JP5196101B2 - Soft magnetic ferrite, magnetic circuit and inductance element - Google Patents

Description

  The present invention relates to a magnetic material for high frequency, and particularly relates to a hexagonal ferrite used for electronic components such as choke coils and noise removing elements and radio wave absorbers in a high frequency band from several MHz to several GHz.

  In recent years, with the increase in the frequency of signals from mobile phones, wireless LANs, personal computers, etc., elements used inside the apparatus are also required to be usable at high frequencies. In response to such demands, spinel ferrites conventionally used are difficult to use because there is a frequency limit called a snake limit in the high frequency band. Therefore, hexagonal ferrite having a hexagonal crystal structure has been studied as a high frequency material exceeding the frequency limit.

  Among hexagonal ferrites, it is known that Z-type ferrite and Y-type ferrite containing Co in particular have a relatively high magnetic permeability and exhibit excellent high frequency characteristics. In addition, since Z-type and Y-type ferrites containing Co have a c-plane as an easy magnetization plane, the c-plane of the crystal can be aligned in parallel with the magnetic field application direction by a static magnetic field applied from the outside during molding. . It is possible to improve the magnetic permeability in the magnetic field application direction by aligning the c-plane in parallel with the magnetic field application direction (hereinafter, this operation is referred to as unidirectional orientation, and the surface having the normal direction to which the magnetic field is applied). called the c-axis oriented plane). Further, it is possible to perform an operation of aligning the c-axis direction of crystal grains by a rotating magnetic field applied from the outside at the time of molding (hereinafter, this operation is referred to as plane orientation, and the surface on which this operation has been performed is referred to as an orientation plane). . By performing the plane orientation, it is possible to improve the magnetic permeability in the orientation plane.

  Patent Document 1 discloses that a Z-type ferrite can be plane-oriented by applying a rotating magnetic field.

Japanese Patent Publication No. 35-11280

  Patent Document 1 describes that a Z-type ferrite crystal is obtained by orienting a Z-type ferrite crystal in a plane and having a plane-oriented Z-type ferrite having a relative magnetic permeability of 30 in the orientation plane. However, even if Z-type ferrite has a higher resonance frequency than that of spinel ferrite, the resonance frequency exists at about 1 GHz. At higher frequencies, the relative permeability is significantly attenuated, so that it can be used in a high frequency band of 1 GHz or higher. It was not enough.

  In view of the above points, an object of the present invention is to provide a soft magnetic ferrite that maintains a high magnetic permeability up to a high frequency band and has excellent frequency characteristics, and further provides a magnetic circuit and an inductance element using the same.

  The soft magnetic ferrite of the present invention has ferrite crystal grains having a c-plane as an easy magnetization plane, and has an orientation such that the c-plane of the crystal grains is parallel to at least one direction. It has a shape such that the demagnetizing factor in the direction is larger than 0. A demagnetizing factor greater than 0 means a shape in which a demagnetizing field is generated, and excludes a ring shape that is oriented in the circumferential direction to form a closed magnetic circuit. When the c-plane has an orientation that is parallel to at least one direction and the demagnetizing factor in the direction is larger than 0, the permeability in the direction is 0 when the demagnetizing factor is 0. Compared to the higher frequency side, it is maintained.

In the soft magnetic ferrite, it is desirable that the c-axis is oriented in a plurality of directions in a plane perpendicular to the one direction. Such a configuration is obtained when a unidirectional DC magnetic field is applied to orient the ferrite particles, and is a configuration advantageous for cost reduction obtained by a simple method.

  Furthermore, in the soft magnetic ferrite, it is desirable that the c-axis is oriented in another direction perpendicular to the one direction. By adopting such a configuration, the effect of improving the frequency characteristics of the magnetic permeability can be obtained in an arbitrary direction in a plane perpendicular to the other direction, and the degree of freedom in arrangement in the magnetic circuit used is increased.

  Further, in the soft magnetic ferrite, the frequency at which the real part of relative permeability in the one direction becomes 70% of the real part of relative permeability of 100 MHz is fa70, and the real part of relative permeability in the direction orthogonal to the one direction. When the frequency at which the relative permeability of 100 MHz is 70% is fp70, the maximum value of fa70 / fp70 is 1.2 or more. By adopting a shape in which the demagnetizing factor is larger than 0, the frequency characteristics of the magnetic permeability can be improved. If fa70 / fp70 as an index of the improvement is 1.2 or more, the one direction It is possible to provide a soft magnetic ferrite that is particularly excellent in frequency characteristics of magnetic permeability.

  Furthermore, the soft magnetic ferrite is a Z-type ferrite, and the absolute value of the real part of the relative permeability in the one direction is 6 or more at 3 GHz. With the above configuration, it is possible to improve the frequency characteristics of the magnetic permeability in the one direction, and to achieve a magnetic permeability of 6 or more at 3 GHz, which could not be realized with the conventional concept Z-type ferrite. As a result, the conventional Z-type ferrite can be used in a high frequency region exceeding 1 GHz, which could not be applied.

  The magnetic circuit of the present invention is a magnetic circuit using the soft magnetic ferrite, wherein the one direction is used as a magnetic path direction. By setting the direction in which the frequency characteristic of the magnetic permeability of the soft magnetic ferrite is improved as the magnetic path direction of the magnetic circuit, the magnetic circuit can be functioned up to a higher frequency.

  The inductance element of the present invention is an inductance element using soft magnetic ferrite, wherein the one direction is used as a magnetic path direction. By using the direction in which the frequency characteristic of the magnetic permeability of the soft magnetic ferrite is improved as the magnetic path direction, it is possible to provide an inductance element that exhibits a high impedance up to a higher frequency.

  According to the present invention, it is possible to provide a soft magnetic ferrite that maintains a high magnetic permeability up to a high frequency band and is excellent in frequency characteristics. By using the soft magnetic ferrite of the present invention, it is possible to provide a magnetic circuit that can be used up to a higher frequency, and an inductance element such as a choke coil, an inductor, a radio wave absorber, a magnetic antenna, and a current transformer.

  Hereinafter, although the soft magnetic ferrite of this invention is concretely demonstrated by embodiment of the sintered compact of a hexagonal Z-type ferrite, this invention is not limited to these embodiment. The soft magnetic ferrite according to the present invention can be produced by an ordinary powder metallurgical method applied to the production of ferrite, unless otherwise specified in the present invention. The usual powder metallurgy method is as follows. For example, raw materials are mixed in a wet ball mill and calcined using an electric furnace or the like to obtain calcined powder. Also, the obtained calcined powder is pulverized using a wet ball mill or the like, and the obtained pulverized powder is molded by a press machine and fired using, for example, an electric furnace to obtain a hexagonal Z-type ferrite sintered body. obtain.

  In the present invention, the pulverized powder to be subjected to the molding is produced, for example, as follows. The sintered body obtained as described above is pulverized using a jaw crusher, a disk mill or the like to obtain a coarse powder. The obtained coarse powder is pulverized using a vibration mill, ball mill, jet mill or the like to obtain fine powder. Water is added to the obtained fine powder to form a slurry, which is pressed while applying a magnetic field. The obtained molded body is dried and then re-sintered to obtain a ferrite sintered body.

