) because it becomes a low-cost magnetic field amplification material with excellent efficiency. If the Q value is 3 or more, heat generation when incorporated into an element or system can be reduced, and the temperature of components, etc. can be lowered, which tends to improve stability. If the Q value is 10,000 or less, the cost for improving the homogeneity of the material can be reduced. Here, the complex relative permeability can be measured by a method of measuring the impedance of a toroidal sample with an impedance analyzer, a (vector) network analyzer, or a BH analyzer and converting the result into complex relative permeability, or, depending on the frequency region (for example, when measuring using a network analyzer at 500 MHz or more), by the S-parameter method or the like.

[0075] The magnetic material for magnetic field amplification of this embodiment also has the characteristic that the frequency dependence of the relative magnetic permeability is small. For example, in applications such as wireless power supply, power is supplied at a frequency of 13.56 MHz, so a magnetic material with small changes in the real term μ' of the relative magnetic permeability in the range of 2 MHz to 20 MHz, including that frequency, has excellent efficiency and can be preferably used. Furthermore, there are many materials whose relative magnetic permeability changes significantly even at 5 MHz or less, and even in applications in this frequency range, a material with a stable real term of the relative magnetic permeability in the range of 2 MHz to 20 MHz can be preferably used. In these applications, materials with large changes in μ' within the above frequency range also have a tendency for μ" to deviate greatly from 0, and therefore for tan δ to deteriorate. The ratio of the real term of the relative permeability at 20 MHz to the real term of the relative permeability at 2 MHz is preferably 0.8 or more, and more preferably 0.9 or more. Furthermore, the ratio of the real term of the relative permeability at 20 MHz to the real term of the relative permeability at 2 MHz may be 1.1 or less. When this ratio of the real term of the relative permeability is 0.8 or more, there is a tendency for the decrease in energy efficiency to be reduced and for heat generation in devices incorporating the magnetic material to be reduced. Furthermore, when the ratio of the real term of the relative permeability is 1.1 or less, there is a tendency for input / output control for the device to be easier.

[0076] The magnetic material for magnetic field amplification of this embodiment may contain a resin. A composite material of a magnetic material and a resin is called a bonded magnetic material, and the resin contained in this bonded magnetic material may be a thermosetting resin or a thermoplastic resin. Examples of thermoplastic resins include polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), polyethylene (PE), and thermoplastic elastomers. Examples of thermosetting resins include epoxy resin, phenolic resin, urea resin, melamine resin, guanamine resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, polyurethane resin, silicone resin, polyimide resin, alkyd resin, furan resin, dicyclopentadiene resin, acrylic resin, allyl carbonate resin, and thermosetting elastomers commonly referred to as rubber.

[0077] The resin content in the bonded magnetic material is preferably 0.1% by mass or more and 95% by mass or less. A resin content of 0.1% by mass or more further improves impact resistance, while a resin content of 95% by mass or less can suppress extreme decreases in relative permeability and magnetization. Furthermore, for applications requiring both high relative permeability and impact resistance, the resin content of the bonded magnetic material of this embodiment is more preferably in the range of 0.5% by mass or more and 50% by mass or less for the same reasons as above. When used as a transformer for a high-frequency circuit with particularly excellent efficiency, a content of 1% by mass or more and 15% by mass or less is most preferable. Furthermore, in order to achieve a particularly high real term of relative permeability as a magnetic field amplification magnetic material of this embodiment and particularly improve absorption characteristics as an ultrahigh-frequency absorption material, a content of 15% by mass or less is also preferable, although this varies somewhat depending on the application. Compacts that do not undergo sintering and do not contain resin, such as compacts using auxiliary agents such as volatile organic solvents, are extremely brittle and are extremely difficult to use as magnetic field amplification materials such as magnetic cores for wireless power supply coils and inductors, which are subject to loads, or as ultra-high frequency absorption materials for 5G+ and 6G mobile devices that are frequently carried and subjected to impacts. Furthermore, compacts containing many air gaps, such as compacts pressed at a pressure of 1.5 GPa or less, tend to be unsuitable for high-temperature applications because they suffer from oxidation degradation, extreme embrittlement, and reduced impact resistance when exposed to temperatures above 50°C for long periods of time. Therefore, in compacts for such applications, the resin content is preferably 0.1% by mass or more and 95% by mass or less, more preferably 0.5% by mass or more and 50% by mass or less, and even more preferably 1% by mass or more and 15% by mass or less.

[0078] The resin compound for the bonded magnetic material can be obtained, for example, by using a kneader to mix and / or knead a phosphorus compound with a rare earth-iron-nitrogen-based magnetic powder and a resin, or by mixing and / or kneading a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder and a resin, at 180° C. or higher and 300° C. or lower. For example, the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder and a resin are mixed in a mixer, and then kneaded and extruded in a twin-screw extruder. The extruded strands are air-cooled and then cut into pieces several millimeters in size using a pelletizer, thereby obtaining the resin compound for the bonded magnetic material of this embodiment in pellet form.

