JP4858941B2 - Method for manufacturing magnetic material - Google Patents

Description

The present invention relates to a process for producing a magnetic material is effectively used in electronic components and electronic equipment.

Ferrite, which is a general term for magnetic oxides mainly composed of Fe ₂ O ₃ , has a characteristic that the crystal structure and magnetic properties vary greatly depending on the composition and manufacturing method. At present, such properties are utilized. In addition to permanent magnets and electromagnetic wave absorbing materials, they are already widely used as magnetic core materials and magnetic recording materials.
In recent years, the importance of ferrite materials has further increased. For example, (1) With the development of information communication technology, ferrite as a perpendicular magnetic recording material capable of high-density perpendicular magnetic recording exceeding 100 Gbit / inch ² can be used. In addition, (2) In view of the fact that the frequency of use is increasing due to the miniaturization and high density of equipment accompanying the development of power electronics technology, it has high electrical resistivity in addition to magnetic characteristics for use in a higher frequency range. Ferrite is desired.
In particular, magnetic materials used for switching power supplies and other transformer cores are urgently required to cope with higher frequencies, and low loss at high frequencies is strongly required to prevent heat generation when downsized. It has been.

Here, generally, a transformer magnetic core material is roughly divided into an oxide ferrite material and a metal material. However, metal materials have the advantage that both the saturation magnetic flux density B _s and the magnetic permeability μ are high, while the electrical resistivity ρ is as low as about 10 ⁻⁶ to 10 ⁻⁴ Ω · cm. There was a drawback that loss was increased.

  Ferrite materials, on the other hand, have a saturation magnetic flux density that is only about 1/2 that of metal materials, but the electrical resistivity ρ is about 1 Ω · cm for MnZn materials that are usually used, compared to metal materials. High values can be obtained. Therefore, eddy current loss is small, (1) it can be used up to relatively high frequencies without any special measures, (2) it can be easily made in a complicated shape, and (3) it is low in cost. . Therefore, this ferrite-based material is often used as a transformer magnetic core material generally used for a switching power supply or the like that handles a high switching frequency.

However, even when such a ferrite-based material is used at a high frequency of the order of MHz or higher, there is a problem in that the electric resistance is not sufficient, and eddy current loss increases to generate heat. Therefore, a material having an electrical resistivity increased to about 10 to 100 Ω · cm by adding CaO or SiO ₂ has been produced (see Patent Document 1). However, such an additive reacts with the ferrite itself. Even if the magnetic characteristics are deteriorated and the eddy current loss is reduced to some extent, the hysteresis loss is increased. As a result, there is a problem that the total loss is not reduced so much.
In addition, NiZn ferrite having a higher electric resistance than that of MnZn, and Mg ferrite made of MgFe ₂ O _{4 having} a higher electric resistance than that have already been developed (see Non-Patent Document 1). Nevertheless, there is a problem that sufficient performance cannot be obtained when the device is operated at a high frequency on the order of MHz. In addition, in order to make ferrite more practical material, a study has been reported in which part of Fe of Li—Zn—Cu ferrite is replaced with Mn to improve electric resistance (see Non-Patent Document 2). However, this was not sufficient theoretically and performance.

By the way, the molecular formula of ferrite is generally expressed as MO · Fe ₂ O ₃ (M is a divalent metal ion). This group of substances is called spinel ferrite because it has the same crystal structure as the mineral spinel (MgO.Al ₂ O ₃ ). Spinel type ferrite forms a unit cell with 8 [MFe ₂ O ₄ ] molecules and has a crystal structure as shown in FIG. Here, the unit cell contains 24 metal ions and 32 oxygen ions. There are two types of positions where metal ions enter, A and B. There are eight A positions, and they are tetrahedrally surrounded by four adjacent oxygen ions O ²⁻ , and are referred to as 8a points or tetrahedral positions. Also, there are 16 B positions, and they are octahedrally surrounded by six adjacent oxygen ions O ²⁻ , and are called 16d points or octahedral positions.
In this case, there are three ways of entering metal ions, M is called a normal spinel entering the A position, M is called a reverse spinel entering the B position, and it belongs to an intermediate between the normal spinel and the reverse spinel. There is something. That is, the positive spinel has ^{M 2+} ions whole A position, ^{which Fe 3+} ions enter the whole B ^position, represented by ^{_{M 2+ [Fe 3+ 2] O}} 2- 4. In the reverse spinel type, all M ²⁺ ions enter the B position, and half of the Fe ³⁺ ions enter the A position and the B position, and are represented by Fe ³⁺ [Fe ³⁺ M ²⁺ ] O ²⁻ ₄ . Further, the intermediate of the normal spinel and the reverse spinel is one in which M is distributed to both the A position and the B position, and the MgFe ₂ O ₄ belongs to it.

As described above, since various combinations of spinel ferrite can be realized by mixing raw materials, it is possible to create a magnetic material having a very varied composition. Among them, MgFe ₂ O ₄ is known as a relatively high electric resistance among soft magnetic spinel ferrites.
However, even though there are various combinations, in the high frequency region of the MHz order, in addition to the magnetic properties of permeability μ and magnetization σ _s , the electrical resistivity ρ is sufficiently high to reduce high frequency loss, particularly iron loss. Effective ferrites with excellent magnetic and electrical properties have not been satisfactorily provided until now.
JP-A-1-234357 Takei Take, “Theory and Application of Ferrite”, Maruzen, p. 44-48 (1960) T.A. Murase, T .; Aoki, H .; Umeda, Abs. Spring Meeting J.M. Jpn. Soc. Powder & Powder Metallurgy, p. 108 (2004)

Accordingly, the present invention is to solve the above problems, the permeability μ at the high frequency band, the magnetization sigma _s and the electrical resistivity ρ is higher, and an object thereof is to provide a manufacturing method of iron loss even less magnetic material.

As a result of repeating various studies to solve the above problems, the present inventor added Mn to the Fe site of Mg ferrite composed of MgFe ₂ O ₄ exhibiting relatively high electrical resistance among soft magnetic spinel ferrites. That is, it was found that further improvement of the electrical resistivity ρ and other characteristics can be expected by substituting part of Fe of MgFe ₂ O ₄ with Mn, and the present invention was completed.