The soft magnetic ferrite according to the present invention will be specifically described below. In the present invention, a ferrite whose c-plane is an easily magnetized surface is targeted. Among soft magnetic ferrites, those having an easily magnetized surface can be oriented by utilizing their properties to have anisotropy. Examples of soft magnetic ferrite having an easy magnetization surface include hexagonal Z-type ferrite and hexagonal Y-type ferrite. These have a c-plane perpendicular to the c-axis as a magnetic field easy surface. One of the features of the soft magnetic ferrite according to the present invention is that the crystal grains of the soft magnetic ferrite are oriented so that the c-plane is parallel to one direction. A typical embodiment of the soft magnetic ferrite that can implement such a configuration is a soft magnetic ferrite sintered body. In other words, the crystal grains constituting the soft magnetic ferrite sintered body only need to be oriented so that the c-plane is parallel to one direction. Corresponds to single crystal ferrite. The hexagonal Z-type ferrite and hexagonal Y-type ferrite are typically represented by Ba ₃ Co ₂ F ₂₄ O ₄₁ and Ba ₂ Co ₂ F ₁₂ O ₂₂ , respectively. The hexagonal Z-type ferrite sintered body and the hexagonal Y-type ferrite sintered body, which are soft magnetic ferrites, are sintered bodies containing such a hexagonal Z-type ferrite phase or hexagonal Y-type ferrite. It is also possible to substitute a part of Ba with Sr, or a part of Co with at least one of Cu, Zn, and Ni. The hexagonal Z-type ferrite sintered body partially includes other phases such as a hexagonal ferrite phase (W phase, Y phase, M phase) other than the Z phase, a spinel phase, and a BaFe ₂ O ₄ phase. Also good. In order to obtain a high sintered body density, it is preferable that 17 to 21 mol% BaO, 6 to 13 mol% CoO, and the balance Fe ₂ O ₃ are the main components. On the other hand, the hexagonal Y-type ferrite sintered body partially includes other phases such as a hexagonal ferrite phase (W phase, Z phase, M phase) other than the Y phase, spinel phase, BaFe ₂ O ₄ phase. You can leave. Furthermore, it is preferable to Li the contained 0.05 to 1.0 wt% with _Li 2 CO ₃ in terms relative to the main component. The main component composition range and the Li content are suitable for increasing the density of the sintered body.

In the case of a hexagonal Z-type ferrite sintered body, Li and Si may be combined. When Li is contained together with Si, a synergistic effect of improvement in specific sintered body density and permeability can be obtained. Even if Si is a small amount, it shows the effect of composite inclusion with Li and the effect of increasing volume resistivity, but if it is less than 0.05% by mass in terms of SiO ₂ , these substantial effects are not exhibited, whereas it exceeds 0.5% by mass Therefore, the volume resistivity is not improved, and the magnetic permeability and the sintered body density are lowered. Therefore, the range of 0.05 to 0.5% by mass is preferable. By including Si in the above-mentioned range in combination with Li, the initial permeability due to the inclusion of Li while the sintered body density is 4.95 × 10 ³ kg / m ³ or more and the volume resistivity is 10 ⁴ Ω · m or more. The improvement effect can be exhibited. Furthermore, in order to improve the volume resistivity, 0.05 to 5% by mass of Mn as a divalent metal ion in terms of Mn ₃ O ₄ may be contained.

  Next, the configuration of the soft magnetic ferrite according to the present invention will be described in further detail using a hexagonal Z-type ferrite sintered body as an example. The oriented soft magnetic ferrite according to the present invention can be divided into, for example, those based on unidirectional orientation and plane orientation described in detail below, but the content of the present invention is not limited to these two kinds of orientation methods. If the soft magnetic ferrite has anisotropy that exhibits a high magnetic permeability in a specific direction, the effect of the present invention is exhibited. It is not necessary for all crystal grains constituting the soft magnetic ferrite to be completely unidirectionally or plane-oriented, and disorder of the orientation is allowed. For example, when oriented by a magnetic field as described later, the orientation depends on the applied magnetic field strength, but the hexagonal Z-type ferrite sintered body shows a tendency of unidirectional orientation or plane orientation on X-ray diffraction. That's fine.

Unidirectional orientation is orientation in which the c-plane is oriented parallel to one direction, but the orientation of the c-axis, which is the normal line, does not matter, and is oriented by a uniaxial magnetic field, that is, a DC magnetic field. Corresponds to this. In this case, the c-axis is oriented in a plane direction perpendicular to the one direction, and is typically oriented randomly in the in-plane direction. The degree of orientation in the case of unidirectional orientation can be confirmed by an X-ray diffraction pattern as follows. First, in the X-ray diffraction pattern of one plane of the hexagonal Z-type ferrite sintered body, the integrated intensity sum of all diffraction peaks derived from the hexagonal Z-type ferrite included in the measurement range of 2θ = 20 to 80 °. Is taken as ΣI (HKL), and the sum of integrated intensities of diffraction peaks of all (HK0) planes with L = 0 included in the above range is taken as ΣI (HK0). That is, ΣI (HKL) is obtained by integrating the diffraction peaks of hexagonal Z-type ferrite over the entire 2θ of 20 ° to 80 °. Note that I (HKL) represents the integrated intensity of the diffraction peak from the lattice plane represented by the index (HKL). Here, when I (HKL) is θ (HKL) and the peak angle of the diffraction line on the (HKL) plane is θ (HKL) −0.4 ° to θ (HKL) + 0.4 °. The integrated value is used. Hereinbefore defines the degree of orientation fc _⊥ from .SIGMA.I (HKL) and ΣI (HK0). The degree of orientation fc _⊥ is given by _{fc ⊥ = ΣI (HK0) /} ΣI (HKL). Large The degree of orientation fc _⊥, i.e., that ΣI molecule (hk0) is large, in terms of doing X-ray diffraction, c-axis indicate that many grains directed toward said surface direction ing. Among the hexagonal Z-type ferrites, the composition represented by Ba ₃ Co ₂ Fe ₂₄ O ₄₁ has a direction perpendicular to the c-axis, that is, the c-plane becomes an easily magnetized surface. The fact that there are many crystal grains facing the surface direction means that the magnetic permeability in the direction perpendicular to the surface becomes high.

When the degree of orientation fc _⊥ 0.4 or more, the permeability in the direction perpendicular to the plane is performed X-ray diffraction is particularly high. In the present invention, a surface having this degree of orientation is referred to as a c-axis oriented surface. More preferably, it is 0.45 or more. It is preferable that the c-axis of more crystal grains is oriented in the plane direction in which X-ray diffraction is performed. As an ideal state, FIG. 1 shows a state where the c-axes of all crystal grains are oriented in the plane direction in which X-ray diffraction is performed. As apparent from FIG. 1, the c-plane of each crystal grain is perpendicular to the plane on which X-ray diffraction is performed. In this case, as long as the c-plane, which is the easy magnetization plane, is perpendicular to the plane on which X-ray diffraction is performed, the direction perpendicular to the plane on which X-ray diffraction is performed no matter which direction of the c-axis is directed. It can be seen that the permeability increases. In this case, the state where the c-axis direction is also aligned in one direction corresponds to the case where the surface is aligned as in Patent Document 1. That is, the plane orientation is an orientation state in which the c-plane is aligned in parallel with one in-plane direction because the c-axis is aligned in one direction. This is the case when oriented by a rotating magnetic field.

