JP2005247670A - Mn-Ni-Zn TYPE FERRITE - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Mn-Ni-Zn type ferrite having squareness ratio remarkably increased without lowering the specific resistance and deteriorating other magnetic characteristics when Fe<SB>2</SB>O<SB>3</SB>component is controlled to <50 mol% and Fe<SP>2+</SP>content is decreased. <P>SOLUTION: The Mn-Ni-Zn type ferrite contains ≥45.0 mol% and <50.0 mol% Fe<SB>2</SB>O<SB>3</SB>, ≥0.1 mol% and ≤5.0 mol% NiO and ≥3.0 mol% and <15.5 mol% ZnO and the balance being MnO as base components and each content of P, B, S and Cl contained in the ferrite is controlled respectively to <50 massppm P, <20 massppm B, <30 massppm S and <50 massppm Cl. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an Mn-Ni-Zn ferrite having a high square resistance, a high specific resistance, a small coercive force, and a ratio of a saturation magnetic flux density to a residual magnetic flux density (residual magnetic flux density / saturation magnetic flux density). is there.

  For example, in a switching power supply circuit, a saturable core is often used as a mag amplifier and to suppress noise. This saturable core material is required to have a high saturation magnetic flux density, a low loss, and above all a large squareness ratio. Here, the squareness ratio is obtained by dividing the residual magnetic flux density by the saturation magnetic flux density. The saturable core is required to have such characteristics that the inductance changes rapidly in the material. As the squareness ratio becomes smaller, the change in inductance becomes smaller. Therefore, a saturable core having a large squareness ratio is suitable.

Therefore, amorphous metal magnetic materials that satisfy the above-mentioned characteristics are mainly used for this type of application.
However, this amorphous metal magnetic material has two major drawbacks. First, the cost is increased due to the material and the manufacturing method, and because it is a metal, the specific resistance is very low on the order of μΩ · m.

In this regard, ferrite, which is an oxide magnetic material, is inferior in terms of saturation magnetic flux density compared to amorphous metal magnetic material, but can be manufactured at low cost, and has a specific resistance that is at least 10 ³ times higher. .

In particular, among ferrites, Ni-Zn ferrite has a high squareness ratio and at the same time has a very high specific resistance of 10 ⁵ Ω · m. However, although Ni-Zn ferrite is not as much as an amorphous metal magnetic material, NiO as a raw material is problematic because it is expensive and the price fluctuates severely.

On the other hand, Mn-Zn ferrite has a small coercive force in addition to a high saturation magnetic flux density as compared with Ni-Zn ferrite. Moreover, the price of MnO used as a raw material is also advantageous compared to NiO. However, the conventional Mn—Zn ferrite contains a large amount of Fe ²⁺ having positive magnetic anisotropy, so that the residual magnetic flux density is small and the squareness ratio is about 0.3 at most. At the same time, electrons are easily exchanged between Fe ³⁺ and Fe ²⁺ , resulting in a problem that the specific resistance is reduced to the order of 0.1 Ω · m.

As a means for solving this problem, there is a method of increasing the specific resistance by reducing the amount of Fe ²⁺ contained in the Mn-Zn ferrite. That is, Patent Documents 1 to 3 propose to reduce the Fe ²⁺ content and increase the specific resistance by setting the Fe ₂ O ₃ component to less than 50 mol%.

  However, the Mn-Zn ferrites described in these documents are mainly focused on either increasing the resistance, increasing the permeability, or reducing the loss. That is, in these documents, there is no description regarding the residual magnetic flux density as well as the squareness ratio. Moreover, when actually manufactured, it may lead to a decrease in specific resistance and deterioration of other magnetic characteristics, and thus it is difficult to stably obtain Mn-Zn ferrite having a large squareness ratio.

Furthermore, since the example shown in Patent Document 3 is fired in a very low oxygen concentration atmosphere,
a) Strict sealing of firing furnace and atmosphere control b) The use of pure nitrogen is required (since industrial nitrogen contains at least 1-20 ppm by volume of oxygen). These regulations are problematic in terms of both production efficiency and cost when considering industrialization.
Japanese Patent Laid-Open No. 7-230909 JP 2000-277316 A JP 2001-151565 A

The present invention advantageously solves the above-mentioned problems, and reduces Fe ²⁺ content by reducing the Fe ₂ O ₃ component to less than 50 mol%, and further adding a proper amount of NiO, thereby reducing specific resistance and Another object of the present invention is to provide an Mn-Ni-Zn-based ferrite that realizes a significant increase in squareness ratio without causing deterioration of magnetic characteristics.

