Composite magnetic powder and method for producing the same

Abstract

The present invention provides a composite magnetic powder which is capable of exhibiting excellent magnetic characteristics. This composite magnetic powder contains: iron oxide; an additive element A that is composed of one or more elements selected from among cobalt (Co) and manganese (Mn); and an additive element B that is composed of one or more elements selected from among zirconium (Zr), hafnium (Hf), cesium (Cs) and titanium (Ti).

Description

Technical Field

[0001] The present disclosure relates to composite magnetic powder and a method for manufacturing the same.

Background Art

[0002] In the field of magnetic materials, there is an increasing demand for higher performance products and larger data capacities, and research on improving the performance of materials is being actively conducted. Along with this, the development of magnetic materials aiming at high coercivity and high magnetization has been carried out.

[0003] Among them, as magnetic powder having a coercivity of, for example, 10 kOe or more, neodymium iron boron, samarium iron nitride, platinum iron, and iron oxide having a crystal structure of epsilon type (ε-Fe 2 O 3 ) and the like can be mentioned. When the magnetic particles are formed of neodymium iron boron, samarium iron nitride, etc. among these magnetic powders, since an ingot obtained by homogenously alloying neodymium iron boron, samarium iron nitride, etc. at a high temperature is finally pulverized, there are many particles having a size on the micron order. When the magnetic particles are formed of platinum iron, since it contains a large amount of platinum group elements as main components, the resource risk and the manufacturing cost increase.

[0004] On the other hand, when the magnetic particles are formed of ε-Fe 2 O 3 , since iron oxide is an inexpensive material, magnetic particles can be manufactured without incurring manufacturing costs while avoiding resource risks. As a method for manufacturing magnetic particles using ε-Fe 2 O 3 , for example, a method for manufacturing ε-Fe 2 O 3 from silica xerogel has been proposed (see, for example, Non-Patent Document 1).

[0005] Also, a technique for manufacturing magnetic particles of ε-Fe 2 O 3 having a particle size of 5 to 40 nm has been proposed (see, for example, Non-Patent Document 2). Non-Patent Document 2 discloses ε-Fe 2 O 3It is described that a ferromagnetic phase transition occurs when the particle size is 7.5 nm or more.

[0006] Furthermore, in order to improve the magnetic properties of magnetic particles, various elements are proposed to be substituted for a part of ε-Fe 2 O 3 or Fe (see, for example, Patent Documents 1, 2, 3, and Non-Patent Document 3, etc.).

[0007] For example, Patent Document 1 discloses a method of obtaining a coercive force of 31 kOe at room temperature by substituting a part of iron oxide with rhodium.

[0008] In Patent Document 2, a method of producing nanoparticles (particle size 30 nm) represented by the general formula ε-Ga 2 O 3 (where 0.10 ≦ x ≦ 0.67) in which a part of the iron ions of ε-Fe x Fe 2-x O 3 is substituted with gallium ions is proposed. Patent Document 2 describes that these nanoparticles effectively and selectively absorb millimeter waves in a high frequency region from 30 GHz to 150 GHz depending on the substitution amount of gallium.

[0009] Patent Document 3 describes that alkaline earth metals such as barium are added as a shape-retaining agent to iron compound particles in the synthesis of ε-Fe2O3 to obtain rod-shaped ε-Fe2O3.

[0010] Patent Document 4 discloses that by adding other elements to ε-Fe 2 O 3 to narrow the particle size distribution and reduce the content of particles that do not contribute to the magnetic recording properties, an iron-based oxide magnetic particle powder with a narrow coercive force distribution and suitable for high recording density of a magnetic recording medium can be obtained. In Patent Document 4, the general formula ε-A x B y C z Fe 2-x-y-z O 3(However, A is one or more divalent metal elements selected from Co, Ni, Mn, and Zn, B is one or more tetravalent metal elements selected from Ti and Sn, C is one or more trivalent metal elements selected from In, Ga, and Al, and 0 < x < 1, 0 < y < 1, 0 < z < 1), and an iron-based oxide represented thereby is used.)

[0011] In Patent Document 5, it is described that by depositing one or two hydroxides or hydrous oxides of Al ions and Y ions on iron-based oxide magnetic powder, surface-modified iron-based oxide magnetic particle powder with good solid-liquid separation during the manufacturing process, good dispersibility in paint, and low elution amount of water-soluble alkali metals can be obtained.)

[0012] Also, according to Non-Patent Document 4, attempts have been reported to increase the magnetization by doping ε-iron oxide with several percent of cobalt.)

[0013] On the other hand, it has long been known that spinel-type cobalt ferrite exhibits remarkably large magnetocrystalline anisotropy and magnetoelastic effects compared to magnetite and other ferrites. (Non-Patent Document 5) As patent documents related to cobalt ferrite, there are those related to magnetic powder and its manufacturing method, as well as magnetic recording media and its manufacturing method, showing a magnetic powder and its manufacturing method with small variation in coercive force using radiation. (Patent Document 6))

[0014] Furthermore, Patent Document 7 manufactures magnetic particles by melting and rapidly cooling the components of glass and spinel ferrite to form an amorphous body and then heat-treating it. Also, in Non-Patent Document 6, CoFe with an average particle size of 22.5 nm, saturation magnetization of 69.9 emu / g, and coercive force of 1785 Oe is synthesized by liquid-phase synthesis.) 2 O 4 particles are synthesized.)

[0015] Also, in Patent Document 8, in a magnetic material containing epsilon iron oxide, in order to obtain a magnetic material with excellent magnetic properties, a step of coating superparamagnetic Fe 3 O 4 with a silicon compound, and the coated superparamagnetic Fe 3 O4 is heat-treated in an oxidizing atmosphere to obtain γ-Fe 2 O 3 and ε-Fe 2 O 3 to form a duplex phase. After going through this process, the heat-treated γ-Fe 2 O 3 and ε-Fe 2 O 3 duplex phase is extracted by dissolving a silicon compound in an alkaline solution, and a manufacturing method of a composite magnetic material equipped with each and related technologies are provided.

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Non-Patent Documents

[0017]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0018] However, in these prior art documents, there is only a description of magnetization, and the relationship with coercive force is not clearly shown.

[0019] By the way, further improvement of magnetic properties is expected for such magnetic materials.

[0020] Therefore, it is desirable to provide a composite magnetic powder capable of exhibiting excellent magnetic properties and a method for producing the same.

[0021] The composite magnetic powder as one embodiment of the present disclosure includes iron oxide, additive element A which is one or more elements of Co (cobalt) and Mn (manganese), and additive element B which is one or more elements of Zr (zirconium), Hf (hafnium), Cs (cesium) and Ti (titanium). The composite magnetic powder of the present disclosure may further include additive element D which is one or more elements of Sm (samarium) and Nd (neodymium).

[0022] According to the present disclosure, it is possible to provide a composite magnetic powder having a nano-composite magnet structure in which magnetic exchange coupling works, including ε-Fe 2 O 3 with a small particle size, adjustable magnetization and coercive force, and excellent magnetic properties with sufficient bonding between the soft phase and the hard phase and no distortion. Note that the effects of the present disclosure are not limited to this, and any effects described in this specification may be applicable.