In order to distinguish between the case of the unidirectional orientation in which the c-plane is oriented in parallel in the specific direction and the surface orientation, the following evaluation by X-ray diffraction may be performed. As shown in FIG. 1, the c-plane is oriented in a direction perpendicular to the plane on which X-ray diffraction is performed (the c-plane is parallel to the direction), and the c-axis is random in the plane direction perpendicular to the direction. As an index for judging the state of the X-ray diffraction, the fc _/ in X-ray diffraction is at least on two planes perpendicular to the c-axis orientation plane (corresponding to the above-mentioned plane performing X-ray diffraction) and perpendicular to each other. _The degree of orientation fc _// calculated from _/ = I (0018) / I (110) is adopted. A configuration in which the degree of orientation fc _// is 0.3 or more is preferable. The large degree of orientation fc _// indicates that there are many crystal grains having the c-axis in the direction perpendicular to the observation surface. This ensures that the c-axis is randomly oriented by being satisfied at least in two planes perpendicular to each other. By doing so, high magnetic permeability can be obtained even in a direction parallel to the c-axis orientation plane. The ratio with respect to the magnetic permeability in the direction perpendicular to the c-axis orientation plane can also be set to 0.25 or more, and a hexagonal Z-type ferrite sintered body having an excellent balance of magnetic permeability can be provided. For plane orientation, there is a possibility to meet the one surface (surface of the surface alignment direction) in fc _// 0.3 or perpendicular to the c-axis-oriented plane, fc _// in two perpendicular surfaces to each other 0.3 The above cannot be satisfied.

It suffices that the hexagonal Z-type ferrite sintered body has a c-axis oriented plane that satisfies the above conditions. If the sintered body is a rectangular parallelepiped, for example, as a result of evaluating the degree of orientation fc _⊥ performing X-ray diffraction in one plane of its surface, if said surface is a c-axis-oriented plane, at the same right angle The degree of orientation fc _// may be evaluated at two other surfaces perpendicular to each other.

  In the present invention, in addition to the method of unidirectional orientation as described above, the effect can be sufficiently exhibited by orientation called plane orientation described in detail below. Unidirectional orientation is an in-plane direction perpendicular to the one direction, in addition to the orientation that the c-plane of ferrite grains having the c-plane as an easily magnetized plane is parallel to at least one direction. In this configuration, the c-axis is oriented in one direction.

In order to obtain a high magnetic permeability and a high sintered body strength, the density of the hexagonal Z-type ferrite sintered body is preferably 4.7 × 10 ³ kg / m ³ or more, and 5.0 × 10 ³ kg. A sintered body density of / m ³ or more is more preferable.

  As described above, the hexagonal Z-type ferrite with improved magnetic permeability by improving the orientation has a frequency characteristic of magnetic permeability compared with the case where the magnetic permeability is improved by controlling other factors such as composition and structure. Is also advantageous. When other factors are controlled to improve the magnetic permeability, the magnetic anisotropy and the like also change, so that the frequency characteristics deteriorate and the magnetic permeability decreases at a lower frequency. On the other hand, when the magnetic permeability is improved by controlling the orientation, since the magnetic anisotropy is not changed, the influence on the frequency characteristics is reduced.

  Moreover, from the viewpoint of improving the frequency characteristics of the magnetic permeability, it is preferable that the average crystal grain size of the sintered body is in the range of 3 to 50 μm. Here, the crystal grain size of the sintered body is the longest (maximum diameter) of the line segments that can be drawn inside the observed crystal grain, the long axis being the major axis, and the crystal grain diameter being perpendicular to the major axis and drawn inside the crystal grain Among the possible line segments, the longest axis was defined as the minor axis, and the average of the minor axis and the major axis was defined as the crystal grain size of each individual particle. The average crystal grain size may be obtained by evaluating an arbitrary 100 particles and taking the average thereof.

The oriented hexagonal Z-type ferrite sintered body described above is obtained, for example, by using the following method for producing a hexagonal Z-type ferrite sintered body. That is, a molding step of forming a hexagonal Z-type ferrite powder having a specific surface area in the range of 800 to 4000 m ² / kg in a uniaxial magnetic field to obtain a molded body, and a firing step of sintering the molded body Then, a hexagonal Z-type ferrite sintered body is obtained. Usually, a finely pulverized ferrite powder is used in order to improve sinterability. On the other hand, in the method for producing a hexagonal Z-type ferrite sintered body according to the present invention, the specific surface area of the hexagonal Z-type ferrite powder is preferably controlled to 800 to 4000 m ² / kg. This achieves high orientation and high magnetic permeability. If the specific surface area is too small, the density of the sintered body is difficult to increase and the orientation is low. On the other hand, if the specific surface area is too large, the orientation is lowered and coarse particles are easily generated.

  As the molding method, pressure molding, extrusion molding, injection molding and the like can be used, but particularly simple pressure molding is desirable. In the case of pressure molding, a vertical magnetic field molding method in which the magnetic field application direction and the pressurization direction are parallel, or a transverse magnetic field molding method in which the magnetic field application direction and the pressurization direction are perpendicular to each other can be used. Therefore, the transverse magnetic field forming method is preferable. The same applies to the case of producing a plane alignment material. In this case, it is desirable that the pressing direction and the direction of the rotating magnetic field are orthogonal.

  Orientation is performed by molding in a magnetic field. As a magnetic field application method, a uniaxial magnetic field or a rotating magnetic field may be used as described above. In addition, the molding can be performed by dry molding using dry powder, but in order to improve the orientation, a slurry obtained by mixing hexagonal Z-type ferrite powder with a medium such as water. It is preferable to carry out by wet molding using. Although the kind of water as a medium does not specifically limit this, What is necessary is just to use cheap tap water, for example. Impurity ions can also be reduced using ion-exchanged water or distilled water. The slurry concentration, that is, the weight ratio of the hexagonal Z-type ferrite powder in the slurry may be 85 wt% or less. If the content exceeds 85 wt%, the friction between the particles increases, the particles are not sufficiently rotated, and the degree of orientation is lowered. From the viewpoint of obtaining high orientation, it is more preferable to perform molding with the concentration of hexagonal Z-type ferrite powder in the slurry being 65 wt% or less. On the other hand, the slurry concentration is preferably 50 wt% or more. If it is less than 50%, it takes a lot of time for dehydration at the time of molding, and the productivity is lowered. Further, when the dry hexagonal Z-type ferrite powder is stirred and then molded while applying a magnetic field in the mold cavity, the agglomeration of the hexagonal Z-type ferrite powder is released to further enhance the orientation. be able to.

  In addition, in the case of a wet molding method using pressurization using slurry, the slurry may be supplied by pressurizing and injecting the slurry into the mold cavity during application of the magnetic field, or after applying the slurry into the cavity. The method of applying may be used. The medium in the slurry is removed from dewatering holes and clearances formed in the cavities when pressurized. The molded hexagonal Z-type ferrite powder, that is, the molded body is sufficiently dried and then subjected to sintering.