Now, in the Mn-Ni-Zn ferrite in which the Fe ²⁺ content is reduced by making the Fe ₂ O ₃ component less than 50 mol%, large specific resistance and excellent magnetic properties cannot be stably obtained. When the cause was examined, it was found that abnormal grain growth was involved in the ferrite production process. In other words, abnormal grain growth is a phenomenon that occurs when the grain growth balance is locally lost for some reason, and is often observed particularly during production using powder metallurgy. In this abnormally grown grain, a substance that greatly impedes the movement of the domain wall such as impurities and lattice defects is mixed, so that the coercive force is increased. At the same time, since the formation of crystal grain boundaries becomes insufficient, the specific resistance is lowered, and other magnetic characteristics are greatly deteriorated.

Furthermore, the inventors pay attention to the fact that most of the raw material of ferrite, especially the main raw material Fe ₂ O ₃ depends on the scale generated during iron making, and the scale-derived Fe ₂ O ₃ raw material and the above-mentioned The relationship with abnormally grown grains was investigated. As a result, ferrite containing P, B, S and Cl impurities inevitably mixed in steel (scale) induces abnormal grain growth, resulting in the magnetic properties and resistivity of soft magnetic ferrite. It has been newly found that it has a serious adverse effect on various properties.

  That is, in the technique described in Patent Document 1 or 3 described above, since there is no restriction on such impurities, the desired characteristics described in the same document can be obtained only by following the technical contents disclosed in these documents. Production of Mn-Zn ferrite having the above has been difficult in practice. Further, in the technique described in Patent Document 2, although P is limited, other impurities are not mentioned at all.

The present invention is based on the above findings.
That is, the gist configuration of the present invention is as follows.
(1) Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%,
NiO: 0.1 mol% or more and 5.0 mol% or less,
ZnO: 3.0 mol% or more and less than 15.5 mol% and
MnO: The balance is the basic component,
P, B, S and Cl contained in the ferrite are
P: less than 50 massppm,
B: Less than 20 massppm
S: less than 30 massppm and
Cl: Mn-Ni-Zn ferrite characterized by being less than 50 massppm.

(2) In the ferrite, as an additive
CaO: 0.005-0.200 mass% and
SiO ₂ : 0.001 to 0.050 mass%
The Mn-Ni-Zn ferrite according to (1) above, which contains one or two selected from the above.

(3) In the ferrite, as an additive
ZrO ₂ : 0.005 to 0.100 mass%,
Ta ₂ O ₅ : 0.005 to 0.100 mass%,
HfO ₂ : 0.005 to 0.100 mass% and
Nb ₂ O ₅ : 0.005 to 0.100 mass%
The Mn—Ni—Zn ferrite according to (1) or (2) above, which contains one or more selected from among the above.

  The Mn—Ni—Zn ferrite of the present invention has a specific resistance of 30Ω at a Curie temperature of 180 ° C. or higher and a room temperature (23 ° C.) satisfying the H-class insulation defined in JIS C4003, which has not been realized in the past. -It has excellent characteristics such as m or more, coercive force of 20.0 A / m or less, and squareness ratio of 0.70 or more.

  According to the present invention, there is provided an Mn-Ni-Zn-based ferrite having a high specific resistance at room temperature (23 ° C), a small coercive force, and a large squareness ratio while maintaining the Curie temperature at 180 ° C or higher. can do.

A further increase in specific resistance and a decrease in coercive force can be achieved by adding an appropriate amount of one or _two of CaO and SiO ₂ to this ferrite and utilizing the effect of grain boundary segregation. Furthermore, the effect which combined said effect is acquired by adding combining these.

  Further, the ferrite of the present invention limits the amount of impurities and suppresses the occurrence of abnormal grain growth and the deterioration of characteristics due to the change in atmosphere. Therefore, it is possible to use a powder metallurgy method during the production, and furthermore, it is possible to use, for example, industrial nitrogen containing 1 to 20 ppm by volume of oxygen at the time of cooling during firing. Therefore, stable production with reduced production cost and abnormal grain growth is realized.