[0079] The bonded magnetic material of this embodiment can be produced by molding the resin compound using an appropriate molding machine. Specifically, for example, the resin compound melted in the barrel of the molding machine is injection-molded into a mold to which a magnetic field is applied, aligning the easy axis of magnetization (orientation process), thereby obtaining a magnetically oriented molded bonded magnetic material. Furthermore, sheet-shaped bonded magnetic material sheets for magnetic field amplification and for ultra-high frequency absorption can be produced by calendering or hot-press molding the pellet-shaped resin compound. By rolling this to a thickness of 20 μm to 200 μm, a magnetic material for magnetic field amplification with a high real term of relative magnetic permeability can be obtained. For example, this can be used as a magnetic material compact for magnetic field amplification for RFID tags, or as a magnetic material compact for ultra-high frequency absorption for mobile devices.

[0080] <Magnetic Material for Ultra-High Frequency Absorption> The magnetic material for ultra-high frequency absorption of this embodiment is characterized by containing a rare earth-iron-nitrogen magnetic powder containing a phosphorus compound, R (R is at least one element selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the entire R component), Fe, and N.

[0081] The magnetic material for absorbing ultra-high frequencies of this embodiment contains a rare earth-iron-nitrogen based magnetic powder and a phosphorus compound, and therefore has a high imaginary term of relative permeability, with μ" being 0.2 or more in the range of 1 GHz or more and 0.11 THz or less, and also as a magnetic material for magnetic field amplification, the majority of the range is μ" being 0.1 or more in the range of 1 MHz or more and less than 1 GHz. The magnetic material for absorbing ultra-high frequencies of this embodiment is not particularly limited as long as it contains a phosphorus compound and a rare earth-iron-nitrogen based magnetic powder containing R (R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm is less than 50 atomic % of the total R component), Fe, and N, but for example, the magnetic powder of the above-mentioned embodiment can be used.

[0082] The average particle size of rare earth-iron-nitrogen magnetic powder used in magnetic materials for ultra-high frequency absorption is preferably 0.1 μm or more and 10 μm or less. For the reasons mentioned above, in the ultra-high frequency range of 1 GHz or more, powders with a particle size of 3 μm or more tend to have a reduced relative magnetic permeability due to the skin effect. Therefore, the particle size should be 0.1 μm or more, and direct contact between magnetic particles should be avoided as much as possible. For example, even if a 30 μm rare earth-iron-nitrogen magnetic powder is crushed to 5 μm or less to be used in an ultra-high frequency magnetic material, the magnetic powder particles may come into contact with each other and become conductive when molded, resulting in an average size of 30 μm for the conductive agglomerates. In this case, the effect of particle size on high-frequency characteristics will be the same as when the powder is used before crushing, defeating the purpose of crushing. In particular, when producing magnetic sheets, molding methods that simultaneously apply heat and pressure, such as hot pressing and calendering, are often used, and in this case, it is preferable that an insulating film such as a phosphorus compound firmly adheres to the surface of the magnetic particles so that even if the magnetic particles aggregate within the molded body matrix, the magnetic particles are electrically insulated from each other.By coating the surface of magnetic powder that tends to aggregate with a fine and moderately soft phosphorus compound that is not as hard as ferrite or transition metal oxides, a high-density, high-frequency magnetic material with high relative permeability can be obtained by simultaneously applying heat and pressure.

[0083] The magnetic material for absorbing ultra-high frequencies of this embodiment is characterized by a high imaginary term μ" of relative permeability even at ultra-high frequencies. For example, the imaginary term μ" of relative permeability at a frequency of 1 GHz or more but less than 20 GHz is preferably 0.2 or more, and more preferably 0.3 or more. Furthermore, the imaginary term μ" of relative permeability at a frequency of 20 GHz or more but less than 1 THz is preferably 0.1 or more, and even more preferably 0.2 or more. Furthermore, the magnetic material for absorbing ultra-high frequencies of this embodiment can have the imaginary term μ" of relative permeability at a frequency of 10 GHz be 0.2 or more, preferably 0.47 or more, more preferably 0.5 or more, and even more preferably 0.55 or more. In the magnetic material for absorbing ultra-high frequencies of this embodiment, the imaginary term μ″ of the relative permeability at a frequency of 10 GHz can be 5 or less, and may be 4 or less. Furthermore, in the magnetic material for absorbing ultra-high frequencies of this embodiment, the imaginary term μ″ of the relative permeability at a frequency of 0.11 THz, for example, can be 0.02 or more, preferably 0.05 or more, more preferably 0.1 or more, and even more preferably 0.2 or more. In the magnetic material for absorbing ultrahigh frequencies of this embodiment, the imaginary term μ" of the relative permeability at a frequency of 0.11 THz can be 2 or less, and may be 1.5 or less. In addition, in the magnetic material for absorbing ultrahigh frequencies of this embodiment, the ratio of the imaginary term μ" of the relative permeability at 0.11 THz to the imaginary term μ" of the relative permeability at a frequency of 10 GHz is preferably 0.03 or more, and more preferably 0.1 or more. In the magnetic material for absorbing ultrahigh frequencies of this embodiment, the ratio of the imaginary term μ" of the relative permeability at 0.11 THz to the imaginary term μ" of the relative permeability at a frequency of 10 GHz is preferably 5 or less, and more preferably 1 or less. When the ratio of the imaginary term μ" of the relative permeability at 0.11 THz to the imaginary term μ" of the relative permeability at a frequency of 10 GHz of the magnetic material for absorbing ultrahigh frequencies is in the above range, better absorption characteristics can be exhibited over a wide frequency band.