The method for producing the ferrite magnetic material of the present invention capable of solving the above problems is as follows : ( 1 ) at least the general formula Mg (Fe _1-x Mn _x ) ₂ O ₄ (x is the solid solution amount of Mn, 0 <x ≦ 0.4), a method for producing a spinel ferrite magnetic material in which a part of Fe of MgFe ₂ O ₄ ferrite is substituted with Mn,
A step of preparing a mixed aqueous solution by dissolving starting materials composed of nitrates of Mg, Fe, and Mn in distilled water;
Adding citric acid and ethylene glycol to the mixed aqueous solution to prepare a metal-citrate complex;
A step of obtaining a precursor by heating and stirring the metal-citric acid complex until gelled, and then drying;
A step of obtaining a calcined powder from the precursor by heat-treating after pulverizing the precursor;
After sizing the calcined powder, a step of pressure molding to produce a molded body, and
Sinter the molded body to produce a sintered body;
Consists of
The precursor is heated and stirred with the metal-citrate complex at a temperature of 80 ° C. to 120 ° C. and 2 hours to 8 hours, and then a temperature of 130 ° C. to 180 ° C. and a condition of 12 hours to 36 hours. Obtained by drying with
The calcined powder is obtained by pulverizing the precursor and then heat-treating in the atmosphere at a temperature of 600 ° C. to 1000 ° C. and 1 hour to 8 hours,
The shaped body is prepared by sizing the calcined powder and then pressure-molding under a condition of 50 MPa to 150 MPa by uniaxial mold molding,
The sintered body is produced by sintering the molded body in the atmosphere at a temperature of 1200 ° C. to 1400 ° C., 1 hour to 4 hours, and 20 MPa to 50 MPa by hot pressing.
It is characterized by this.

Here, (2) the Mg, Fe, starting material consisting of nitrates of Mn is magnesium nitrate (II) hexahydrate (Mg and _{(NO 3)} 2 · 6H ₂ O, iron (III) nitrate Kyumizu dihydrate and _{(Fe (NO 3) 3 ·} 9H 2 O, is preferably composed of a manganese (II) nitrate hexahydrate _{(Mn (NO 3) 2 ·} 6H 2 O.
( 3 ) The citric acid is preferably composed of anhydrous citric acid (C (CH ₂ COOH) ₂ (OH) (COOH)) or citric acid monohydrate C ₆ H ₈ O ₇ .H ₂ O.

[Definition of terms]
In this specification, the complex polymerization method or the citric acid gel method means that a stable chelate complex is formed between a plurality of types of metal ions and citric acid, and this is dissolved and dispersed in ethylene glycol. A method in which a metal complex is confined in a polyester in a uniform state by heat polymerization esterification, and then the polymer metal complex is heated and fired to synthesize a target substance. The network structure of the polymer metal complex obtained in this way is mainly formed by ester polymerization and copolymerization and is very stable, so the mobility of metal ions is small, and the subsequent baking process There is an effect that can suppress aggregation and segregation of metal elements.
In one embodiment of the present invention described below, a metal nitrate is dissolved in water, citric acid is added to form a metal citrate complex, and ethylene glycol is added thereto for ester polymerization to obtain a gel, which is calcined. The method of obtaining an oxide by calcination is called a complex polymerization method or a citric acid gel method.

The solid phase method indicates a method of synthesizing a target substance through calcination after weighing and mixing a plurality of kinds of raw material powders as starting materials in a predetermined amount. Also called solid-phase reaction method.
Hot press refers to a method in which powder or a preformed raw material is placed in a mold and pressure-sintered while being heated at a high temperature. In addition to obtaining a dense sintered body close to the theoretical density, and controlling the microstructure of the sintered body, it is possible to produce sintered bodies with excellent mechanical and physical properties such as high-strength sintered bodies. is there. In addition, the interface contact between different materials is improved, and there are advantages such that crystals or different materials can be bonded.
Furthermore, the lattice constant means the lengths a, b, and c of the unit lattice of the crystal lattice and the angles α, β, and γ between them. Lattice constant is one of crystal data and is an important factor for material identification.

The volume magnetization indicates a magnetic moment M per unit volume. Also called the strength of magnetization. The unit is [emu / cm ³ ]. The magnetism of a substance is reduced to the magnetic moment of atoms and molecules. When a magnetic field is applied to the magnetic material, the magnetic moment changes its direction in the direction of the magnetic field, resulting in magnetization. The strength of magnetization is also called magnetic polarization (J) and is a vector. In addition, applying a magnetic field to a magnetic material to align the magnetic moment in one direction is called “magnetizing”. The magnetization characteristics of a magnetic material are generally irreversible and change in a curvilinear manner. Such an irreversible characteristic is called hysteresis.
In one embodiment of the present invention described below, the mass magnetization (unit [emu / g]) denoted by σ _s is simply referred to as “magnetization”.

The strength of magnetization when a magnetic field is saturated by applying a magnetic field is called saturation magnetization (J _s ). Corresponding magnetic flux density B at this time is referred to as saturation magnetic flux density B _s. The point at which saturation is reached is called the S point.
When the magnetic field is removed after saturation magnetization, the magnitude of magnetization does not become zero due to the presence of hysteresis, and a certain magnitude of magnetization remains. It is called a residual magnetization magnitude of the magnetization expressed in J _r. Furthermore, when a magnetic field in the reverse direction is applied to the magnetic material in the residual magnetization state, the magnitude of magnetization becomes zero with a certain magnitude of the applied magnetic field. The magnitude of the magnetic field at this time is referred to as "coercive force", represented by H _c. A substance with a small coercive force is called a soft magnetic material. Conversely, a substance having a large coercive force is called a hard magnetic material (permanent magnet or the like). The value of the coercive force varies greatly in the magnetic material.

The Bohr magneton M _B, a minimum unit of magnetic moment, it is assumed that points to the unit of magnetic moment with the magnetic dipole of the order of magnitude of atoms. According to quantum mechanics, it is known that the magnetic moment M _l is an integer multiple of the Bohr magneton M _B by electron orbital motion.

  Super-exchange interaction is an interaction between magnetic ions mediated by negative ions such as oxygen and halogen and crystal water mediated between magnetic ions in magnetic compounds, that is, transitions such as manganese oxides. In metal oxides and halides, this indicates a magnetic interaction between spins on two localized transition metals by the mediation of a negative ion (oxygen ion) sandwiched between them. Here, although the transition metal is located at a position separated by an oxygen atom, the interaction can work quantum mechanically. Based on the theory of this mechanism, various magnetic phenomena of transition metal compounds so far can be elucidated.