The present invention will be specifically described below.
First, the reason why the basic component is limited to the above range in the present invention will be described. In addition, the basic component composition in the present invention is a case where all Fe and Mn contained are converted as Fe ₂ O ₃ and MnO.

Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol% Among the basic components, Fe ₂ O ₃ increases the amount of Fe ²⁺ when it is excessively contained, which decreases the specific resistance of Mn-Zn ferrite. In addition, the squareness ratio decreases. In order to avoid this, the amount of Fe ₂ O ₃ needs to be suppressed to less than 50.0 mol%. However, if the amount is too small, this causes an increase in coercive force and a decrease in Curie temperature. Therefore, the minimum content is 45.0 mol%.

NiO: 0.1 mol% or more and 5.0 mol% or less
The solid solution of NiO increases the negative magnetic anisotropy energy of Mn-Zn ferrite and increases the residual magnetic flux density. As a result, it has the effect of increasing the squareness ratio at room temperature (23 ° C). Therefore, NiO is contained at least 0.1 mol% or more. However, if the amount is larger than the appropriate amount, the magnetic anisotropy increases excessively and the coercive force is increased, so that the amount is within the range of 5.0 mol% or less.

ZnO: 3.0mol% or more and less than 15.5mol%
ZnO can lower the coercive force with its solid solution, and for that purpose, it should contain at least 3.0 mol%. However, if the content is higher than the appropriate value, the Curie temperature is lowered and the JIS-standard H-type insulation is not satisfied. Therefore, it is less than 15.5 mol%.

MnO: balance The present invention is Mn-Ni-Zn ferrite, and the balance of the main component composition needs to be MnO. The reason is that by containing MnO, good magnetic properties such as high saturation magnetic flux density, low loss, and high magnetic permeability can be obtained.

P: less than 50 massppm, B: less than 20 massppm, S: less than 30 massppm and Cl: less than 50 massppm P, B, S and Cl are all components inevitably contained in the raw iron oxide. If these contents are very small, there is no problem, but if they are contained in a certain amount or more, abnormal grain growth of the ferrite is induced, and the various properties of the obtained ferrite are seriously adversely affected. Ferrite with a composition with a Fe ₂ O ₃ content of less than 50 mol% after the above conversion is more likely to cause crystal grain growth than that with a content of 50 mol% or more, thus causing abnormal grain growth. It becomes easy. Therefore, in order to suppress abnormal grain growth, it is necessary to limit the contents of P, B, S and Cl to less than 50, 20, 30 and 50 ppm, respectively. A high degree of compatibility with magnetic force can be achieved.

In order to suppress the contents of P, B, S and Cl within the above ranges, it is necessary to use a high-purity raw material having a small impurity content, for example, with respect to Fe ₂ O ₃ , MnO, ZnO or the like used as the raw material. There is. Further, the medium used for mixing and grinding such as a ball mill may be mixed due to wear, and therefore it is desirable to use a medium having a small content of these impurities.

CaO: 0.005~0.200mass% and SiO _2: chose from among the 0.001~0.050mass% 1 alone or in combination of two or
Both CaO and SiO ₂ have the effect of increasing the electrical resistance of ferrite by segregating at the grain boundaries, and also reducing the residual vacancies in the grains by relaxing the moving speed of the grain boundaries during grain growth. Has the effect of lowering. In order to obtain these effects, it is necessary to add CaO: 0.005 mass% or more and SiO ₂ : 0.001 mass% or more. On the other hand, if too much is added, abnormal grain growth in the ferrite grains is induced, leading to a decrease in specific resistance and an increase in coercive force. Therefore, it is desirable that the upper limit is CaO: 0.200 mass% and SiO ₂ : 0.050 mass%.