[0084] The magnetic material for ultra-high frequency absorption of this embodiment contains a rare earth-iron-nitrogen magnetic powder and a phosphorus compound, enabling ultra-wide frequency band ultra-high frequency absorption from 1 GHz to 1 THz, and is distinct from magnetic materials that have low relative permeability in a narrow band of about 10 GHz, such as uniaxial magnetocrystalline anisotropy materials expected to be used at such ultra-high frequencies, such as hexagonal ferrite, borides, and epsilon iron oxide. For in-plane magnetocrystalline anisotropy materials that have lower electrical resistivity than oxide materials but higher resistance than metal-based materials and maintain high-frequency characteristics up to 1 THz, the inclusion of a phosphorus compound with high electrical resistivity in the magnetic powder is a major feature.

[0085] More specific applications of magnetic materials for absorbing ultra-high frequency waves include mobile communication devices, small mobile phone base stations, and cloud base stations that are applied to 5G (5th Generation Mobile Communication System), 5G+ (5th Generation Plus Mobile Communication System), and 6G (6th Generation Mobile Communication System), as well as components for absorbing ultra-high frequency signals and spurious signals that are applied to infrastructure equipment such as those devices and antennas, and components for absorbing ultra-high frequency signals and spurious signals that are applied to infrastructure equipment such as those devices and antennas, and components for ITS (Intelligent Transport System). Examples of such components include components for absorbing ultra-high frequency signals and spurious signals for equipment and devices used in systems such as HDMI (High-Definition Multimedia Interface), Wireless LAN (Wireless Local Area Network), and satellite broadcasting (Ka-band), as well as electromagnetic noise absorption components that remove mainly the second to seventh harmonics from personal computers.

[0086] The magnetic material for ultra-high frequency absorption of this embodiment may contain a resin. A composite material of a magnetic material and a resin is called a bonded magnetic material, and the resin contained in this bonded magnetic material may be a thermosetting resin or a thermoplastic resin. Examples of thermoplastic resins include polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer (LCP), polyamide (PA), polypropylene (PP), polyethylene (PE), and thermoplastic elastomers. Examples of thermosetting resins include epoxy resin, phenolic resin, urea resin, melamine resin, guanamine resin, unsaturated polyester resin, vinyl ester resin, diallyl phthalate resin, polyurethane resin, silicone resin, polyimide resin, alkyd resin, furan resin, dicyclopentadiene resin, acrylic resin, allyl carbonate resin, and thermosetting elastomers commonly known as rubber.

[0087] The resin content in the bonded magnetic material is preferably 0.1% by mass or more and 95% by mass or less. A resin content of 0.1% by mass or more further improves impact resistance, while a resin content of 95% by mass or less can suppress extreme decreases in relative permeability and magnetization. Furthermore, for the bonded magnetic material of this embodiment, in applications requiring both high relative permeability and impact resistance, a range of 0.5% by mass or more and 50% by mass or less is more preferable for the same reasons as above. When used as a transformer for a high-frequency circuit with particularly excellent efficiency, a range of 1% by mass or more and 15% by mass or less is even more preferable. Furthermore, in order to achieve a particularly high real term of relative permeability as a magnetic field amplification magnetic material of this embodiment and particularly improve absorption characteristics as an ultrahigh-frequency absorption material, a content of 15% by mass or less is also preferable, although this varies somewhat depending on the application. Compacts that do not undergo sintering and do not contain resin, such as compacts using auxiliary agents such as volatile organic solvents, are extremely brittle and are extremely difficult to use as magnetic field amplification materials such as magnetic cores for wireless power supply coils and inductors, which are subject to loads, or as ultra-high frequency absorption materials for 5G+ and 6G mobile devices that are frequently carried and subjected to impacts. Furthermore, compacts containing many air gaps, such as compacts pressed at a pressure of 1.5 GPa or less, tend to be unsuitable for high-temperature applications because they suffer from oxidation degradation, extreme embrittlement, and reduced impact resistance when exposed to temperatures above 50°C for long periods of time. Therefore, in compacts for such applications, the resin content is preferably 0.1% by mass or more and 95% by mass or less, more preferably 0.5% by mass or more and 50% by mass or less, and even more preferably 1% by mass or more and 15% by mass or less.

[0088] The resin compound for the bonded magnetic material can be obtained, for example, by using a kneader to mix and / or knead a phosphorus compound with a rare earth-iron-nitrogen-based magnetic powder and a resin, or by mixing and / or kneading a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder and a resin, at 180° C. or higher and 300° C. or lower. For example, the phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder and a resin are mixed in a mixer, and then kneaded and extruded in a twin-screw extruder. The extruded strands are air-cooled and then cut into pieces several millimeters in size using a pelletizer, thereby obtaining the resin compound for the bonded magnetic material of this embodiment in pellet form.

[0089] The bonded magnetic material of this embodiment can be produced by molding the resin compound using an appropriate molding machine. Specifically, for example, the resin compound melted in the barrel of the molding machine is injection-molded into a mold to which a magnetic field is applied, aligning the easy axis of magnetization (orientation process), thereby obtaining a magnetically oriented molded bonded magnetic material. Furthermore, sheet-shaped bonded magnetic material sheets for magnetic field amplification and for ultra-high frequency absorption can be produced by calendering or hot-press molding the pellet-shaped resin compound. By rolling this to a thickness of 20 μm to 200 μm, a magnetic material for magnetic field amplification with a high real term of relative magnetic permeability can be obtained. For example, this can be used as a magnetic material compact for magnetic field amplification for RFID tags, or as a magnetic material compact for ultra-high frequency absorption for mobile devices.