The magnetic permeability μ refers to an index representing how easily magnetic flux can pass through a magnetic material, that is, the amount of change in magnetic flux when a certain magnetic field is applied. The magnetic permeability indicates the ease of magnetization and is one factor for evaluating the characteristics of the magnetic material. Similar to the magnetic permeability, the magnetic susceptibility indicates the relationship between the magnetic field and the magnetization.
In general, the magnetic permeability μ is defined by the following equation.
μ = (Φ / A) / ((N · I) / L) = B / H
Here, H (or (N · I) / L) is a magnetic field and a force for sending a magnetic flux per unit length of the path, and B (or Φ / A) is an amount of the magnetic flux Φ that flows in the unit area of the path as a result. (Magnetic flux density), A is a cross-sectional area, N is the number of turns of the solenoid, I is a current passing through the solenoid, and L is a magnetic path length.
Similarly to the above-described magnetic permeability, what indicates the relationship between the magnetic field and magnetization is called magnetic susceptibility (magnetic susceptibility). In general, the magnetic susceptibility χ is defined by the following equation.
χ = J / H
Here, H is a magnetic field, and J is the strength of magnetization. As represented by the above equation, when a magnetic field is acting on the magnetic material, its magnetization is a function of the magnetic field.

Furthermore, a material having a high magnetic permeability characteristic in which a large magnetic flux density is induced by applying a slight magnetic field from the outside is referred to as a high magnetic permeability material. Also called soft magnetic material. A high permeability material is required to have a high permeability μ, a small coercive force H _c , a high saturation magnetic flux density B _s and a small loss. Ferrite, which is a soft magnetic material that is an oxide, generally has a high electric resistance, and can generally be used for high frequencies.

  The iron loss indicates the energy loss of the magnetic core per unit volume. If there is energy loss in the magnetic core, the magnetic flux cannot immediately respond to the change of the externally applied magnetic field, and a delay angle δ (= loss angle) is generated. Tan δ is called a loss coefficient and is an important parameter in high-frequency materials. A smaller value means an excellent magnetic core with less loss. That is, iron loss is an important parameter that determines material quality. This iron loss is generally divided into hysteresis loss, eddy current loss, and residual loss. Hysteresis loss refers to energy loss per unit volume when a ferromagnetic material is magnetized over one period. Therefore, the hysteresis loss per unit time increases as the frequency becomes higher. When an AC magnetic field is applied to the magnetic material, current flows back into the magnetic material by electromagnetic induction and Joule heat is generated. This current is called eddy current, and the loss is called eddy current loss. Therefore, as with the hysteresis loss, the eddy current loss per unit time increases as the frequency increases. An oxide such as ferrite has an electrical resistivity that is an order of magnitude higher than that of a metal magnetic material, and the loss due to eddy current is less than that of a metal magnetic material, but at present, the loss increases as the frequency increases. .

According to the present invention, the magnetic permeability in order of MHz or higher frequency band mu, magnetization sigma _s and the electrical resistivity ρ is higher, the core loss can be provided a method for producing fewer magnetic material.

According to the present invention, Mg (Fe _1-x Mn _x ) ₂ O ₄ solid solution powder can be prepared by a plurality of manufacturing methods, and further sintered to produce a dense sintered body. It becomes possible.
According to one embodiment of the present invention, which is not limited to the following, after calcining in the atmosphere at 1,200 ° C. for 2 hours by a solid phase method, 1,350 ° C./30 MPa / 2 hours using a hot press. Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 <x ≦ 0.4) ceramics sintered under the conditions of: electrical resistivity ρ, permeability μ, magnetization when x = 0.2 composition All σ _s showed the maximum value. This is presumably because super-exchange interaction worked complicatedly by adding Mn to the Fe site of MgFe ₂ O ₄ .
The Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 <x ≦ 0.4) powder prepared by the complex polymerization method is crystallized at the precursor stage, and spinel is obtained from the result of X-ray diffraction. A diffraction pattern of the phase was confirmed. Further, the Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 <x ≦ 0.4) powder obtained by one example takes an intermediate of a normal spinel and a reverse spinel, and Mg ²⁺ is located at the 8a position. The ratio of (A position) was 16%.
Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 <x ≦ 0.4) ceramics obtained by sintering fine particle powder prepared by complex polymerization method under conditions of 1,350 ° C./30 MPa / 2 hours by hot pressing As in the case of using the solid phase method, the electric and magnetic characteristics showed the maximum values when the composition was x = 0.2. The ceramic produced by the complex polymerization method has high μ and σ _s although the average particle diameter G _s is small, so it is considered that the uniformity inside the crystal particles is high.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
First, the case of preparing a calcined powder of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention by a solid phase method, and then the Mg (Fe ₁₋ of the present invention by a complex polymerization method is described. _x Mn _{x) 2} O ₄ when prepared calcined powder of ferrite magnetic material is described. At the same time, it will be described a manner to produce a sintered body of _{Mg (Fe 1-x Mn x} ) 2 O 4 ferrite magnetic material of the present invention from the calcined powder obtained in the above method. Various characteristics of the calcined powder and the sintered body accompanying the composition change of the solid solution will be described later using examples.
FIG. 1 is a process diagram for preparing a calcined powder of the ferrite magnetic material of the present invention by a complex polymerization method, and FIG. 2 is a process for producing a sintered body from the calcined powder of the ferrite magnetic material of the present invention. FIG.

[First Embodiment]
_First, the procedure for preparing a calcined powder of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention by a solid phase method will be described. In the case of the solid phase method, a plurality of kinds of raw material powders as starting materials are weighed and mixed in a predetermined amount, and then subjected to calcination (heat treatment) to prepare a target calcined powder.
In obtaining the calcined powder from the mixed powder, the mixed powder is preferably heat-treated in the air at a temperature of 1100 ° C. to 1250 ° C. and for 3 hours to 8 hours.

Next, in order to obtain a sintered body (ceramics) of ferrite processed into a core or the like, it is necessary to prepare a sintered body from the calcined powder. The process for producing a sintered body from the calcined powder will be described with reference to the process chart shown in FIG.
That is, the calcined powder 8 is sized and pressure-molded to produce a compact (mixed compact) 9, and then the compact 9 is sintered to produce Mg (Fe _1-x Mn _x ) A sintered body 10 of ₂ O ₄ ferrite magnetic material is prepared.

The molded body 9 is preferably produced by pressure-molding the calcined powder 8 after sizing and uniaxial mold molding under conditions of 50 MPa to 150 MPa.
The sintered body 10 is preferably produced by sintering the molded body 9 in the atmosphere by hot pressing at a temperature of 1200 ° C. to 1400 ° C., 1 hour to 4 hours, and 20 MPa to 50 MPa.

Through the above steps, the sintered body 10 can be produced in addition to the calcined powder 8 of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention.