Brief Description of the Drawings

[0023]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0024] For further improving the performance of magnetic materials, there is a demand for nano-magnet powders that have both high coercivity and residual magnetization and also an improved maximum energy product. In order to provide such magnetic powders, it is desirable that they are composite magnetic powders in which ferrite particles having a spinel structure with high magnetization, ε-iron oxide-based particles, and a ferrite coating layer are well connected to each other by an exchange interaction. Generally, a composite magnetic material for magnets in which a hard magnetic phase and a soft magnetic phase are connected by an exchange interaction is called an exchange spring magnet or a nanocomposite magnet and has the following characteristics. It has a soft magnetic phase in the magnet, and the magnetizations of the soft magnetic phase and the hard magnetic phase are linked to each other by an exchange interaction. Therefore, the magnetization of the soft magnetic phase is prevented from reversing by the magnetization of the hard magnetic phase when a reverse magnetic field is applied, showing characteristics as if the soft magnetic phase does not exist. Here, however, the hard magnetic phase and the soft magnetic phase are relative terms, with the ε-iron oxide-based particles corresponding to the hard magnetic phase and the ferrite particles having a spinel structure with high magnetization corresponding to the soft magnetic phase.

[0025] In a composite material of hard magnetism and soft magnetism that are not connected by an exchange interaction, when a small reverse magnetic field is applied from the outside, the magnetization of the soft magnetic phase easily reverses, and even when the magnetic field is returned to zero, the magnetization of the reversed soft magnetic phase does not return to its original state. That is, the presence of the soft magnetic phase deteriorates the magnet characteristics. Therefore, when usually producing a high-performance magnet material, the soft magnetic phase is thoroughly removed. In contrast, in an exchange spring magnet, due to the exchange interaction, the magnetization of the soft magnetic phase is linked to the magnetization of the hard magnetic phase, and thus, supported by the magnetic anisotropy of the magnetization of the hard magnetic phase, it does not easily reverse even when a reverse magnetic field is applied. Also, when the magnetic field is returned to zero, it returns to its original state. Therefore, the presence of the soft magnetic phase does not deteriorate the magnet characteristics, and higher magnetic characteristics are obtained than those of a single hard magnetic material. Generally, as one of the requirements for the above exchange spring magnets, it is essential that the soft magnetic phase has a higher magnetization than the hard magnetic phase, and it is reasonable to composite spinel-type ferrite particles corresponding to the high-magnetization soft magnetic phase with the ε-iron oxide-based particles which are the hard magnetic phase with low magnetization.

[0026] The characteristics of the exchange spring magnet of the present disclosure are that there is no inflection point in the magnetic field region of the magnetic curve (taking the range between 0 to 5 kOe and 10 k to 20 kOe as a guide), and it depicts a smooth trajectory. Despite the presence of the soft magnetic phase, it behaves like a single magnet, and whether there is an inflection point in this region can be considered as one of the indicators of whether it is an exchange spring magnet.

[0027] In the conventional manufacturing method, particles containing iron oxide are heat-treated at a temperature at which ε-Fe 2 O 3 is generated (for example, 850 to 1250 °C) to obtain particles having ε-Fe 2 O 3 . Particles having ε-Fe 2 O 3 have excellent magnetic properties, but they cannot be said to have a sufficiently high saturation magnetization and require some improvement. On the other hand, for spinel-type iron oxide particles, there are no particles with a particle diameter of 40 nm or less and a high coercive force. Even if a powder containing both is prepared, it cannot be said that it exhibits a sufficient exchange coupling effect, and the powder has an inflection point (distortion) in the magnetic loop.

[0028] An object of the present disclosure is to provide a composite magnetic powder having a nanocomposite magnet structure capable of adjusting magnetization and coercive force and having no inflection point (distortion) in the magnetic loop, and a method for manufacturing the same. At the same time, improving the magnetic anisotropy of magnetic particles is also considered.

[0029] In order to exhibit properties that could not be achieved with conventional nanomagnetic materials considering particle size, namely, high magnetization and high coercivity, the present inventors diligently studied the use of oxides. As a result, it was found that by using a powder obtained by compounding epsilon iron oxide and spinel-type iron oxide, magnetic coupling can be achieved, and a composite magnetic powder that exhibits functions suitable for the purpose can be obtained. By controlling its composition, crystal structure, microstructure, and particle size, and further establishing its manufacturing method, the present disclosure has been completed. That is, the composite magnetic powder in one embodiment of the present disclosure contains epsilon-type iron oxide and spinel-type iron oxide, and further contains Zr, Hf, Cs, and Ti.

[0030] The manufacturing method of the composite magnetic powder in the present disclosure includes mixing a first compound containing iron element, which contains one or more of iron nitrate, iron acetate, and iron sulfate, a second compound containing Co as the additive element A, and a third compound containing one or more elements of Zr, Hf, Cs, and Ti as the additive element B to form a mixture, and then adding a silicon compound to the mixture to form a silica xerogel containing the iron element, the additive element A, and the additive element B in silica, and heat-treating the silica xerogel at 850°C to 1250°C for 4 hours to 50 hours to form a composite magnetic powder containing epsilon-type iron oxide, the additive element A, and the additive element B. Or, mixing a first compound containing iron element, which contains one or more of iron nitrate, iron acetate, and iron sulfate, a second compound containing Co as the additive element A, a third compound containing one or more elements of Zr, Hf, Cs, and Ti as the additive element B, and a fourth compound containing one or more elements of Sm and Nd as the additive element D to form a mixture, and then adding a silicon compound to the mixture to form a silica xerogel containing the iron element, the additive element A, the additive element B, and the additive element D in silica, and heat-treating the silica xerogel at 850°C to 1250°C for 4 hours to 50 hours to form a composite magnetic powder containing epsilon-type iron oxide, the additive element A, the additive element B, and the additive element D.

[0031] The composite magnetic powder in the present disclosure contains epsilon-type iron oxide, spinel-type iron oxide, and an additive element, and the additive element is one or more elements selected from Zr, Hf, Cs, Ti, Sm, and Nd.

[0032] According to the present disclosure, it is possible to provide a composite magnetic powder having a nano-composite magnet structure in which magnetic exchange coupling containing ε-Fe 2 O 3 works, which has a small particle size, adjustable magnetization and coercive force, and excellent magnetic properties with sufficient bonding between the soft phase and the hard phase and no distortion.

[0033] Hereinafter, embodiments of the present disclosure will be described. Note that the embodiments are not limited by the following description and can be appropriately changed without departing from the gist of the present disclosure.

[0034] <Composite magnetic powder> The composite magnetic powder (hereinafter also referred to as "magnetic powder") according to the embodiment has a compound of "epsilon-type iron oxide (hereinafter also referred to as ε-Fe 2 O 3 ), spinel-type iron oxide, additive element A, and additive element B" and "silicon".

[0035] Additive element A is one or more elements selected from Co and Mn. As additive element A contained in the spinel-type iron oxide, Co is desirable, and Mn may be contained instead of Co. Alternatively, as additive element A contained in the spinel-type iron oxide, both Co and Mn may be contained. At this time, the content of additive element A is preferably 1 to 30 atomic% and more preferably 3 to 20 atomic% when the total atomic% of iron, additive element A, additive element B, and additive element D in the iron oxide is 100. Additive element A may be contained in the magnetic particles in a form solid-solved in ε-Fe 2 O 3 or in the form of an oxide.