  The hexagonal Z-type ferrite powder can be obtained by calcination and pulverization in a powder state as in a normal process, but a method obtained by pulverizing a hexagonal Z-type ferrite sintered body Is preferable from the viewpoint of grindability. In order to orient, the particles constituting the hexagonal Z-type ferrite powder are preferably single crystals. In this respect, since the grain growth is progressing in the sintered body, if the sintered body is pulverized, it is easy to obtain a powder containing many particles that are single crystals. Therefore, the method of pulverizing the hexagonal Z-type ferrite sintered body to obtain powder is a powder adjustment method suitable for orientation in a magnetic field. In this case, it is preferable that the average crystal grain size of the hexagonal Z-type ferrite sintered body subjected to the pulverization is 5 to 200 μm. In addition, although it is also possible to shape | mold using the hexagonal Z-type ferrite powder which grind | pulverized the powder after calcination like a normal process, the average of the hexagonal Z-type ferrite in the powder after calcination also in this case The crystal grain size is preferably 5 to 200 μm. Furthermore, in any case, including the method of pulverizing a hexagonal Z-type ferrite sintered body to obtain a powder and the method of using a hexagonal Z-type ferrite powder obtained by pulverizing the calcined powder, the powder used for molding is substantially In particular, it is more preferable not to contain a hexagonal M-type ferrite phase. The hexagonal M-type ferrite phase exhibits uniaxial anisotropy with the c-axis as the easy axis of magnetization, and is oriented in the direction of the uniaxial applied magnetic field. This is because an alignment state (plane alignment) different from the alignment state according to the invention is generated. Here, substantially not containing a hexagonal M-type ferrite phase means that the peak of the hexagonal M-type ferrite with respect to the intensity of the peak (1016) which is the maximum intensity of the hexagonal Z-type ferrite in X-ray diffraction. (006) The intensity ratio of the peak is 5% or less. The soft magnetic ferrite may be a mixed phase of hexagonal Z-type ferrite and Y-type ferrite, but is preferably composed mainly of Z-type ferrite or Y-type ferrite in order to suppress variation in characteristics. . When hexagonal Z-type ferrite is mainly used, it is particularly preferable that the powder to be molded is hexagonal Z-type ferrite substantially not including Y-type ferrite and spinel ferrite. The phrase “substantially free of Y-type ferrite and spinel ferrite” means that the ratio of the intensity of the (0012) peak of the Y-type ferrite to the intensity of the maximum peak of the hexagonal Z-type ferrite (1016) is 5% or less. The ratio of the intensity of the (440) peak of spinel ferrite is 7% or less. On the other hand, when hexagonal Y-type ferrite is mainly used, it is particularly preferable that the powder to be molded is hexagonal Y-type ferrite substantially not including Z-type ferrite and spinel ferrite. The phrase “substantially free of Z-type ferrite and spinel ferrite” means that the ratio of the intensity of the (1016) peak of the Z-type ferrite to the intensity of the (110) peak, which is the maximum intensity of the hexagonal Y-type ferrite, is 5% or less. The ratio of the intensity of the (440) peak of spinel ferrite is 7% or less.

  In the hexagonal Z-type ferrite sintered body obtained by molding in a magnetic field as described above, orientation disorder may occur in the vicinity of the surface. Therefore, by removing the surface by processing, the ratio of the portion with a high degree of orientation increases in the entire sintered body, which is advantageous in obtaining high magnetic permeability. Further, removing the surface by processing leads to suppression of orientation in the sintered body, and hence variation in magnetic permeability. It is sufficient that at least a part of the sintered body is processed. Regardless of the processed surface by polishing or cutting, the surface is deleted.

  A sintered body of hexagonal ferrite with oriented crystals produced as described above is processed into a shape that can generate a demagnetizing factor greater than 0 using a dicer, a slicer, or a parallel grinding machine. The shape to be processed is, for example, a rectangular shape, a cube, a thin plate shape, a cylindrical rod, a prismatic rod, a ring shape with a gap inserted, or the like that generates a demagnetizing factor greater than 0 for the magnetic path used. Any shape is acceptable. By using in such a shape, the frequency characteristics of the excellent magnetic permeability of the Z-type ferrite can be further used up to the high frequency side.

  Among the sintered hexagonal ferrites that have been processed as described above, it is particularly desirable that the direction in which a high magnetic permeability is obtained along the magnetic path, particularly when evaluated in a non-demagnetizing field. . This corresponds to, for example, a unidirectionally oriented magnetic field application direction. Or in the case of plane orientation, it corresponds to using the direction in the oriented plane. In the case of plane orientation, a gap that crosses the magnetic path may be provided in a ring sample whose annular surface is parallel to the orientation plane. In addition to the plane orientation and the unidirectional orientation as described above, as long as the c-plane is oriented along the magnetic path, the shape may be such that a demagnetizing field that prevents the magnetic path is generated. This greatly improves the frequency characteristics of the magnetic permeability. In the present invention, in the soft magnetic ferrite oriented so that the c-plane of the crystal grains is parallel to one direction, the frequency characteristics are improved when the demagnetizing field is generated, and the frequency characteristics are further improved. This is based on the knowledge that the effect has significant anisotropy. Matching the one direction in which the c-plane is oriented in parallel with at least one direction and the direction in which the demagnetizing field is generated, in other words, the direction having a high magnetic permeability in the evaluation with no demagnetizing field, that is, It has been found that introducing a demagnetizing field in the direction of magnetic field application during molding is extremely effective in maintaining the magnetic permeability to the higher frequency side. That is, it has been found that in the evaluation with no demagnetizing field, an extremely large frequency characteristic improvement effect can be obtained as compared with the case of performing processing such as providing a gap in the direction of low magnetic permeability. When the c-plane is oriented parallel to the magnetic path to be used, a particularly remarkable effect can be obtained by using a shape that can effectively generate a demagnetizing field with respect to the magnetic path. By using such a configuration, it is possible to provide a hexagonal ferrite having a high magnetic permeability even in a band equal to or higher than the resonance frequency in one direction.

  Although the reason why the effect of the demagnetizing field varies depending on the orientation direction as described above is not yet clear, the permeability component that deteriorates the frequency characteristics such as the movement of the domain wall only in the direction in which the c-plane is parallel is removed by the introduction of the demagnetizing field. It is presumed that the mode of magnetization due to rotational magnetization becomes dominant. Such a phenomenon occurs not only in the unidirectionally oriented Z-type ferrite and the plane-oriented Z-type ferrite described below as examples, but also in a Y-type ferrite having an easily magnetized surface. In addition, not only soft magnetic ferrite such as hexagonal ferrite but also the same magnetocrystalline anisotropy appears macroscopically, for example, a compact or crystalline orientation in which a thin disc-shaped metal magnetic powder is oriented. The same effect can be produced even with a thin film or a single crystal having an easily magnetized surface. In the present invention, even if the material is densified, the mode of magnetization due to rotation is dominant. In particular, the saturation magnetization increases and the permeability increases in the densified sample. For example, it is more desirable to use at 90% or more of the theoretical density.