[Second Embodiment]
In the following, a description will be given with respect to a procedure for preparing a calcined powder of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention by a complex polymerization method.
FIG. 1 is a process diagram for preparing a calcined powder of the ferrite magnetic material of the present invention by a complex polymerization method. The complex polymerization method includes a step of preparing a mixed aqueous solution 2 by dissolving starting materials composed of nitrates 1a to 1c of Mg, Fe, and Mn in distilled water, and adding citric acid 3 and ethylene glycol 4 to the mixed aqueous solution 2. The precursor powder is prepared by preparing the metal-citrate complex 5 and heating and stirring the metal-citrate complex 5 until it becomes a gel, and then drying the obtained metal-citrate complex gel 6. 7 and further, the precursor powder 7 is pulverized and then subjected to heat treatment, whereby the precursor powder 7 is used to temporarily prepare the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention. And a step of obtaining the sintered powder 8.

  Here, the metal-citrate complex gel 6 can be prepared by heating and stirring the metal-citrate complex 5 at 80 ° C. to 120 ° C. and 2 hours to 8 hours until it becomes a gel. preferable.

  The precursor 7 is preferably prepared by drying the metal-citrate complex gel 6 at a temperature of 130 ° C. to 180 ° C. and a condition of 12 hours to 36 hours.

Further, the calcined powder 8 of Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material is obtained by pulverizing the precursor 7 into a powder form, which is heated to 600 ° C. to 1000 ° C. in the atmosphere, and 1 It is preferable to prepare by heat treatment under conditions of time to 8 hours.

A sintered body 10 is produced from the calcined powder 8 and finally processed into a core or the like. The steps for producing the sintered body 10 are as shown in FIG.
The complex polymerization method described above is a production method capable of preparing a homogeneous and fine particle powder, and according to this, calcining of a higher quality Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material The powder 8 and the sintered body 10 can be manufactured.

Hereinafter, the present invention will be described in more detail with reference to an example. Example 1 describes the case where the calcined powder of the ferrite magnetic material of the present invention is prepared by a solid phase method, and Example 2 illustrates the case of calcining the ferrite magnetic material of the present invention by a complex polymerization method. Will be described. In addition, the following description shall be based on an accompanying drawing.
Here, FIG. 3 is a diagram showing an X-ray diffraction pattern when the calcined powder of ferrite magnetic material obtained by the solid phase method is analyzed using powder X-ray diffraction, and FIG. 4 is obtained by the solid phase method. FIG. 5 is a graph showing the relationship between the measurement frequency f and the electrical resistivity ρ of a sintered body of ferrite magnetic material, and FIG. 5 is a diagram after thermal demagnetization in a certain frequency band of the sintered body of ferrite magnetic material obtained by the solid phase method. FIG. 6 is a diagram showing the relationship of the magnetic permeability μ in a state where the magnetization direction of the magnetic material as a whole is almost zero, and FIG. 6 shows the magnetization in a certain magnetic field of a sintered body of ferrite magnetic material obtained by the solid phase method. FIG. 7 is a diagram showing the temperature dependence of σ _s , FIG. 7 is a diagram showing an X-ray diffraction pattern when a precursor powder of a ferrite magnetic material obtained by a complex polymerization method is analyzed using powder X-ray diffraction, and FIG. Is a temporary magnetic material of ferrite obtained by the complex polymerization method. FIG. 9 is a diagram showing the change in the lattice constant a of the sintered powder, FIG. 9 is a diagram showing the relationship between the measurement frequency f of the sintered ferrite magnetic material obtained by the complex polymerization method and the electrical resistivity ρ, and FIG. FIG. 11 is a diagram showing the relationship of magnetic permeability μ after thermal demagnetization in a certain frequency band of a sintered body of ferrite magnetic material obtained by the body polymerization method, and FIG. 11 shows the sintered body of ferrite magnetic material obtained by the complex polymerization method. It is a figure which shows the various characteristics which _concern on magnetization (sigma) _s .
Further, in each of the following examples, as a comparative example for the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention, a sample not containing Mn (x = 0) and the solid solution amount x of Mn Data, measurement results, etc. when = 0.5 and x = 0.6 will be described as appropriate.

[Preparation of powder and sintered body]
First, a process for preparing a calcined powder of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention by a solid phase method will be described. A process for producing a sintered body of materials will be described.

The solid phase method itself is a known method of synthesizing a target substance through calcination after weighing and mixing a plurality of kinds of raw material powders as starting materials in a predetermined amount. In this example, first, MgO, α-Fe ₂ O ₃ , and MnCO ₃ are used so that the final composition is Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6). The starting material was weighed and prepared. In this example, MgO had a purity of 99.9% and an average particle diameter φ = 0.35 μm, α-Fe ₂ O _{3 had} a purity of 99.9% and an average particle diameter φ = 0.06 μm, MnCO ₃ Used were those having a purity of 99.0% and an average particle diameter φ = 5.4 μm.
Thereafter, the starting material was dissolved in water or methanol, wet mixed, and dried to obtain a mixed powder. Further, the mixed powder is heat-treated at 1,150 ° C. to 1,200 ° C. for 2 hours in the air, whereby Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0. 6) A calcined powder was obtained.

Next, a sintered body was produced from the calcined powder through the following steps. In addition, about the process of producing a sintered compact from calcined powder, it is completely the same as the case where a calcined powder is obtained by the complex polymerization method, and is demonstrated with the process diagram shown in FIG.
That is, as shown in FIG. 2, first, Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6) calcined powder 8 is sized, and this is pressure-molded to form a compact ( Mixed green compact) 9 was produced. In this example, sizing was performed after adding a small amount of distilled water to the calcined powder 8. The opening diameter of the equipment used for sizing was about 75 μm. Further, in this example, the calcined powder after the sizing was press-molded at a pressure of 98 MPa by uniaxial mold molding of φ = 20 mm to produce a compact 9.
Thereafter, the molded body 9, 1,350 ° C. in air using a hot press, 2 hours sintered by sintering at 30 MPa, _Mg from the shaped body _{9 (Fe 1-x Mn x} ) 2 O 4 (0 ≦ x ≦ 0.6) A sintered body 10 was obtained.