[0036] Additive element B is one or more elements selected from Zr, Hf, Cs, and Ti. Additive element B is ε-Fe 2 O3 Or it may be in a form solid-solved in a spinel-type oxide, or may be contained in the composite magnetic powder in the form of an oxide as a film or a conjugate on the surface of each magnetic particle.

[0037] The content of additive element B is preferably 1 to 15 atomic %, more preferably 2 to 10 atomic %, when the total atomic % of iron in iron oxide, additive element A, additive element B, and additive element D is 100. If the content of additive element B is 1 atomic % or more, the effect of the additive element is exhibited. Therefore, even if the heat treatment in manufacturing the composite magnetic powder according to the embodiment is performed at a low temperature, excellent magnetic properties can be exhibited in the composite magnetic powder according to the embodiment, and ε-Fe 2 O 3 can be generated. If the content of additive element B is 20 atomic % or less, an increase in the proportion of a substance having no magnetism such as the additive element can be suppressed, and thus the composite magnetic powder according to the embodiment can exhibit high magnetic properties.

[0038] Additive element D is one or more elements selected from Sm and Nd. Additive element D may be in a form solid-solved in ε-Fe 2 O 3 or a spinel-type oxide, or may be contained in the composite magnetic powder in the form of an oxide as a film or a conjugate on the surface of each magnetic particle.

[0039] The content of additive element D is preferably 0 to 10 atomic %, more preferably 2 to 5 atomic %, when the total atomic % of iron in iron oxide, additive element A, additive element B, and additive element D is 100. If the content of additive element D is 1 atomic % or more, the effect of the additive element is exhibited. Therefore, even if the heat treatment in manufacturing the composite magnetic powder according to the embodiment is performed at a low temperature, excellent magnetic properties can be exhibited in the composite magnetic powder according to the embodiment, and ε-Fe 2 O 3 can be generated. If the content of additive element D is 15 atomic % or less, an increase in the proportion of a substance having no magnetism such as additive element D can be suppressed, and thus the composite magnetic powder according to the embodiment can exhibit high magnetic properties.

[0040] The particle size of the magnetic particles according to the embodiment was measured as follows: observe an arbitrary number (for example, 300) of magnetic particles with a transmission electron microscope (TEM), consider a line parallel to a certain direction as shown in FIG. 1, measure the longest length at which the particles are cut along that line as the particle size, and the average of these is defined as the average particle size.

[0041] The magnetic properties of the composite magnetic powder according to the embodiment can be confirmed using, for example, a Physical Property Measurement System (PPMS), an automatic magnetization property measurement device (BH curve tracer), or the like.

[0042] The composite magnetic powder according to the embodiment is ε-Fe 2 O 3 and spinel-type iron oxide, and a compound other than iron oxide containing additive element A or additive element B, and contains additive element A or additive element B in a state of being dissolved in ε-Fe 2 O 3 or spinel-type iron oxide, a compound other than iron oxide, or in the form of an oxide, and contains ε-Fe 2 O 3 and spinel-type iron oxide and additive element A or additive element B in a composite state. Thereby, excellent magnetic properties with magnetic properties in which the magnetism of the hard phase and the soft phase are exchange-coupled can be exhibited.

[0043] <Manufacturing method of composite magnetic powder> The manufacturing method of the composite magnetic powder according to this embodiment will be described. The manufacturing method of the composite magnetic powder according to this embodiment is a method of heat-treating silica xerogel containing a compound containing Fe element to produce a composite magnetic powder containing ε-Fe 2 O 3 or spinel-type iron oxide, or an oxide of additive element A, additive element B, or additive element D. The spinel-type iron oxide contains cobalt and may further contain other elements such as Mn. Additive element B is any one or more elements of Zr, Hf, Cs, and Ti. Additive element D is one or more elements of Sm (samarium) and Nd (neodymium).

[0044] The method for manufacturing the composite magnetic powder of the present embodiment includes a step of adding a silicon compound to a solution containing at least one of iron nitrate, iron acetate, or iron sulfate as a first compound containing iron element, a second compound containing Co as additive element A, and a third compound containing a nitrate or acetate of additive element B to produce silica xerogel containing iron element, additive element A, and additive element B in silica, and a step of heat-treating the silica xerogel at 850 to 1250 °C for 4 to 50 hours to produce a composite magnetic powder containing epsilon-type iron oxide, spinel-type iron oxide particles, and an oxide of additive element A or additive element B. Alternatively, the method for manufacturing the composite magnetic powder of the present embodiment includes a step of adding a silicon compound to a solution containing at least one of iron nitrate, iron acetate, or iron sulfate as a first compound containing iron element, a second compound containing Co as additive element A, a third compound containing a nitrate or acetate of additive element B, and a fourth compound containing a nitrate or acetate of additive element D to produce silica xerogel containing iron element, additive element A, additive element B, and additive element D in silica, and a step of heat-treating the silica xerogel at 850 to 1250 °C for 4 to 50 hours to produce a composite magnetic powder containing epsilon-type iron oxide, spinel-type iron oxide particles, and an oxide of additive element A or additive element B.

[0045] In the method for manufacturing the composite magnetic powder of the present embodiment, a first compound containing iron element, a second compound containing Co as additive element A, and a third compound containing at least one element of Zr, Hf, Cs, and Ti as additive element B are mixed to prepare a solution containing the first compound, the second compound, and the third compound. Alternatively, in the method for manufacturing the composite magnetic powder of the present embodiment, a first compound containing iron element, a second compound containing Co as additive element A, a third compound containing at least one element of Zr, Hf, Cs, and Ti as additive element B, and a fourth compound containing at least one element of Sm and Nd as additive element D are mixed to prepare a solution containing the first compound, the second compound, the third compound, and the fourth compound. As the solution containing the first compound and the second compound, for example, an aqueous solution in which iron element and additive elements are dissolved in water can be used.

[0046] The first compound is a compound containing an iron element. As the compound containing an iron element, from the viewpoint of suppressing the formation of iron oxide (α-Fe 2 O 3 ) with an alpha-type crystal structure in the composite magnetic powder according to the embodiment, for example, iron nitrate (Fe(NO 3 ) 3 ), iron acetate (Fe(CH 3 CO 2 ) 2 ), or iron sulfate (FeSO 4 ) etc. are used. The first compound contains any one or more of iron nitrate, iron acetate, or iron sulfate. Also, as the first compound, hydrates of these compounds containing an iron element can be used.

[0047] The second compound contains Co as additive element A, and may also contain Mn. As the compound containing additive element A, for example, nitrates or acetates containing additive element A are used. Hydrates of the compounds containing additive element A can be used.

[0048] The content of additive element A in the spinel-type iron oxide is preferably 1 to 30 atomic% when the total atomic% of iron, additive element A, additive element B, and additive element D is 100, and the saturation magnetization can be controlled by the addition amount.