  As described above, the demagnetizing factor of hexagonal ferrite oriented with respect to the magnetic path to be used is preferably larger than zero. From the viewpoint of improving the frequency characteristics of magnetic permeability, the demagnetizing field coefficient is more preferably greater than 0.005 and not greater than 0.3. This is because the effect of high frequency provided by the present invention is less likely to be exhibited at 0.005 or less, and the upper limit is not particularly defined from the viewpoint of improving frequency characteristics, but is desirably 0.3 or less. This is because if the demagnetizing factor exceeds 0.3 with respect to the magnetic path to be used, the absolute value of the magnetic permeability obtained is extremely lowered. Since the demagnetizing factor is greater than 0.005 and 0.3 or less, it is desirable to use the direction in the plate plane as the magnetic path direction in a thin plate shape such as a disk or a square plate. Further, if a longitudinal direction is used as a magnetic path direction in a rod shape such as a cylindrical bar or a square bar, a desired demagnetizing factor can be obtained. Or even if it is the shape similar to these, an effective demagnetizing factor should just be in said range. In the case of plane orientation, there is a direction with high magnetic permeability in any direction in the orientation plane in the evaluation with a non-demagnetizing field, so that the ring shape or the similar shape in which the annular plane is parallel to the orientation plane. Even if a gap across the road is inserted, the above effect is exhibited. By controlling the relationship between the orientation direction and the shape of the anisotropic ferrite oriented in this way, the permeation exceeding the level perceived as the material property of the material is achieved despite the use of the same material. The frequency characteristics of magnetic susceptibility can be realized. As a result, for example, with conventional hexagonal Z-type ferrite, it is possible to use at 2 GHz or higher, which is considered to be difficult to apply, and further at 3 GHz or higher.

The demagnetizing field coefficient is calculated as follows. Of the rectangular parallelepiped soft magnetic ferrite, the measurement direction is the X direction, the plate perpendicular direction is the Z direction, the direction perpendicular to both X and Z is the Y direction, the demagnetizing factor in the measurement direction is Nx, and the sample dimension in the measurement direction L, plate thickness T, Y dimension W
Nx = T / (L (1+ (T (1 + L / W) / L)))
Approximate as By using this relational expression, for example, the demagnetizing factor of a thin rectangular parallelepiped plate, a rectangular parallelepiped or the like can be calculated (reference: Journal of Applied Physics, Volume 94, Number 6, P4013-4017).

  By preparing the hexagonal Z-type ferrite of the present invention and assuming that the frequency that becomes 70% of the real part of the relative permeability of 100 MHz is f70, in the case of unidirectional orientation, f70 in one direction which is the magnetic field application direction is Assuming fa70 and f70 in the direction perpendicular to the one direction as the magnetic field application direction being fp70, a value of 1.2 or more can be obtained as fa70 / fp70. The direction perpendicular to the one direction, which is the magnetic field application direction, is the plane direction, but it is only necessary to obtain 1.2 or more as fa70 / fp70 in relation to the direction indicating the lowest f70. It is sufficient to satisfy 1.2 or more as fa70 / fp70 in the direction. Similarly, in the case of plane orientation, when f70 in one direction of the orientation in-plane direction as the magnetic field application direction is fa70 and f70 in the direction orthogonal to the one direction is fp70, 1 as fa70 / fp70 is 1 A value of .2 or higher can be obtained. In the case of plane orientation, the direction of taking fp70 can be taken in the orientation plane in addition to the direction orthogonal to the orientation plane direction, but 1.2 or more as fa70 / fp70 in relation to the direction showing the lowest f70. Therefore, the above condition is satisfied if at least fa70 / fp70 satisfies 1.2 or more in any direction orthogonal to the one direction. The fact that fa70 / fp70 is large indicates that the change in the extension of the frequency characteristic varies depending on the magnetic field application direction, and the elongation in one direction which is the magnetic field application direction is particularly large. If fa70 / fp70 is 1.2 or more, the effect of extending the frequency characteristic in one direction, which is the direction in which the magnetic field is applied, is exhibited as a sufficiently significant difference. It is possible to apply to the frequency band exceeding the used frequency. This also has the advantage that the frequency characteristics can be controlled without changing the material design. As a more preferable aspect, the value of fa70 / fp70 can be set to 1.5 or more, further 2.0 or more by optimizing the orientation direction and the direction of use of the shape, and the frequency characteristics are remarkably improved. be able to.

  In the hexagonal Z-type ferrite according to the present invention having the above-described configuration, an excellent value of f70 of 1 GHz or more can be obtained. In the case of the unidirectional orientation in which the c-axis is oriented in the in-plane direction perpendicular to the one direction, by setting the demagnetizing field coefficient to 0.03 or more, f70 becomes 1.5 GHz or more, and the frequency characteristics are further improved. In the case of unidirectional orientation in which the c-axis is oriented in an in-plane direction perpendicular to one direction, and in the case of plane orientation in which the c-axis is oriented in another direction perpendicular to the one direction, By setting the demagnetizing factor to 0.05 or more, f70 can be set to a higher value of 2.0 GHz or more. In addition, the absolute value of the relative permeability real part up to 3 GHz is measured by the principle of the one-turn coil method using (high frequency magnetic material measurement system) manufactured by Keycom Corporation.

  The soft magnetic ferrite of the present invention can be used, for example, as a magnetic core for a magnetic circuit or an inductance element, and exhibits excellent frequency characteristics as a magnetic core. The soft magnetic ferrite oriented so that the c-plane of the crystal grain is parallel to at least one direction is shaped as described above, and the one direction is a magnetic path direction through which the magnetic flux flows. If a circuit or an inductance element is configured, extremely excellent frequency characteristics are exhibited. According to such a usage method in a magnetic circuit or an inductance element, the frequency characteristics of oriented soft magnetic ferrite can be effectively used. For example, it can be used for inductors, choke coils, magnetic antennas, current transformers, and the like.

First, Fe ₂ O ₃ , BaCO ₃ , and Co ₃ O ₄ are mixed so that the main component composition has a ratio such as Fe ₂ O ₃ : 70.2 mol%, BaO: 18.8 mol%, and CoO: 11.0 mol%. Mn ₃ O ₄ , Li so as to have a ratio of Mn ₃ O ₄ : 3.0% by mass, Li ₂ CO ₃ : 0.4% by mass, SiO ₂ : 0.13% by mass with respect to this main component. ₂ CO ₃ and SiO ₂ were added and mixed for 16 hours in a wet ball mill. Note that Mn ₃ O ₄ , Li ₂ CO ₃ , and SiO ₂ may be added during pulverization performed after calcination. Next, this was calcined in the atmosphere at 1200 ° C. for 2 hours. This calcined powder was pulverized in a wet ball mill for 18 hours. A binder (PVA) was added to the prepared pulverized powder and granulated. After granulation, compression molding was performed, followed by sintering at 1300 ° C. for 3 hours in an oxygen atmosphere. The obtained sintered body was crushed with a jaw crusher and coarsely pulverized with a disk mill to obtain coarsely pulverized powder. Further, the coarsely pulverized powder was pulverized with a vibration mill for 3 hours. After pulverization, the resulting slurry was allowed to stand until sedimentation occurred, and the supernatant was removed to adjust the slurry concentration to 73%. When the powder obtained by drying the slurry was evaluated by XRD, this powder was substantially Z-type single phase, and the (0012) peak of Y-type ferrite, the (006) peak of M-type ferrite, and (440) of spinel ferrite. The intensity ratio of the peak of Z) to the peak of (0016) of the Z-type ferrite was 3% or less. Moreover, when the specific surface area of this pulverized powder was evaluated by gas adsorption method (BET method) using Model-1201 manufactured by Macsorb, the powder specific surface area was 2350 m ² / kg. The slurry produced as described above was wet-molded in a magnetic field. Here, the molding pressure was 87.5 MPa, and a uniaxial magnetic field of 0.85 MA / m was applied in a direction orthogonal to the pressing direction. This molding method is referred to as molding method 1. The obtained molded body was re-sintered again under the same conditions as in the above-mentioned sintering, and a cubic sintered body having a size of about 10 mm square was obtained. Hereinafter, the magnetic field application direction is referred to as the H direction, the permeability in the H direction is referred to as μ _H , and the surface having the H direction as a normal line is referred to as H-plane. Similarly, in the press direction, the P direction, μ _P , P− In the case of the direction orthogonal to the plane, the magnetic field application direction, and the press direction, they are referred to as the L direction, μ _L , and L-plane. Furthermore, the slurry was wet-formed in a rotating magnetic field. Here, the molding pressure was 29.1 MPa, and a rotating magnetic field of 0.48 MA / m was applied in a direction perpendicular to the pressing direction. After applying the rotating magnetic field, molding was performed while applying a uniaxial magnetic field in a direction perpendicular to the molding direction. This molding method is referred to as molding method 2. The obtained molded body was sintered at 1310 ° C. to obtain a sintered body of 40 × 40 × 7 mm ³ . Hereinafter, the uniaxial magnetic field application direction applied during pressing in forming method 2 is referred to as the H direction, the magnetic permeability in the H direction is referred to as μ _H , and the surface having the H direction as a normal line is referred to as H-plane. In the case of the direction, the P direction, μ _P , P-plane, the direction of the uniaxial magnetic field application direction, and the direction orthogonal to the press direction are respectively referred to as the L direction, μ _L , and L-plane.