One or more selected from ZrO ₂ : 0.005 to 0.100 mass%, Ta ₂ O ₅ : 0.005 to 0.100 mass%, HfO ₂ : 0.005 to 0.100 mass% and Nb ₂ O ₅ : 0.005 to 0.100 mass% As additives, ZrO ₂ , Ta ₂ 0 ₅ , HfO ₂ and Nb ₂ O ₅ may be added singly or in combination. All of these substances are compounds having a high melting point, and when added to Mn-Ni-Zn ferrite, they have a function of reducing crystal grains, thereby increasing specific resistance and simultaneously reducing coercive force. . However, when the added amount is less than the appropriate value, the effect cannot be obtained, and when the added amount is large, the specific resistance decreases and the coercive force increases due to the generation of abnormal grains. For this reason, it is desirable that each be within the above range.

  In addition, although the additive demonstrated for every group above is effective as above-mentioned even if individual addition for every group is carried out, even when it adds by the combination of a some group, it demonstrates an effect similarly. Also in that case, in order to suppress the occurrence of abnormal grain growth and increase in holding power, it is desirable to suppress the amount of the additive within the above range.

Next, a preferred method for producing the Mn—Ni—Zn ferrite of the present invention will be described.
First, Fe ₂ O ₃ , ZnO, NiO, and MnO powders are weighed so as to have a predetermined ratio, and after sufficient mixing, calcining is performed. Next, the obtained calcined powder is pulverized. Furthermore, when adding the above-mentioned additives, they are added at a predetermined ratio and pulverized simultaneously with the calcined powder. In this operation, it is necessary to sufficiently homogenize the powder so that the concentration of the added component is not biased. The powder of the target composition is granulated using an organic binder such as polyvinyl alcohol, and pressure is applied, followed by molding and firing under appropriate firing conditions.

  Here, since the amount of impurities in the Mn-Ni-Zn ferrite of the present invention is limited, the abnormal grain growth that becomes a problem when using a powder metallurgical method and the fluctuation of the atmosphere during firing are considered. However, it is difficult to cause characteristic deterioration such as an increase in coercive force. Therefore, as described above, a powder metallurgical technique can be used at the time of production, and industrial nitrogen containing, for example, 1 to 20 ppm by volume of oxygen can be used at the time of cooling during firing.

In the Mn-Ni-Zn ferrite thus obtained, the amount of Fe ²⁺ is greatly reduced as compared with the conventional Mn-Zn ferrite. Therefore, the low specific resistance, which has been a problem of the conventional Mn-Zn ferrite, rises from the order of 0.1 Ω · m to about 300 times. Moreover, the squareness ratio is increasing by adding NiO.

When all the contained Fe and Mn are converted as Fe ₂ O ₃ and MnO, each raw material powder weighed so that Fe ₂ O ₃ , ZnO, NiO and MnO have the ratio shown in Table 1 is After mixing for 16 hours, calcination was performed in air at 925 ° C. for 3 hours. Next, it was pulverized with a ball mill for 12 hours, polyvinyl alcohol was added to the obtained mixed powder and granulated, and a toroidal core was formed by applying a pressure of 1.2 ton / cm ² . After that, this molded body is inserted into a firing furnace and fired at a maximum temperature of 1350 ° C. When cooling after firing, an industrial containing oxygen partial pressure of 10 volume ppm in the temperature range from 1100 ° C to 500 ° C A sintered core having an outer diameter of 25 mm, an inner diameter of 15 mm and a height of 5 mm was obtained.
With respect to each sample thus obtained, the specific resistance and coercivity at the Curie temperature and room temperature were measured, and the squareness ratio was calculated by measuring the saturation magnetic flux density and the residual magnetic flux density.
The obtained results are also shown in Table 1.

  In addition, since all the raw materials including iron oxide were used, the final contents of P, B, S, and Cl were 5 ppm each for all samples. .

  As shown in the table, Sample Nos. 1-3, 1-5, 1-6 and 1-10, which are invention examples, have a Curie temperature of 180 ° C. or higher, a specific resistance at room temperature of 30 Ω · m or higher and The coercive force is 20.0 A / m or less, and the squareness ratio is 0.70 or more.

On the other hand, since the comparative examples (sample numbers 1-1 and 1-2) in which Fe ₂ O ₃ is 50.0 mol% or more contain a large amount of Fe ²⁺ , the squareness ratio and the specific resistance are greatly reduced. On the contrary, in the comparative example (sample number 1-11) in which Fe ₂ O ₃ is insufficient, the Curie temperature is lowered and the coercive force is increased.