[0049] The third compound contains any one or more elements of Zr, Hf, Cs, and Ti as additive element B, and contains, for example, one or more nitrates or acetates containing additive element B. As the third compound, hydrates of the compounds containing additive elements can be used.

[0050] The content of added element B is preferably 1 to 15 atomic % and more preferably 1.5 to 10 atomic % when the total atomic % of iron, added element A, added element B, and added element D is 100. When the content of the added element increases, a non-magnetic substance is generated, which causes a decrease in magnetization.

[0051] The fourth compound contains at least one element selected from Sm and Nd as added element D. For example, it contains one or more nitrates or acetates containing added element D. As the fourth compound, a hydrate of a compound containing added element D can be used.

[0052] The content of added element D is preferably 0 to 10 atomic % and more preferably 1 to 5 atomic % when the total atomic % of iron, added element A, added element B, and added element D is 100. When the content of added element D increases, a non-magnetic substance is generated, which causes a decrease in magnetization.

[0053] Next, a silicon compound is added to the solution containing the first compound, the second compound, the third compound, and the fourth compound to produce silica xerogel in which the iron element and the added elements are contained, for example, in a state dispersed in silica.

[0054] Examples of the silicon compound include trimethylmethoxysilane, trimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, methyltrimethoxysilane, tetramethoxysilane, methyltriethoxysilane, tetraethoxysilane, methyldimethoxysilane, dimethylethoxysilane, dimethylvinylmethoxysilane, dimethylvinylethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, diphenyldiethoxysilane, phenyltriethoxysilane, vinyltriethoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropylmethyldichlorosilane, γ-chloropropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, etc. Among these, from the viewpoints of the reactivity between the iron element and the additive elements and the dispersibility of the iron element and the additive elements, methyltriethoxysilane or tetraethoxysilane is preferred. These silicon compounds may be used alone or in combination of two or more.

[0055] The ratio (M1 / M2) of the number of moles (M1) of the silicon element to the number of moles (M2) when the atomic percentages of the iron element and additive elements A and B combined are 100 is preferably 2 to 5, more preferably around 3.

[0056] Alcohols such as ethanol and propanol may be added to the solution containing the first compound, the second compound, the third compound, the fourth compound, and the silicon compound from the viewpoint of promoting the hydrolysis reaction of the silicon compound. Among the types of silicon compounds, there are generally silicon compounds having hydrophobicity. Therefore, when the solution containing the first compound and the second compound is an aqueous solution, it is preferable to add alcohols to the aqueous solution in order to cause a hydrolysis reaction between the silicon compound and water.

[0057] Furthermore, nitric acid may be added to the solution containing the first compound, the second compound, the third compound, the fourth compound, and the silicon compound in order to accelerate the hydrolysis reaction between the silicon compound and water. By reacting the solution containing the first compound, the second compound, the third compound, the fourth compound, the silicon compound, and nitric acid at, for example, 60 to 80°C for, for example, 4 to 6 hours while stirring, the hydrolysis reaction between the silicon compound and water can be accelerated.

[0058] By allowing the solution in which the silicon compound has been hydrolyzed to stand at about 30°C, for example, silica xerogel containing the iron element, additive element A, additive element B, and additive element D in silica is produced.

[0059] The heat treatment conditions are adjusted according to the composition of the magnetic particles, the (M1 / M2) ratio, the particle size, the desired magnetic properties, and the like. Next, the obtained silica xerogel is heat-treated in the air at 850 to 1250°C for 4 to 6 hours using, for example, an electric furnace, etc., to obtain ε-Fe 2 O 3 and a composite magnetic powder containing the additive elements is produced. Also, spinel-type iron oxide is produced at a lower temperature than ε-Fe 2 O 3 Furthermore, by heat-treating for up to 50 hours, the development of the crystal phase can be promoted.

[0060] When the heat treatment temperature is less than 850°C, ε-Fe 2 O 3 is not sufficiently produced, and when the heat treatment temperature exceeds 1200°C, the production amount of the α-Fe 2 O 3 phase increases.

[0061] When the heat treatment time is less than 4 hours, ε-Fe 2 O 3 sufficient to exhibit excellent magnetic properties may not be sufficiently produced in the composite magnetic powder according to the embodiment, and when the heat treatment time exceeds 6 hours, ε-Fe 2 O 3Although the production amount of spinel-type iron oxide may not change much, in terms of crystal development, it is possible to control magnetic properties such as coercive force over time.

[0062] Next, in order to remove or reduce the silica remaining around the composite magnetic powder due to silica xerogel, the remaining silica may be dissolved and removed using an alkaline aqueous solution containing sodium hydroxide, potassium hydroxide, etc. At this time, a non-magnetic layer may be left on the surface of the magnetic particles to achieve magnetic isolation. This is because when magnetically isolated magnetic particles are finer than the single-domain particle diameter and have a particle diameter about five times the exchange coupling length, the magnetization reversal follows the Stoner·Wallfarth model by the aligned rotation of spins, and the coercive force is given by the anisotropy magnetic field of the ferromagnetic phase = 2K1 / (saturation magnetization), so the coercive force increases. K1 is the anisotropy energy constant of the magnet phase.

[0063] The composite magnetic powder according to the embodiment thus obtained contains ε-Fe 2 O 3 and spinel-type iron oxide, additive element A, and additive element B, and the additive elements are included in the form of being dissolved in ε-Fe 2 O 3 or spinel-type iron oxide or in the form of an oxide, and contains ε-Fe 2 O 3 and spinel-type iron oxide, additive element A, additive element B, and additive element D in a composite state. As a result, excellent magnetic properties with magnetic properties in which the magnetism of the hard phase and the soft phase are exchange-coupled can be exhibited, so it can be suitably used as a magnetic material such as a high-density magnetic recording medium.

[0064] Examples of high-density magnetic recording media include magnetic tapes, which are particularly tape-shaped. The manufacturing method is generally as follows, but is not particularly limited. A magnetic layer is formed on one side of a film, cut, wound around a bobbin called a reel, and attached to a plastic container or the like. The magnetic layer is formed by coating, vapor deposition, sputtering, etc., and is formed on one side or both sides. The basic structure of the magnetic tape consists of a base film, which is the base of the tape, and a magnetic layer in which magnetic powder is mixed with a binder (adhesive) or the like. When coating, the magnetic powder is mixed with an adhesive or sticky substance and applied to the base film.

[0065] Furthermore, the magnetic layer in the form of a film or bulk using this magnetic powder can be applied as a radio wave absorber, and a magnetic iron oxide that resonates magnetically in a high-frequency band of millimeter waves or higher is provided as a radio wave absorption material in the radio wave absorption layer, so that radio waves in a high-frequency band of dozens of gigahertz or higher can be converted into heat by magnetic loss. In addition, it can correspond to a wide range of radio waves in combination with a conventional radio wave absorber corresponding to frequencies below millimeter waves. The manufacturing method of the radio wave absorption layer generally involves mixing a resin binder and magnetic particles and molding them into a film or bulk form, or molding only the magnetic particles and then manufacturing a bulk body nanocrystallized by a pulse current pressure sintering device or the like, but is not particularly limited.