[0090] The present disclosure will be described in more detail with reference to the following examples, but the present disclosure is not limited to these examples. The evaluation methods used in the examples are as follows.

[0091] (1) DSC Heat Generation Initiation Temperature 20 mg of the phosphorus compound-coated magnetic powder was weighed out and subjected to DSC analysis using a high-temperature differential scanning calorimeter (DSC6300, manufactured by Hitachi High-Tech Science Corporation) under the measurement conditions of an air atmosphere (200 mL / min), room temperature to 400°C (heating rate: 20°C / min), and alumina (20 mg) as the reference, to measure the heat generation initiation temperature. A high heat generation initiation temperature means that heat generation due to oxidation is less likely to occur, and therefore the phosphorus compound coating is more densely formed.

[0092] (2) P Content The P concentration in the phosphorus compound coated magnetic powder was measured using ICP atomic emission spectroscopy (ICP-AES).

[0093] (3) Total Carbon Content (TC) The total carbon (TC) content in the phosphorus compound coated magnetic powder was measured using a combustion catalytic oxidation type total organic carbon (TOC) meter (manufactured by Shimadzu Corporation; model: SSM-5000A).

[0094] (4) Thickness, atomic concentration, and crystallinity of the phosphorus compound coating The thickness and atomic concentration of the phosphorus compound coating on the surface of the phosphorus compound-coated magnetic powder were measured as follows. First, the obtained magnetic powder was dispersed in epoxy resin and solidified, and then a cross-section was extracted using a focused ion beam (FIB) to obtain a cross-sectional sample for measurement. For the obtained sample, the respective values ​​were estimated using an STEM (FEI, model number Talos F200X; acceleration voltage 200 kV) and an STEM-EDX (system: FEI, model number SuperX, detector: Bruker SDD detector) attached to the STEM. The atomic concentration in the phosphorus compound coating was determined by line analysis from the outside to the inside of the phosphorus compound-coated magnetic powder in 0.184 nm steps, observing the continuous changes in the atomic concentration of each constituent element, and measuring the range in which the phosphorus (P) atomic concentration was 1 atomic % or more. At this time, depending on the measurement location, there is a risk that a large amount of carbon (C) in the resin used to prepare the cross-sectional sample may be detected in some locations, so the atomic concentration was calculated as the total of elements excluding C. In addition, the crystallinity of the phosphorus compound coating on the surface of the phosphorus compound-coated magnetic powder was determined using TEM-ED. When no lattice fringes were visible in the TEM image and the ED image showed a halo pattern, that part was determined to be an amorphous phase. The size of the phosphorus-containing nanocrystalline compound was roughly determined from the spread of the lattice fringes in the TEM image and the relationship between the size of the ED observation area and the ring pattern.

[0095] (5) Measurement of Complex Relative Permeability in the Range of 1 MHz to 1 GHz The phosphorus compound-coated magnetic powder was mixed with an epoxy resin, a thermosetting resin, and then kneaded to produce a resin compound. This resin compound was placed in a mold with an inner diameter of 3.1 mm and an outer diameter of 8 mm, molded under a pressure of 0.8 GPa, and then thermally cured in vacuum at 150°C for 2 hours to produce a toroidal molded body. Using this sample, the complex relative permeability in the frequency range of 1 MHz to 1 GHz was evaluated using an impedance analyzer (HP4291B, manufactured by Hewlett-Packard) from the inductance value determined using a single-turn inductor-type test fixture.

[0096] (6) Measurement of Complex Relative Permeability from 1 MHz to 0.11 THz A resin compound was prepared by mixing and kneading the phosphorus compound-coated magnetic powder with a thermoplastic resin, polyamide ester ether elastomer, at 180°C. This resin compound was hot-press molded at 190°C and a pressure of 12.7 MPa to prepare a magnetic sheet measuring 100 mm x 100 mm x 1 mm. A sample piece with an inner diameter of 3.1 mm and an outer diameter of 8 mm was cut from this magnetic sheet to prepare a toroidal compact. Using this sample, the complex relative permeability from 1 MHz to 1 GHz was evaluated in the same manner as in (5) above.

[0097] Furthermore, a sample piece of a different size from the above toroidal compact, with an inner diameter of 3.04 mm and an outer diameter of 7 mm, was cut from the above magnetic sheet to produce another toroidal compact. Using this sample, the complex relative permeability in the frequency range of 1 GHz to 18 GHz was evaluated from the S-parameter values ​​obtained by the coaxial method using a network analyzer (N5290A, manufactured by Keysight Technologies). Furthermore, the complex relative permeability of the 100 mm x 100 mm x 1 mm magnetic sheet obtained by the above method was evaluated from the S-parameter values ​​obtained by the free-space method using the above network analyzer in the frequency range of 18 GHz to 0.11 THz.

[0098] Comparative Example 1: Using iron sulfate and neodymium sulfate as raw materials, a precipitation method was used to prepare Nd with an average particle size of 9 μm that was not phosphorus-treated. ２ Fe １７ N ３ A magnetic powder was prepared.