Moreover, in the comparative example (sample number 1-4) which does not contain NiO, since the value of residual magnetic flux density is low, the squareness ratio at room temperature is less than 0.70. On the contrary, in the comparative example (sample number 1-7) containing a large amount of NiO, the coercive force is significantly increased due to excessive increase in the negative magnetocrystalline anisotropy energy.
On the other hand, when attention is focused on ZnO, the comparative example (sample number 1-8) containing ZnO in a larger amount than the scope of the invention has a Curie temperature of less than 180 ° C., which is problematic in practice. On the other hand, in the comparative example (sample number 1-9) in which ZnO is insufficient, the coercive force is increased.

Using various iron oxide raw materials having different contents of P, B, S and Cl, the content in the sample is finally P: 50 ppm or less, B: 20 ppm or less, S: 30 ppm or less, and Cl: 50 ppm or less. After calculating so that all Fe and Mn contained are converted as Fe ₂ O ₃ and MnO, Fe ₂ O ₃ : 49.0 mol%, ZnO: 10.0 mol%, NiO: 2.0 mol% and the balance: The raw materials were weighed so as to have a composition of MnO, mixed for 16 hours using a ball mill, and then calcined in air at 925 ° C. for 3 hours. Next, it was pulverized with a ball mill for 12 hours. Polyvinyl alcohol was added to the obtained mixed powder and granulated, and a toroidal core was formed by applying a pressure of 1.2 ton / cm ² . After that, this compact is put into a firing furnace and fired at a maximum temperature of 1350 ° C. When cooling after firing, industrial nitrogen containing oxygen partial pressure of 10 volume ppm in the temperature range from 1100 ° C to 500 ° C A sintered core having an outer diameter of 25 mm, an inner diameter of 15 mm and a height of 5 mm was obtained.
For each of these samples, the specific resistance and coercive force at room temperature were measured, and the squareness ratio was calculated by measuring the saturation magnetic flux density and the residual magnetic flux density. The Curie temperature determined by the main component composition was 210 ° C. for all samples.
The obtained results are shown in Table 2.

As shown in the table, P, B, S and Cl components are less than 50, 20, 30 and 50 massppm, respectively, and no abnormal grain growth is observed in any of the inventive examples (sample numbers 1-6, 2-1). Even in the composition containing NiO, excellent values of a specific resistance of 30 Ω · m or more and a coercive force of 20.0 A / m or less were obtained.
On the other hand, in any of the comparative examples (sample numbers 2-2 to 2-7) including more than one appropriate value among the four components of P, B, S and Cl, generation of abnormal particles was confirmed. . Therefore, both the coercive force and the specific resistance are greatly deteriorated.

To the mixed powder having the same composition as in Example 2 (however, P, B, S and Cl are all adjusted to 5 massppm), CaO and SiO ₂ are added as additives so that the final composition has the ratio shown in Table 3, respectively. Grinding was performed for 12 hours with a ball mill. This mixed powder is granulated by adding polyvinyl alcohol, and a toroidal core is formed by applying a pressure of 1.2 ton / cm ² , and then the formed body is placed in a firing furnace and fired at a maximum temperature of 1350 ° C. When cooling, it was carried out in an industrial nitrogen flow containing oxygen partial pressure of 10 ppm by volume in the temperature range from 1100 ° C to 500 ° C, and a sintered body core having an outer diameter of 25 mm, an inner diameter of 15 mm and a height of 5 mm was obtained. .
For each of these samples, the specific resistance and coercive force at room temperature were measured, and the squareness ratio was calculated by measuring the saturation magnetic flux density and the residual magnetic flux density. The Curie temperature determined by the main component composition was 210 ° C. for all samples.
The obtained results are shown in Table 3.

From the results in Table 3, the invention example (sample numbers 3-1 to 3-3) to which one or _two of CaO and SiO ₂ are added can confirm an increase in specific resistance. However, in the comparative example (sample numbers 3-4 to 3-6) containing more than either of CaO and SiO _{2 at} an appropriate value, abnormal grain growth occurs, and both the magnetic properties and the specific resistance are greatly deteriorated. Yes.