[0066] This magnetic powder can form a permanent magnet material by being mixed with a resin. The manufacturing method involves kneading the magnetic powder and a resin binder, further dispersing the magnetic particles, and then performing molding and processing, but is not particularly limited. These can be made into bonded magnets that can be used in small motors used in AV equipment, OA equipment, automotive electrical components, etc., and magnet rolls of copiers. Alternatively, a bulk body nanocrystallized by a pulse current pressure sintering device or the like can be manufactured after molding only the magnetic particles, but is not particularly limited. Thereby, it can be made into a sintered body permanent magnet material.

[0067] This magnetic powder is considered to be usable as a biomolecule labeling agent, drug carrier, etc. that utilize magnetic properties by combining magnetic particles and biomolecules. Magnetic particles are materials that move when a magnetic force is applied from the outside. Also, nanosized magnetic particles can be absorbed in the body and can be used as carriers for drug delivery systems (DDS) that introduce complexes of genes and drugs into cells. For example, in order to examine whether the function of a target protein remains ineffective or becomes effective due to the action of a drug, it is necessary to extract the target protein from among many proteins. As a method for extracting it, a drug is immobilized around magnetic particles to lift the standard protein. The production methods of these biomolecule labeling agents and drug carriers are not particularly limited, but for example, in the case of the emulsion polymerization method, monomer, emulsifier, polymerization initiator, magnetic particles, and water are used for mixing and dispersion, polymerization is initiated, and after producing a polymer dispersion liquid encapsulating the magnetic particles, genes and drugs are immobilized on its surface.

Example

[0068] Hereinafter, examples and comparative examples will be shown to more specifically explain the embodiments, but the embodiments are not limited by these examples.

[0069] <Examples 1 to 8> [Preparation of Magnetic Powder] In Example 1, 14.54 g of iron(III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) was dissolved in water, and then 0.93 g of cobalt(II) nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O) as the second compound and zirconium oxynitrate (dihydrate) ZrO(NO 3 ) 2 ·2H 20.21 g of O was added to an aqueous solution in which iron(III) nitrate nonahydrate was dissolved and dissolved. Then, the obtained aqueous solution and tetraethyl orthosilicate (TEOS) were mixed in ethanol. Nitric acid was added to this solution, and after stirring at 40 °C for 2 hours, it was dried at 50 °C. As a result, silica gel in which iron elements and compounds of cobalt and zirconium were dispersed in silica was produced. Next, this silica gel was heat-treated at about 1150 °C to produce a composite magnetic powder containing iron oxide and cobalt and zirconium. The silica remaining around the composite magnetic powder was put into a 5N aqueous sodium hydroxide solution, and then the aqueous sodium hydroxide solution was heated to 70 °C and allowed to stand for 24 hours to remove the silica. Thereafter, the composite magnetic powder was washed by repeating ultrasonic dispersion in water and ethanol and solid-liquid separation by a centrifuge. In addition, Examples 2 to 8 were synthesized by the same operation except that the amounts of iron(III) nitrate nonahydrate and cobalt(II) nitrate hexahydrate were changed as shown in Table 1 so that cobalt as additive element A was adjusted to be from 3% to 20%.

[0070] <Comparative Examples 1 to 6> In Comparative Example 1 corresponding to Example 2, Comparative Example 2 corresponding to Example 3, Comparative Example 3 corresponding to Example 1, Comparative Example 5 corresponding to Example 5, and Comparative Example 6 corresponding to Example 8, zirconium dinitrate oxide (dihydrate) was not added. In Comparative Example 4 corresponding to Example 1, zirconium dinitrate oxide (dihydrate) was not added, and further the heat treatment temperature was set to 1200 °C, and magnetic particles were synthesized in the same manner for subsequent operations.

[0071] [Evaluation] The average particle diameter, crystallinity, and magnetic properties of the composite magnetic powder after silica removal were evaluated. (Measurement of Average Particle Diameter) The particle size of the magnetic particles according to the embodiment was measured as follows: Observe an arbitrary number (for example, 300) of magnetic particles with a transmission electron microscope (TEM). Consider a line parallel to a certain direction as shown in Fig. 1, and measure the longest length along which the particles are cut along that line as the particle size. The average of these measured values was taken as the average particle size. By measuring in a certain direction, the difference in particle size due to the difference in the measurement direction occurring in rod-shaped particles can be ignored by measuring a large number of particles. As shown in Fig. 2 and Table 1, the average particle size of the composite magnetic powder after silica removal was 5 to 40 nm, and the shape of the particles was spherical or slightly cylindrical. As shown in Fig. 3, the particle size decreased as the cobalt content increased. The particle size can be controlled by the cobalt content. Also, although not yet identified, as shown in Fig. 4, a thin phase that joins the particles between the particles was observed. The obtained composite magnetic powder after silica removal was subjected to XRD using an XRD apparatus (Empyrean manufactured by PANalytical). Fig. 5 shows the XRD measurement results of the composite magnetic powder obtained at each heat treatment temperature. For X-ray diffraction, Co-Kα rays were used as the X-ray source. Note that the XRD peaks of ε-Fe 2 O 3 are 32.3°, 35.0°, 38.3°, 41.1°, 42.7°, 46.0°, 47.1°, 48.5°, 53.6°, 55.1°, 57.6°. The XRD peaks of spinel-type iron oxide are 21.3°, 35.2°, 41.5°, 43.4°, 50.6°. As the cobalt content increased, the ε-iron oxide phase decreased and the cobalt ferrite phase increased. At a cobalt content of 20%, almost only a very small amount of the ε-iron oxide phase was observed, and it was almost a cobalt ferrite phase. (Confirmation of Magnetic Properties) The magnetic properties of the obtained composite magnetic powder after silica removal were measured by PPMS. As magnetic properties, coercive force and saturation magnetization were measured. The measurement results of the magnetic properties of the composite magnetic powder are shown in FIGS. 6 and 7. FIG. 6 shows the magnetic curves of Examples 1 to 6, which are magnetic curves without distortion. On the other hand, FIG. 7 shows the magnetic curves of Comparative Examples 1 to 4. Distortion is observed. To show these clearly, FIGS. 8 and 9 show the curves obtained by differentiating the magnetic curves of Example 4 or Comparative Example 3. As can be seen from these results, there is no peak in Example 4 of FIG. 8, and a peak that is an inflection point is observed in Comparative Example 3 of FIG. 9. FIG. 10 shows the relationship between the cobalt amount and the magnetic properties of Examples 1 to 8. As the cobalt amount increased, the saturation magnetization increased and the coercive force gradually decreased. Thus, the saturation magnetization and the coercive force can be controlled by the cobalt amount. FIG. 11 shows the relationship between the particle size and the magnetic properties of Examples 1 to 8. As the particle size increased, the saturation magnetization decreased and the coercive force increased.