[Evaluation of powder and sintered body]
About Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6) calcined powder obtained through the above steps, powder X-ray diffraction (XRD: using Cu Kα ray) And so on), and the phase was identified.
In addition to identifying the crystal phase by XRD, the sintered body was observed for the microstructure of the fracture surface with a scanning electron microscope (SEM). In addition, the average particle diameter G _s is calculated by the intercept method, the relative density is measured by the Archimedes method, and the bulk density is measured, and then the theoretical density (MgFe ₂ O ₄ : 4.53 [Mg / m ³ ]) is calculated. Calculated. Here, in this example, the theoretical density of the MgFe ₂ O ₄ is obtained from “Powder Diffraction File, Card No. 17-464, International Center for Diffraction Data, Newtown Square, PA, 1974”.
Further, with respect to the sintered body, the electrical characteristics (electric resistivity ρ) were measured in addition to the magnetic characteristics of the magnetic permeability μ and the magnetization σ _s by an appropriate method.

[Structure and characteristics of powder and sintered body]
As shown in FIG. 3, the X-ray diffraction pattern of the Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6) calcined powder obtained through the above steps is x = 0 (comparison). Example), when calcined under conditions of 1,150 ° C. for 2 hours at 0.2, and 1,200 ° C. for 2 hours when x = 0.4, at least completely with a cubic spinel structure It became clear that it was in agreement. At this time, the lattice constant a of the calcined powder linearly increases up to x = 0.4 with increasing solid solution amount of Mn (x = 0: a = 0.8373 nm → x = 0.4: a = 0.8413 nm) and thereafter a constant value (a = 0.8413 nm). Further, since a γ-Mn ₂ O ₃ phase other than the spinel phase was observed in the sample of x> 0.4 composition, the solid solution limit is assumed to be up to x = 0.4. Therefore, in order to obtain the effect of the present invention, for example, it is considered that x is preferably 0.05 or more and 0.4 or less. The same is presumed when the complex polymerization method is used.
Next, the relative density of the sintered body obtained in this example did not depend on the increase of x, and became ˜99.5% for each composition. The relative density is calculated using the theoretical density calculated from the molecular weight, the coordination number Z = 8, the Avogadro number and the lattice constant.
Further, the average particle diameter G _s calculated by the intercept method increased from 9.6 (x = 0) μm to 22 (x = 0.4) μm as x increased. The intercept method was referred to “MIMendelson, J. Am. Ceram. Soc., 52, 443-446 (1969)”.

[Electrical characteristics]
Next, FIG. 4 shows the relationship between the measurement frequency f and the electrical resistivity ρ of the sintered ferrite magnetic material obtained in this example. As the frequency increased, ρ decreased. Here, the electrical resistivity ρ was measured while forming an Ag electrode on the surface of the surface-ground sintered body and changing the frequency f = 100 Hz to 10 MHz using an impedance measuring instrument.
At a frequency f = 100 Hz, the electrical resistivity ρ increases from ρ≈5.0 × 10 ³ Ω · cm of the comparative sample (x = 0) to which Mn is not added to when x = 0.2. The maximum value was ρ = 9.8 × 10 ⁷ Ω · cm (x = 0.2). As a result, according to the ferrite magnetic material of this example, it was confirmed that an increase in resistance exceeding a maximum of 4 digits can be realized as compared with the comparative sample (x = 0) not added with Mn. .
Also, looking at the electrical resistivity in the MHz band, when the solid solution amount of Mn is x = 0.2, compared with the case where Mn is not added, the frequency f = 1 MHz is less than two digits, f It was confirmed that a resistance increase of an order of magnitude could be achieved even at 10 MHz.

In this example, when the amount of Mn added is further increased from x = 0.2, the resistance starts to decrease. In general, the electrical conductivity in ferrite is considered to be caused by hopping conduction between Fe and Bivalent (“A. Nakamura, T. Kodama, T. Konoike, and K. Tomono, J. Jpn. Soc. Powder & Powder Metallurgy, 48, 145-149 (2000) ”), the added Mn worked as an acceptor in the grains, so that the electrical resistance increased sharply compared to x = 0 (comparative example). It is considered a thing. On the other hand, when x = 0.2 or more, it is considered that the electrical resistivity ρ is reduced due to hopping conduction between trivalent and tetravalent Mn.
In many cases, electrical conduction of metals and semiconductors is caused by conduction electrons that move almost freely in a substance, and the mean free path of electrons is longer than the interatomic distance. On the other hand, in amorphous semiconductors and certain ionic crystals, electrons are almost in a localized state, and electrical conduction is carried out by jumping (hopping) between them one after another. May have. This is called hopping conduction. In this case, the mean free path of electrons is about the distance between atoms (in impurity conduction, the distance between impurity atoms), and the electric conductivity is much smaller than that of free electrons. Contrasting behavior is shown. Also, since the leap process is aided by atomic thermal oscillation, the electrical conductivity increases with increasing temperature.

[Magnetic properties]
FIG. 5 shows the relationship of the magnetic permeability μ after thermal demagnetization at the measurement frequency f = 100 Hz to 1 MHz of the sintered body of the ferrite magnetic material obtained in this example. Here, the magnetic permeability μ is demagnetized when the sintered body is ultrasonically processed into a ring shape (the outer diameter is approximately 15 to 16 mm (see the values of D in FIGS. 5 and 10), the inner diameter is 4 mm, and the thickness is 3 mm). Therefore, after performing heat treatment (thermal demagnetization) at 500 ° C. for 1 hour considering that the MgFe ₂ O ₄ Curie temperature T _c is 440 ° C. (see Non-Patent Document 1), each impedance measurement device is used. It calculated | required by measuring in the range of f = 100Hz-10MHz.
As in the case of the electrical resistivity ρ, it was confirmed that the magnetic permeability showed the maximum value when x = 0.2 in this example. Further, the magnetic permeability μ decreases as the frequency increases. This is because, as the frequency increases, the magnetic induction of the magnetic core cannot generally follow the change in the applied AC magnetic field, and generally causes a delay. Therefore, a loss occurs as the frequency increases, and the permeability μ decreases. It is done. Note that a parameter of the loss coefficient tan δ representing the performance of the magnetic core can be used as a measure of the magnitude of energy loss accompanying the magnetic induction delay of the magnetic core. The main magnetic loss is eddy current loss, which is caused by the flow of eddy current that hinders the AC magnetic flux across the magnetic material.
According to this example, when x = 0.2, the maximum permeability μ≈70 was obtained at f = 100 Hz. Further, even when looking at the permeability at f = 1 MHz, a value of about 80% of the maximum value was obtained.