[0099] [Preparation of Nd—Fe sulfuric acid solution] FeSO 4 was added to 2.0 kg of pure water. ４ ・7H ２ 5.0 kg of Nd ２ O ３ 0.45 kg of Nd and 0.70 kg of 70% sulfuric acid were added and thoroughly stirred to completely dissolve the Nd—Fe solution. Then, pure water was added to the resulting solution to adjust the final Fe concentration to 0.726 mol / L and the Nd concentration to 0.106 mol / L, thereby preparing a Nd—Fe sulfuric acid solution.

[0100] [Precipitation step] The entire amount of the prepared Nd—Fe sulfuric acid solution was added dropwise to 20 kg of pure water maintained at a temperature of 40°C over a period of 70 minutes from the start of the reaction while stirring, and simultaneously 15% aqueous ammonia was added dropwise to adjust the pH to 7-8. This yielded a slurry containing Nd—Fe hydroxide. The obtained slurry was washed with pure water by decantation, and the hydroxide was subjected to solid-liquid separation. The separated hydroxide was dried in an oven at 100°C for 10 hours.

[0101] [Oxidation Step] The hydroxide obtained in the precipitation step was calcined in air at 1000° C. for 1 hour, and after cooling, red Nd—Fe oxide was obtained as a raw material powder.

[0102] [Pretreatment Step] 100 g of Nd—Fe oxide was placed in a steel container to give a bulk thickness of 10 mm. The container was placed in a furnace, and the pressure was reduced to 100 Pa. Then, while introducing hydrogen gas, the temperature was raised to the pretreatment temperature of 850° C. and maintained at that temperature for 15 hours to obtain a black powder partial oxide.

[0103] [Reduction step] 60 g of the partial oxide obtained in the pretreatment step and 19.2 g of metallic calcium having an average particle size of approximately 6 mm were mixed and placed in a furnace. After evacuating the furnace, argon gas (Ar gas) was introduced. The temperature was raised to 1,045°C and maintained for 45 minutes to obtain Fe—Nd alloy particles.

[0104] [Nitriding step] Subsequently, the temperature inside the furnace was cooled to 100°C, and then the furnace was evacuated to a vacuum. While introducing nitrogen gas, the temperature was increased to 450°C and maintained at that temperature for 29 hours to obtain an aggregated product containing magnetic particles.

[0105] [Water washing step] The aggregated product obtained in the nitriding step was poured into 3 kg of pure water and stirred for 30 minutes. After standing, the supernatant was drained by decantation. The process of pouring into pure water, stirring, and decantation was repeated 10 times. Next, 2.5 g of 99.9% acetic acid was poured into the product and stirred for 15 minutes. After standing, the supernatant was drained by decantation. The process of pouring into pure water, stirring, and decantation was repeated twice, followed by dehydration and drying, followed by mechanical crushing to obtain Nd ２ Fe １７ N ３A magnetic powder (average particle size 9 μm) was obtained.

[0106] Example 1 Nd prepared in Comparative Example 1 ２ Fe １７ N ３ The magnetic powder was subjected to a phosphoric acid treatment as follows: As a phosphate treatment solution, 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate were mixed in a mass ratio of 1:6:1, and the pH was adjusted to 2 with pure water and diluted hydrochloric acid. ４ A solution with a concentration adjusted to 20% by mass was prepared. The Nd—Fe—N magnetic powder obtained in the water washing process was stirred for 1 minute in a dilute hydrochloric acid solution (1000 g water:70 g hydrogen chloride) to remove surface oxide films and contaminants. The solution was then repeatedly drained and refilled until the conductivity of the supernatant liquid reached 100 μS / cm or less, yielding a slurry containing 10% by mass of Nd—Fe—N anisotropic magnetic powder. While stirring the resulting slurry, 100 g of the prepared phosphate treatment solution was poured into the treatment tank. Then, 6% by mass of hydrochloric acid was added as needed to control the pH of the phosphate treatment reaction slurry within a range of 2.0±0.1, which was maintained for 30 minutes. The resulting solution was then subjected to suction filtration, dehydration, and vacuum drying to obtain a phosphorus compound-coated Nd—Fe—N anisotropic magnetic powder.

[0107] Example 2 Nd prepared in Comparative Example 1 ２ Fe １７ N ３ The magnetic powder was subjected to phosphoric acid treatment as follows: To prepare the phosphoric acid treatment solution, 85% orthophosphoric acid, sodium dihydrogen phosphate, and sodium molybdate dihydrate were mixed in a mass ratio of 1:6:1, and the pH was adjusted to 2.5 with pure water and diluted hydrochloric acid. ４ The concentration was adjusted to 20% by mass. The Nd—Fe—N magnetic powder obtained in the water washing process was stirred for 1 minute in a dilute hydrochloric acid solution (1000 g water: 70 g hydrogen chloride) to remove surface oxide films and contaminants. After this, the water was drained and poured repeatedly until the conductivity of the supernatant liquid reached 100 μS / cm or less, yielding a slurry. While stirring the resulting slurry, 100 g of the prepared phosphate treatment solution was poured into the treatment tank. The pH of the treatment tank rose from 2 to 6 over 5 minutes. After stirring for 15 minutes, the powder was subjected to suction filtration, dehydration, and vacuum drying to obtain a phosphorus compound-coated Nd—Fe—N anisotropic magnetic powder.

[0108] The DSC heat generation onset temperature, P content, and total carbon content (TC) were measured by the above-mentioned methods using the magnetic powders produced in Examples 1 and 2 and Comparative Example 1. The measurement results are shown in Table 1 together with the phosphorus treatment conditions.