Nb ₂ O ₅ , Ta ₂ O ₅ , HfO ₂ , and ZrO ₂ were added as final additives to the mixed powder of the same composition as in Example 2 (however, P, B, S and Cl were all adjusted to ₅ massppm). Was added so as to have the ratio shown in Table 4, and pulverized for 12 hours with a ball mill. Polyvinyl alcohol is added to this mixed powder and granulated, and a toroidal core is formed by applying a pressure of 1.2 ton / cm ² , and then the formed body is placed in a firing furnace and fired at a maximum temperature of 1350 ° C. When cooling, it was carried out in an industrial nitrogen flow containing oxygen partial pressure of 10 ppm by volume in the temperature range from 1100 ° C to 500 ° C, and a sintered body core having an outer diameter of 25 mm, an inner diameter of 15 mm and a height of 5 mm was obtained. .
For each of these samples, the specific resistance and coercive force at room temperature were measured, and the squareness ratio was calculated by measuring the saturation magnetic flux density and the residual magnetic flux density. The Curie temperature determined by the main component composition was 210 ° C. for all samples.
Table 4 shows the obtained results.

From the results of Table 4, all of the invention examples (sample numbers 4-1 to 4-15) in which appropriate amounts of one or more of Nb ₂ O ₅ , Ta ₂ O ₅ , HfO ₂ , and ZrO ₂ were added, As a result of the suppression of crystal growth, the specific resistance increased and the coercive force decreased.
However, any of the comparative examples (sample numbers 4-16 to 4-18) containing a large amount exceeding the appropriate range of any one of the four components Nb ₂ O ₅ , Ta ₂ O ₅ , HfO ₂ , and ZrO ₂ However, abnormal grains are generated, and since many impurities and vacancies are contained in the grains, the specific resistance is lowered and the coercive force is also greatly increased.

Mixed powder having the same composition as in Example 2 (however, P, B, S, and Cl are all adjusted to 5 massppm), and one or two of CaO and SiO ₂ as additive components (additive group A), and One or more of ZrO ₂ , Ta ₂ O ₅ , HfO _2, and Nb ₂ O ₅ (additive group B) were added so that the final components were as shown in Table 5, and the mixture was ball milled for 12 hours. Grinding was performed. This mixed powder is granulated by adding polyvinyl alcohol, and a toroidal core is formed by applying a pressure of 1.2 ton / cm ² , and then the formed body is placed in a firing furnace and fired at a maximum temperature of 1350 ° C. Subsequent cooling was performed in an industrial nitrogen flow containing an oxygen partial pressure of 10 ppm by volume in the temperature range from 1100 ° C. to 500 ° C. to obtain a sintered core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm.
For each of these samples, the specific resistance and coercive force at room temperature were measured, and the squareness ratio was calculated by measuring the saturation magnetic flux density and the residual magnetic flux density. The Curie temperature determined by the main component composition was 210 ° C. for all samples.
The results obtained are shown in Table 5.

As shown in Table 5, the specific resistance of the inventive examples (Sample Nos. 5-1 to 5-9) added in combination with the additive groups A and B increased as compared with the case where they were not added, The coercive force decreased.
On the other hand, in any of the comparative examples (sample numbers 5-10 to 5-11) containing any one of these six components in excess of the appropriate value, abnormal grains are generated and many impurities are present in the grains. Both coercive force and specific resistance are greatly deteriorated due to the inclusion of holes.

Claims (3)

Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol%,
NiO: 0.1 mol% or more and 5.0 mol% or less,
ZnO: 3.0 mol% or more and less than 15.5 mol% and
MnO: The balance is the basic component,
P, B, S and Cl contained in the ferrite are
P: less than 50 massppm,
B: Less than 20 massppm
S: less than 30 massppm and
Cl: Mn-Ni-Zn ferrite characterized by being less than 50 massppm. In the ferrite, further as an additive
CaO: 0.005-0.200 mass% and
SiO ₂ : 0.001 to 0.050 mass%
The Mn-Ni-Zn-based ferrite according to claim 1, comprising one or two selected from among them. In the ferrite, further as an additive
ZrO ₂ : 0.005 to 0.100 mass%,
Ta ₂ O ₅ : 0.005 to 0.100 mass%,
HfO ₂ : 0.005 to 0.100 mass% and
Nb ₂ O ₅ : 0.005 to 0.100 mass%
The Mn-Ni-Zn-based ferrite according to claim 1 or 2, which contains one or more selected from among the above.