Further, FIG. 6 shows a graph of the temperature dependence of the magnetization σ _s in the magnetic field H = 1 [T] of the sintered body of the ferrite magnetic material obtained in this example. Here, the magnetization σ _s is obtained by pulverizing the sintered body of each composition using an alumina mortar, and using the SQUID magnetization measurement device, the obtained powder is subjected to a temperature T under the condition of a magnetic field H = 1 [T]. = Measured in a range of 10 to 300K.
At room temperature (300 K = about 27 ° C.), σ _s = 35.9 [emu / g] in the case of the comparative sample (x = 0) to which Mn is not added, whereas the solid solution amount of Mn = 0. When 2, σ _s took the maximum value, and σ _s = about 50 [emu / g]. It is considered that the decrease in magnetization due to the temperature rise is due to the disorder of the regular arrangement of moments due to thermal disturbance.

Regarding the point that an optimal magnetic structure is formed when the composition is x = 0.2, MgFe ₂ O ₄ described in the section of “Background Art” takes an intermediate between a normal spinel and a reverse spinel. It is thought that the points are related. In other words, super-exchange interaction works in a complex manner depending on whether the added Mn is replaced with Fe at the 8a position (A position) or 16d position (B position), and Mn is trivalent, tetravalent, and Fe As a result of taking divalent and trivalent mixed atoms, the Bohr magneton can be composed of various combinations. As a result, it is presumed that an optimal magnetic structure was formed at the composition of x = 0.2.

  Also, in the following, in order to realize superior characteristics, an example in which a calcined powder of the ferrite magnetic material of the present invention was newly prepared by a complex polymerization method capable of preparing a homogeneous and fine particle powder was prepared. Will be described.

[Preparation of powder and sintered body]
As in Example 1, first, a process for preparing a calcined powder of the ferrite magnetic material of the present invention by a complex polymerization method will be described, and then a sintered body of the ferrite magnetic material of the present invention will be produced using this process. The process to perform is demonstrated.

  FIG. 1 is a process diagram for preparing a calcined powder of the ferrite magnetic material of the present invention by a complex polymerization method. The complex polymerization method used in this example is also called a citric acid gel method, in which a metal nitrate is dissolved in water, citric acid is added to form a metal citric acid complex, and then ethylene glycol is added thereto for ester polymerization to obtain a gel. In this method, the gel is calcined and calcined to obtain an oxide.

As shown in FIG. 1, first, a mixed aqueous solution 2 was prepared by dissolving starting raw materials 1a to 1c made of nitrates of Mg, Fe, and Mn in distilled water. In this example, starting materials composed of nitrates of Mg, Fe, and Mn are respectively magnesium nitrate (II) hexahydrate (Mg (NO ₃ ) ₂ .6H ₂ O (purity 99.9%) and nitric acid. iron (III) and nonahydrate _{(Fe (NO 3) 3 ·} 9H 2 O ( 99.9%), manganese (II) nitrate hexahydrate _{(Mn (NO 3) 2 ·} 6H 2 O ( purity 99.0%) Each starting material was weighed so as to have a desired composition and then dissolved in distilled water.

Next, citric acid 3 and ethylene glycol 4 were added to mixed aqueous solution 2 to prepare metal-citric acid complex 5. Citric acid 3, consisted of anhydrous citric acid _{(C (CH 2 COOH) 2} (OH) (COOH)) or citric acid monohydrate _{C 6 H 8 O 7 · H} 2 O, ethylene glycol (HOCH ₂ CH ₂ OH) 4 having a purity of 99.5% was used.
In this example, the step of preparing the metal-citric acid complex 5 is carried out by mixing the mixed aqueous solution 2 with a ratio of Mg nitrate 1a: Fe, Mn nitrate 1b, 1c: citric acid 3: ethylene glycol 4, respectively. It was carried out by adding citric acid 3 and ethylene glycol 4 so that the molar ratio was 2: 5: 20.

Then, after heating and stirring the metal-citrate complex 5 until it becomes a gel, the obtained metal-citrate complex gel 6 is dried to obtain Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6) A precursor 7 of ferrite magnetic material was prepared.
In this example, after the metal-citrate complex 5 was heated and stirred at 100 ° C. for 6 hours, the metal-citrate complex gel 6 was dried at 150 ° C. for 24 hours to prepare a precursor 7.

Further, in this example, the obtained precursor 7 was pulverized into a powder form, and this was heat-treated in the atmosphere at 800 ° C. for 2 hours, whereby the precursor powder 7 was converted to Mg (Fe _1-x Mn _x ). ₂ O ₄ (0 ≦ x ≦ 0.6) calcined powder 8 was obtained.

Next, according to the process shown in FIG. 2, the sintered compact 10 was produced from the calcined powder 8.
In addition, about the process of producing the sintered compact 10 from the calcined powder 8, even when the calcined powder is prepared by the solid phase method or when the calcined powder is prepared by the complex polymerization method, there is no process. There is no change. The steps shown in FIG. 2 are as already described in the first embodiment.

[Evaluation of powder and sintered body]
The obtained Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦) was obtained in order to grasp the powder characteristics when using the complex polymerization method compared with those when using the solid phase method. The precursor and calcined powder of 0.6) were analyzed using powder X-ray diffraction (XRD) to identify phases.
As for the sintered body, as in Example 1, the crystal phase was identified by XRD, and the microstructure of the fracture surface was observed by a scanning electron microscope (SEM). In addition, the average particle size G _s is calculated by the intercept method, the relative density is measured by the Archimedes method, and the bulk density is measured, and then the theoretical density (MgFe ₂ O ₄ : 4.505 [Mg / m ³ ]) is calculated. Calculated. The theoretical density of the MgFe ₂ O ₄ used in this example is also obtained from the reference document shown in Example 1.
Furthermore, the magnetic permeability μ, the magnetization σ _s, and the electrical resistivity ρ were appropriately measured for the obtained sintered body. Each measuring procedure is the same as that in the first embodiment.

[Structure and characteristics of powder and sintered body]
As shown in FIG. 7, in the precursor powder 7 of Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6) ferrite of this example obtained by the complex polymerization method, X-ray diffraction was performed. From the results, it was confirmed that the intensity was low in all composition regions and a wide range of spinel phase diffraction images. In the complex polymerization method, the precursor is often amorphous, but this time, the cause of the confirmation of the spinel phase is that the nitrates 1a to 1c are used as starting materials, so that the metal-citrate complex gel is heated and stirred. It is inferred that self-combustion occurred when 6 was obtained, and crystallization occurred due to the heat generated at that time. Further, it was confirmed that the precursor powder is composed of fine particles of several tens of nm.