[0109]

[0110] The powder surfaces of Example 1, which was phosphorus-treated, and Comparative Example 1, which was not phosphorus-treated, were observed using STEM-EDX. The resulting STEM images are shown in Figures 1A and 1C, respectively. In Figure 1A, the gray area is the phosphorus compound coating, the white area is the rare earth-iron-nitrogen magnetic powder base material, and the black area is the area outside the magnetic powder. Also, in Figure 1C, the gray area is the high-oxygen-concentration film (substantially free of phosphorus), the white area is the rare earth-iron-nitrogen magnetic powder base material, and the black area is the area outside the magnetic powder. The film thickness of the phosphorus compound coating of the magnetic powder of Example 1 was approximately 60 nm. The P atomic concentration (atomic %) contained in this phosphorus compound coating was approximately 12 atomic % on average. Figure 2A shows a TEM image and ED diagram of the magnetic powder of Example 1. The part included in the white rectangle is thought to be the phosphorus compound coating, the crystalline phase to the left of it is the rare earth-iron-nitrogen magnetic powder, and the part to the right is thought to be the part outside the magnetic powder (the carbon layer added for conductivity required for measurement when preparing the TEM sample). The phosphorus compound coating of this magnetic powder consisted of a "phosphorus-containing nanocrystalline compound" and a "phosphorus-containing amorphous" with a particle size of 1 to 5 nm. On the other hand, as shown in Figure 1C, a 5 to 10 nm high-oxygen-concentration film was present on the surface of the magnetic powder of Comparative Example 1, but almost no phosphorus was detected in the line analysis described below, and no phosphorus compound coating was observed.

[0111] 3A and 3C show the results of line analysis by STEM-EDX for Example 1 and Comparative Example 1, respectively. In Fig. 3A, a region of approximately 40 nm was observed in the phosphorus compound coating where the atomic concentration ratio of Nd was higher than that of Fe, and the atomic concentration of Nd was higher than that of the magnetic powder base material. In this region, the average atomic concentration ratio of Nd to Fe, Nd / Fe, was approximately 2.2, which was approximately 11 times the average Nd / Fe ratio of the rare earth-iron-nitrogen magnetic powder base material.

[0112] Figure 1B shows the results of STEM-EDX observation of the surface area of ​​the magnetic powder of Example 2. The film thickness of the phosphorus compound coating of the magnetic powder was found to be approximately 20 nm. Figure 2B shows a TEM image and ED diagram of the magnetic powder. The phosphorus compound coating of the magnetic powder consisted of a "phosphorus-containing nanocrystalline compound" and a "phosphorus-containing amorphous" with a particle size of 1 to 5 nm. The concentration of P atoms contained in this phosphorus compound coating was approximately 4 atomic %. Compared to the magnetic powder of Example 1, the film thickness of the phosphorus compound coating showed a smaller value.

[0113] Figure 3B shows the results of line analysis by STEM-EDX for Example 2. In Figure 3B, a region of approximately 4 nm was observed in the phosphorus compound coating where the Nd atomic concentration was higher than in the magnetic powder matrix. In this region, the average atomic concentration ratio of Nd to Fe, Nd / Fe, was approximately 0.45.

[0114] Examples 3 and 4, Comparative Example 2 Using the phosphorus-treated powders of Examples 1 and 2 and the non-phosphorus-treated powders of Comparative Example 1, samples for measuring complex relative permeability at 1 MHz to 1 GHz were prepared by the method described above (toroidal compacts (resin added amount 6 mass%) with densities of 5.76 (Example 3), 5.55 (Example 4), and 5.75 (Comparative Example 2)). The frequency dependence of complex relative permeability at 1 MHz to 1 GHz was measured by the method described above, and the results are shown in FIG. 4, and the evaluation results of the high-frequency characteristics are shown in Table 2.

[0115] 4, the "ratio of the real term of the relative permeability at 20 MHz to the real term of the relative permeability at 2 MHz" of Examples 3 and 4 and Comparative Example 2 was 0.92, 0.84, and 0.60, respectively. In Examples 3 and 4, the ratio was within the range of 0.8 to 1.1, but in Comparative Example 2 it was less than 0.8.

[0116]

[0117] Examples 5 and 6, Comparative Example 3 Using the phosphorus-treated powders of Examples 1 and 2 and the non-phosphorus-treated powders of Comparative Example 1, samples for measuring complex relative permeability at frequencies of 1 MHz to 0.11 THz were prepared by the method described above (magnetic sheets (resin added amount 8 mass%) with densities of 4.96 (Example 5), 4.95 (Example 6), and 4.95 (Comparative Example 3)). The frequency dependence of the complex relative permeability at frequencies of 1 MHz to 0.11 THz was measured by the method described above for Example 5, and the results are shown in FIG. 5. The evaluation results of the high-frequency characteristics for Examples 5 and 6 and Comparative Example 3 are shown in Table 3.

[0118] 5 and Table 3, the "ratio of the imaginary term of the relative permeability at 0.11 THz to the imaginary term of the relative permeability at 10 GHz" for Examples 5 and 6 and Comparative Example 3 was 0.44, 0.03, and 0.02, respectively. In Examples 5 and 6, the ratio was within the range of 0.03 or more and 5 or less, but in Comparative Example 3, it was less than 0.03.