[0072] <Examples 9 to 29> In Example 9, 14.38 g of iron(III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) was dissolved in water, and then 0.93 g of cobalt(II) nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O) as the second compound and zirconium oxynitrate (dihydrate) ZrO(NO 3 ) 2 ·2H 20.32 g of O was added to an aqueous solution in which iron(III) nitrate nonahydrate was dissolved and dissolved. Then, the obtained aqueous solution and tetraethyl orthosilicate (TEOS) were mixed in ethanol. Nitric acid was added to this solution, and after stirring at 40 °C for 2 hours, it was dried at 50 °C. Thereby, silica gel in which iron element and compounds of cobalt and zirconium were dispersed in silica was produced. Next, this silica gel was heat-treated at about 1150 °C to produce a composite magnetic powder containing iron oxide and cobalt and zirconium. The silica remaining around the composite magnetic powder was put into a 5N aqueous sodium hydroxide solution, and then the aqueous sodium hydroxide solution was heated to 70 °C and allowed to stand for 24 hours to remove the silica. Thereafter, the composite magnetic powder was washed by repeating dispersion by ultrasonic waves in water and ethanol and solid-liquid separation by a centrifuge. Examples 10 to 27 were synthesized by the same operation except that the amounts of iron(III) nitrate nonahydrate, cobalt(II) nitrate hexahydrate, and zirconium oxynitrate (dihydrate) were changed. Figure 12 is an X-ray diffraction spectrum of the composite magnetic powders of Example 1, Example 9, Example 17, Example 25, and Example 27. Peaks of ε-iron oxide and spinel-type cobalt iron oxide are observed respectively. Regardless of the amount of zirconium, each peak appears at the same angle without shifting, indicating that zirconium doping has little effect. Figure 13 is a TEM photograph of Example 18 and a mapping diagram showing the abundance of each element (O, Si, Fe, Co, Zr). In the parts circled in the iron display and cobalt display figures, areas with less cobalt and more iron, and areas with both cobalt and iron being abundant are observed, indicating that the composition is non-uniform. Also, in the part circled in the zirconium display figure, zirconium is abundant, and it was found that iron is less in the iron display figure of that part.

[0073] <Example 28> In this Example 28, 14.06 g of iron(III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) was dissolved in water, and then cobalt(II) nitrate hexahydrate (Co(NO 3 )2 ·6H 2 O) 0.93 g, and hafnium chloride (HfCl 4 ) 0.64 g were added to an aqueous solution in which iron(III) nitrate nonahydrate was dissolved and dissolved. Then, the obtained aqueous solution and tetraethyl orthosilicate (TEOS) were mixed in ethanol. Nitric acid was added to this solution, and after stirring at 40 °C for 2 hours, it was dried at 50 °C. As a result, silica gel in which iron element and compounds of cobalt and hafnium were dispersed in silica was produced. Next, this silica gel was heat-treated at about 1150 °C to produce a composite magnetic powder containing iron oxide, cobalt, and hafnium. The silica remaining around the composite magnetic powder was put into a 5N aqueous sodium hydroxide solution, and the silica was removed by leaving the aqueous sodium hydroxide solution at 70 °C for 24 hours. Then, the composite magnetic powder was washed by repeating dispersion by ultrasonic waves in water and ethanol and solid-liquid separation by a centrifuge.

[0074] <Example 29> In this Example 29, 14.06 g of iron(III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) was dissolved in water, and then 0.93 g of cobalt(II) nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O) as the second compound and cesium nitrate (CsNO 30.39 g of was added to an aqueous solution in which iron(III) nitrate nonahydrate was dissolved and dissolved. Thereafter, the obtained aqueous solution and tetraethyl orthosilicate (TEOS) were mixed in ethanol. Nitric acid was added to this solution, and after stirring at 40 °C for 2 hours, it was dried at 50 °C. Thereby, silica gel in which iron element and compounds of cobalt and cesium were dispersed in silica was produced. Next, this silica gel was heat-treated at about 1150 °C to produce a composite magnetic powder containing iron oxide and cobalt and cesium. The silica remaining around the composite magnetic powder was put into a 5N aqueous sodium hydroxide solution, and then the aqueous sodium hydroxide solution was heated to 70 °C and allowed to stand for 24 hours to remove the silica. Thereafter, the composite magnetic powder was washed by repeating dispersion by ultrasonic waves in water and ethanol and solid-liquid separation by a centrifuge.

[0075] <Examples 30 to 31> In Example 30, in Example 16, and in Example 31, in Example 18, instead of zirconium oxynitrate (dihydrate), titanium isopropoxide ([(CH 3 ) 2 CHO] 4 Ti) was used, and the subsequent operations were carried out in the same manner to synthesize a magnetic powder.

[0076] <Comparative Example 7> In Example 18, instead of zirconium oxynitrate (dihydrate), aluminum nitrate nonahydrate (Al(NO 3 ) 3 ·9H 2 O) was used, and the subsequent operations were carried out in the same manner to synthesize a magnetic powder.

[0077] The TEM photograph of Comparative Example 9 is shown in Fig. 14. The particles are a mixture of particles from 5 nm to 50 nm. The X-ray diffraction spectrum of the magnetic powder of Comparative Example 9 is shown in Fig. 15. The ε-iron oxide phase and the cobalt ferrite phase are observed. The magnetic curve of Comparative Example 9 is shown in Fig. 16. It has a saturation magnetization of 43.3 emu / g and a coercive force of 3.4 kOe, but distortion is seen in the curve. The curve obtained by differentiating the magnetic curve of Comparative Example 9 is shown in Fig. 17. Since a peak indicating an inflection point is observed, the exchange coupling is not working sufficiently.

[0078] The ratios of the elements used in each of the above Examples and Comparative Examples, the particle diameters, the crystal phases confirmed by XRD, the saturation magnetization of the magnetic powder, the magnetization after reaching saturation in the magnetic hysteresis and then setting the magnetic field to zero (residual magnetization), residual magnetization / saturation magnetization (square ratio), coercive force, heat treatment conditions, and the presence or absence of distortion of the magnetic curve are shown in Table 1. In magnetic recording as well as in permanent magnets, the closer the square ratio is to 1, the better.

[0079]

Table 1

[0080] From this table, it was found that in the Examples, the average particle diameter was 30 nm or less and the crystal phase was ε-iron oxide or ferrite of the spinel phase. In both the Examples and Comparative Examples, when the cobalt amount was increased, the saturation magnetization and residual magnetization increased regardless of the zirconia amount, and the coercive force decreased. Also, with the increase in the cobalt amount, the spinel phase increased in the crystal phase. The particle diameter of the Comparative Examples was 20 nm or less.

[0081] <Examples 32 and 33> In Example 32, 13.25 g of iron(III) nitrate nonahydrate (Fe(NO 3 ) 3 ·9H 2 O) was dissolved in water, and then 1.63 g of cobalt(II) nitrate hexahydrate (Co(NO 3 ) 2 ·6H 2 O) as the second compound, 0.22 g of zirconium oxynitrate (dihydrate) ZrO(NO 3 ) 2 ·2H 2 O as the third compound, and 0.22 g of samarium(III) nitrate hexahydrate (Sm(NO 3 ) 2 ·6H 2 O as the fourth compound were added to the aqueous solution in which the iron(III) nitrate nonahydrate was dissolved and dissolved. The subsequent operations were the same as in Example 1 to synthesize the magnetic powder. Regarding Example 33 as well, the raw materials were added and dissolved in amounts corresponding to the compositions shown in Table 2 below, and the subsequent operations were the same as in Example 1 to synthesize the magnetic powder.