Next, when the calcined powder 8 was examined, the result of X-ray diffraction confirmed that the calcined powder of each composition was a single phase of a cubic spinel structure, that is, a cubic spinel ferrite. It was.
Further, as shown in FIG. 8, the change in the lattice constant a calculated by refining the X-ray diffraction data of the calcined powder of each composition by the least square method is the same as in Example 1 in the amount of solid solution of Mn. As it increases, it increases linearly up to x = 0.4 (x = 0: a = 0.8384 nm → x = 0.4: a = 0.8394 nm), and thereafter a constant value (a = 0.8394 nm) showed that. As in Example 1, since a γ-Mn ₂ O ₃ phase other than the spinel phase was observed in the sample of x> 0.4 composition (x = 0.5, x = 0.6), the solid solution limit was x It is inferred that = 0.4.

When the sintered body 10 was also examined, the relative density of the sintered body 10 obtained in this example did not depend on the increase of x, and was ˜99.0% for each composition. The average particle size G _s calculated by the intercept method increased from 4.8 (x = 0) μm to 5.6 (x = 0.4) μm as x increased. Thus, in the ferrite produced in the complex polymerization method, compared with the ferrite produced in the solid phase method under the same conditions, it was found to be able to reduce the average particle size G _s.

Furthermore, when the particle diameter of each composition of the Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 ≦ x ≦ 0.6) ferrite of this example was observed with a TEM, the precursor 7 was about 40 nm for each composition. Although it showed a certain value, the calcined powder 8 increased with the solid solution amount of Mn and was about 115 nm at x = 0 (comparative example), but was about 155 nm at x = 0.4. .
Thus, the sintered body of the Mg (Fe _1-x Mn _x ) ₂ O ₄ (0 <x ≦ 0.4) ferrite magnetic material of the present invention obtained by the complex polymerization method has an average particle diameter G _s = It was revealed that this was a high-density sintered body composed of crystal particles of about 5.0 μm and having a relative density of about 99.0%.
In addition, according to an example, Rietveld analysis revealed that 16% of Mg ²⁺ was present at the 8a position (A position), and that the added Mn was replaced with Fe at the 8a position. .

[Electrical characteristics]
FIG. 9 shows the relationship between the measurement frequency f and the electrical resistivity ρ of the sintered body of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material obtained in this example. As the frequency increased, ρ decreased.
At a frequency f = 100 Hz, the electrical resistivity ρ increases from ρ = 2.0 × 10 ⁴ Ω · cm of the comparative sample (x = 0) to which Mn is not added until x = 0.2. The maximum value was ρ = 9.8 × 10 ⁷ Ω · cm (x = 0.2). As a result, according to the ferrite magnetic material of this example, it was confirmed that an increase in resistance of nearly 4 digits at the maximum could be realized as compared with the comparative sample (x = 0) to which Mn was not added.
Also, looking at the electrical resistivity in the MHz band, as in Example 1, when the Mn solid solution amount x = 0.2, the frequency f = 1 MHz compared to the case where Mn was not added. It has been confirmed that an increase in resistance of a little less than one digit can be realized even at a little less than two digits and f = 10 MHz.
In this example, the resistance also decreases when the amount of Mn added is further increased from x = 0.2. In general, the electrical conductivity in ferrite is caused by hopping conduction between divalent and trivalent Fe. Like in Example 1, the added Mn acts as an acceptor in the grains, so that the electric resistance is x = 0. It is thought that it rose sharply compared with the case of (Comparative Example). On the other hand, when x = 0.2 or more, it is considered that the electrical resistivity ρ is reduced due to hopping conduction between trivalent and tetravalent Mn.

[Magnetic properties]
FIG. 10 also shows the sintered body of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material obtained in this example, after thermal demagnetization at a measurement frequency f = 100 Hz to 1 MHz (500 ° C. for 1 hour). The relationship of the magnetic permeability μ is shown.
As in the case of the electrical resistivity ρ, it was confirmed that the magnetic permeability μ shows the maximum value when x = 0.2 in this example. The magnetic permeability μ depends on the microstructure, the magnetic flux density, and various factors such as magnetic anisotropy and magnetostriction are related to the magnetic permeability. As a result, it is considered that the magnetic permeability showed the maximum value when the composition was x = 0.2.
Further, the magnetic permeability μ decreases as the frequency increases. In the high frequency region, it is known that eddy currents are generated and the magnetization characteristics deteriorate as the magnetization change becomes faster. Therefore, it is considered that the magnetic permeability μ decreases as the frequency increases.
According to this example, when x = 0.2, the maximum magnetic permeability μ = 75 was obtained at f = 100 Hz. Further, even when looking at the permeability at f = 1 MHz, a value of about 80% of the maximum value was obtained.

Further, FIG. 11A shows the temperature dependence of the magnetization σ _s in the magnetic field H = 1 [T] of the sintered body of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material obtained in this example. FIG. 11B shows a magnetic field H = −2 [T] at room temperature of the sintered body of the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material obtained in this example. A graph of the change in magnetization σ _{s in} the range of 2 to 2 [T], and FIG. 11 (c) show the Mg (Fe _1-x Mn _x ) ₂ O of the present invention in both the solid phase method and the complex polymerization method. _{4 (x} = 0.2) shows a comparison table of the average particle diameter G _s and magnetic properties in case the preparation of the ferrite magnetic material.
Referring to FIG. 11A, at room temperature (300 K = about 27 ° C.), σ _s = about 40 [emu / g] in the case of a comparative sample (x = 0) without addition of Mn, When the solid solution amount x = 0.2, σ _s took the maximum value, and σ _s = about 50 [emu / g]. As in the first embodiment, the decrease in magnetization due to the temperature rise is considered to be because the regular arrangement of moments is disturbed due to thermal disturbance.
Referring also to FIG. 11 (b), the coercive force _{H c} is any composition also about 10mT _{next, Mg (Fe 1-x Mn} x) 2 O 4 ferrite magnetic material of the present invention obtained in this example, all It became clear that the properties of soft magnetic materials were exhibited.
Further, referring to FIG. 11 (c), the ferrite produced by the complex polymerization method has a smaller average particle diameter G _s than that of the ferrite produced by the solid phase method under the same conditions. Since σ _s is improved, it is presumed that the uniformity inside the crystal grains is high.
As for the point that an optimal magnetic structure is formed when the composition is x = 0.2, as in the case of Example 1, Fe and Mn take a mixed valence in a complicated manner. As a result of the exchange interaction, it is considered that an optimal magnetic structure was formed when the composition was x = 0.2.

[Modification]
As mentioned above, although this invention was demonstrated in detail by the Example etc., this invention is not limited to the structure and conditions as described in the said Example at all, and various deformation | transformation are possible.