[0119]

[0120] In particular, in Example 5, as shown in FIG. 5 , excellent ultra-high frequency absorption characteristics were obtained, with the imaginary term μ″ of the complex relative permeability being 0.2 or more in the ultra-wide ultra-high frequency region of 1 GHz or more and 0.11 THz or less. The phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder of the present disclosure has the characteristics of an in-plane magnetocrystalline anisotropy material, which is different from uniaxial magnetocrystalline anisotropy materials, further improved by the electrical insulation effect between the powder particles of the phosphorus compound coating portion.

[0121] As can be seen from Table 3, the magnetic powder of Example 6, in which the thickness of the phosphorus compound coating portion was 20 nm, had a higher μ" in the ultra-high frequency range at 0.11 THz, compared to the comparative examples in which the thickness of the high-oxygen concentration film was approximately 5 to 10 nm. Furthermore, the magnetic powder of Example 5, partly because it had a phosphorus compound coating portion approximately 60 nm thick, was able to further reduce the effect of eddy currents, and exhibited a high μ" value of 0.26 even in the ultra-high frequency range of 0.11 THz. Furthermore, at 10 GHz, Example 5 showed an improvement in μ" compared to Comparative Example 3, which is thought to be due to the reduction in eddy current loss. On the other hand, the coating layer of the magnetic powder of Example 6 was thinner than the magnetic powder of Example 5, and the volume fraction of the magnetic powder, which is the base material, in the magnetic material of Example 6 was higher, so it is thought that the improvement in μ" due to natural resonance resulted in a larger μ" value than Example 5.

[0122] According to the manufacturing method of the present disclosure, it is possible to obtain a phosphorus compound-coated rare earth-iron-nitrogen-based magnetic powder having excellent magnetic field amplification properties and ultra-high frequency absorption properties. The obtained magnetic powder can be suitably used as a magnetic material for magnetic field amplification and ultra-high frequency absorption.

[0123] The present disclosure includes the following aspects: (Item 1) A method for producing a magnetic powder, comprising a phosphorus treatment step of adding an inorganic acid to a slurry containing a rare earth-iron-nitrogen based magnetic powder containing R (where R is at least one element selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R components), Fe, and N, water, and a phosphorus-containing substance, to obtain a phosphorus compound and a rare earth-iron-nitrogen based magnetic powder.

[0124] (Item 2) The method for producing magnetic powder according to Item 1, wherein in the phosphorus treatment step, the inorganic acid is added to adjust the pH of the slurry to 1 or more and 4.5 or less.

[0125] (Item 3) The method for producing a magnetic powder according to item 1 or 2, wherein the phosphorus content contained in the phosphorus compound and the rare earth-iron-nitrogen magnetic powder is 0.02% by mass or more and 4% by mass or less.

[0126] (Item 4) The method for producing a magnetic powder according to any one of Items 1 to 3, further comprising, after the phosphorus treatment step, an oxidation step of heat-treating the phosphorus compound and the rare earth-iron-nitrogen-based magnetic powder in an oxygen-containing atmosphere.

[0127] (Item 5) A magnetic material for magnetic field amplification, comprising a rare earth-iron-nitrogen magnetic powder containing a phosphorus compound and R (R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm is less than 50 atomic % with respect to the entire R component), Fe, and N.

[0128] (Item 6) The magnetic material for magnetic field amplification according to Item 5, wherein the ratio of the real term of the relative permeability at 20 MHz to the real term of the relative permeability at 2 MHz is 0.8 or more and 1.1 or less.

[0129] (Item 7) The magnetic material for magnetic field amplification according to item 5 or 6, wherein the ratio of the real term to the imaginary term in the relative permeability at 20 MHz is 3 or more and 10,000 or less.

[0130] (Item 8) The magnetic material for magnetic field amplification according to any one of Items 5 to 7, wherein the phosphorus compound coats the surface of the rare earth-iron-nitrogen based magnetic powder.

[0131] (Item 9) The magnetic material for magnetic field amplification according to any one of Items 5 to 8, wherein the phosphorus content is 0.02% by mass or more and 4% by mass or less relative to the phosphorus compound and the rare earth-iron-nitrogen-based magnetic powder.

[0132] (Item 10) The magnetic material for magnetic field amplification according to any one of Items 5 to 9, which is used for wireless power supply.

[0133] (Item 11) The magnetic material for magnetic field amplification according to any one of Items 5 to 10, further comprising a resin in addition to the rare earth-iron-nitrogen based magnetic powder.

[0134] (Item 12) A magnetic material for absorbing ultra-high frequencies, comprising a phosphorus compound and a rare earth-iron-nitrogen magnetic powder containing R (R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm is less than 50 atomic % with respect to the entire R component), Fe, and N.

[0135] (Item 13) A magnetic material for absorbing ultra-high frequencies according to Item 12, wherein the imaginary term in the relative permeability at 0.11 THz is 0.02 or more.

[0136] (Item 14) The magnetic material for absorbing ultra-high frequencies according to item 12 or 13, wherein the ratio of the imaginary term in the relative permeability at 0.11 THz to the imaginary term in the relative permeability at 10 GHz is 0.03 or more.