The sintered body produced by the forming method 1 and the forming method 2 is cut to obtain a cross section having a normal direction of the magnetic field application direction to which a uniaxial magnetic field is applied, and X-ray diffraction (XRD) at the cut surface is obtained. : X ray diffraction) measurement was performed to evaluate the degree of orientation fc _⊥ . That is, XRD is performed in the measurement range of 2θ = 20 to 80 °, and in the obtained X-ray diffraction pattern, the integrated intensity sum of all diffraction peaks of hexagonal Z-type ferrite is ΣI (HKL), and L = 0 The sum of integral intensities of all (HK0) diffraction peaks was ΣI (HK0). _{fc ⊥ = ΣI (HK0) /} ΣI was calculated degree of orientation fc _⊥ from the equation (HKL). On the other hand, the sample was cut so as to obtain a cross section having the press direction as a normal line and a cross section having a normal direction as a magnetic field application direction and a direction perpendicular to the press direction, and XRD measurement was performed on these cut surfaces, and fc _/// Evaluated. These planes are two planes that are perpendicular to each other and perpendicular to the cross section having the normal direction of the magnetic field application described above. The degree of orientation fc _// defined here is a value obtained by dividing the diffraction peak intensity generated from the lattice plane of index (0018) of Z-type ferrite by the diffraction intensity generated from the lattice plane of index (110).

  Ni-Zn ferrite, which is an isotropic spinel ferrite, was also prepared as a comparative sample. Since this sample is isotropic, a ring-shaped sample was molded and sintered, and the frequency characteristic of the complex permeability in a non-demagnetizing field from 10 MHz to 1.8 GHz was measured with an impedance meter 4291B (manufactured by Agilent). The real part of the relative permeability at 100 MHz of this sample was 14.3. This sample is referred to as Comparative Example 1.

  The sintered body density and orientation degree of the oriented Z-type ferrite produced by the molding method 1 and the molding method 2 produced as described above are shown in Table 1 below.

Samples produced by the molding method 1 have an fc _// of 1.4 or more for both L-plane and P-plane, and the c-axis is also in the direction perpendicular to the magnetic field application direction (the direction parallel to the c-axis orientation plane). A hexagonal Z-type ferrite sintered body that is oriented randomly and has a small unidirectional orientation in the c-axis orientation plane is obtained. On the other hand, the fc _// of the P-plane of the sample prepared by the molding method 2 has a very strong I (0018) observation, and the (110) plane diffraction peak is hidden behind the (0018) plane diffraction peak. However, it was clear that fc _// exceeded 0.3. Further, fc _⊥ in H-plane is 0.7 or more. On the other hand, fc _// in L-plane is a small value of 0.1 or less, which is smaller than fc _{// in} P-plane, and the c-axis is concentrated in a specific direction in the H plane. It was confirmed. From this, it was confirmed that the sintered body produced by the molding method 2 was plane-oriented.

  The frequency characteristics of the relative permeability in one direction in a shape in which a demagnetizing field does not occur in the hexagonal Z-type ferrite sintered body produced by the forming method 1 and the forming method 2 were evaluated by the method described below. That is, the magnetic permeability of the ferrite sintered body in one direction cannot be measured simply with a ring sample, so three ring samples whose ring annular surfaces are parallel to H-plane, P-plane or L-plane are used. The magnetic permeability in the H direction, P direction, and L direction was calculated from the magnetic permeability measurement results of these ring samples.

  Before touching the evaluation method, the necessary relational expressions are derived. The longitudinal direction and the lateral direction along the plate surface of the magnetic plate having anisotropy are defined as the Y direction (for example, P direction) and the X direction (for example, H direction), respectively. It is assumed that a ring sample having a sufficiently small difference is cut out, N-turn winding is applied to the ring sample, and current I is passed through the winding to measure the initial permeability. The cross-sectional area of the ring sample is S. When θ and r are defined for the ring sample at the origin as shown in FIG. 2, the following equation is obtained.

  Further, assuming that there is no leakage of magnetic flux from the ring sample and the magnitude of the magnetic flux density vector inside the ring sample is constant, the following equation is obtained.

Here, if the magnetic permeability in the X direction and the magnetic permeability in the Y direction are respectively set to μx and μy (μx, μy and μ _xyplane shown below are _assumed to be relative magnetic permeability).

From the formulas 1 to 3 and Ampere's law, B ₀ = (1 / μ _x + 1 / μ _y ) ⁻¹ × NI / πr (formula 4)
The relationship is obtained. Here, since the self-inductance L is the ratio of the interlinkage magnetic flux and current,
Using the relationship of Equation 4,
_{L = NΦ / I = NB 0} S / I = S (1 / μ x + 1 / μ y) -1 × N 2 / π is obtained. For vacuo _{(μx = μy = 1),} L 0 = SN 2 / from a 2.pi.r, placing the permeability observed from the ring sample and _{μ xyplane μ xyplane = L / L} 0 = 2 × (1 / Μ _x + 1 / μ _y ) ⁻¹ (Formula 5)
The relationship is obtained.