For example, in the above embodiment, no particular additive was added to the starting material, but for example, a small amount of additive was added to the finely pulverized calcined powder 8, and these were sufficiently sized and mixed. After that, by performing pressure molding and sintering, it is possible to further improve the electrical characteristics and magnetic characteristics of the sintered body 10. Preferable additives include those selected from Ca, CaO, SiO ₂ , Al ₂ O ₃ or a mixture of two or more thereof. Further, the amount added is preferably 0.01 wt% or more and 10 wt% or less, although it varies depending on the type of additive. Note that the basic characteristics are not lost by adding the additive.

In each of the above examples, the ferrite magnetic material of the present invention was produced by a solid phase method and a complex polymerization method, but the production method is not limited to these. It is sufficiently possible to produce the ferrite magnetic material of the present invention by applying a known production method.
Here, with respect to conventionally known MnZn-based or NiZn-based soft magnetic ferrite materials, even if production is attempted using a complex polymerization method, when heat treatment is performed in the air after polymerization with citric acid, (1) The cubic spinel structure is destroyed, and (2) Fe is liberated and the iron oxide α-Fe ₂ O ₃ is precipitated from the spinel, so that the function as a ferrite is lost (becomes a simple compound). There was a problem that. However, the Mg (Fe _1-x Mn _x ) ₂ O ₄ ferrite magnetic material of the present invention based on Mg ferrite has no liberation of Fe, even when manufactured using a complex polymerization method, and is therefore According to the invention, it is possible to provide a chemically stable ferrite magnetic material.
Furthermore, the ferrite magnetic material of the present invention is based on Mg ferrite, and like MgO, the possibility of plastic deformation by heating can be expected.

  In each of the above examples, when the sintered body 10 was obtained, the molded body 9 was obtained by press-molding the calcined powder 8 in advance by uniaxial mold molding, but the forming means of the molded body was uniaxial mold molding. It is not specifically limited to.

  As described above, the present invention is not limited to the configurations described in the above embodiments and the like, and those skilled in the art can devise various modifications based on the basic technical idea and teachings disclosed above. Things are self-explanatory.

As described above, the present invention is novel and useful for providing a method for manufacturing a ferrite magnetic material having a low iron loss in a high frequency band, with less decrease in magnetic permeability, preventing an increase in iron loss. Is clear.

It is a process figure in preparing the calcined powder of the ferrite magnetic material of the present invention by a complex polymerization method. It is a process figure in producing a sintered compact from the calcining powder of the ferrite magnetic material of this invention. It is a figure which shows the X-ray-diffraction pattern at the time of analyzing the calcined powder of the ferrite magnetic material obtained by the solid-phase method using powder X-ray diffraction. It is a figure which shows the relationship between the measurement frequency f of the sintered compact of the ferrite magnetic material obtained by the solid-phase method, and electrical resistivity (rho). It is a figure which shows the relationship of the permeability (mu) after the thermal demagnetization in a certain frequency band of the sintered compact of the ferrite magnetic material obtained by the solid-phase method. It is a figure which shows the temperature dependence of magnetization (sigma) _s in a certain magnetic field of the sintered compact of the ferrite magnetic material obtained by the solid-phase method. It is a figure which shows the X-ray diffraction pattern at the time of analyzing the precursor powder of the ferrite magnetic material obtained by the complex polymerization method using powder X-ray diffraction. It is a figure which shows the change of the lattice constant a of the calcination powder of the ferrite magnetic material obtained by the complex polymerization method. It is a figure which shows the relationship between the measurement frequency f and the electrical resistivity (rho) of the sintered compact of the ferrite magnetic material obtained by the complex polymerization method. It is a figure which shows the relationship of the permeability (mu) after the thermal demagnetization in a certain frequency band of the sintered compact of the ferrite magnetic material obtained by the complex polymerization method. It is a figure which shows the various characteristics which _concern on magnetization (sigma) _{s of the} sintered compact of the ferrite magnetic material obtained by the complex polymerization method. It is a figure which shows the crystal structure of a spinel type ferrite.

Explanation of symbols

1a-1c Starting material
2 Mixed aqueous solution 3 Citric acid 4 Ethylene glycol 5 Metal-citric acid complex 6 Metal-citric acid complex gel 7 Precursor powder 8 Calcined powder 9 Mixed green compact 10 Sintered body

Claims (3)

At least the general formula Mg (Fe _1-x Mn _x ) ₂ O ₄ (X is the solid solution amount of Mn, 0 <x ≦ 0.4), MgFe ₂ O ₄ A method for producing a spinel type ferrite magnetic material in which a part of Fe of ferrite is substituted with Mn,
  A step of preparing a mixed aqueous solution by dissolving starting materials composed of nitrates of Mg, Fe, and Mn in distilled water;
  Adding citric acid and ethylene glycol to the mixed aqueous solution to prepare a metal-citrate complex;
  A step of obtaining a precursor by heating and stirring the metal-citric acid complex until gelled, and then drying;
  A step of obtaining a calcined powder from the precursor by heat-treating after pulverizing the precursor;
  After sizing the calcined powder, a step of pressure molding to produce a molded body, and
  Sinter the molded body to produce a sintered body;
Consists of
  The precursor is heated and stirred with the metal-citrate complex at a temperature of 80 ° C. to 120 ° C. and 2 hours to 8 hours, and then a temperature of 130 ° C. to 180 ° C. and a condition of 12 hours to 36 hours. Obtained by drying with
  The calcined powder is obtained by pulverizing the precursor and then heat-treating in the atmosphere at a temperature of 600 ° C. to 1000 ° C. and 1 hour to 8 hours,
  The shaped body is prepared by sizing the calcined powder and then pressure-molding under a condition of 50 MPa to 150 MPa by uniaxial mold molding,
  The sintered body is produced by sintering the molded body in the atmosphere at a temperature of 1200 ° C. to 1400 ° C., 1 hour to 4 hours, and 20 MPa to 50 MPa by hot pressing.
A method for producing a ferrite magnetic material, wherein: The starting material consisting of the Mg, Fe and Mn nitrates is magnesium nitrate (II) hexahydrate (Mg (NO ₃ ) ₂ ・ 6H ₂ O and iron (III) nitrate nonahydrate (Fe (NO ₃ ) ₃ ・ 9H ₂ O and manganese nitrate (II) hexahydrate (Mn (NO ₃ ) ₂ ・ 6H ₂ The method for producing a ferrite magnetic material according to claim 1, comprising O. The citric acid is anhydrous citric acid (C (CH ₂ COOH) ₂ (OH) (COOH)) or citric acid monohydrate C ₆ H ₈ O ₇ ・ H ₂ The method for producing a ferrite magnetic material according to claim 1, wherein the ferrite magnetic material is made of O.