Claims

1. A method for producing a magnetic powder, comprising a phosphorus treatment step of adding an inorganic acid to a slurry containing a rare earth-iron-nitrogen based magnetic powder containing R (where R is at least one element selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, the Sm content is less than 50 atomic % of the total R components), Fe, and N, water, and a phosphorus-containing substance, to obtain a phosphorus compound and a rare earth-iron-nitrogen based magnetic powder.

2. 2. The method for producing magnetic powder according to claim 1, wherein in the phosphorus treatment step, the inorganic acid is added to adjust the pH of the slurry to 1 or more and 4.5 or less.

3. 3. The method for producing magnetic powder according to claim 1, wherein the phosphorus content contained in the phosphorus compound and the rare earth-iron-nitrogen magnetic powder is 0.02% by mass or more and 4% by mass or less.

4. 3. The method for producing magnetic powder according to claim 1, further comprising, after the phosphorus treatment step, an oxidation step of heat-treating the phosphorus compound and the rare earth-iron-nitrogen-based magnetic powder in an oxygen-containing atmosphere.

5. A method for producing a magnetic powder as described in claim 1 or 2, wherein the phosphorus compound is precipitated by reaction between a metal component contained in the rare earth-iron-nitrogen magnetic powder and a phosphorus component contained in the phosphorus-containing material.

6. A method for producing a magnetic powder as described in claim 1 or 2, wherein at least a portion of the surface of the rare earth-iron-nitrogen based magnetic powder is coated with the phosphorus compound, or the phosphorus compound is present between the rare earth-iron-nitrogen based magnetic powder.

7. The rare earth-iron-nitrogen magnetic powder has at least a part of its surface coated with the phosphorus compound to form a phosphorus compound coating portion, 3. The method for producing magnetic powder according to claim 1, wherein the phosphorus compound coating portion has an R-rich region in which the R atom concentration is higher than the R atom concentration in the rare earth-iron-nitrogen magnetic powder.

8. The method for producing magnetic powder according to claim 1, wherein the rare earth-iron-nitrogen magnetic powder is made of Nd 2 Fe 17 N 3 .

9. A magnetic material for magnetic field amplification, comprising a rare earth-iron-nitrogen magnetic powder containing a phosphorus compound, R (R is at least one selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R component), Fe, and N.

10. 10. The magnetic material for magnetic field amplification according to claim 9, wherein the ratio of the real term of the relative permeability at 20 MHz to the real term of the relative permeability at 2 MHz is 0.8 or more and 1.1 or less.

11. 11. The magnetic material for magnetic field amplification according to claim 9 or 10, wherein the ratio of the real term to the imaginary term in the relative permeability at 20 MHz is 3 or more and 10,000 or less.

12. A magnetic material for magnetic field amplification as described in claim 9 or 10, wherein at least a portion of the surface of the rare earth-iron-nitrogen based magnetic powder is coated with the phosphorus compound, or the phosphorus compound is present between the rare earth-iron-nitrogen based magnetic powder.

13. The rare earth-iron-nitrogen magnetic powder has at least a part of its surface coated with the phosphorus compound to form a phosphorus compound coating portion, 11. The magnetic material for magnetic field amplification according to claim 9, wherein the phosphorus compound coating portion has an R-rich region in which the R atom concentration is higher than the R atom concentration in the rare earth-iron-nitrogen magnetic powder.

14. 11. The magnetic material for magnetic field amplification according to claim 9, wherein the phosphorus content is 0.02% by mass or more and 4% by mass or less relative to the phosphorus compound and the rare earth-iron-nitrogen magnetic powder.

15. 11. The magnetic material for magnetic field amplification according to claim 9, further comprising a resin in addition to the rare earth-iron-nitrogen magnetic powder.

16. A magnetic material for absorbing ultra-high frequencies, comprising a rare earth-iron-nitrogen magnetic powder containing a phosphorus compound, R (R is at least one element selected from Y, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, Tm, Lu, and Sm, and when Sm is contained, Sm accounts for less than 50 atomic % of the total R component), Fe, and N.

17. 17. The magnetic material for absorbing ultra-high frequencies according to claim 16, wherein the imaginary term in the relative permeability at 0.11 THz is 0.02 or more.

18. 18. The magnetic material for absorbing ultra-high frequencies according to claim 16 or 17, wherein the ratio of the imaginary term in the relative permeability at 0.11 THz to the imaginary term in the relative permeability at 10 GHz is 0.03 or more.

19. A magnetic material for absorbing ultra-high frequency waves as described in claim 16 or 17, wherein at least a portion of the surface of the rare earth-iron-nitrogen based magnetic powder is coated with the phosphorus compound, or the phosphorus compound is present between the magnetic rare earth-iron-nitrogen based powders.

20. The rare earth-iron-nitrogen magnetic powder has at least a part of its surface coated with the phosphorus compound to form a phosphorus compound coating portion, 18. The magnetic material for absorbing ultra-high frequency waves according to claim 16, wherein the phosphorus compound coating portion has an R-rich region in which the R atom concentration is higher than the R atom concentration in the rare earth-iron-nitrogen magnetic powder.

21. A magnetic material for absorbing ultra-high frequency waves as described in claim 16 or 17, wherein the phosphorus content is 0.02 mass% or more and 4 mass% or less relative to the phosphorus compound and the rare earth-iron-nitrogen magnetic powder.

22. A magnetic material for absorbing ultra-high frequencies as described in claim 16 or 17, which further contains a resin in addition to the rare earth-iron-nitrogen based magnetic powder.