[0082] <Examples 34 to 37> In Example 34, 14.06 g of iron(III) nitrate nonahydrate (Fe(NO 3 )) 3 ·9H 2 O) was dissolved in water, and then 0.93 g of cobalt(II) nitrate hexahydrate (Co(NO 3 )) 2 ·6H 2 O) as the second compound, 0.21 g of zirconium oxynitrate (dihydrate) ZrO(NO 3 )) 2 ·2H 2 O as the third compound, and 0.21 g of neodymium(III) nitrate hexahydrate Nd(NO 3 )) 2 ·6H 2 O were added to the aqueous solution in which iron(III) nitrate nonahydrate was dissolved and dissolved. The subsequent operations were the same as in Example 1 to synthesize magnetic powder. Regarding Examples 35 to 37, raw materials were added and dissolved in amounts according to the compositions shown in Table 2, and the subsequent operations were the same as in Example 1 to synthesize magnetic powder.

[0083] Also, FIG. 18 shows the X-ray diffraction spectra of the composite magnetic powders of Example 33, Example 36, and Example 37. From the X-ray diffraction spectra shown in FIG. 18, it was found that the cobalt ferrite phase occupied a large part and the ε-iron oxide phase was contained from the peak at 38.3°. Also, it was confirmed that no peak of samarium oxide or neodymium oxide appeared near 36°. Regarding the magnetic powders obtained in Examples 32 to 37, the elemental ratios, particle diameters, crystal phases confirmed by XRD, saturation magnetization of the magnetic powders, magnetization when the magnetic field was set to zero after reaching saturation in magnetic hysteresis (residual magnetization), residual magnetization / saturation magnetization (square ratio), coercive force, heat treatment conditions, and the presence or absence of distortion of the magnetic curve are shown in Table 2.

[0084]

Table 2

[0085] From the results of Examples 32 to 37 shown in Table 2, it was found that by adding the additive element D, ferrite with an average particle size of 30 nm or less and a crystal phase of ε-iron oxide or spinel phase can be synthesized at a lower heat treatment temperature than in other examples without adding the additive element D.

[0086] Under the heat treatment conditions of raising the temperature to 1150 °C at a heating rate of 10 °C / min and holding this for 6 hours, when changing cobalt from 3% to 20% in the case of 2% zirconium (Examples 1 to 8), the particle size changes from 26.7 nm to 14.5 nm. At this time, the crystal phase was composed of the ε-phase and the spinel phase. The magnetic properties can have the saturation magnetization changed from 23.6 emu / g to 71.4 emu / g, and the coercive force can be changed from 8.8 kOe to 2.4 kOe according to the saturation magnetization. Also, the squareness ratio obtained by dividing the residual magnetization by the saturation magnetization decreased from 3% to 14% of the cobalt amount, but increased slightly to 0.42 above that. Also, the squareness ratio at the same cobalt amount for Examples 1 to 4 and Comparative Examples 1 to 3 and 5 was a larger value for the examples compared to the comparative examples. When comparing Examples 1 to 8 with the conditions of adding the same additive element A without adding any additive element B (Comparative Examples 1 to 6), although the saturation magnetization of the examples is small, the coercive force is larger, and the coercive force is 2.1 kOe or more. Furthermore, no distortion is seen in the magnetic loop curve in the examples. This indicates that it is a composite magnetic powder having a nanocomposite magnet structure in which magnetic exchange coupling acts. On the other hand, Comparative Examples 1 to 5 have distortion in the magnetic loop curve, and although no distortion was seen in the magnetic loop curve of Comparative Example 6, its coercive force is only 1.5 kOe.

[0087] Next, also in the case where the zirconium amount is 3% (Examples 9 to 13), for the samples heated at 1150 °C for 6 hours, the squareness ratio decreased as the cobalt amount increased. Also, the saturation magnetization changed from 23.2 emu / g to 53.6 emu / g, and the coercive force changed from 6.8 kOe to 3.5 kOe.

[0088] When the zirconium content is 5% (Examples 14 to 22), for the samples heated at 1150 °C for 6 hours, although the particle sizes of some were not measured, they could be changed from 19.0 nm with 8% cobalt to 11.4 nm with 20% cobalt. As the cobalt content increased, the magnetic properties changed such that the saturation magnetization changed from 17.3 emu / g to 69.2 emu / g, and the coercive force could be changed from 4.3 kOe to 2.7 kOe according to the saturation magnetization. Furthermore, due to different heat treatment conditions as in Examples 14 and 15, even though the squareness ratio was the same, the coercive force differed greatly, such as from 4.3 kOe to 15.5 kOe.

[0089] Even when the zirconium content was 8% or 10%, with 8% cobalt content, the saturation magnetization was 36.3 emu / g and 35.5 emu / g respectively, and the coercive force was 3.9 kOe for both. In the examples, when comparing examples with the same 8% cobalt content but different zirconium contents, in Example 24 with 5% zirconium, the squareness ratio was the largest, reaching 0.44.

[0090] Furthermore, the magnetic properties can also be adjusted by the heat treatment temperature and heat treatment time. Even when using hafnium, cesium, and titanium instead of zirconium, those with a magnetic loop curve without distortion were obtained. On the other hand, when aluminum was added, there was distortion. Also, by changing the amount of additive element A, changing the type and amount of additive element B, and controlling the heat treatment conditions, composite magnetic powders with various saturation magnetizations and coercive forces can be obtained.

[0091] As described above, the present disclosure has been specifically described with reference to the embodiments and experimental examples. However, the present disclosure is not limited to the above embodiments and the like, and various modifications are possible.

[0092] For example, the configurations, methods, processes, shapes, materials, numerical values, etc. cited in the above-described embodiments and experimental examples are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used as necessary. Specifically, the magnetic recording medium of the present disclosure may include components other than the substrate, underlayer, magnetic layer, back layer, and barrier layer. Further, chemical formulas such as compounds are representative, and if they are common names of the same compound, they are not limited to the valences, etc. described.

[0093] In addition, the configurations, methods, processes, shapes, materials, numerical values, etc. of the above-described embodiments and experimental examples can be combined with each other as long as they do not deviate from the gist of the present disclosure.