Considering the relationship as shown in Equation 5, three types of ring samples are cut out so that the annular surface is H-plane, L-plane, or P-plane, and 10 MHz to 1 with an impedance meter 4291B (manufactured by Agilent). The complex relative magnetic permeability (μ _H-plane , μ _L-plane , μ _P-plane ) up to 8 GHz was measured. The dimensions of the sample were an outer diameter of 6.8 mm, an inner diameter of 3.2 mm, and a thickness of 1.5 mm. The magnetic permeability in each direction was calculated from the measured value using the following formula.
[mu] _H = {(-1 / [mu] _H-plane ) + (1 / [mu] _L-plane ) + (1 / [mu] _P-plane )} ^-1
_{μ L = {(1 / μ} H-plane) + (- 1 / μ L-plane) + (1 / μ P-plane)} -1
_{μ P = {(1 / μ} H-plane) + (1 / μ L-plane) + (- 1 / μ P-plane)} -1
Hereinafter, this method is called a ring method. In this measurement method, μ _H-plane , μ _L-plane , and μ _P-plane , which are the original data used for calculating the directional magnetic permeability, are evaluated in a non _- demagnetizing magnetic field, and thus the directional magnetic permeability given by the above equation is used. Also shows a value in a non-demagnetizing field.

  The frequency characteristics of the magnetic permeability in the H, L, and P directions of the sintered bodies produced by the forming method 1 and the forming method 2 using the ring method described above were evaluated. The results are shown in FIGS. From FIG. 3, it can be seen that the molding method 1 has a high permeability exceeding 50 at 100 MHz in the H direction. It can also be seen that a permeability of about 10 is obtained in the orthogonal L and P directions. The magnetic permeability in each direction obtained by the above is calculated by evaluating and calculating a ring sample having a different orientation in the normal of the annular surface from one sintered body. The given samples will be referred to as Comparative Examples 2 to 4 (Comparative Example 2: H direction, Comparative Example 3: L direction, Comparative Example 4: P direction). On the other hand, it can be seen that the sample produced by the molding method 2 has a high magnetic permeability exceeding 35 and 25 at 100 MHz in the H and L directions, respectively. In the case of the molding method 2, the permeability in the P direction is a low value of 4 at 100 MHz. A ring sample having a different orientation in the normal of the annular surface was evaluated and calculated from one sintered body, and the samples provided with magnetic permeability in each direction are temporarily referred to as Comparative Examples 6 to 8. I will do it. (Comparative Example 6: H direction, Comparative Example 7: L direction, Comparative Example 8: P direction)

  In order to evaluate the direction dependency of the magnetic permeability under the influence of the demagnetizing field, the evaluation was performed by a high frequency thin film magnetic permeability measuring device PMF-3000 (manufactured by Ryowa Denshi Co., Ltd.). Three types of plate-shaped samples shown in Table 2 were prepared. As for the evaluation direction of the magnetic permeability, the frequency characteristics of the magnetic permeability in the 8 mm direction in the processed shapes 1 and 3 and the 5 mm direction in the processed shape 2 were evaluated.

  The demagnetizing factor of the expected measurement direction in three types of thin plate shapes was calculated as follows. The calculation method is as described above.

A sample of processed shape 1 was cut out from the sintered body produced by molding method 1. A sample cut out so that the longitudinal direction (8 mm direction) of the processed shape 1 and the H direction are parallel to each other is referred to as Example 1. Samples cut from the same sintered body so that the L direction and the P direction are parallel to the longitudinal direction (8 mm direction) of the processed shape 1 are referred to as Examples 2 and 3, respectively. A sample having a processed shape 2 was cut out from the sintered body produced by the molding method 1. A sample cut out so that one side of a 5 × 5 mm ² square of the processed shape 2 is parallel to the H direction is referred to as Example 4. Samples cut out from the same sintered body so that the L direction and the P direction are parallel to one side of a 5 × 5 mm ² square of the processed shape 2 are referred to as Examples 5 and 6, respectively. A sample having a processed shape 3 was cut out from the sintered body produced by the molding method 1. A sample cut out so that the longitudinal direction (8 mm direction) of the processed shape 3 and the H direction are parallel to each other is referred to as Example 7. Samples cut out from the same sintered body so that the L direction and the P direction are parallel to the longitudinal direction (8 mm direction) of the processed shape 1 are referred to as Examples 8 and 9, respectively. A sample having a processed shape 2 was cut out from the sintered body produced by the molding method 2. A sample cut out so that one side of a 5 × 5 mm ² square of the processed shape 2 is parallel to the H direction is referred to as Example 10. Samples cut out from the same sintered body so that the L direction and the P direction are parallel to one side of a 5 × 5 mm ² square of the processed shape 2 are referred to as Examples 11 and 12, respectively. In addition, a sample having a processed shape 2 was cut out from the Ni—Zn ferrite in a random orientation. This is referred to as Comparative Example 5.

  The frequency characteristics of the complex permeability in the directions of Examples 1 to 12 and Comparative Example 5 were evaluated by PMF-3000. The evaluation direction of the permeability is shown in Table 3. The measured relative permeability real part was normalized so that the relative permeability real part of 100 MHz was 1. The evaluation results of Examples 1 to 12 and Comparative Examples 1 to 8 are shown in FIGS.

  From the frequency characteristics shown in FIGS. 5 to 11, the frequency characteristic f70 at which the permeability value at 100 MHz becomes 70% was evaluated. Table 3 shows the molding method, processed shape, cutting orientation, demagnetizing factor in the measurement direction, and f70 value of Examples 1 to 12 and Comparative Examples 1 to 8, respectively.

  Comparing Comparative Example 1 and Comparative Example 5 as shown in Table 3 and FIG. 11, it can be seen that the frequency characteristic of the permeability is shifted to the high frequency side due to the effect of the demagnetizing field, and f70 is from 0.36 GHz to 0. It increases to .8 GHz but does not exceed 1 GHz. On the other hand, as shown in FIG. 5 and Table 3, in Example 4 of the molding method 1 related to the unidirectional orientation, f70 is 2.47 GHz, which is the same demagnetizing factor (0.054) as compared with Comparative Example 5. There is a particularly high value. In addition, it can be seen that f70 increases as the demagnetizing factor increases with Comparative Example 2, Examples 1, 4, and 7, and the demagnetizing factor is 0.039 or more, 1.6 GHz or more, and a high value exceeding 1 GHz. can get. Furthermore, it shows excellent frequency characteristics of magnetic permeability with a demagnetizing factor of 0.054 or more and 2.47 GHz or more, and a demagnetizing factor of 0.097 or more and 2.76 GHz or more. As shown in Comparative Examples 3 and 4 and Examples 2, 3, 5, 6, 8, and 9, f70 increases even when evaluated in the L and P directions as the demagnetizing factor increases. However, as shown in Examples 2 and 3, in the case of the L and P directions, the increase in f70 is small compared to Example 1 (f70 is 1.6 GHz) which has the same demagnetizing factor as 1.14 GHz and 1.07 GHz. . It can be seen that even in Examples 8 and 9 in which the demagnetizing factor is 0.097, f70 is lower than that in Example 7 having the same demagnetizing factor as 1.87 GHz and 1.59 GHz. From these facts, it can be seen that the increase in f70 due to the increase in the demagnetizing factor is the H direction having the highest μ in the non-demagnetizing field evaluation.