[0094] Further, the present technology can adopt the following configurations. (1) Iron oxide, an additive element A which is one or more elements among Co (cobalt) and Mn (manganese), and an additive element B which is one or more elements among Zr (zirconium), Hf (hafnium), Cs (cesium), and Ti (titanium) and a composite magnetic powder. (2) The content of the additive element A is 1 to 30 atomic% when the total atomic% of iron in the iron oxide, the additive element A, and the additive element B is 100, and the content of the additive element B is 1 to 15 atomic% when the total atomic% of iron in the iron oxide, the additive element A, and the additive element B is 100. The composite magnetic powder according to (1) above. (3) further includes an additive element D which is one or more elements among Sm and Nd, the content of the additive element A is 1 to 30 atomic% when the total atomic% of iron in the iron oxide, the additive element A, the additive element B, and the additive element D is 100, The content of the additive element B is 1 to 15 atomic% when the total atomic% of iron in the iron oxide, the additive element A, the additive element B, and the additive element D is 100, The content of the additive element D is 0 to 10 atomic% when the total atomic% of iron in the iron oxide, the additive element A, the additive element B, and the additive element D is 100. The composite magnetic powder according to (1) above. (4) The iron oxide consists of spinel-type iron oxide. The composite magnetic powder according to any one of (1) to (3) above. (5) The iron oxide consists of epsilon-type iron oxide and spinel-type iron oxide. The composite magnetic powder according to any one of (1) to (3) above. (6) The iron oxide consists of spinel-type iron oxide and a conjugate. The composite magnetic powder according to any one of (1) to (3) above. (7) The iron oxide consists of epsilon-type iron oxide, spinel-type iron oxide, and a conjugate. The composite magnetic powder according to any one of (1) to (3) above. (8) The conjugate is an oxide containing Zr, Hf, Cs, and Ti or a silicate oxide containing Zr, Hf, Cs, and Ti. The composite magnetic powder according to (6) or (7) above. (9) A method for producing the composite magnetic powder according to any one of (1) to (8) above, After mixing a first compound containing an iron element, which contains one or more of iron nitrate, iron acetate, and iron sulfate, a second compound containing Co as the additive element A, and a third compound containing one or more elements of Zr, Hf, Cs, and Ti as the additive element B to form a mixture, adding a silicon compound to the mixture to form a silica xerogel containing the iron element, the additive element A, and the additive element B in silica, Heat-treat the silica xerogel at 850°C to 1250°C for 4 hours to 50 hours to produce a composite magnetic powder containing epsilon-type iron oxide, the additive element A, and the additive element B, or, mix a first compound containing iron element, which contains one or more of iron nitrate, iron acetate, and iron sulfate, a second compound containing Co as the additive element A, a third compound containing one or more elements of Zr, Hf, Cs, and Ti as the additive element B, and a fourth compound containing one or more elements of Sm and Nd as the additive element D to produce a mixture, and then add a silicon compound to the mixture to produce a silica xerogel containing the iron element, the additive element A, the additive element B, and the additive element D in silica, heat-treat the silica xerogel at 850°C to 1250°C for 4 hours to 50 hours to produce a composite magnetic powder containing epsilon-type iron oxide, the additive element A, the additive element B, and the additive element D, A method for manufacturing a composite magnetic powder comprising the above. (10) A magnetic material having the composite magnetic powder according to any one of (1) to (8) above. (11) A high-density magnetic recording medium having the composite magnetic powder according to any one of (1) to (8) above. (12) The high-density magnetic recording medium according to (11) above, which is in tape form. (13) A film-like or bulk radio wave absorber containing the magnetic material according to (10) above. (14) A film-like or bulk permanent magnet material containing the magnetic material according to (10) above. (15) A biomolecule labeling agent combined with the composite magnetic powder according to any one of (1) to (8) above and a biomolecule.

[0095] The magnetic material according to the present disclosure is useful for high-density magnetic recording medium applications because even if it is composed of fine particles, it has a large coercive force. The basic structure of the magnetic tape consists of a base film that is the base of the tape and a magnetic layer in which magnetic particles are mixed with a binder (adhesive) or the like. It is a coating obtained by mixing magnetic powder with an adhesive substance and applying it to the base film. The magnetic particles according to the present disclosure can be used regardless of the tape manufacturing method. Furthermore, since the magnetic material according to the present disclosure is an oxide, it has stability as a material, and the coercive force can be controlled by the Si / (Fe + addition) molar ratio, heat treatment conditions, etc. Therefore, it is considered that it can be used for a film-like or bulk radio wave absorber obtained by mixing magnetic particles with a binder, a permanent magnet material, a carrier for a biomolecule labeling agent or a drug that utilizes magnetic properties by combining magnetic particles and biomolecules.

[0096] This application claims priority based on Japanese Patent Application No. 2020-007833, filed on January 21, 2020, with the Japan Patent Office, and all the contents of this application are incorporated herein by reference.

[0097] Those skilled in the art can conceive various modifications, combinations, sub-combinations, and changes according to design requirements and other factors, but it is understood that they are included within the scope of the appended claims and their equivalents.

Claims

1. Epsilon-type iron oxide and spinel-type iron oxide, an additive element A which is one or more elements among Co (cobalt) and Mn (manganese), an additive element B which is one or more elements among Zr (zirconium), Hf (hafnium) and Cs (cesium), and a composite magnetic powder having a nanocomposite magnet structure.

2. The content of the additive element A is 1 to 30 atomic% when the total atomic% of iron in the iron oxide, the additive element A and the additive element B is 100, and the content of the additive element B is 1 to 15 atomic% when the total atomic% of iron in the iron oxide, the additive element A and the additive element B is 100. The composite magnetic powder according to Claim 1.

3. further comprising an additive element D which is one or more elements among Sm and Nd, the content of the additive element A is 1 to 30 atomic% when the total atomic% of iron in the iron oxide, the additive element A, the additive element B and the additive element D is 100, the content of the additive element B is 1 to 15 atomic% when the total atomic% of iron in the iron oxide, the additive element A, the additive element B and the additive element D is 100, and the content of the additive element D is 1 to 10 atomic% when the total atomic% of iron in the iron oxide, the additive element A, the additive element B and the additive element D is 100. The composite magnetic powder according to Claim 1.

4. A method for producing the composite magnetic powder according to any one of Claims 1 to 3, comprising: mixing a first compound containing iron element, which contains one or more of iron nitrate, iron acetate and iron sulfate, a second compound containing Co as the additive element A, and a third compound containing one or more elements among Zr, Hf and Cs as the additive element B to form a mixture, and then adding a silicon compound to the mixture to form a silica xerogel containing the iron element, the additive element A and the additive element B in silica; heat-treating the silica xerogel at 850°C to 1250°C for 4 hours to 50 hours to form a composite magnetic powder containing epsilon-type iron oxide, the additive element A and the additive element B; and or A first compound containing iron element and containing one or more of iron nitrate, iron acetate and iron sulfate, a second compound containing Co as the additive element A, and a third compound containing one or more elements of Zr, Hf and Cs as the additive element B, and a fourth compound containing one or more elements of Sm and Nd as the additive element D are mixed to form a mixture, and then a silicon compound is added to the mixture to form a silica xerogel containing the iron element, the additive element A, the additive element B and the additive element D in silica. The silica xerogel is heat-treated at 850 °C to 1250 °C for 4 hours to 50 hours to produce a composite magnetic powder containing epsilon-type iron oxide, the additive element A, the additive element B and the additive element D. A method for manufacturing a composite magnetic powder including the above.

5. A magnetic material having the composite magnetic powder according to any one of Claims 1 to 3.

6. A high-density magnetic recording medium having the composite magnetic powder according to any one of Claims 1 to 3.

7. The high-density magnetic recording medium according to Claim 6, which is in tape form.

8. A film-like or bulk radio wave absorber containing the magnetic material according to Claim 5.

9. A film-like or bulk permanent magnet material containing the magnetic material according to Claim 5.

10. A biomolecule labeling agent obtained by combining the composite magnetic powder according to any one of Claims 1 to 3 with a biomolecule.

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