  As shown in Table 3 and FIGS. 8 and 9, even in the sintered body produced by the forming method 2, compared to Comparative Examples 6 and 7, Examples 11 and 12 having a higher demagnetizing factor showed an increase in f70. In Examples 11 and 12 (demagnetizing factor 0.054), it can be seen that f70 shows a high value of 1.82 GHz and 2.27 GHz. That is, it is suggested that the forming method 2 related to the plane orientation can also obtain excellent magnetic permeability frequency characteristics of a demagnetizing factor of 0.054 or more and 2.27 GHz or more. On the other hand, when Comparative Example 8 and Example 12 that are evaluations in the P direction were compared, the value of f70 decreased with an increase in the demagnetizing factor. From these facts, it can be seen that in the sintered body produced by the forming method 2, the f70 increased due to the increase of the demagnetizing factor in the H and L directions, which are high directions of μ in the non-demagnetizing field evaluation. The L direction is also a magnetic field application direction, and in this respect, the L direction is similar in behavior to the H direction.

  The sintered body produced by the forming method 1 is considered to have the c-plane parallel to the H direction (magnetic field application direction) by XRD described above. Here, the frequency at which the real part of relative permeability in the H direction becomes 70% of the real part of relative permeability at 100 MHz is fa70, and the real part of relative permeability in the L and P directions becomes 70% of the real part of relative permeability at 100 MHz. If the frequency is fp70, fa70 / fp70 can be calculated from Table 3. Further, the sintered body produced by the molding method 2 is considered to have the c-plane parallel to all directions in the P-plane by the XRD diffraction described above. In this case, fa70 can be evaluated with respect to the magnetic permeability in an arbitrary direction within the plane, but in the following, the case where the H direction and the L direction are set to fa70 is separately calculated and represented. The fa70 / fp70 calculated as described above is shown in Table 4 below.

  Table 4 shows that fa70 / fp70 was as low as 1.0 in both the L and P directions in the evaluation of the demagnetizing factor 0 in the molding method 1. However, in the case of the demagnetizing factor 0.039, fa70 / fp70 values of 1.4, 1.5, and 1.2 were obtained in the L direction and the P direction, respectively. When the demagnetizing factor was 0.054, the maximum value was 2.2, which was even higher, and when the demagnetizing factor was 0.097, the maximum value was 1.7. Further, from Table 4, in the forming method 2, the evaluation of the demagnetizing factor 0 was as low as 1.1 at the maximum, although it differs depending on whether fa is in the H or L direction. It was also found that a demagnetizing factor of 0.054 can obtain a maximum value of 2.1 when fa is 70 in the L direction. As described above, the maximum value of the ratio of fa 70 evaluated with respect to the direction parallel to the c-plane of the crystal and fp 70 in the direction perpendicular thereto increases with the introduction of the demagnetizing factor, particularly in the vicinity of the demagnetizing factor 0.054. A value greater than 2 is obtained.

  The absolute value of the real part of relative permeability up to 3 GHz was measured by the principle of the one-turn coil method using (High Frequency Magnetic Material Measurement System) manufactured by Keycom Corporation. The values of the relative permeability real part of 0.1 GHz, 0.5 GHz, 1 GHz, 2 GHz, and 3 GHz of Comparative Example 5, Examples 4, 5, 6 and Examples 10, 11, 12 were evaluated and are shown in Table 5. .

  From Table 5, in Example 4, the c-plane is oriented so as to be parallel to one direction, and in Example 4 in which the one direction coincides with the longitudinal direction of the rectangular parallelepiped, the magnetic permeability almost decreases even at 1 GHz. And a permeability of 16 or more. The examples shown in Table 4 show very excellent frequency characteristics of magnetic permeability, 11 or higher at 2 GHz, and 5 or higher at 3 GHz. In particular, by optimizing the orientation direction and the direction in which the shape is used, a frequency characteristic of magnetic permeability of 13 or more at 2 GHz and 8 or more even at 3 GHz is exhibited. Taking Example 4 as an example, it can be seen that 9.3 at 3 GHz, which is three times higher than that of Comparative Example 5, is obtained. On the other hand, in the cases of the L and P directions as in Examples 5 and 6, a large value of f70 in Table 3 is obtained, but superiority is not recognized as an absolute value compared to Comparative Example 5. That is, it shows that the behavior of the change in the frequency characteristic is remarkably different depending on the orientation direction. Taking Examples 10 to 12 produced by the molding method 2 as examples, Examples 10 and 11 show higher magnetic permeability at each frequency than the comparative example, and especially compared with 5.6 and 8.8 at 3 GHz. A value two to three times that of Example 5 was obtained. On the other hand, in Example 12 in the P direction, the magnetic permeability was lower than that in Comparative Example 5 at each frequency, and no superiority was observed. That is, even in the case of the molding method 2 which is plane orientation, the behavior of the change in the frequency characteristics is remarkably different depending on the orientation direction.

It is a conceptual diagram which shows the state in which the c-axis of a crystal grain has faced the observation surface direction. It is a figure which shows the definition of r, (theta), and a line element in a ring sample. It is a figure which shows the frequency characteristic of the complex magnetic permeability of H, L, and P direction of the sintered compact of the comparative example produced with the shaping | molding method 1. FIG. It is a figure which shows the frequency characteristic of the complex permeability of H, L, and P direction of the sintered compact of the comparative example produced with the shaping | molding method 2. FIG. It is a figure shown with the frequency characteristic of the complex magnetic permeability of the H direction in Example 1, 4, 7 and the comparative example 2. FIG. It is a figure shown with the frequency characteristic of the complex magnetic permeability of the L direction in Example 2, 5, 8 and the comparative example 3. FIG. It is a figure shown with the frequency characteristic of the complex magnetic permeability of the P direction in Example 3, 6, 9 and the comparative example 4. FIG. It is a figure shown with the frequency characteristic of the complex magnetic permeability of the H direction in Example 10 and Comparative Example 6. It is a figure shown with the frequency characteristic of the complex magnetic permeability of the L direction in Example 11 and Comparative Example 7. It is a figure shown with the frequency characteristic of the complex magnetic permeability of the P direction in Example 12 and Comparative Example 8. It is a figure shown with the frequency characteristic of the complex permeability in comparative example 1 and comparative example 5.

Claims (6)

a ferrite crystal grain having a c-plane as an easily magnetized plane, and an orientation such that the c-plane of the crystal grain is parallel to at least one direction, and the demagnetizing factor in the one direction is 0 have a larger such a shape,
A soft magnetic ferrite having a c-axis oriented in a plurality of directions within a plane perpendicular to the one direction . a ferrite crystal grain having a c-plane as an easily magnetized plane, and an orientation such that the c-plane of the crystal grain is parallel to at least one direction, and the demagnetizing factor in the one direction is 0 It has a shape that grows,
A soft magnetic ferrite, wherein a c-axis is oriented in another direction perpendicular to the one direction. The frequency at which the real part of the relative permeability in the one direction is 70% of the real part of the relative permeability of 100 MHz is fa70, and the real part of the relative permeability in the direction orthogonal to the one direction is 70 of the relative permeability of 100 MHz. 3. The soft magnetic ferrite according to claim 1, wherein the maximum value of fa70 / fp70 is 1.2 or more, where fp70 is a frequency at which% is obtained. The soft magnetic ferrite according to any one of claims 1 to 3, wherein the soft magnetic ferrite is a Z-type ferrite, and an absolute value of a real part of relative permeability in the one direction is 6 or more at 3 GHz. . 5. A magnetic circuit using the soft magnetic ferrite according to claim 1, wherein the one direction is used as a magnetic path direction. An inductance element using the soft magnetic ferrite according to any one of claims 1 to 4, wherein the one direction is used as a magnetic path direction.

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